G e n i t o u r i n a r y I m a g i n g • R ev i ew Uyeda et al. Acute and Emergent Genitourinary Conditions
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Genitourinary Imaging Review
Jennifer W. Uyeda1 Bradley S. Gans Aaron Sodickson Uyeda JW, Gans BS, Sodickson A
Imaging of Acute and Emergent Genitourinary Conditions: What the Radiologist Needs to Know OBJECTIVE. Acute and emergent genitourinary conditions require accurate and rapid diagnosis to minimize patient morbidity and mortality. CONCLUSION. Radiologists’ familiarity with the various conditions of the urinary system and of the male and female reproductive organs is important given the widespread use of imaging for the diagnosis of common clinical entities presenting to the emergency department.
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mergent genitourinary conditions require timely diagnosis and treatment to ensure a favorable clinical outcome and to prevent morbidity and mortality. CT is typically the imaging modality of choice for most emergent conditions of the genitourinary tract, and ultrasound is used less frequently. MRI is primarily used as a problem-solving modality because of its improved soft-tissue characterization and higher resolution. The aim of this article is to summarize the role of imaging in diagnosing acute and emergent genitourinary conditions using a case-based approach and to show how imaging can aid in the diagnosis of common clinical entities presenting to the emergency department. Keywords: emergency, female reproductive system, genitourinary, male reproductive system, urinary system DOI:10.2214/AJR.14.14117 Received November 10, 2014; accepted after revision December 17, 2014. A. Sodickson received a research grant from Siemens Healthcare. 1
All authors: Department of Radiology, Emergency Radiology Section, Brigham and Women’s Hospital, 75 Francis St, Boston, MA 02115. Address correspondence to J. W. Uyeda ([email protected]).
WEB This is a web exclusive article. AJR 2015; 204:W631–W639 0361–803X/15/2046–W631 © American Roentgen Ray Society
Urinary System Patient 1 45-year-old man with acute onset of right flank pain—The diagnosis is urolithiasis. Urolithiasis is a condition in which there are dense calculi within the kidney or ureteral lumen and possible hydroureteronephrosis, with dilatation of the ureter proximal to the calculus and normal-caliber ureter distal to the calculus (Fig. 1). Secondary signs of ureterolithiasis include hydroureteronephrosis, perinephric and periureteral inflammatory stranding, and unilateral renal enlargement or a subtle hypodensity related to parenchymal edema. Differential diagnosis—The differential diagnosis is pelvic phlebolith. The comet-tail sign, in which eccentric soft tissue is seen adjacent to the calcification, is a reliable feature of phleboliths; phleboliths tend to have lucent centers, whereas calculi have dense cen-
ters [1]. The “soft-tissue rim” sign is a halo of soft tissue around the calcification that is very specific for a ureteral calculus with a specificity of 90–100% [1]. Urolithiasis affects 1.2 million Americans per year with a recurrence rate of up to 75% within 20 years [1]. Imaging—Unenhanced MDCT is the imaging modality of choice for the evaluation of urinary calculi with a sensitivity and specificity of 95–98% and 96–100%, respectively [1–3] (Fig. 1A); however, contrast-enhanced CT also has a high accuracy for stone detection. In addition to detecting urolithiasis, CT can be used to assess genitourinary tract and extraurinary abnormalities. CT accurately identifies the stone burden and location of calculi and reveals the presence of an obstruction or hydronephrosis (Fig. 1B). Determination of stone composition can have important therapeutic implications. Approximately 70–80% of calculi are calciumbased, whereas 5–10% are uric acid stones that form in acidic urine and can be dissolved medically with urinary alkalinization [1]. Attenuation measurements of stones have been shown to have some utility in differentiating among the different stone subtypes, but substantial overlap persists [1]. Dual-energy CT has shown an improved ability to differentiate uric acid–based stones from calcium-based stones because it relies on the x-ray absorption characteristics of stones at two x-ray energies [4–7]. Ultrasound is ideal for detecting the presence and severity of hydronephrosis and assessing for cortical thinning due to chron-
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Uyeda et al.
rupture is seen as the presence of extravesicular contrast material on CT cystography. In intraperitoneal bladder rupture, contrast material accumulates around the bowel loops and in the peritoneal recesses including the paracolic gutters, rectovesical or rectouterine pouch, and subphrenic space [12, 13] (Fig. 2A). In extraperitoneal rupture, the extravasated contrast material tracks into the perivesicular and prevesical space of Retzius to form the classic “molar tooth” sign [12, 13] (Fig. 2B). Combined intraperitoneal and extraperitoneal bladder ruptures involve both spaces. Blunt abdominal trauma is responsible for most bladder injuries, although bladder rupture can also occur after penetrating trauma [14]. Gross hematuria is present in up to 95%
of bladder rupture cases and should prompt further evaluation, particularly in the setting of pelvic fractures. Microscopic hematuria is typically present in the remaining 5%. Bladder rupture is classified as extraperitoneal (70%), intraperitoneal (20%), or mixed (10%) [12–16]. Intraperitoneal bladder rupture requires surgical repair to prevent intraabdominal sepsis [17]. It commonly results from a sudden increase in pressure on a distended bladder, which tears at the bladder dome, the only part covered by peritoneum and also the weakest point of the bladder [12, 13, 15]. In contrast, extraperitoneal bladder rupture is associated with pelvic fractures causing perforation of the bladder wall [12]. Imaging—CT cystography has largely replaced conventional cystography for the evaluation of suspected bladder rupture, with a sensitivity and specificity of 100% and 95%, respectively [17]. Approximately 300–400 mL of dilute water-soluble contrast material is instilled through a Foley catheter [14] to accomplish full distention of the bladder, which is necessary for accurate detection of bladder rupture. Key points—First, bladder injury requires a high index of suspicion particularly in trauma patients with pelvic fractures or gross or microscopic hematuria. Second, CT cystography is the test of choice to identify and characterize bladder injuries. Third, intraperitoneal rupture (20%) is a surgical emergency occurring at the bladder dome, whereas extraperitoneal rupture (70%) is managed nonsurgically.
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Fig. 1—Ureterovesical junction and ureteral calculi. A, 34-year-old man with acute onset of left flank pain. Axial unenhanced CT image shows left ureterovesical junction calculus (arrow) with mild hydroureteronephrosis and periureteral stranding. B, 63-year-old woman with acute onset of left flank pain. Coronal unenhanced CT image shows proximal left ureteral calculus (arrow), associated mild hydroureteronephrosis, and additional nonobstructing left lower pole calculus.
ic obstruction [2]. However, ultrasound has variable sensitivity and specificity for detecting renal calculi, ranging from 24% to 80% and from 82% to 100%, respectively, and the accuracy of calculus measurements is debated [2, 8, 9]. A large segment of the ureteral course of the ureters cannot be well assessed using ultrasound. Nevertheless, ultrasound may have a role in the imaging evaluation of young patients because of radiation exposure concerns in this population. Radiography has a sensitivity of 45–85% for stone detection [10, 11]. MR urography may be used when ionizing radiation is of concern, but calculus detection is limited, with a sensitivity of approximately 50% [10, 11]. Treatment—Management of and urologic interventions to treat urolithiasis are guided by patient symptoms in combination with the location, size, and composition of the calculi. In general, nonobstructing renal calculi smaller than 10 mm in an asymptomatic patient are observed, whereas larger calculi in a patient with or without symptoms may undergo an intervention including shock wave lithotripsy, ureterorenoscopy, or percutaneous nephrolithotomy [1, 2]. The rate of spontaneous ureteral stone passage depends on stone size, with excellent success for stones smaller than approximately 6 mm but diminishing rates for larger stones [1]. Key points—First, unenhanced CT is the imaging modality of choice for calculus detection. Second, the location, size, and composition of calculi dictate treatment. Patient 2 18-year-old woman in a motor vehicle collision with a pelvic fracture and gross hematuria—The diagnosis is bladder rupture. Bladder
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Fig. 2—Intraperitoneal bladder rupture and extraperitoneal bladder rupture. A, 27-year-old woman who was in high-speed motor vehicle collision. Sagittal CT cystogram shows focal defect in bladder dome (arrow) with contrast material surrounding loops of bowel and in rectouterine pouch; these findings are consistent with intraperitoneal bladder rupture. B, 31-year-old man who was in motorcycle crash. Sagittal CT cystogram shows focal defect at base of bladder (arrow). Contrast material is seen in prevesicular space, which is finding consistent with extraperitoneal bladder rupture.
