Multimodality Imaging of the Postpartum or Posttermination Uterus: Evaluation Using Ultrasound, Computed Tomography, and Magnetic Resonance Imaging Sherelle L. Laifer-Narin, MD, Ellie Kwak, MD, Hyonah Kim, MD, Elizabeth M. Hecht, MD, and Jeffrey H. Newhouse, MD
Postpartum and posttermination complications are common causes of morbidity and mortality in women of reproductive age. These complications can be broadly categorized into vascular, infectious, surgical, and neoplastic etiologies, or are due to ectopic implantation of placental or endometrial tissue. Causes of postpartum vascular complications include retained products of conception, arteriovenous malformation, and pseudoaneurysm. Infectious entities include endometritis, abscess, wound cellulitis, and pelvic septic thrombophlebitis. Postsurgical complications include uterine scar dehiscence, bladder flap hematoma, and subfascial hematoma. Neoplastic complications include the spectrum of gestational trophoblastic neoplasms. Ectopic tissue implantation complications include abnormal placentation and uterine scar endometriosis. Imaging is essential for diagnosis, and radiologists must be familiar with and aware of these entities so that accurate treatment and management can be obtained. In this review, we illustrate the imaging findings of common postpartum and posttermination complications on ultrasound, computed tomography, and magnetic resonance imaging.
A study by the World Health Organization determined that the global maternal mortality rate was 210 maternal deaths per 100,000 live births in 2010 compared with 400 maternal deaths per 100,000 live births in 1990, most of which occurred in third-world countries. Although the rate of maternal deaths in the United States was low compared with developing countries, there was a relative increase in mortality rate between 1990 and 2010 in the United States.1 Common complications involving the postpartum uterus include vascular, infectious, surgical, and neoplastic etiologies, or ectopic implantation of placental or endometrial tissue. Radiologists play an important role in diagnosing postpartum complications thereby facilitating early intervention and treatment. Ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) are the imaging modalities used in evaluation and diagnosis of postpartum complications. In this study, imaging findings of common postpartum and posttermination complications are described.
Introduction
Normal Postpartum Uterus
In light of the significant advances in peripartum and postpartum care, maternal mortality is often thought to be a problem exclusive to developing countries.
The postpartum, or puerperal, period is defined as immediately after delivery of the fetus and placenta to approximately 6-8 weeks after delivery. During the postpartum period, the appearance of the uterus can be variable as it undergoes physiological changes while gradually returning to its baseline. A study of 42 women revealed that the postpartum uterus measures up to 92 mm in the anteroposterior dimension on postpartum day 1, which gradually involutes and measures up to 38.9 mm on postpartum day 56.2 The uterine cavity is also variable in size, ranging
From the Department of Radiology, New York Presbyterian Columbia University Medical Center, New York, NY. Reprint requests: Sherelle L. Laifer-Narin, MD, Department of Radiology, New York Presbyterian Columbia University Medical Center, 630 W 168th St, New York, NY 10032. E-mail: [email protected]. Curr Probl Diagn Radiol 2014;43:374–385. & 2014 Mosby, Inc. All rights reserved. 0363-0188/$36.00 + 0 http://dx.doi.org/10.1067/j.cpradiol.2014.06.001
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from 15.8 mm in the anteroposterior dimension immediately after delivery to 4 mm on postpartum day 56.2 Ultrasound is the first imaging modality of choice in evaluating the postpartum uterus. The postpartum uterus can demonstrate variable appearance of the endometrial cavity, which may be empty, or contain foci of gas, simple fluid, or echogenic material. Echogenic material can be seen in 51% of women at 1 week postpartum and in 6% at 3 weeks postpartum.3 Echogenic material without vascularity seen on color Doppler image in a postpartum uterus likely represents blood products. However, if vascularity is seen, other etiologies and various complications should be considered based on specific findings.
Vascular Postpartum complications of vascular origin include uterine bleeding, arteriovenous malformation (AVM), and pseudoaneurysm. The initial imaging modality of choice is ultrasound, followed by CT or MRI or both for more complex cases. Uterine Hemorrhage Uterine hemorrhage is defined as loss of greater than 500 mL of blood after the third stage of labor. Early hemorrhage occurs less than 24 hours after delivery and is related to uterine atony and retained products of conception and may be mimicked by vaginal laceration. Late hemorrhage occurs more than 24 hours after delivery and is related to abnormal involution of the placental site or RPOC. Diagnosis of hemorrhage is clinical; however, imaging studies are used to identify sources of bleeding and exclude vascular causes of hemorrhage that could warrant surgical intervention. Once these surgical causes are excluded, treatment options include uterotonic medications, arterial embolization, or in severe cases, hysterectomy. An ultrasound image shows a normal-appearing postpartum uterus with or without echogenic material consistent with blood clots. If an intrauterine clot or mass is found, there will be no associated vascularity on color Doppler (Fig 1). In more complex cases that warrant further workup with CT or MRI, intrauterine blood of varying density or intensity will be seen without associated contrast enhancement. Arteriovenous Malformation Uterine AVM may be congenital or acquired from prior trauma, infection, endometriosis, gestational
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FIG 1. Intrauterine hematoma. Transvaginal power Doppler ultrasound image demonstrates a heterogeneous, avascular intrauterine collection, compatible with a hematoma (arrows). (Color version of figure is available online.)
trophoblastic disease, or fibromas. Patients present with intermittent bleeding, lower abdominal pain, dyspareunia, and less frequently, high-output cardiac failure. Diagnosis can be made using ultrasound, which is the imaging modality of choice. On ultrasound, multiple hypoechoic or anechoic serpentine spaces within the myometrium can be seen with turbulent flow on color Doppler (Fig 2A). Spectral analysis demonstrates highvelocity and low resistive index (Fig 2B). CT or MRI can be performed to identify and localize feeding arteries of AVM, which facilitates confirmation of diagnosis and treatment planning. CT scan also demonstrates numerous anomalous blood vessels communicating with the uterine arteries in the wall of the uterus and parametrium. MRI shows serpiginous signal voids on spin-echo sequences with prominent parametrial vessels and focal disruption of the junctional zone. Angiography is considered to be the gold standard. Angiography demonstrates a nidus of vessels supplied by enlarged feeding arteries with early venous drainage (Fig 2C).4 Treatment choices include methylergonovine, intra-arterial embolization, or hysterectomy.5 Uterine Artery Pseudoaneurysm A pseudoaneurysm is defined as a collection of blood within the extraluminal space with a persistent communication through a defect in the arterial wall. Uterine artery pseudoaneurysm (UAP) is usually associated with prior surgical interventions, such as cesarean section or dilation and curettage.6,7 UAP may be suspected when patients who are postpartum or posttermination present
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with pain and vaginal bleeding. Initial workup involves ultrasound, which may demonstrate a hypoechoic intrauterine lesion on gray scale, with vascularity demonstrated on color Doppler and bidirectional systolic and diastolic flow with aliasing on spectral Doppler. Angiography has traditionally been the gold standard, however, with advancement of CT and MR techniques, CT or MR angiograms are now the first techniques. CT scan may reveal an enhancing, round outpouching with a communication to a parent artery (Fig 3). In cases of life threatening hemorrhage, treatment involves uterine artery embolization or hysterectomy.