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Acute and Emergent Genitourinary Conditions Patient 3 69-year-old woman with acute right flank pain—The diagnosis is retroperitoneal hematoma. Retroperitoneal hematoma is seen as a high-density retroperitoneal collection with an occasional blood-fluid level (Figs. 3A–3C) and occasional associated lesion (Fig. 3C). Retroperitoneal hematoma can occur in the setting of trauma (Fig. 3A) or may be spontaneous, with possible causes including anticoagulation therapy, hemorrhagic diathesis, hemorrhage from a retroperitoneal mass, and abdominal aortic aneurysm rupture [18, 19]. The incidence in patients receiving anticoagulation therapy is roughly 1–7%, and coagulation parameters do not need to be outside the therapeutic range for this diagnosis [20]. Patients present with abdominal, hip, or back pain and are often managed conservatively with supportive care and correction of the underlying coagulopathy [21, 22]. In a series of 89 patients with anticoagulation therapy–related spontaneous retroperitoneal hematoma, 68% were managed conservatively, 25% required interventional radiology embolization, and 7% underwent surgical hematoma evacuation [21]; of these patients, 75% received blood transfusions [21]. Imaging—When retroperitoneal hemorrhage is suspected, unenhanced CT is often performed (Fig. 3B). Although IV contrast material is not necessary to make the diagnosis, it can help to identify areas of active extravasation, which may prompt more aggressive management [22]. CT can also identify an underlying lesion responsible for the hemorrhage such as a renal cell carcinoma, renal angiomyolipoma (Fig. 3C), or adrenal myelolipoma.
Patient 4 21-year-old woman with a history of urinary tract infections presents with flank pain— The diagnosis is pyelonephritis. Pyelonephritis is seen on imaging as renal parenchymal edema, often with one or more wedge-shaped areas of decreased enhancement and with decreased corticomedullary differentiation. A “striated nephrogram”—consisting of linear areas of decreased enhancement from the papilla to the cortex—can also be seen (Fig. 4A). Urothelial thickening and enhancement of the renal pelvis and ureter are suggestive of pyelitis (i.e., urinary tract infection ascending to the collecting system) and may be seen with or without parenchymal changes indicative of pyelonephritis. Differential diagnosis—The differential diagnosis is a ureteral stone, renal infarct, and renal malignancy. Pyelonephritis is an acute bacterial infection of the kidneys and usually results from ascending infection in a patient with bacterial cystitis. These patients typically present with fever, leukocytosis, flank pain, and costovertebral angle tenderness [23, 24].
Imaging—Pyelonephritis is typically a clinical diagnosis. The primary role of imaging is to exclude the most concerning complication of renal or perinephric abscess in severe cases (Fig. 4B) and to exclude obstructive uropathy requiring urinary decompression. The sensitivity of ultrasound for pyelonephritis is low because the kidneys typically have a normal appearance [25]. Parenchymal edema may cause subtle changes in echogenicity with a loss of distinction between the cortex and the renal sinus fat and may also result in focal decreased perfusion on Doppler sonography. Ultrasound is useful to identify other renal abnormalities including hydronephrosis, stone disease, and renal abscess. CT shows a higher sensitivity for pyelonephritis with typical findings. A striated nephrogram results from inflammatory debris obstructing the renal tubules [25, 26] (Fig. 4A). Although the imaging appearances of renal infarct and pyelonephritis overlap, renal infarct may be differentiated from pyelonephritis by the presence of a thin rim of overlying cortical enhancement (termed the “cortical rim” sign) due to the presence of collateral blood flow to the renal capsule [27]. Malignancies, including renal and transitional cell carcinoma, can occasionally mimic infection (Fig. 4C). Whenever malignancy is suspected, subsequent imaging after the resolution of the infection may help to reveal an underlying lesion, or alternatively MRI may identify an underlying solid mass. Key points—First, pyelonephritis is an acute bacterial renal infection evident on CT as a striated nephrogram or as wedge-shaped cortical enhancement defects.
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Key points—First, suspect retroperitoneal bleeding in patients on anticoagulation therapy with abdominal, hip, or back pain. Second, CT should be performed when retroperitoneal hemorrhage is suspected. Active hemorrhage can be detected on contrastenhanced CT. Third, most cases of anticoagulation therapy–related retroperitoneal hemorrhage are managed conservatively. Embolization and surgery are reserved for cases refractory to conservative measures.
Fig. 3—Imaging findings of different causes of retroperitoneal hemorrhage. A, 25-year-old woman who was in motor vehicle collision. Axial contrast-enhanced CT image shows right adrenal gland hematoma (arrow) with surrounding hemorrhage in retroperitoneum. B, 55-year-old man on anticoagulation therapy. Unenhanced axial CT image shows large left retroperitoneal hematoma (arrow) resulting in anterior displacement of kidney. C, 33-year-old man with tuberous sclerosis and acute back pain. Axial contrast-enhanced CT image shows left angiomyolipoma that has spontaneously undergone hemorrhage (arrow). Bilateral angiomyolipomas are seen.
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Fig. 4—Various renal abnormalities with overlapping imaging appearances. A, 53-year-old woman with recent diagnosis of urinary tract infection who presented with fever and back pain. Axial contrast-enhanced CT image shows “striated nephrogram” in right kidney (arrow) and mild perinephric stranding. B, 64-year-old woman with recent history of urinary tract infection. Coronal contrast-enhanced CT image shows hypodense renal abscess with thick peripherally enhancing wall and resulting mass effect on renal parenchyma (arrow). C, 67-year-old man with incidental renal findings. Coronal contrast-enhanced CT image shows left renal hypodense lesion with peripheral solid nodule (arrow) that is highly concerning for renal cell carcinoma (RCC). Additional smaller solid lesion (arrowhead) suspicious for RCC is seen in upper pole of right kidney.
Second, differential considerations include renal infarcts or masses. Repeat imaging after treatment of the infection can be helpful to differentiate among infection, infarct, and malignancy. Patient 5 75-year-old diabetic man presents with flank pain, hypotension, and urinary retention—The diagnosis is emphysematous pyelonephritis (EPN). EPN appears on imaging as small bubbles or linear foci of parenchymal gas, gas-fluid levels, fluid collections, parenchymal enlargement and destruction, and tissue necrosis [25, 28] (Fig. 5A). Differential diagnosis—The differential diagnosis for air within the renal parenchyma is EPN, renal abscess, traumatic renal injury, and iatrogenic renal injury. EPN is an emergent life-threatening necrotizing infection of the kidney characterized by gas within the renal parenchyma or perinephric tissues [25, 28, 29]. EPN is associated with a high mortality rate of up to 75% [25, 28, 29]; 90% of patients have uncontrolled diabetes [25, 28]. Imaging—CT is the study of choice for patients who present acutely with flank pain and systemic manifestations of infection. CT is the most sensitive and specific modality to diagnose EPN and to assess the extent of disease. Ultrasound shows echogenic nondependent foci of gas with reverberation artifact and low-level echoes, also known as “dirty shadowing.” The distinction of EPN from emphysematous pyelitis, in which gas is limited to the collecting system, is crucial because the latter is a less aggressive upper uri-
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Fig. 5—Imaging appearance of emphysematous pyelonephritis (EPN) versus emphysematous pyelitis. A, 64-year-old man with urinary tract infection. Coronal contrast-enhanced CT image shows gas within left retroperitoneum and renal parenchyma (arrow), which is consistent with EPN. B, 43-year-old woman with urinary tract infection. Axial unenhanced CT image shows gas within collecting system bilaterally (arrows), which is consistent with emphysematous pyelitis.
nary tract infection with a significantly lower mortality [25] (Fig. 5B). Renal abscesses develop as a result of the progression of an ascending urinary infection or liquefactive necrosis [25, 26, 30, 31] (Fig. 4A). Up to 15% of patients have a negative urine culture at presentation [25]. CT is the most accurate modality for the diagnosis of renal abscess, which typically appears as a well-defined hypodense mass with a thick and irregular enhancing wall [26]. Renal abscesses may contain gas in rare cases [26]. Trauma or iatrogenic injury can introduce air in the renal parenchyma and can be mistaken for EPN. Patients may have a recent history of trauma with other associated in-
juries or may have recently undergone renal abscess drainage or a renal biopsy. Key points—First, EPN is a life-threatening necrotizing infection with a poor prognosis that requires urgent diagnosis and aggressive medical or surgical treatment. Second, EPN must be differentiated from emphysematous pyelitis, a less aggressive infection with a significantly lower mortality. Male Reproductive Organs Patient 6 18-year-old man with acute testicular pain and swelling—The diagnosis is epididymitis and orchitis. Epididymitis and orchitis manifest as heterogeneity, enlargement,
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Acute and Emergent Genitourinary Conditions and hypoechogenicity of the epididymis or testicle with associated hypervascularity on color Doppler imaging [32, 33] (Fig. 6A). Reactive hydroceles and scrotal edema and thickening are commonly seen. Doppler flow can be helpful in differentiating epididymitis and orchitis from testicular torsion with absent flow. Differential diagnosis—The differential diagnosis for acute testicular pain and swelling is orchitis and epididymitis, testicular torsion, testicular rupture, testicular trauma, and testicular tumor. Epididymitis and orchitis are the most common causes of acute scrotal pain. Patients typically present with testicular pain and swelling. If untreated, epididymitis may continue to ascend and result in orchitis and, in severe cases, in abscess or testicular infarction (Fig. 6B). Epididymitis and orchitis typically result from an ascending infection, commonly Escherichia coli in older men and Neisseria gonorrheae or Chlamydia trachomatis in sexually active younger males. Because of the order of ascent, the epididymal tail is infected first with subsequent infection of the body and head, followed by the testicular parenchyma. Testicular torsion is a surgical emergency, and early diagnosis is crucial to restore blood flow and salvage the testicle [33]. Adolescent males are most commonly affected. On ultrasound, the absence of blood flow in the symptomatic testicle is pathognomonic for torsion (Fig. 6C). However, arterial flow can be maintained in partial torsion, and hyperemia mimicking orchitis can be seen after spontaneous detorsion. The testicle may appear normal in early torsion, but with continued ischemia, the testicle becomes enlarged and heterogeneous. Prompt urologic consultation with detorsion and orchiopexy is essential for testicular salvage. Testicular salvage rates are greatest if surgery is performed within 6 hours of onset. After 24 hours of ischemia, the testicle is usually no longer salvageable. In the setting of trauma, the testicle may develop hematoma, contusion, fracture, or rupture (Fig. 6D). Signs of testicular injury include focal areas of heterogeneous testicular echogenicity corresponding to areas of infarction or contusion, hematocele, or a discrete fracture line. Testicular rupture manifests as discontinuity of the linear echogenic tunica albuginea surrounding the testicle and possible protrusion of the seminiferous tubules [33]. The diagnosis of testicular rup-
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Fig. 6—Spectrum of ultrasound findings of acute testicular abnormalities. A, 23-year-old man with left scrotal pain for 4 days. Sagittal color Doppler ultrasound image of left epididymis and testicle shows increased vascularity in epididymis and testicle; these findings are consistent with epididymitis and orchitis. B, 34-year-old man with left scrotal pain for 2 weeks. Transverse color Doppler ultrasound image of left testicle shows testicular abscess with no internal vascularity. C, 18-year-old man with left scrotal pain for 3 hours. Transverse power Doppler ultrasound image of testicles shows decreased vascular flow in left testicle with heterogeneity of parenchyma (arrow). D, 22-year-old man who sustained blunt trauma to scrotum. Ultrasound image of testicle shows focal avascular hypoechogenic region suggestive of testicular contusion.