Infectious Puerperal sepsis causes at least 75,000 maternal deaths every year worldwide,8 and puerperal infectious morbidity affects 5%-10% of pregnant women.9 Cesarean section is the single most important risk factor for postpartum infection. Postpartum infectious entities include endometritis, wound infection, infected products of conception, or thrombophlebitis. Patients typically present with fever, pelvic pain, and leukocytosis. Endometritis Endometritis is a clinical diagnosis; however, imaging is often used to exclude concurrent pathology. Ultrasound is often the first-line modality to evaluate a
FIG 2. Uterine arteriovenous malformation: (A) transvaginal grayscale image shows heterogeneous myometrium containing serpiginous vessels (arrows); (B) spectral Doppler image demonstrates low-resistance, high-velocity flow, suggestive of arteriovenous shunting; and (C) angiogram demonstrates an arteriovenous malformation (*) supplied by multiple feeding branches (arrow) from the internal iliac artery. (Color version of figure is available online.)
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FIG 3. Uterine artery pseudoaneurysm. Postcontrast axial CT scan shows a round structure demonstrating intense enhancement (arrow), similar to the nearby arteries, which was consistent with a pseudoaneurysm.
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FIG 4. Endometritis. Transvaginal ultrasound shows a thickened endometrium containing intracavitary echogenic foci consistent with gas (arrow).
febrile postpartum patient to exclude RPOC, infected hematoma, or abscess. Ultrasound is preferable given its ease of access, cost-effectiveness, and lack of radiation. On ultrasound, the uterus may demonstrate a thickened, heterogenous endometrium or appear normal with common postpartum findings such as intracavitary fluid or gas.10 Clinical correlation with fever or pelvic pain is critical in diagnosing endometritis. CT and MRI can be used to further exclude superimposed abscess or infected hematoma. Similar to the ultrasound examination, CT may demonstrate a thickened endometrium, possibly with fluid, gas, and debris within the endometrial cavity (Fig 4). MRI can also visualize similar findings to CT images, with gas demonstrated as a signal void on T1- and T2-weighted images. Use of contrast can help identify a fluid collection within the endometrium, which will require further intervention. Treatment of endometritis involves antibiotics and evacuation of drainable fluid collections.
adjacent to or separate from the uterus and nonspecific inflammatory changes. If the abscess is beyond the field of view, the study may be unremarkable. CT is the imaging modality of choice to evaluate for presence of an abscess. A pelvic abscess is demonstrated as a peripherally enhancing, thick-walled fluid collection with inflammatory changes of the surrounding pelvic fat (Fig 6). CT can help visualize the size and location of the abscess. In addition, CT can delineate the relationship of the abscess to the surgical abdominal incision or the uterine incision. MRI is rarely used to diagnose an abscess. When it is used, however, it demonstrates a mass with thick, irregular, enhancing wall that contains fluid with low to intermediate signal intensity on T1-weighted images and hyperintense signal on T2-weighted images. Septic Pelvic Thrombophlebitis Septic pelvic thrombophlebitis (SPT) is caused by inflammatory or infectious etiologies, including severe endometritis and bacteremia, often related to recent delivery or surgery such as cesarean section.11 In these cases, infection can extend and involve the pelvic vessels causing inflammation and thrombosis. Clinically, patients with SPT present with fever and flank or lower abdominal pain, with abdominal tenderness and occasional abdominal mass on physical examination and do not respond to standard antibiotic therapy. A direct diagnosis of SPT is rarely made by imaging, but in some patients ovarian vein thrombosis
Superficial Wound Infection Superficial wound infection is a clinical diagnosis in which the surgical wound demonstrates edema, erythema, and possible drainage. CT can be performed to assess integrity of the surgical wound and exclude an associated abscess or wound dehiscence. CT scan shows subcutaneous fat stranding in the region of the surgical incision (Fig 5). In cases where a subcutaneous wound abscess is associated, a rim-enhancing fluid collection will be seen along the superficial incision. Abscess Abscesses can be isolated findings or associated with endometritis. Ultrasound may identify a fluid collection Curr Probl Diagn Radiol, November/December 2014
FIG 5. Superficial wound infection. Postcontrast axial CT image shows inflammatory changes of the subcutaneous fat in the region of the cesarean section wound. Foci of air are likely postsurgical.
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FIG 6. Uterine abscess. Postcontrast axial CT image shows a fluid collection with an enhancing wall. Uterine dehiscence is also present (between arrows).
may be identified. Diagnostic imaging for ovarian vein thrombosis includes ultrasound, CT, and MRI. Ultrasound has a limited role but may demonstrate an echogenic mass within an enlarged ovarian vein. CT and MRI are preferred imaging modalities of choice for SPT. On a CT scan, ovarian vein thrombosis is demonstrated as a filling defect within the ovarian vein, possibly with venous enlargement. On MRI, variable T1 and T2 signals of the thrombus are seen within the enlarged ovarian vein (Fig 7). In the postcontrast venous phase images, a filling defect or absence of flow is noted in the ovarian vein.
approximately 1 in 700-2400 cesarean births. The mechanism is believed to be secondary to infectious incisional necrosis leading to dehiscence.12 Patients present with nonspecific signs, such as pain or malaise. Ultrasound or MRI is used to exclude uterine dehiscence in a postsurgical patient. Ultrasound findings can range from a normal examination in cases of small, subtle defects to findings of a thinned and irregular uterine wall and myometrial defect in more obvious cases (Fig 8A). CT may be able to demonstrate a myometrial defect. However, MRI is used if clinical suspicion persists, given its superiority in delineating soft tissue anatomy and pathology. MRI demonstrates a myometrial defect, and fluid or blood may be seen between the uterine layers. The sagittal images are most helpful when localizing the site of dehiscence and evaluating involvement of adjacent structures such as the bladder (Fig 8B). Treatment may involve only antibiotics in very minor dehiscence, but most cases need to undergo surgical repair. Postsurgical Hematoma Postsurgical hematomas are common complications related to intraoperative vascular injury, such as the uterine vessels in cases of bladder flap hematoma, and epigastric vessels in cases of subfascial hematoma. Patients present with pain, decreased hemoglobin, and in severe cases, hemodynamic instability. CT is often used as a first-line modality due to its fast scan time and ability to delineate anatomy of the hematoma in relation to the adjacent organs. Treatment can be
Surgical An increasing number of patients undergo cesarean section, with the latest National Vital Statistics Reports performed by Centers for Disease Control and Prevention revealing 32.8% cesarean delivery rate in 2012. Diagnostic imaging for postsurgical complications is therefore essential in management of postpartum patients. Common postsurgical complications seen in cesarean section patients include uterine scar dehiscence, bladder flap hematoma, and subfascial hematoma. Uterine Scar Dehiscence Uterine scar dehiscence refers to discontinuity of the uterine scar involving the myometrial or serosal layers or both. Uterine dehiscence is rare with an incidence of
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FIG 7. Septic pelvic thrombophlebitis. Axial gradient-echo image demonstrates a partially occlusive thrombus in an enlarged right ovarian vein (arrow).
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bladder wall (Fig 9A). However, distinguishing a bladder flap hematoma from an abscess can be difficult on ultrasound. On a CT scan, a hyperdense collection is identified anterior to the anterior lower uterine segment and posterior to the bladder (Fig 9B). If gas is seen within the collection, superimposed infection is suggested. MRI is not commonly used to diagnose a hematoma. If performed, a collection with variable signal intensity will be seen depending on the age of blood products in the same anatomical space between the anterior lower uterine segment and the posterior to the bladder (Fig 9C). Subfascial Hematoma Subfascial hematoma is caused by injury to the epigastric vessels, resulting in a collection of blood within the prevesical space. On an ultrasound image, a subfascial hematoma is identified by a heterogeneous fluid collection or mass anterior to the bladder and posterior to the abdominal wall (Fig 10A). Similar to a bladder flap hematoma, distinguishing between a hematoma and abscess is difficult on ultrasound. On CT and MR images, a hyperdense or T1 hyperintense mass or collection is seen within the prevesical space, posterior to the rectus muscle and transversalis fascia but anterior to the peritoneum and umbilicovesical fascia (Fig 10B and C). Again, superimposed infection should be considered when gas is present within the collection. FIG 8. Uterine wound dehiscence. (A) Transvaginal ultrasound shows echogenic structures (*) that represent sutures. The uterus is tented and fixed anteriorly to the anterior abdominal wall (between arrows). (B) T2WI sagittal image shows a myometrial defect (between the arrows) in the anterior uterine wall. Concurrent bladder flap hematoma (H) is present. T2WI, T2-weighted image.
supportive in cases of small hematomas without hemodynamic compromise, whereas patients with ongoing bleeding, hemodynamic instability, or clinically significant mass effect will undergo surgical exploration and hematoma evacuation. Bladder Flap Hematoma Bladder flap hematoma refers to a hematoma in the vesicouterine space between the posterior wall of the bladder and the cesarean section incision on the anterior lower uterine segment. In the presence of a bladder flap hematoma, the incision site should be scrutinized for potential wound dehiscence. On an ultrasound image, a bladder flap hematoma can be identified as a heterogeneous solid mass or collection between the lower uterine segment and the posterior
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Neoplastic Gestational trophoblastic disease encompasses a spectrum of trophoblastic cell proliferation disorders, some of which have malignant potential. Invasive mole, choriocarcinoma, and placental site trophoblastic tumor are classified as persistent trophoblastic neoplasia.13 Ultrasound is the first-line modality for diagnosis, whereas MRI is usually reserved for complicated cases. Once the diagnosis has been made, CT is useful for determining extent of disease. Treatment is dilation and curettage and chemotherapy for invasive disease. Invasive Mole Invasive mole is defined as invasion of the myometrium by trophoblastic overgrowth. These develop in 10% of treated complete hydatiform moles and less often in cases of partial moles. They are locally invasive but usually do not have metastatic potential. Patients usually present with vaginal bleeding and are found to have rising or persistently elevated levels of
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FIG 9. Bladder flap hematoma: (A) transvaginal ultrasound shows an oval, heterogeneous, solid collection (*) anterior to the uterus (U) and posterior to the bladder (B); (B) noncontrast sagittal CT image shows a hyperdense collection (*) between the bladder and the anterior lower uterine segment; and (C) coronal T1WI with fat saturation shows a heterogeneous hyperintense collection (*) posterosuperior to the bladder (B) and anterior to the uterus (U). T1WI, T1-weighted image.
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FIG 10. Subfascial hematoma. (A) Transabdominal ultrasound shows a heterogeneous hematoma (*) anterior to the normal uterus (U). (B and C) Noncontrast axial and sagittal CT images demonstrate heterogeneously hyperdense collections (*) in the prevesical space with fluid-fluid levels.
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abundant vascularity and low resistive index. On CT and MR images, choriocarcinoma is seen as a hypervascular, heterogeneous, ill-defined mass with peripheral enhancement and central necrosis (Fig 12).15 The involved myometrium may appear heterogeneous owing to bleeding or necrosis. In addition, dilated and tortuous myometrial and parametrial arteries are identified.
Ectopic or Residual Implantation of Endometrial or placental tissue
FIG 11. Invasive mole. Transvaginal ultrasound demonstrates fluid and debris in endometrial cavity with intense neovascularity in the myometrium extending to the periphery (arrows). In the setting of persistently elevated β-hCG levels unresponsive to methotrexate therapy, this constellation of findings may suggest invasive mole. Pathology results of hysterectomy specimen confirmed invasive mole. β-hCG, beta human chorionic gonadotropin. (Color version of figure is available online.)
Retained Products of Conception RPOC are of placental trophoblastic origin, as the trophoblast adheres and attaches to the uterine endometrium, leading to formation of the placenta. Incidence depends on the gestational age of the pregnancy, most frequently occurring after secondtrimester delivery or termination.16 Patients can
beta human chorionic gonadotropin. Owing to elevated levels of beta human chorionic gonadotropin, multiple luteinized follicular cysts or theca lutein cysts may develop, resulting in an enlarged appearance of the ovaries. On an ultrasound image, invasive mole is seen as a focal echogenic cystic mass within the myometrium, which may be uniform or complex. Marked vascularity is visualized on color Doppler (Fig 11), and high-velocity, low-resistance waveform is seen on spectral Doppler. On an MR image, invasive mole is identified as a heterogenous T1 and T2 endometrial or myometrial mass, which may be due to tumor necrosis or hemorrhage. Additional characteristics include distortion or obliteration of uterine layers and engorged surrounding vasculature owing to hypervascular nature of the tumor. Postcontrast images may demonstrate enhancement of viable tumors.14 Choriocarcinoma Choriocarcinoma is a chorionic epithelial neoplasm that can arise after a molar pregnancy or nonmolar pregnancy. Blood-borne metastases tend to develop early, usually to the lung and brain. Patients initially present with abdominal pain, possibly with dyspnea in the presence of lung metastases, or headache or seizure with brain metastases. On gray-scale ultrasound, choriocarcinoma is identified as an echogenic intrauterine mass with possible invasion into the myometrium and adjacent structures. Color and spectral Doppler demonstrates
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FIG 12. Choriocarcinoma. (A) Postcontrast axial CT image shows normal-appearing postpartum uterus. Multiple enlarged theca lutein cysts are seen bilaterally. (B) However, hypoenhancing lesions in the right kidney represent metastases (arrows). (Color version of figure is available online.)