ture is vital because it mandates immediate surgical exploration and repair. Testicular neoplasm is the most common nonhematologic malignancy in males between the ages of 15 and 50 years [34]. Although the typical presentation of a testicular neoplasm is a painless unilateral testicular mass, approximately 10% of patients with a testicular neoplasm will present with pain and the neoplasm may be misdiagnosed as epididymitis or orchitis [32, 34]. The two major categories of testicular tumors are germ cell (90–95%) and stromal (5–10%) tumors [34] Ultrasound is the initial study for the diagnosis followed by CT and MRI for staging. Testicular orchitis and epididymitis, testicular torsion, testicular rupture, and testicular tumor can have similar and overlapping imaging appearances, particularly on ultrasound. Clinical history is helpful for the accurate diagnosis, but misdiagnosis is com-
mon. Follow-up imaging can also be used to differentiate epididymoorchitis from tumors because infectious processes will resolve after appropriate treatment. Key points—First, testicular epididymitis or orchitis, testicular torsion, testicular rupture, and testicular tumor can have similar imaging appearances. Second, testicular torsion and testicular rupture require urgent surgical intervention to preserve testicular function. Third, the absence of testicular blood flow in torsion is pathognomonic. However, two scenarios must be kept in mind: Testicular arterial flow may be present in partial torsion, and hyperemia after detorsion can mimic orchitis. Patient 7 32-year-old man with pelvic pain after trauma—The diagnosis is penile fracture. Penile fracture is seen as a focal disruption of the tunica albuginea with an adjacent he-
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Uyeda et al. matoma and can be seen on both ultrasound and MRI (Fig. 7). Penile fractures result most commonly secondary to an external bending force applied to an erect penis during sexual intercourse. Unilateral rupture of the tunica albuginea is most common, and concomitant urethral injury occurs in 10–20% of cases, warranting a low threshold for retrograde urethrography [33, 35, 36]. Clinically, penile fractures are experienced as a cracking sensation followed by rapid detumescence and severe penile pain, swelling, and bruising [33, 36]. Most penile fractures are immediately repaired to avoid the complications of conservative management including nodule formation at the site of the fracture, penile deformity, erectile dysfunction, and painful erection. Imaging—Ultrasound imaging is readily accessible and is optimally performed with a linear high-frequency (7.5–10 MHz) transducer. Ultrasound delineates the fracture as an interruption of the thin echogenic tunica albuginea and can be used to assess the extent of the injury [33]. The presence of echogenic foci of air within the corpora cavernosa suggests an associated urethral injury [33]. MRI accurately localizes the fracture site so that a small focal incision can be used rather than an extensive degloving surgical technique [33, 36]. The patient should be supine with the penis dorsiflexed against the lower abdomen, and a surface coil should be used with a small FOV, resulting in high-resolution thin-section images. Triplane sagittal, coronal, and axial T2-weighted sequences and at least two planes of T1-weighted spin-echo sequences should be acquired [33, 36]. The contrast between the corpora and fascial layers of the penis is best seen on T2weighted images, and an interruption of the low-signal-intensity tunica albuginea at the site of the penile fracture is best seen on T2weighted images [33, 36] (Fig. 7). Key points—First, ultrasound is readily available for the diagnosis and evaluation of penile fractures; however, MRI may be used in equivocal or complicated cases and may aid surgeons in choosing a surgical approach. Second, associated urethral injuries occur in 10–20% of penile fractures, and a high clinical suspicion of urethral injury warrants retrograde urethrography. Female Reproductive Organs Patient 8 23-year-old woman with acute pelvic pain—The diagnosis is tuboovarian abscess
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Fig. 7—Ultrasound and MRI findings of penile fracture. A, 21-year-old man who presented after trauma to penis. Gray-scale ultrasound image shows focal defect in echogenic tunica albuginea (arrow). B, 32-year-old man who presented after impalement of penis. Coronal T2-weighted image of penis shows penile fracture with focal rupture of tunica albuginea of left corpus cavernosa (arrow) and adjacent hematoma.
(TOA). A TOA has a variable appearance on ultrasound and may be a solid, cystic, or complex mass in the adnexa or cul-de-sac with adjacent fluid [37, 38] (Fig. 8A). CT findings suggestive of TOA include uniformly thick walls with internal septations. Pyosalpinx is a common associated finding manifesting as a fluid-filled tubular structure with a thick enhancing peripheral wall [38, 39]. On MRI, a TOA is typically hypointense on T1-weighted imaging and heterogeneously hyperintense on T2-weighted imaging, although the signal intensity is variable and depends on the internal protein concentration and viscosity [39]. Hypointense meshlike strands secondary to adhesions or fibrosis are common findings on T2-weighted images and may enhance on contrast-enhanced T1-weighted images [39] (Fig. 8B). Differential diagnosis—The differential diagnosis is TOA, ovarian torsion, and ovarian tumors.
Pelvic inflammatory disease (PID) is an infection of the upper genital tract usually seen in sexually active young women. A late and serious complication of PID is TOA. Risk factors include the presence of an intrauterine device and multiple sexual partners [37, 39]. Clinically, TOA and PID present similarly; the distinction is usually made using ultrasound, although CT and MRI are increasingly being performed as confirmatory or problem-solving examinations or even as the initial imaging modality [39, 40]. TOAs are frequently mistaken radiologically and clinically for ovarian malignancy, so the detection of imaging signs of infection is vital in differentiating the two diagnoses [39, 41]. Imaging—Pelvic ultrasound is the most common initial imaging modality in patients who present with acute pelvic pain [37, 39, 42–45], but CT and MRI can also be the primary modality.
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Fig. 8—Ultrasound and MRI findings of tuboovarian abscess (TOA). A, 25-year-old woman with pelvic pain and history of pelvic inflammatory disease. Gray-scale ultrasound image of right ovary shows complex heterogeneous TOA. B, 31-year-old woman with pelvic pain. Axial gadolinium-enhanced fat-saturated T1-weighted image shows complex right adnexal mass with thick enhancing internal septations (arrow); these findings are consistent with TOA.