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FIG 13. (A and B) Retained products of conception. Patient 1: (A) transvaginal spectral Doppler shows high-velocity, low-resistance flow within a vascular intracavitary mass, which remains attached to the endometrium and Patient 2: (B) axial postcontrast CT image shows a dense, heterogeneous intracavitary mass (*). Patient 3: (C and D) Retained products of conception with placenta accreta. Sagittal T2WI (C) and postcontrast T1WI (D) with fat saturation demonstrate a nonenhancing mass in the myometrium of the anterior lower uterine segment, extending into the cervix, compatible with retained cervical placenta accreta (*). T1WI, T1-weighted image; T2WI, T2-weighted image. (Color version of figure is available online.)
present with pain, fever, and vaginal bleeding. Ultrasound with color Doppler is the modality of choice, although there is a high false-positive rate ranging from 17%-51%.17 Sonographic findings of RPOC include a solid, echogenic intracavitary mass that extends to the endometrium with abundant vascularity demonstrated on color Doppler and high-velocity, low-resistance flow on spectral Doppler (Fig 13A). Blood products or normal, involuting endometrium may also demonstrate
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intracavitary echogenic material on gray-scale ultrasound, and careful examination with color Doppler is recommended to differentiate RPOC from blood products. CT scan may show a dense, heterogeneous intracavitary mass, which is again indistinguishable from an intrauterine clot (Fig 13B). In such cases, MRI may be used to delineate more soft tissue detail by demonstrating a variably enhancing, intracavitary soft tissue mass with associated disruption of the uterine layers or tumor extension into the
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myometrium (Fig 13C and D). Contrast can help determine vascularity of the mass and depth of myometrial invasion, although these findings are not specific to RPOC and overlap with gestational trophoblastic disease. Treatment options for RPOC include uterotonic medications, methotrexate, transarterial embolization, dilation and curettage, and hysteroscopic removal. Abnormal Placentation Abnormal placentation refers to abnormal placental adherence. Three degrees of adherence are recognized. Placenta accreta is placental implantation directly onto the myometrium without the normal intervening decidua basalis and fibrinoid layer of Nitabuch. Placenta increta is myometrial invasion of placental tissue. Placenta percreta is invasion through the serosal layer of the uterus with possible contiguous extension to adjacent structures (Fig 14).18 Highest risk factors for abnormal placentation are prior cesarean section and prior abnormal placentation with other risk factors being older maternal age, postprocedural adhesions, and multiparity.19 Patients are commonly asymptomatic and diagnosed during prenatal care. For this reason, imaging modalities that involve radiation exposure such as CT are not commonly used for diagnosis of abnormal placentation. Ultrasound can identify anterior placental, whereas MRI is more optimal in evaluating posterior placental implantation. Findings most sensitive for diagnosing placenta accreta on ultrasound are the presence of multiple placental lacunae. Placental lacunae are irregular placental vascular spaces with turbulent flow and are described as having a “swiss cheese” or “moth-eaten” appearance. Other findings include loss of retroplacental clear space, thinning and distortion of myometrium, bulging of the uterine wall, and irregularity of the bladder-uterus interface. MR image may demonstrate heterogeneous appearance of the placenta with an irregular uterine contour, bulging of the placenta into the bladder, and loss of bladder-uterus interface.19,20 T2-weighted images can identify hypointense, dark intraplacental bands. Treatment is cesarean section and possible cesarean hysterectomy. Uterine Scar Endometriosis Endometriosis is defined as ectopic location of normal endometrial tissue. Endometriosis in the cesarean scar can be seen in postcesarean-section patients.
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FIG 14. Placenta percreta. (A) Transabdominal ultrasound image shows inferior placenta (*) that covers the internal os. The placentamyometrium interface is not visualized and the placenta extends to the bladder surface (B). (B and C) Sagittal and coronal T2WIs shows the placenta previa extending through the myometrium with loss of normal bladder mucosa (arrow), consistent with placenta percreta. T2WI, T2-weighted image. (Color version of figure is available online.)
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FIG 15. Uterine scar endometriosis. Soft tissue gray scale (A) and color Doppler (B) ultrasound images of the suprapubic region show a heterogeneously echogenic subcutaneous mass with internal vascularity. Postcontrast axial CT (C) and T1W fat saturation images (D) show 2 enhancing nodules (arrows) in the subcutaneous fat overlying the region of the cesarean section wound. (Color version of figure is available online.)
Abdominal wall implantation is estimated to occur in 0.03%-1% of postcesarean-section patients with an approximate delay of symptoms of 3-6 years.20 Clinical presentation is cyclical pain in the region of the cesarean scar, where a palpable mass may be present. Ultrasound is often used as a first-line imaging study to evaluate the palpable subcutaneous mass. Ultrasound demonstrates a round or oval, heterogeneously hypoechoic, vascular lesion along the cesarean-section scar (Fig 15A and B). Small cystic areas may be present owing to blood pooling from recent hemorrhage. Hyperemia may be seen on color Doppler owing to inflammatory changes. CT or MRI is used to evaluate extent of disease. CT scan demonstrates an enhancing soft tissue lesion with or without surrounding inflammatory changes (Fig 15C). MR image demonstrates a soft tissue lesion with variable T1 hyperintense signal related to blood products of varying ages (Fig 15D). Treatment is wide surgical resection of the implants.
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Summary Postpartum or posttermination patients may suffer from complications of various causes, including vascular, infectious, surgical, and neoplastic etiologies and ectopic implantation of placental or endometrial tissue. Diagnosis of common postpartum complications can be challenging because of the variable appearance of the postpartum uterus and variable clinical or surgical history of the patient. The normal postpartum uterus varies in size and orientation, as it undergoes natural involution and physiological changes to return to its pregravid state. The endometrial cavity often contains blood products, debris, or gas during the postpartum or posttermination period, which are normal imaging findings in the absence of clinical symptoms. In patients with clinical symptoms, ultrasound, CT, or MRI can be used for imaging and diagnosis depending on the suspected etiologies. Ultrasound is the first imaging modality of choice in most complications of vascular
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origin, including uterine hemorrhage, RPOC, AVM, pseudoaneurysm, bladder flap, or subfascial hematoma. Neoplastic conditions such as invasive mole and choriocarcinoma, or ectopic or abnormal tissue implantation may also be initially diagnosed on ultrasound. Cross-sectional imaging can be performed for further delineating the anatomy of ultrasound findings and evaluating the extent of disease for treatment planning. CT is used in the diagnosis of infectious or postsurgical complications involving the deep pelvis such as abscess or SPT. Owing to its fast scan time, CT can be helpful in assessing for postsurgical hemorrhage or hematoma in immediate postoperative patients. MRI is useful when delineation of the zonal anatomy is critical for diagnosis, such as uterine wound or scar dehiscence, abnormal placentation, or uterine scar endometriosis. MRI can be used in diagnosing ovarian vein thrombosis in cases of possible SPT, if CT does not visualize the findings and clinical suspicion remains high. Common postpartum complications that are diagnosed clinically include endometritis and superficial wound infection. In these cases, imaging studies may be helpful in excluding associated findings, such as abscess formation or SPT. Identification of postpartum and posttermination complications is essential for minimizing morbidity and mortality in these patients. Recognizing common and uncommon entities is crucial for accurate diagnosis and management.
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with treated gestational trophoblastic tumors. Radiology 2002; 222:640-4. Henrich W, Fuchs I, Luttkus A, et al. Pseudoaneurysm of the uterine artery after cesarean delivery: Sonographic diagnosis and treatment. J Ultrasound Med 2002;21:1431-4. Matsubara S, Nonaka H, Kobayashi M, et al. Uterine artery pseudoaneurysm after dilation and curettage in a woman with multiple hepatic and pulmonary cavernous hemangiomas. Int J Gynaecol Obstet 2014;125:84-5. van Dillen J, Zwart J, Schutte J, et al. Maternal sepsis: Epidemiology, etiology and outcome. Curr Opin Infect Dis 2010;23:249-54. Maharaj D. Puerperal pyrexia: A review. Part I. Obstet Gynecol Surv 2007;62:393-9. Lev-Toaff AS, Baka JJ, Toaff ME, et al. Diagnostic imaging in puerperal febrile morbidity. Obstet Gynecol 1991;78:50-5. Brown CE, Stettler RW, Twickler D, et al. Puerperal septic pelvic thrombophlebitis: Incidence and response to heparin therapy. Am J Obstet Gynecol 1999;181:143-8. Rivlin ME, Carroll CS Sr, Morrison JC. Infectious necrosis with dehiscence of the uterine repair complicating cesarean delivery: A review. Obstet Gynecol Surv 2004;59:833-7. Kani KK, Lee JH, Dighe M, et al. Gestatational trophoblastic disease: Multimodality imaging assessment with special emphasis on spectrum of abnormalities and value of imaging in staging and management of disease. Curr Probl Diagn Radiol 2012;41:1-10. Hricak H, Demas BE, Braga CA, et al. Gestational trophoblastic neoplasm of the uterus: MR assessment. Radiology 1986;161:11-6. Yahata T, Kodama S, Kase H, et al. Primary choriocarcinoma of the uterine cervix: Clinical, MRI, and color Doppler ultrasonographic study. Gynecol Oncol 1997;64:274-8. Sellmyer MA, Desser TS, Maturen KE, et al. Physiologic, histologic, and imaging features of retained products of conception. Radiographics 2013;33:781-96. Durfee SM, Frates MC, Luong A, et al. The sonographic and color Doppler features of retained products of conception. J Ultrasound Med 2005;24:1181-6 [quiz 8-9]. Miller DA, Chollet JA, Goodwin TM. Clinical risk factors for placenta previa-placenta accreta. Am J Obstet Gynecol 1997; 177:210-4. Leyendecker JR, Gorengaut V, Brown JJ. MR imaging of maternal diseases of the abdomen and pelvis during pregnancy and the immediate postpartum period. Radiographics 2004;24:1301-16. Rodgers SK, Kirby CL, Smith RJ, et al. Imaging after cesarean delivery: Acute and chronic complications. Radiographics 2012;32:1693-712.
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Postpartum and posttermination complications are common causes of morbidity and mortality in women of reproductive age. These complications can be broadly categorized into vascular, infectious, surgical, and neoplastic etiologies, or are due to ectopic implantation of placental or endometrial tissue. Causes of postpartum vascular complications include retained products of conception, arteriovenous malformation, and pseudoaneurysm. Infectious entities include endometritis, abscess, wound cellulitis, and pelvic septic thrombophlebitis. Postsurgical complications include uterine scar dehiscence, bladder flap hematoma, and subfascial hematoma. Neoplastic complications include the spectrum of gestational trophoblastic neoplasms. Ectopic tissue implantation complications include abnormal placentation and uterine scar endometriosis. Imaging is essential for diagnosis, and radiologists must be familiar with and aware of these entities so that accurate treatment and management can be obtained. In this review, we illustrate the imaging findings of common postpartum and posttermination complications on ultrasound, computed tomography, and magnetic resonance imaging.
A study by the World Health Organization determined that the global maternal mortality rate was 210 maternal deaths per 100,000 live births in 2010 compared with 400 maternal deaths per 100,000 live births in 1990, most of which occurred in third-world countries. Although the rate of maternal deaths in the United States was low compared with developing countries, there was a relative increase in mortality rate between 1990 and 2010 in the United States.1 Common complications involving the postpartum uterus include vascular, infectious, surgical, and neoplastic etiologies, or ectopic implantation of placental or endometrial tissue. Radiologists play an important role in diagnosing postpartum complications thereby facilitating early intervention and treatment. Ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) are the imaging modalities used in evaluation and diagnosis of postpartum complications. In this study, imaging findings of common postpartum and posttermination complications are described.
Introduction
Normal Postpartum Uterus
In light of the significant advances in peripartum and postpartum care, maternal mortality is often thought to be a problem exclusive to developing countries.
The postpartum, or puerperal, period is defined as immediately after delivery of the fetus and placenta to approximately 6-8 weeks after delivery. During the postpartum period, the appearance of the uterus can be variable as it undergoes physiological changes while gradually returning to its baseline. A study of 42 women revealed that the postpartum uterus measures up to 92 mm in the anteroposterior dimension on postpartum day 1, which gradually involutes and measures up to 38.9 mm on postpartum day 56.2 The uterine cavity is also variable in size, ranging
From the Department of Radiology, New York Presbyterian Columbia University Medical Center, New York, NY. Reprint requests: Sherelle L. Laifer-Narin, MD, Department of Radiology, New York Presbyterian Columbia University Medical Center, 630 W 168th St, New York, NY 10032. E-mail: [email protected]. Curr Probl Diagn Radiol 2014;43:374–385. & 2014 Mosby, Inc. All rights reserved. 0363-0188/$36.00 + 0 http://dx.doi.org/10.1067/j.cpradiol.2014.06.001
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from 15.8 mm in the anteroposterior dimension immediately after delivery to 4 mm on postpartum day 56.2 Ultrasound is the first imaging modality of choice in evaluating the postpartum uterus. The postpartum uterus can demonstrate variable appearance of the endometrial cavity, which may be empty, or contain foci of gas, simple fluid, or echogenic material. Echogenic material can be seen in 51% of women at 1 week postpartum and in 6% at 3 weeks postpartum.3 Echogenic material without vascularity seen on color Doppler image in a postpartum uterus likely represents blood products. However, if vascularity is seen, other etiologies and various complications should be considered based on specific findings.