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Acute and Emergent Genitourinary Conditions Ovarian torsion is the fifth most common surgical gynecologic emergency, and early recognition is crucial to restore blood flow and salvage the ovary [40, 46]. The ovary is partially or completely twisted around its vascular pedicle, which initially compromises low-pressure venous and lymphatic outflow, resulting in edema and enlargement. As vascular compromise advances, there is loss of the normally low-resistance diastolic arterial flow followed by the loss of arterial flow even during systole, which results in thrombosis, ischemia, and hemorrhagic infarction [40, 46]. In 50–90% of the cases, an underlying ovarian mass serves as a lead point—most commonly, a cyst or a mature cystic teratoma [40, 46]. The most common finding is ovarian enlargement with peripheral follicles, and color Doppler ultrasound may show a twisted vascular pedicle, the so-called “whirlpool” sign. Additional findings on CT and MRI include ascites, deviation of the uterus toward the ipsilateral torsed ovary, ipsilateral engorged pelvic vessels, and unusual location of the enlarged edematous ovary toward the midline or rotated toward the contralateral side [40, 46] (Figs. 9B and 9C). Ovarian tumors can be benign or malignant and tend to be asymptomatic unless they are associated with ovarian torsion [40, 46, 47]. MRI may be performed in cases of sonographically indeterminate adnexal masses to ensure timely diagnosis and guide subsequent management. Treatment—Patients with TOA are treated as conservatively as possible to preserve fertility. Management is usually with IV antibiotics alone, with a success rate of up to 87% [44, 48]. Recent data suggest that concomitant treatment of TOA with imagingguided aspiration may be a safe and effec-
tive first-line treatment [44, 48]. Surgical intervention is usually reserved for refractory TOA cases. Key points—First, TOA, ovarian torsion, and ovarian tumors can have overlapping imaging appearances on pelvic ultrasound. Second, ovarian torsion is a surgical emergency and requires urgent surgical intervention to preserve ovarian function. Patient 9 26-year-old woman with positive HCG value and pelvic pain—The diagnosis is ectopic pregnancy. Ectopic pregnancy is visualized on imaging as an extrauterine pregnancy where a fetal heartbeat may be present. More commonly, ectopic pregnancies are seen as an extraovarian adnexal mass that can manifest as a tubal ring containing a yolk sac and embryo, a tubal ring with only a yolk sac and no embryo, or a complex mass separate from the ovary (Fig. 10A). Differential diagnosis—The differential diagnosis of a pregnant patient with pain and vaginal bleeding is a normal intrauterine pregnancy, an ectopic pregnancy, and spontaneous abortion. Ectopic pregnancy is the leading cause of maternal death in first-trimester pregnancy [42]. Early detection is essential to decrease maternal mortality and preserve fertility [42]. If an ectopic pregnancy is suspected, the initial evaluation includes a quantitative serum HCG level and pelvic ultrasound [42]. The risk of rupture increases with the increase in size of the ectopic pregnancy, and any unstable patient with a clinical suspicion of a ruptured ectopic pregnancy should undergo surgical exploration [42] (Fig. 10B). Imaging—Ectopic pregnancies are most commonly located in the fallopian tube.
The detection of a live extrauterine embryo containing a heartbeat has 100% specificity but lacks sensitivity because it is a rare finding [42, 43]. More commonly, in the setting of a positive pregnancy test, an extraovarian adnexal mass is used as a criterion for the diagnosis of ectopic pregnancy [43] (Fig. 10A). Differentiating an ovarian corpus luteum cyst, a normal finding in pregnancy, from an ectopic pregnancy is important. A corpus luteum cyst arises within or is exophytic from the ovary, whereas an ectopic pregnancy is almost always distinct from the ovary. Motion separate from the ovary during gentle pressure on a transvaginal probe can be a helpful differentiator because a corpus luteum cyst always moves together with the ovary. On color Doppler imaging, a “ring of fire” can be a helpful finding that indicates hypervascularity due to high-velocity low-impedance flow in the ectopic pregnancy, but this finding must be interpreted with caution because it may also be seen around a corpus luteum cyst [42, 43]. When the uterus and ovaries appear normal on sonography, the differential diagnosis includes normal pregnancy, ectopic pregnancy, and spontaneous abortion. From 5% to 18% of ectopic pregnancies are detected only on repeat ultrasound, necessitating the need for follow-up imaging when neither an intrauterine pregnancy nor an ectopic pregnancy is visualized [43]. Key points—First, ectopic pregnancy must be excluded in the absence of an intrauterine gestational sac in a pregnant patient with vaginal bleeding. Second, an adnexal mass separate from the ovary is the most common ultrasound finding suggestive of an ectopic pregnancy.
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Fig. 9—28-year-old woman with acute pelvic pain. A, Sagittal color Doppler ultrasound image shows heterogeneous left adnexal mass. B, Axial contrast-enhanced CT image shows slightly dense mass (arrow) with surrounding crescentic hypodensity in left adnexa extending to midline. C, Coronal T2-weighted image obtained approximately 1 hour after CT (B) shows torsed edematous left ovary (arrow) rotated toward contralateral side.
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Fig. 10—Ultrasound and CT findings of ectopic pregnancy. A, 26-year-old woman with first-trimester pregnancy with acute pelvic pain. Sagittal (left) and coronal (right) ultrasound images show right adnexal mass (cursors) separate from ovary that contains yolk sac; these findings are consistent with fallopian tube ectopic pregnancy. B, 34-year-old woman with first-trimester pregnancy, acute pelvic pain, and hypotension. Contrast-enhanced CT image shows right adnexal rupture ectopic pregnancy with hemoperitoneum (arrow).
Summary Some common and rare genitourinary conditions of the urinary system and of the male and female reproductive organs have been reviewed, including relevant differential diagnostic considerations. Radiologists’ familiarity with the imaging findings of acute and emergent genitourinary conditions is imperative to enable accurate and timely diagnosis and treatment to ensure a favorable clinical outcome for patients. References 1. Kambadakone AR, Eisner BH, Catalano OA, Sahani DV. New and evolving concepts in the imaging and management of urolithiasis: urologists’ perspective. RadioGraphics 2010; 30:603–623 2. Eisner BH, McQuaid JW, Hyams E, Matlaga BR. Nephrolithiasis: what surgeons need to know. AJR 2011; 196:1274–1278 3. Fielding JR, Silverman SG, Samuel S, Zou KH, Loughlin KR. Unenhanced helical CT of ureteral stones: a replacement for excretory urography in planning treatment. AJR 1998; 171:1051–1053 4. Stolzmann P, Kozomara M, Chuck N, et al. In vivo identification of uric acid stones with dualenergy CT: diagnostic performance evaluation in patients. Abdom Imaging 2010; 35:629–635 5. Primak AN, Fletcher JG, Vrtiska TJ, et al. Noninvasive differentiation of uric acid versus non-uric acid kidney stones using dual-energy CT. Acad Radiol 2007; 14:1441–1447 6. Qu M, Ramirez-Giraldo JC, Leng S, et al. Dualenergy dual-source CT with additional spectral filtration can improve the differentiation of nonuric acid renal stones: an ex vivo phantom study. AJR 2011; 196:1279–1287 7. Vrtiska TJ, Takahashi N, Fletcher JG, Hartman RP, Yu L, Kawashima A. Genitourinary applica-
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tions of dual-energy CT. AJR 2010; 194:1434– 1442 8. Ray AA, Ghiculete D, Pace KT, Honey RJ. Limitations to ultrasound in the detection and measurement of urinary tract calculi. Urology 2010; 76:295–300 9. Fowler KA, Locken JA, Duchesne JH, Williamson MR. US for detecting renal calculi with nonenhanced CT as a reference standard. Radiology 2002; 222:109–113 10. Semins MJ, Feng Z, Trock B, Bohlman M, Hosek W, Matlaga BR. Evaluation of acute renal colic: a comparison of non-contrast CT versus 3-T noncontrast HASTE MR urography. Urolithiasis 2013; 41:43–46 11. Regan F, Kuszyk B, Bohlman ME, Jackman S. Acute ureteric calculus obstruction: unenhanced spiral CT versus HASTE MR urography and abdominal radiograph. Br J Radiol 2005; 78:506– 511 12. Gross JS, Rotenberg S, Horrow MM. Resident and fellow education feature: bladder injury— types, mechanisms, and diagnostic imaging. RadioGraphics 2014; 34:802–803 13. Vaccaro JP, Brody JM. CT cystography in the evaluation of major bladder trauma. RadioGraphics 2000; 20:1373–1381 14. Mirvis SE, Kubal WS, Shanmuganathan K, Soto JA, Yu J. Problem solving in emergency radiology. Philadelphia, PA: Elsevier/Saunders, 2014 15. Sandler CM, Hall JT, Rodriguez MB, Corriere JN Jr. Bladder injury in blunt pelvic trauma. Radiology 1986; 158:633–638 16. Soto JA, Lucey BC. Emergency radiology. Philadelphia, PA: Mosby/Elsevier, 2009 17. Deck AJ, Shaves S, Talner L, Porter JR. Computerized tomography cystography for the diagnosis of traumatic bladder rupture. J Urol 2000; 164:43–46