Vascular Postpartum complications of vascular origin include uterine bleeding, arteriovenous malformation (AVM), and pseudoaneurysm. The initial imaging modality of choice is ultrasound, followed by CT or MRI or both for more complex cases. Uterine Hemorrhage Uterine hemorrhage is defined as loss of greater than 500 mL of blood after the third stage of labor. Early hemorrhage occurs less than 24 hours after delivery and is related to uterine atony and retained products of conception and may be mimicked by vaginal laceration. Late hemorrhage occurs more than 24 hours after delivery and is related to abnormal involution of the placental site or RPOC. Diagnosis of hemorrhage is clinical; however, imaging studies are used to identify sources of bleeding and exclude vascular causes of hemorrhage that could warrant surgical intervention. Once these surgical causes are excluded, treatment options include uterotonic medications, arterial embolization, or in severe cases, hysterectomy. An ultrasound image shows a normal-appearing postpartum uterus with or without echogenic material consistent with blood clots. If an intrauterine clot or mass is found, there will be no associated vascularity on color Doppler (Fig 1). In more complex cases that warrant further workup with CT or MRI, intrauterine blood of varying density or intensity will be seen without associated contrast enhancement. Arteriovenous Malformation Uterine AVM may be congenital or acquired from prior trauma, infection, endometriosis, gestational
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FIG 1. Intrauterine hematoma. Transvaginal power Doppler ultrasound image demonstrates a heterogeneous, avascular intrauterine collection, compatible with a hematoma (arrows). (Color version of figure is available online.)
trophoblastic disease, or fibromas. Patients present with intermittent bleeding, lower abdominal pain, dyspareunia, and less frequently, high-output cardiac failure. Diagnosis can be made using ultrasound, which is the imaging modality of choice. On ultrasound, multiple hypoechoic or anechoic serpentine spaces within the myometrium can be seen with turbulent flow on color Doppler (Fig 2A). Spectral analysis demonstrates highvelocity and low resistive index (Fig 2B). CT or MRI can be performed to identify and localize feeding arteries of AVM, which facilitates confirmation of diagnosis and treatment planning. CT scan also demonstrates numerous anomalous blood vessels communicating with the uterine arteries in the wall of the uterus and parametrium. MRI shows serpiginous signal voids on spin-echo sequences with prominent parametrial vessels and focal disruption of the junctional zone. Angiography is considered to be the gold standard. Angiography demonstrates a nidus of vessels supplied by enlarged feeding arteries with early venous drainage (Fig 2C).4 Treatment choices include methylergonovine, intra-arterial embolization, or hysterectomy.5 Uterine Artery Pseudoaneurysm A pseudoaneurysm is defined as a collection of blood within the extraluminal space with a persistent communication through a defect in the arterial wall. Uterine artery pseudoaneurysm (UAP) is usually associated with prior surgical interventions, such as cesarean section or dilation and curettage.6,7 UAP may be suspected when patients who are postpartum or posttermination present
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with pain and vaginal bleeding. Initial workup involves ultrasound, which may demonstrate a hypoechoic intrauterine lesion on gray scale, with vascularity demonstrated on color Doppler and bidirectional systolic and diastolic flow with aliasing on spectral Doppler. Angiography has traditionally been the gold standard, however, with advancement of CT and MR techniques, CT or MR angiograms are now the first techniques. CT scan may reveal an enhancing, round outpouching with a communication to a parent artery (Fig 3). In cases of life threatening hemorrhage, treatment involves uterine artery embolization or hysterectomy.
Infectious Puerperal sepsis causes at least 75,000 maternal deaths every year worldwide,8 and puerperal infectious morbidity affects 5%-10% of pregnant women.9 Cesarean section is the single most important risk factor for postpartum infection. Postpartum infectious entities include endometritis, wound infection, infected products of conception, or thrombophlebitis. Patients typically present with fever, pelvic pain, and leukocytosis. Endometritis Endometritis is a clinical diagnosis; however, imaging is often used to exclude concurrent pathology. Ultrasound is often the first-line modality to evaluate a
FIG 2. Uterine arteriovenous malformation: (A) transvaginal grayscale image shows heterogeneous myometrium containing serpiginous vessels (arrows); (B) spectral Doppler image demonstrates low-resistance, high-velocity flow, suggestive of arteriovenous shunting; and (C) angiogram demonstrates an arteriovenous malformation (*) supplied by multiple feeding branches (arrow) from the internal iliac artery. (Color version of figure is available online.)
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FIG 3. Uterine artery pseudoaneurysm. Postcontrast axial CT scan shows a round structure demonstrating intense enhancement (arrow), similar to the nearby arteries, which was consistent with a pseudoaneurysm.
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FIG 4. Endometritis. Transvaginal ultrasound shows a thickened endometrium containing intracavitary echogenic foci consistent with gas (arrow).
febrile postpartum patient to exclude RPOC, infected hematoma, or abscess. Ultrasound is preferable given its ease of access, cost-effectiveness, and lack of radiation. On ultrasound, the uterus may demonstrate a thickened, heterogenous endometrium or appear normal with common postpartum findings such as intracavitary fluid or gas.10 Clinical correlation with fever or pelvic pain is critical in diagnosing endometritis. CT and MRI can be used to further exclude superimposed abscess or infected hematoma. Similar to the ultrasound examination, CT may demonstrate a thickened endometrium, possibly with fluid, gas, and debris within the endometrial cavity (Fig 4). MRI can also visualize similar findings to CT images, with gas demonstrated as a signal void on T1- and T2-weighted images. Use of contrast can help identify a fluid collection within the endometrium, which will require further intervention. Treatment of endometritis involves antibiotics and evacuation of drainable fluid collections.
adjacent to or separate from the uterus and nonspecific inflammatory changes. If the abscess is beyond the field of view, the study may be unremarkable. CT is the imaging modality of choice to evaluate for presence of an abscess. A pelvic abscess is demonstrated as a peripherally enhancing, thick-walled fluid collection with inflammatory changes of the surrounding pelvic fat (Fig 6). CT can help visualize the size and location of the abscess. In addition, CT can delineate the relationship of the abscess to the surgical abdominal incision or the uterine incision. MRI is rarely used to diagnose an abscess. When it is used, however, it demonstrates a mass with thick, irregular, enhancing wall that contains fluid with low to intermediate signal intensity on T1-weighted images and hyperintense signal on T2-weighted images. Septic Pelvic Thrombophlebitis Septic pelvic thrombophlebitis (SPT) is caused by inflammatory or infectious etiologies, including severe endometritis and bacteremia, often related to recent delivery or surgery such as cesarean section.11 In these cases, infection can extend and involve the pelvic vessels causing inflammation and thrombosis. Clinically, patients with SPT present with fever and flank or lower abdominal pain, with abdominal tenderness and occasional abdominal mass on physical examination and do not respond to standard antibiotic therapy. A direct diagnosis of SPT is rarely made by imaging, but in some patients ovarian vein thrombosis
Superficial Wound Infection Superficial wound infection is a clinical diagnosis in which the surgical wound demonstrates edema, erythema, and possible drainage. CT can be performed to assess integrity of the surgical wound and exclude an associated abscess or wound dehiscence. CT scan shows subcutaneous fat stranding in the region of the surgical incision (Fig 5). In cases where a subcutaneous wound abscess is associated, a rim-enhancing fluid collection will be seen along the superficial incision. Abscess Abscesses can be isolated findings or associated with endometritis. Ultrasound may identify a fluid collection Curr Probl Diagn Radiol, November/December 2014
FIG 5. Superficial wound infection. Postcontrast axial CT image shows inflammatory changes of the subcutaneous fat in the region of the cesarean section wound. Foci of air are likely postsurgical.
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FIG 6. Uterine abscess. Postcontrast axial CT image shows a fluid collection with an enhancing wall. Uterine dehiscence is also present (between arrows).
may be identified. Diagnostic imaging for ovarian vein thrombosis includes ultrasound, CT, and MRI. Ultrasound has a limited role but may demonstrate an echogenic mass within an enlarged ovarian vein. CT and MRI are preferred imaging modalities of choice for SPT. On a CT scan, ovarian vein thrombosis is demonstrated as a filling defect within the ovarian vein, possibly with venous enlargement. On MRI, variable T1 and T2 signals of the thrombus are seen within the enlarged ovarian vein (Fig 7). In the postcontrast venous phase images, a filling defect or absence of flow is noted in the ovarian vein.
approximately 1 in 700-2400 cesarean births. The mechanism is believed to be secondary to infectious incisional necrosis leading to dehiscence.12 Patients present with nonspecific signs, such as pain or malaise. Ultrasound or MRI is used to exclude uterine dehiscence in a postsurgical patient. Ultrasound findings can range from a normal examination in cases of small, subtle defects to findings of a thinned and irregular uterine wall and myometrial defect in more obvious cases (Fig 8A). CT may be able to demonstrate a myometrial defect. However, MRI is used if clinical suspicion persists, given its superiority in delineating soft tissue anatomy and pathology. MRI demonstrates a myometrial defect, and fluid or blood may be seen between the uterine layers. The sagittal images are most helpful when localizing the site of dehiscence and evaluating involvement of adjacent structures such as the bladder (Fig 8B). Treatment may involve only antibiotics in very minor dehiscence, but most cases need to undergo surgical repair. Postsurgical Hematoma Postsurgical hematomas are common complications related to intraoperative vascular injury, such as the uterine vessels in cases of bladder flap hematoma, and epigastric vessels in cases of subfascial hematoma. Patients present with pain, decreased hemoglobin, and in severe cases, hemodynamic instability. CT is often used as a first-line modality due to its fast scan time and ability to delineate anatomy of the hematoma in relation to the adjacent organs. Treatment can be
Surgical An increasing number of patients undergo cesarean section, with the latest National Vital Statistics Reports performed by Centers for Disease Control and Prevention revealing 32.8% cesarean delivery rate in 2012. Diagnostic imaging for postsurgical complications is therefore essential in management of postpartum patients. Common postsurgical complications seen in cesarean section patients include uterine scar dehiscence, bladder flap hematoma, and subfascial hematoma. Uterine Scar Dehiscence Uterine scar dehiscence refers to discontinuity of the uterine scar involving the myometrial or serosal layers or both. Uterine dehiscence is rare with an incidence of
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FIG 7. Septic pelvic thrombophlebitis. Axial gradient-echo image demonstrates a partially occlusive thrombus in an enlarged right ovarian vein (arrow).
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bladder wall (Fig 9A). However, distinguishing a bladder flap hematoma from an abscess can be difficult on ultrasound. On a CT scan, a hyperdense collection is identified anterior to the anterior lower uterine segment and posterior to the bladder (Fig 9B). If gas is seen within the collection, superimposed infection is suggested. MRI is not commonly used to diagnose a hematoma. If performed, a collection with variable signal intensity will be seen depending on the age of blood products in the same anatomical space between the anterior lower uterine segment and the posterior to the bladder (Fig 9C). Subfascial Hematoma Subfascial hematoma is caused by injury to the epigastric vessels, resulting in a collection of blood within the prevesical space. On an ultrasound image, a subfascial hematoma is identified by a heterogeneous fluid collection or mass anterior to the bladder and posterior to the abdominal wall (Fig 10A). Similar to a bladder flap hematoma, distinguishing between a hematoma and abscess is difficult on ultrasound. On CT and MR images, a hyperdense or T1 hyperintense mass or collection is seen within the prevesical space, posterior to the rectus muscle and transversalis fascia but anterior to the peritoneum and umbilicovesical fascia (Fig 10B and C). Again, superimposed infection should be considered when gas is present within the collection. FIG 8. Uterine wound dehiscence. (A) Transvaginal ultrasound shows echogenic structures (*) that represent sutures. The uterus is tented and fixed anteriorly to the anterior abdominal wall (between arrows). (B) T2WI sagittal image shows a myometrial defect (between the arrows) in the anterior uterine wall. Concurrent bladder flap hematoma (H) is present. T2WI, T2-weighted image.
supportive in cases of small hematomas without hemodynamic compromise, whereas patients with ongoing bleeding, hemodynamic instability, or clinically significant mass effect will undergo surgical exploration and hematoma evacuation. Bladder Flap Hematoma Bladder flap hematoma refers to a hematoma in the vesicouterine space between the posterior wall of the bladder and the cesarean section incision on the anterior lower uterine segment. In the presence of a bladder flap hematoma, the incision site should be scrutinized for potential wound dehiscence. On an ultrasound image, a bladder flap hematoma can be identified as a heterogeneous solid mass or collection between the lower uterine segment and the posterior
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Neoplastic Gestational trophoblastic disease encompasses a spectrum of trophoblastic cell proliferation disorders, some of which have malignant potential. Invasive mole, choriocarcinoma, and placental site trophoblastic tumor are classified as persistent trophoblastic neoplasia.13 Ultrasound is the first-line modality for diagnosis, whereas MRI is usually reserved for complicated cases. Once the diagnosis has been made, CT is useful for determining extent of disease. Treatment is dilation and curettage and chemotherapy for invasive disease. Invasive Mole Invasive mole is defined as invasion of the myometrium by trophoblastic overgrowth. These develop in 10% of treated complete hydatiform moles and less often in cases of partial moles. They are locally invasive but usually do not have metastatic potential. Patients usually present with vaginal bleeding and are found to have rising or persistently elevated levels of
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FIG 9. Bladder flap hematoma: (A) transvaginal ultrasound shows an oval, heterogeneous, solid collection (*) anterior to the uterus (U) and posterior to the bladder (B); (B) noncontrast sagittal CT image shows a hyperdense collection (*) between the bladder and the anterior lower uterine segment; and (C) coronal T1WI with fat saturation shows a heterogeneous hyperintense collection (*) posterosuperior to the bladder (B) and anterior to the uterus (U). T1WI, T1-weighted image.