18. Besir FH, Gul M, Ornek T, Ozer T, Ucan B, Kart L. Enoxaparin-associated giant retroperitoneal hematoma in pulmonary embolism treatment. N Am J Med Sci 2011; 3:524–526 19. González C, Penado S, Llata L, Valero C, Riancho JA. The clinical spectrum of retroperitoneal hematoma in anticoagulated patients. Medicine (Baltimore) 2003; 82:257–262 20. Chan YC, Morales JP, Reidy JF, Taylor PR. Management of spontaneous and iatrogenic retroperitoneal haemorrhage: conservative management, endovascular intervention or open surgery? Int J Clin Pract 2008; 62:1604–1613 21. Sunga KL, Bellolio MF, Gilmore RM, Cabrera D. Spontaneous retroperitoneal hematoma: etiology, characteristics, management, and outcome. J Emerg Med 2012; 43:e157–e161 22. Furlan A, Fakhran S, Federle MP. Spontaneous abdominal hemorrhage: causes, CT findings, and clinical implications. AJR 2009; 193:1077–1087 23. Conley SP, Frumkin K. Acute lobar nephronia: a case report and literature review. J Emerg Med 2014; 46:624–626 24. Takhar SS, Moran GJ. Diagnosis and management of urinary tract infection in the emergency department and outpatient settings. Infect Dis Clin North Am 2014; 28:33–48 25. Craig WD, Wagner BJ, Travis MD. Pyelonephritis: radiologic-pathologic review. RadioGraphics 2008; 28:255–277 26. Kawashima A, Sandler CM, Goldman SM, Raval BK, Fishman EK. CT of renal inflammatory disease. RadioGraphics 1997; 17:851–866 27. Bankoff MS, Sarno RC, Mitcheson HD. Computed tomography differentiation of pyelonephritis and renal infarction. J Comput Tomogr 1984; 8:239–243 28. Wan YL, Lee TY, Bullard MJ, Tsai CC. Acute gas-producing bacterial renal infection: correlation between imaging findings and clinical outcome. Radiology 1996; 198:433–438 29. Akhtar AL, Elsayes KM, Woodward S. AJR teaching file: diabetic patient presenting with right flank pain and fever. AJR 2010; 194(suppl 6):[web]WS31–WS33 30. Cronan JJ, Amis ES, Dorfman GS. Percutaneous drainage of renal abscesses. AJR 1984; 142:351– 354 31. Kim SH, Kim YW, Lee HJ. Serious acute pyelonephritis: a predictive score for evaluation of deterioration of treatment based on clinical and radiologic findings using CT. Acta Radiol 2012; 53:233–238 32. Carkaci S, Ozkan E, Lane D, Yang WT. Scrotal sonography revisited. J Clin Ultrasound 2010; 38:21–37 33. Avery L, Scheinfeld MH. Imaging of penile and scrotal emergencies. RadioGraphics 2013;
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Acute and Emergent Genitourinary Conditions 33:721–740 34. Kreydin EI, Barrisford GW, Feldman AS, Preston MA. Testicular cancer: what the radiologist needs to know. AJR 2013; 200:1215–1225 35. Pretorius ES, Siegelman ES, Ramchandani P, Banner MP. MR imaging of the penis. RadioGraphics 2001; 21:S283–S298 36. Kirkham AP, Illing RO, Minhas S, Allen C. MR imaging of nonmalignant penile lesions. RadioGraphics 2008; 28:837–853 37. Lareau S, Beigi R. Pelvic inflammatory disease and tubo-ovarian abscess. Infect Dis Clin North Am 2008; 22:693–708 38. Hiller N, Sella T, Lev-Sagi A, Fields S, Lieberman S. Computed tomographic features of tuboovarian abscess. J Reprod Med 2005; 50:203– 208 39. Kim SH, Kim SH, Yang DM, Kim KA. Unusual
causes of tubo-ovarian abscess: CT and MR imaging. RadioGraphics 2004; 24:1575–1589 40. Duigenan S, Oliva E, Lee SI. Ovarian torsion: diagnostic features on CT and MRI with pathologic correlation. AJR 2012; 198:[web]W122–W131 41. Hawnaur JM, Reynolds K, McGettigan C. Magnetic resonance imaging of actinomycosis presenting as pelvic malignancy. Br J Radiol 1999; 72:1006–1011 42. Lin EP, Bhatt S, Dogra VS. Diagnostic clues to ectopic pregnancy. RadioGraphics 2008; 28:1661–1671 43. Levine D. Ectopic pregnancy. Radiology 2007; 245:385–397 44. Gjelland K, Ekerhovd E, Granberg S. Transvaginal ultrasound-guided aspiration for treatment of tubo-ovarian abscess: a study of 302 cases. Am J Obstet Gynecol 2005; 193:1323–1330
45. Timor-Tritsch IE, Lerner JP, Monteagudo A, Murphy KE, Heller DS. Transvaginal sonographic markers of tubal inflammatory disease. Ultrasound Obstet Gynecol 1998; 12:56–66 46. Chang HC, Bhatt S, Dodgra VS. Pearls and pitfalls in diagnosis of ovarian torsion. RadioGraphics 2008; 28:1355–1368 47. Spencer JA, Forstner R, Cunha TM, Kinkel K; ESUR Female Imaging Sub-Committee. ESUR guidelines for MR imaging of the sonographically indeterminate adnexal mass: an algorithmic approach. Eur Radiol 2010; 20:25–35 48. Goharkhay N, Verma U, Maggiorotto F. Comparison of CT- or ultrasound-guided drainage with concomitant intravenous antibiotics vs. intravenous antibiotics alone in the management of tuboovarian abscesses. Ultrasound Obstet Gynecol 2007; 29:65–69
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Genitourinary Imaging Review
Jennifer W. Uyeda1 Bradley S. Gans Aaron Sodickson Uyeda JW, Gans BS, Sodickson A
Imaging of Acute and Emergent Genitourinary Conditions: What the Radiologist Needs to Know OBJECTIVE. Acute and emergent genitourinary conditions require accurate and rapid diagnosis to minimize patient morbidity and mortality. CONCLUSION. Radiologists’ familiarity with the various conditions of the urinary system and of the male and female reproductive organs is important given the widespread use of imaging for the diagnosis of common clinical entities presenting to the emergency department.
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mergent genitourinary conditions require timely diagnosis and treatment to ensure a favorable clinical outcome and to prevent morbidity and mortality. CT is typically the imaging modality of choice for most emergent conditions of the genitourinary tract, and ultrasound is used less frequently. MRI is primarily used as a problem-solving modality because of its improved soft-tissue characterization and higher resolution. The aim of this article is to summarize the role of imaging in diagnosing acute and emergent genitourinary conditions using a case-based approach and to show how imaging can aid in the diagnosis of common clinical entities presenting to the emergency department. Keywords: emergency, female reproductive system, genitourinary, male reproductive system, urinary system DOI:10.2214/AJR.14.14117 Received November 10, 2014; accepted after revision December 17, 2014. A. Sodickson received a research grant from Siemens Healthcare. 1
All authors: Department of Radiology, Emergency Radiology Section, Brigham and Women’s Hospital, 75 Francis St, Boston, MA 02115. Address correspondence to J. W. Uyeda ([email protected]).
WEB This is a web exclusive article. AJR 2015; 204:W631–W639 0361–803X/15/2046–W631 © American Roentgen Ray Society
Urinary System Patient 1 45-year-old man with acute onset of right flank pain—The diagnosis is urolithiasis. Urolithiasis is a condition in which there are dense calculi within the kidney or ureteral lumen and possible hydroureteronephrosis, with dilatation of the ureter proximal to the calculus and normal-caliber ureter distal to the calculus (Fig. 1). Secondary signs of ureterolithiasis include hydroureteronephrosis, perinephric and periureteral inflammatory stranding, and unilateral renal enlargement or a subtle hypodensity related to parenchymal edema. Differential diagnosis—The differential diagnosis is pelvic phlebolith. The comet-tail sign, in which eccentric soft tissue is seen adjacent to the calcification, is a reliable feature of phleboliths; phleboliths tend to have lucent centers, whereas calculi have dense cen-
ters [1]. The “soft-tissue rim” sign is a halo of soft tissue around the calcification that is very specific for a ureteral calculus with a specificity of 90–100% [1]. Urolithiasis affects 1.2 million Americans per year with a recurrence rate of up to 75% within 20 years [1]. Imaging—Unenhanced MDCT is the imaging modality of choice for the evaluation of urinary calculi with a sensitivity and specificity of 95–98% and 96–100%, respectively [1–3] (Fig. 1A); however, contrast-enhanced CT also has a high accuracy for stone detection. In addition to detecting urolithiasis, CT can be used to assess genitourinary tract and extraurinary abnormalities. CT accurately identifies the stone burden and location of calculi and reveals the presence of an obstruction or hydronephrosis (Fig. 1B). Determination of stone composition can have important therapeutic implications. Approximately 70–80% of calculi are calciumbased, whereas 5–10% are uric acid stones that form in acidic urine and can be dissolved medically with urinary alkalinization [1]. Attenuation measurements of stones have been shown to have some utility in differentiating among the different stone subtypes, but substantial overlap persists [1]. Dual-energy CT has shown an improved ability to differentiate uric acid–based stones from calcium-based stones because it relies on the x-ray absorption characteristics of stones at two x-ray energies [4–7]. Ultrasound is ideal for detecting the presence and severity of hydronephrosis and assessing for cortical thinning due to chron-
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rupture is seen as the presence of extravesicular contrast material on CT cystography. In intraperitoneal bladder rupture, contrast material accumulates around the bowel loops and in the peritoneal recesses including the paracolic gutters, rectovesical or rectouterine pouch, and subphrenic space [12, 13] (Fig. 2A). In extraperitoneal rupture, the extravasated contrast material tracks into the perivesicular and prevesical space of Retzius to form the classic “molar tooth” sign [12, 13] (Fig. 2B). Combined intraperitoneal and extraperitoneal bladder ruptures involve both spaces. Blunt abdominal trauma is responsible for most bladder injuries, although bladder rupture can also occur after penetrating trauma [14]. Gross hematuria is present in up to 95%
of bladder rupture cases and should prompt further evaluation, particularly in the setting of pelvic fractures. Microscopic hematuria is typically present in the remaining 5%. Bladder rupture is classified as extraperitoneal (70%), intraperitoneal (20%), or mixed (10%) [12–16]. Intraperitoneal bladder rupture requires surgical repair to prevent intraabdominal sepsis [17]. It commonly results from a sudden increase in pressure on a distended bladder, which tears at the bladder dome, the only part covered by peritoneum and also the weakest point of the bladder [12, 13, 15]. In contrast, extraperitoneal bladder rupture is associated with pelvic fractures causing perforation of the bladder wall [12]. Imaging—CT cystography has largely replaced conventional cystography for the evaluation of suspected bladder rupture, with a sensitivity and specificity of 100% and 95%, respectively [17]. Approximately 300–400 mL of dilute water-soluble contrast material is instilled through a Foley catheter [14] to accomplish full distention of the bladder, which is necessary for accurate detection of bladder rupture. Key points—First, bladder injury requires a high index of suspicion particularly in trauma patients with pelvic fractures or gross or microscopic hematuria. Second, CT cystography is the test of choice to identify and characterize bladder injuries. Third, intraperitoneal rupture (20%) is a surgical emergency occurring at the bladder dome, whereas extraperitoneal rupture (70%) is managed nonsurgically.
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Fig. 1—Ureterovesical junction and ureteral calculi. A, 34-year-old man with acute onset of left flank pain. Axial unenhanced CT image shows left ureterovesical junction calculus (arrow) with mild hydroureteronephrosis and periureteral stranding. B, 63-year-old woman with acute onset of left flank pain. Coronal unenhanced CT image shows proximal left ureteral calculus (arrow), associated mild hydroureteronephrosis, and additional nonobstructing left lower pole calculus.
ic obstruction [2]. However, ultrasound has variable sensitivity and specificity for detecting renal calculi, ranging from 24% to 80% and from 82% to 100%, respectively, and the accuracy of calculus measurements is debated [2, 8, 9]. A large segment of the ureteral course of the ureters cannot be well assessed using ultrasound. Nevertheless, ultrasound may have a role in the imaging evaluation of young patients because of radiation exposure concerns in this population. Radiography has a sensitivity of 45–85% for stone detection [10, 11]. MR urography may be used when ionizing radiation is of concern, but calculus detection is limited, with a sensitivity of approximately 50% [10, 11]. Treatment—Management of and urologic interventions to treat urolithiasis are guided by patient symptoms in combination with the location, size, and composition of the calculi. In general, nonobstructing renal calculi smaller than 10 mm in an asymptomatic patient are observed, whereas larger calculi in a patient with or without symptoms may undergo an intervention including shock wave lithotripsy, ureterorenoscopy, or percutaneous nephrolithotomy [1, 2]. The rate of spontaneous ureteral stone passage depends on stone size, with excellent success for stones smaller than approximately 6 mm but diminishing rates for larger stones [1]. Key points—First, unenhanced CT is the imaging modality of choice for calculus detection. Second, the location, size, and composition of calculi dictate treatment. Patient 2 18-year-old woman in a motor vehicle collision with a pelvic fracture and gross hematuria—The diagnosis is bladder rupture. Bladder
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Fig. 2—Intraperitoneal bladder rupture and extraperitoneal bladder rupture. A, 27-year-old woman who was in high-speed motor vehicle collision. Sagittal CT cystogram shows focal defect in bladder dome (arrow) with contrast material surrounding loops of bowel and in rectouterine pouch; these findings are consistent with intraperitoneal bladder rupture. B, 31-year-old man who was in motorcycle crash. Sagittal CT cystogram shows focal defect at base of bladder (arrow). Contrast material is seen in prevesicular space, which is finding consistent with extraperitoneal bladder rupture.
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Acute and Emergent Genitourinary Conditions Patient 3 69-year-old woman with acute right flank pain—The diagnosis is retroperitoneal hematoma. Retroperitoneal hematoma is seen as a high-density retroperitoneal collection with an occasional blood-fluid level (Figs. 3A–3C) and occasional associated lesion (Fig. 3C). Retroperitoneal hematoma can occur in the setting of trauma (Fig. 3A) or may be spontaneous, with possible causes including anticoagulation therapy, hemorrhagic diathesis, hemorrhage from a retroperitoneal mass, and abdominal aortic aneurysm rupture [18, 19]. The incidence in patients receiving anticoagulation therapy is roughly 1–7%, and coagulation parameters do not need to be outside the therapeutic range for this diagnosis [20]. Patients present with abdominal, hip, or back pain and are often managed conservatively with supportive care and correction of the underlying coagulopathy [21, 22]. In a series of 89 patients with anticoagulation therapy–related spontaneous retroperitoneal hematoma, 68% were managed conservatively, 25% required interventional radiology embolization, and 7% underwent surgical hematoma evacuation [21]; of these patients, 75% received blood transfusions [21]. Imaging—When retroperitoneal hemorrhage is suspected, unenhanced CT is often performed (Fig. 3B). Although IV contrast material is not necessary to make the diagnosis, it can help to identify areas of active extravasation, which may prompt more aggressive management [22]. CT can also identify an underlying lesion responsible for the hemorrhage such as a renal cell carcinoma, renal angiomyolipoma (Fig. 3C), or adrenal myelolipoma.
Patient 4 21-year-old woman with a history of urinary tract infections presents with flank pain— The diagnosis is pyelonephritis. Pyelonephritis is seen on imaging as renal parenchymal edema, often with one or more wedge-shaped areas of decreased enhancement and with decreased corticomedullary differentiation. A “striated nephrogram”—consisting of linear areas of decreased enhancement from the papilla to the cortex—can also be seen (Fig. 4A). Urothelial thickening and enhancement of the renal pelvis and ureter are suggestive of pyelitis (i.e., urinary tract infection ascending to the collecting system) and may be seen with or without parenchymal changes indicative of pyelonephritis. Differential diagnosis—The differential diagnosis is a ureteral stone, renal infarct, and renal malignancy. Pyelonephritis is an acute bacterial infection of the kidneys and usually results from ascending infection in a patient with bacterial cystitis. These patients typically present with fever, leukocytosis, flank pain, and costovertebral angle tenderness [23, 24].
Imaging—Pyelonephritis is typically a clinical diagnosis. The primary role of imaging is to exclude the most concerning complication of renal or perinephric abscess in severe cases (Fig. 4B) and to exclude obstructive uropathy requiring urinary decompression. The sensitivity of ultrasound for pyelonephritis is low because the kidneys typically have a normal appearance [25]. Parenchymal edema may cause subtle changes in echogenicity with a loss of distinction between the cortex and the renal sinus fat and may also result in focal decreased perfusion on Doppler sonography. Ultrasound is useful to identify other renal abnormalities including hydronephrosis, stone disease, and renal abscess. CT shows a higher sensitivity for pyelonephritis with typical findings. A striated nephrogram results from inflammatory debris obstructing the renal tubules [25, 26] (Fig. 4A). Although the imaging appearances of renal infarct and pyelonephritis overlap, renal infarct may be differentiated from pyelonephritis by the presence of a thin rim of overlying cortical enhancement (termed the “cortical rim” sign) due to the presence of collateral blood flow to the renal capsule [27]. Malignancies, including renal and transitional cell carcinoma, can occasionally mimic infection (Fig. 4C). Whenever malignancy is suspected, subsequent imaging after the resolution of the infection may help to reveal an underlying lesion, or alternatively MRI may identify an underlying solid mass. Key points—First, pyelonephritis is an acute bacterial renal infection evident on CT as a striated nephrogram or as wedge-shaped cortical enhancement defects.
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Key points—First, suspect retroperitoneal bleeding in patients on anticoagulation therapy with abdominal, hip, or back pain. Second, CT should be performed when retroperitoneal hemorrhage is suspected. Active hemorrhage can be detected on contrastenhanced CT. Third, most cases of anticoagulation therapy–related retroperitoneal hemorrhage are managed conservatively. Embolization and surgery are reserved for cases refractory to conservative measures.
Fig. 3—Imaging findings of different causes of retroperitoneal hemorrhage. A, 25-year-old woman who was in motor vehicle collision. Axial contrast-enhanced CT image shows right adrenal gland hematoma (arrow) with surrounding hemorrhage in retroperitoneum. B, 55-year-old man on anticoagulation therapy. Unenhanced axial CT image shows large left retroperitoneal hematoma (arrow) resulting in anterior displacement of kidney. C, 33-year-old man with tuberous sclerosis and acute back pain. Axial contrast-enhanced CT image shows left angiomyolipoma that has spontaneously undergone hemorrhage (arrow). Bilateral angiomyolipomas are seen.
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Fig. 4—Various renal abnormalities with overlapping imaging appearances. A, 53-year-old woman with recent diagnosis of urinary tract infection who presented with fever and back pain. Axial contrast-enhanced CT image shows “striated nephrogram” in right kidney (arrow) and mild perinephric stranding. B, 64-year-old woman with recent history of urinary tract infection. Coronal contrast-enhanced CT image shows hypodense renal abscess with thick peripherally enhancing wall and resulting mass effect on renal parenchyma (arrow). C, 67-year-old man with incidental renal findings. Coronal contrast-enhanced CT image shows left renal hypodense lesion with peripheral solid nodule (arrow) that is highly concerning for renal cell carcinoma (RCC). Additional smaller solid lesion (arrowhead) suspicious for RCC is seen in upper pole of right kidney.
Second, differential considerations include renal infarcts or masses. Repeat imaging after treatment of the infection can be helpful to differentiate among infection, infarct, and malignancy. Patient 5 75-year-old diabetic man presents with flank pain, hypotension, and urinary retention—The diagnosis is emphysematous pyelonephritis (EPN). EPN appears on imaging as small bubbles or linear foci of parenchymal gas, gas-fluid levels, fluid collections, parenchymal enlargement and destruction, and tissue necrosis [25, 28] (Fig. 5A). Differential diagnosis—The differential diagnosis for air within the renal parenchyma is EPN, renal abscess, traumatic renal injury, and iatrogenic renal injury. EPN is an emergent life-threatening necrotizing infection of the kidney characterized by gas within the renal parenchyma or perinephric tissues [25, 28, 29]. EPN is associated with a high mortality rate of up to 75% [25, 28, 29]; 90% of patients have uncontrolled diabetes [25, 28]. Imaging—CT is the study of choice for patients who present acutely with flank pain and systemic manifestations of infection. CT is the most sensitive and specific modality to diagnose EPN and to assess the extent of disease. Ultrasound shows echogenic nondependent foci of gas with reverberation artifact and low-level echoes, also known as “dirty shadowing.” The distinction of EPN from emphysematous pyelitis, in which gas is limited to the collecting system, is crucial because the latter is a less aggressive upper uri-
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Fig. 5—Imaging appearance of emphysematous pyelonephritis (EPN) versus emphysematous pyelitis. A, 64-year-old man with urinary tract infection. Coronal contrast-enhanced CT image shows gas within left retroperitoneum and renal parenchyma (arrow), which is consistent with EPN. B, 43-year-old woman with urinary tract infection. Axial unenhanced CT image shows gas within collecting system bilaterally (arrows), which is consistent with emphysematous pyelitis.
nary tract infection with a significantly lower mortality [25] (Fig. 5B). Renal abscesses develop as a result of the progression of an ascending urinary infection or liquefactive necrosis [25, 26, 30, 31] (Fig. 4A). Up to 15% of patients have a negative urine culture at presentation [25]. CT is the most accurate modality for the diagnosis of renal abscess, which typically appears as a well-defined hypodense mass with a thick and irregular enhancing wall [26]. Renal abscesses may contain gas in rare cases [26]. Trauma or iatrogenic injury can introduce air in the renal parenchyma and can be mistaken for EPN. Patients may have a recent history of trauma with other associated in-
juries or may have recently undergone renal abscess drainage or a renal biopsy. Key points—First, EPN is a life-threatening necrotizing infection with a poor prognosis that requires urgent diagnosis and aggressive medical or surgical treatment. Second, EPN must be differentiated from emphysematous pyelitis, a less aggressive infection with a significantly lower mortality. Male Reproductive Organs Patient 6 18-year-old man with acute testicular pain and swelling—The diagnosis is epididymitis and orchitis. Epididymitis and orchitis manifest as heterogeneity, enlargement,
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Acute and Emergent Genitourinary Conditions and hypoechogenicity of the epididymis or testicle with associated hypervascularity on color Doppler imaging [32, 33] (Fig. 6A). Reactive hydroceles and scrotal edema and thickening are commonly seen. Doppler flow can be helpful in differentiating epididymitis and orchitis from testicular torsion with absent flow. Differential diagnosis—The differential diagnosis for acute testicular pain and swelling is orchitis and epididymitis, testicular torsion, testicular rupture, testicular trauma, and testicular tumor. Epididymitis and orchitis are the most common causes of acute scrotal pain. Patients typically present with testicular pain and swelling. If untreated, epididymitis may continue to ascend and result in orchitis and, in severe cases, in abscess or testicular infarction (Fig. 6B). Epididymitis and orchitis typically result from an ascending infection, commonly Escherichia coli in older men and Neisseria gonorrheae or Chlamydia trachomatis in sexually active younger males. Because of the order of ascent, the epididymal tail is infected first with subsequent infection of the body and head, followed by the testicular parenchyma. Testicular torsion is a surgical emergency, and early diagnosis is crucial to restore blood flow and salvage the testicle [33]. Adolescent males are most commonly affected. On ultrasound, the absence of blood flow in the symptomatic testicle is pathognomonic for torsion (Fig. 6C). However, arterial flow can be maintained in partial torsion, and hyperemia mimicking orchitis can be seen after spontaneous detorsion. The testicle may appear normal in early torsion, but with continued ischemia, the testicle becomes enlarged and heterogeneous. Prompt urologic consultation with detorsion and orchiopexy is essential for testicular salvage. Testicular salvage rates are greatest if surgery is performed within 6 hours of onset. After 24 hours of ischemia, the testicle is usually no longer salvageable. In the setting of trauma, the testicle may develop hematoma, contusion, fracture, or rupture (Fig. 6D). Signs of testicular injury include focal areas of heterogeneous testicular echogenicity corresponding to areas of infarction or contusion, hematocele, or a discrete fracture line. Testicular rupture manifests as discontinuity of the linear echogenic tunica albuginea surrounding the testicle and possible protrusion of the seminiferous tubules [33]. The diagnosis of testicular rup-
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Fig. 6—Spectrum of ultrasound findings of acute testicular abnormalities. A, 23-year-old man with left scrotal pain for 4 days. Sagittal color Doppler ultrasound image of left epididymis and testicle shows increased vascularity in epididymis and testicle; these findings are consistent with epididymitis and orchitis. B, 34-year-old man with left scrotal pain for 2 weeks. Transverse color Doppler ultrasound image of left testicle shows testicular abscess with no internal vascularity. C, 18-year-old man with left scrotal pain for 3 hours. Transverse power Doppler ultrasound image of testicles shows decreased vascular flow in left testicle with heterogeneity of parenchyma (arrow). D, 22-year-old man who sustained blunt trauma to scrotum. Ultrasound image of testicle shows focal avascular hypoechogenic region suggestive of testicular contusion.
ture is vital because it mandates immediate surgical exploration and repair. Testicular neoplasm is the most common nonhematologic malignancy in males between the ages of 15 and 50 years [34]. Although the typical presentation of a testicular neoplasm is a painless unilateral testicular mass, approximately 10% of patients with a testicular neoplasm will present with pain and the neoplasm may be misdiagnosed as epididymitis or orchitis [32, 34]. The two major categories of testicular tumors are germ cell (90–95%) and stromal (5–10%) tumors [34] Ultrasound is the initial study for the diagnosis followed by CT and MRI for staging. Testicular orchitis and epididymitis, testicular torsion, testicular rupture, and testicular tumor can have similar and overlapping imaging appearances, particularly on ultrasound. Clinical history is helpful for the accurate diagnosis, but misdiagnosis is com-
mon. Follow-up imaging can also be used to differentiate epididymoorchitis from tumors because infectious processes will resolve after appropriate treatment. Key points—First, testicular epididymitis or orchitis, testicular torsion, testicular rupture, and testicular tumor can have similar imaging appearances. Second, testicular torsion and testicular rupture require urgent surgical intervention to preserve testicular function. Third, the absence of testicular blood flow in torsion is pathognomonic. However, two scenarios must be kept in mind: Testicular arterial flow may be present in partial torsion, and hyperemia after detorsion can mimic orchitis. Patient 7 32-year-old man with pelvic pain after trauma—The diagnosis is penile fracture. Penile fracture is seen as a focal disruption of the tunica albuginea with an adjacent he-
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Uyeda et al. matoma and can be seen on both ultrasound and MRI (Fig. 7). Penile fractures result most commonly secondary to an external bending force applied to an erect penis during sexual intercourse. Unilateral rupture of the tunica albuginea is most common, and concomitant urethral injury occurs in 10–20% of cases, warranting a low threshold for retrograde urethrography [33, 35, 36]. Clinically, penile fractures are experienced as a cracking sensation followed by rapid detumescence and severe penile pain, swelling, and bruising [33, 36]. Most penile fractures are immediately repaired to avoid the complications of conservative management including nodule formation at the site of the fracture, penile deformity, erectile dysfunction, and painful erection. Imaging—Ultrasound imaging is readily accessible and is optimally performed with a linear high-frequency (7.5–10 MHz) transducer. Ultrasound delineates the fracture as an interruption of the thin echogenic tunica albuginea and can be used to assess the extent of the injury [33]. The presence of echogenic foci of air within the corpora cavernosa suggests an associated urethral injury [33]. MRI accurately localizes the fracture site so that a small focal incision can be used rather than an extensive degloving surgical technique [33, 36]. The patient should be supine with the penis dorsiflexed against the lower abdomen, and a surface coil should be used with a small FOV, resulting in high-resolution thin-section images. Triplane sagittal, coronal, and axial T2-weighted sequences and at least two planes of T1-weighted spin-echo sequences should be acquired [33, 36]. The contrast between the corpora and fascial layers of the penis is best seen on T2weighted images, and an interruption of the low-signal-intensity tunica albuginea at the site of the penile fracture is best seen on T2weighted images [33, 36] (Fig. 7). Key points—First, ultrasound is readily available for the diagnosis and evaluation of penile fractures; however, MRI may be used in equivocal or complicated cases and may aid surgeons in choosing a surgical approach. Second, associated urethral injuries occur in 10–20% of penile fractures, and a high clinical suspicion of urethral injury warrants retrograde urethrography. Female Reproductive Organs Patient 8 23-year-old woman with acute pelvic pain—The diagnosis is tuboovarian abscess
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Fig. 7—Ultrasound and MRI findings of penile fracture. A, 21-year-old man who presented after trauma to penis. Gray-scale ultrasound image shows focal defect in echogenic tunica albuginea (arrow). B, 32-year-old man who presented after impalement of penis. Coronal T2-weighted image of penis shows penile fracture with focal rupture of tunica albuginea of left corpus cavernosa (arrow) and adjacent hematoma.
(TOA). A TOA has a variable appearance on ultrasound and may be a solid, cystic, or complex mass in the adnexa or cul-de-sac with adjacent fluid [37, 38] (Fig. 8A). CT findings suggestive of TOA include uniformly thick walls with internal septations. Pyosalpinx is a common associated finding manifesting as a fluid-filled tubular structure with a thick enhancing peripheral wall [38, 39]. On MRI, a TOA is typically hypointense on T1-weighted imaging and heterogeneously hyperintense on T2-weighted imaging, although the signal intensity is variable and depends on the internal protein concentration and viscosity [39]. Hypointense meshlike strands secondary to adhesions or fibrosis are common findings on T2-weighted images and may enhance on contrast-enhanced T1-weighted images [39] (Fig. 8B). Differential diagnosis—The differential diagnosis is TOA, ovarian torsion, and ovarian tumors.
Pelvic inflammatory disease (PID) is an infection of the upper genital tract usually seen in sexually active young women. A late and serious complication of PID is TOA. Risk factors include the presence of an intrauterine device and multiple sexual partners [37, 39]. Clinically, TOA and PID present similarly; the distinction is usually made using ultrasound, although CT and MRI are increasingly being performed as confirmatory or problem-solving examinations or even as the initial imaging modality [39, 40]. TOAs are frequently mistaken radiologically and clinically for ovarian malignancy, so the detection of imaging signs of infection is vital in differentiating the two diagnoses [39, 41]. Imaging—Pelvic ultrasound is the most common initial imaging modality in patients who present with acute pelvic pain [37, 39, 42–45], but CT and MRI can also be the primary modality.
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Fig. 8—Ultrasound and MRI findings of tuboovarian abscess (TOA). A, 25-year-old woman with pelvic pain and history of pelvic inflammatory disease. Gray-scale ultrasound image of right ovary shows complex heterogeneous TOA. B, 31-year-old woman with pelvic pain. Axial gadolinium-enhanced fat-saturated T1-weighted image shows complex right adnexal mass with thick enhancing internal septations (arrow); these findings are consistent with TOA.
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Acute and Emergent Genitourinary Conditions Ovarian torsion is the fifth most common surgical gynecologic emergency, and early recognition is crucial to restore blood flow and salvage the ovary [40, 46]. The ovary is partially or completely twisted around its vascular pedicle, which initially compromises low-pressure venous and lymphatic outflow, resulting in edema and enlargement. As vascular compromise advances, there is loss of the normally low-resistance diastolic arterial flow followed by the loss of arterial flow even during systole, which results in thrombosis, ischemia, and hemorrhagic infarction [40, 46]. In 50–90% of the cases, an underlying ovarian mass serves as a lead point—most commonly, a cyst or a mature cystic teratoma [40, 46]. The most common finding is ovarian enlargement with peripheral follicles, and color Doppler ultrasound may show a twisted vascular pedicle, the so-called “whirlpool” sign. Additional findings on CT and MRI include ascites, deviation of the uterus toward the ipsilateral torsed ovary, ipsilateral engorged pelvic vessels, and unusual location of the enlarged edematous ovary toward the midline or rotated toward the contralateral side [40, 46] (Figs. 9B and 9C). Ovarian tumors can be benign or malignant and tend to be asymptomatic unless they are associated with ovarian torsion [40, 46, 47]. MRI may be performed in cases of sonographically indeterminate adnexal masses to ensure timely diagnosis and guide subsequent management. Treatment—Patients with TOA are treated as conservatively as possible to preserve fertility. Management is usually with IV antibiotics alone, with a success rate of up to 87% [44, 48]. Recent data suggest that concomitant treatment of TOA with imagingguided aspiration may be a safe and effec-
tive first-line treatment [44, 48]. Surgical intervention is usually reserved for refractory TOA cases. Key points—First, TOA, ovarian torsion, and ovarian tumors can have overlapping imaging appearances on pelvic ultrasound. Second, ovarian torsion is a surgical emergency and requires urgent surgical intervention to preserve ovarian function. Patient 9 26-year-old woman with positive HCG value and pelvic pain—The diagnosis is ectopic pregnancy. Ectopic pregnancy is visualized on imaging as an extrauterine pregnancy where a fetal heartbeat may be present. More commonly, ectopic pregnancies are seen as an extraovarian adnexal mass that can manifest as a tubal ring containing a yolk sac and embryo, a tubal ring with only a yolk sac and no embryo, or a complex mass separate from the ovary (Fig. 10A). Differential diagnosis—The differential diagnosis of a pregnant patient with pain and vaginal bleeding is a normal intrauterine pregnancy, an ectopic pregnancy, and spontaneous abortion. Ectopic pregnancy is the leading cause of maternal death in first-trimester pregnancy [42]. Early detection is essential to decrease maternal mortality and preserve fertility [42]. If an ectopic pregnancy is suspected, the initial evaluation includes a quantitative serum HCG level and pelvic ultrasound [42]. The risk of rupture increases with the increase in size of the ectopic pregnancy, and any unstable patient with a clinical suspicion of a ruptured ectopic pregnancy should undergo surgical exploration [42] (Fig. 10B). Imaging—Ectopic pregnancies are most commonly located in the fallopian tube.
The detection of a live extrauterine embryo containing a heartbeat has 100% specificity but lacks sensitivity because it is a rare finding [42, 43]. More commonly, in the setting of a positive pregnancy test, an extraovarian adnexal mass is used as a criterion for the diagnosis of ectopic pregnancy [43] (Fig. 10A). Differentiating an ovarian corpus luteum cyst, a normal finding in pregnancy, from an ectopic pregnancy is important. A corpus luteum cyst arises within or is exophytic from the ovary, whereas an ectopic pregnancy is almost always distinct from the ovary. Motion separate from the ovary during gentle pressure on a transvaginal probe can be a helpful differentiator because a corpus luteum cyst always moves together with the ovary. On color Doppler imaging, a “ring of fire” can be a helpful finding that indicates hypervascularity due to high-velocity low-impedance flow in the ectopic pregnancy, but this finding must be interpreted with caution because it may also be seen around a corpus luteum cyst [42, 43]. When the uterus and ovaries appear normal on sonography, the differential diagnosis includes normal pregnancy, ectopic pregnancy, and spontaneous abortion. From 5% to 18% of ectopic pregnancies are detected only on repeat ultrasound, necessitating the need for follow-up imaging when neither an intrauterine pregnancy nor an ectopic pregnancy is visualized [43]. Key points—First, ectopic pregnancy must be excluded in the absence of an intrauterine gestational sac in a pregnant patient with vaginal bleeding. Second, an adnexal mass separate from the ovary is the most common ultrasound finding suggestive of an ectopic pregnancy.
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Fig. 9—28-year-old woman with acute pelvic pain. A, Sagittal color Doppler ultrasound image shows heterogeneous left adnexal mass. B, Axial contrast-enhanced CT image shows slightly dense mass (arrow) with surrounding crescentic hypodensity in left adnexa extending to midline. C, Coronal T2-weighted image obtained approximately 1 hour after CT (B) shows torsed edematous left ovary (arrow) rotated toward contralateral side.
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Fig. 10—Ultrasound and CT findings of ectopic pregnancy. A, 26-year-old woman with first-trimester pregnancy with acute pelvic pain. Sagittal (left) and coronal (right) ultrasound images show right adnexal mass (cursors) separate from ovary that contains yolk sac; these findings are consistent with fallopian tube ectopic pregnancy. B, 34-year-old woman with first-trimester pregnancy, acute pelvic pain, and hypotension. Contrast-enhanced CT image shows right adnexal rupture ectopic pregnancy with hemoperitoneum (arrow).
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