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FIG 10. Subfascial hematoma. (A) Transabdominal ultrasound shows a heterogeneous hematoma (*) anterior to the normal uterus (U). (B and C) Noncontrast axial and sagittal CT images demonstrate heterogeneously hyperdense collections (*) in the prevesical space with fluid-fluid levels.
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abundant vascularity and low resistive index. On CT and MR images, choriocarcinoma is seen as a hypervascular, heterogeneous, ill-defined mass with peripheral enhancement and central necrosis (Fig 12).15 The involved myometrium may appear heterogeneous owing to bleeding or necrosis. In addition, dilated and tortuous myometrial and parametrial arteries are identified.
Ectopic or Residual Implantation of Endometrial or placental tissue
FIG 11. Invasive mole. Transvaginal ultrasound demonstrates fluid and debris in endometrial cavity with intense neovascularity in the myometrium extending to the periphery (arrows). In the setting of persistently elevated β-hCG levels unresponsive to methotrexate therapy, this constellation of findings may suggest invasive mole. Pathology results of hysterectomy specimen confirmed invasive mole. β-hCG, beta human chorionic gonadotropin. (Color version of figure is available online.)
Retained Products of Conception RPOC are of placental trophoblastic origin, as the trophoblast adheres and attaches to the uterine endometrium, leading to formation of the placenta. Incidence depends on the gestational age of the pregnancy, most frequently occurring after secondtrimester delivery or termination.16 Patients can
beta human chorionic gonadotropin. Owing to elevated levels of beta human chorionic gonadotropin, multiple luteinized follicular cysts or theca lutein cysts may develop, resulting in an enlarged appearance of the ovaries. On an ultrasound image, invasive mole is seen as a focal echogenic cystic mass within the myometrium, which may be uniform or complex. Marked vascularity is visualized on color Doppler (Fig 11), and high-velocity, low-resistance waveform is seen on spectral Doppler. On an MR image, invasive mole is identified as a heterogenous T1 and T2 endometrial or myometrial mass, which may be due to tumor necrosis or hemorrhage. Additional characteristics include distortion or obliteration of uterine layers and engorged surrounding vasculature owing to hypervascular nature of the tumor. Postcontrast images may demonstrate enhancement of viable tumors.14 Choriocarcinoma Choriocarcinoma is a chorionic epithelial neoplasm that can arise after a molar pregnancy or nonmolar pregnancy. Blood-borne metastases tend to develop early, usually to the lung and brain. Patients initially present with abdominal pain, possibly with dyspnea in the presence of lung metastases, or headache or seizure with brain metastases. On gray-scale ultrasound, choriocarcinoma is identified as an echogenic intrauterine mass with possible invasion into the myometrium and adjacent structures. Color and spectral Doppler demonstrates
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FIG 12. Choriocarcinoma. (A) Postcontrast axial CT image shows normal-appearing postpartum uterus. Multiple enlarged theca lutein cysts are seen bilaterally. (B) However, hypoenhancing lesions in the right kidney represent metastases (arrows). (Color version of figure is available online.)
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FIG 13. (A and B) Retained products of conception. Patient 1: (A) transvaginal spectral Doppler shows high-velocity, low-resistance flow within a vascular intracavitary mass, which remains attached to the endometrium and Patient 2: (B) axial postcontrast CT image shows a dense, heterogeneous intracavitary mass (*). Patient 3: (C and D) Retained products of conception with placenta accreta. Sagittal T2WI (C) and postcontrast T1WI (D) with fat saturation demonstrate a nonenhancing mass in the myometrium of the anterior lower uterine segment, extending into the cervix, compatible with retained cervical placenta accreta (*). T1WI, T1-weighted image; T2WI, T2-weighted image. (Color version of figure is available online.)
present with pain, fever, and vaginal bleeding. Ultrasound with color Doppler is the modality of choice, although there is a high false-positive rate ranging from 17%-51%.17 Sonographic findings of RPOC include a solid, echogenic intracavitary mass that extends to the endometrium with abundant vascularity demonstrated on color Doppler and high-velocity, low-resistance flow on spectral Doppler (Fig 13A). Blood products or normal, involuting endometrium may also demonstrate
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intracavitary echogenic material on gray-scale ultrasound, and careful examination with color Doppler is recommended to differentiate RPOC from blood products. CT scan may show a dense, heterogeneous intracavitary mass, which is again indistinguishable from an intrauterine clot (Fig 13B). In such cases, MRI may be used to delineate more soft tissue detail by demonstrating a variably enhancing, intracavitary soft tissue mass with associated disruption of the uterine layers or tumor extension into the
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myometrium (Fig 13C and D). Contrast can help determine vascularity of the mass and depth of myometrial invasion, although these findings are not specific to RPOC and overlap with gestational trophoblastic disease. Treatment options for RPOC include uterotonic medications, methotrexate, transarterial embolization, dilation and curettage, and hysteroscopic removal. Abnormal Placentation Abnormal placentation refers to abnormal placental adherence. Three degrees of adherence are recognized. Placenta accreta is placental implantation directly onto the myometrium without the normal intervening decidua basalis and fibrinoid layer of Nitabuch. Placenta increta is myometrial invasion of placental tissue. Placenta percreta is invasion through the serosal layer of the uterus with possible contiguous extension to adjacent structures (Fig 14).18 Highest risk factors for abnormal placentation are prior cesarean section and prior abnormal placentation with other risk factors being older maternal age, postprocedural adhesions, and multiparity.19 Patients are commonly asymptomatic and diagnosed during prenatal care. For this reason, imaging modalities that involve radiation exposure such as CT are not commonly used for diagnosis of abnormal placentation. Ultrasound can identify anterior placental, whereas MRI is more optimal in evaluating posterior placental implantation. Findings most sensitive for diagnosing placenta accreta on ultrasound are the presence of multiple placental lacunae. Placental lacunae are irregular placental vascular spaces with turbulent flow and are described as having a “swiss cheese” or “moth-eaten” appearance. Other findings include loss of retroplacental clear space, thinning and distortion of myometrium, bulging of the uterine wall, and irregularity of the bladder-uterus interface. MR image may demonstrate heterogeneous appearance of the placenta with an irregular uterine contour, bulging of the placenta into the bladder, and loss of bladder-uterus interface.19,20 T2-weighted images can identify hypointense, dark intraplacental bands. Treatment is cesarean section and possible cesarean hysterectomy. Uterine Scar Endometriosis Endometriosis is defined as ectopic location of normal endometrial tissue. Endometriosis in the cesarean scar can be seen in postcesarean-section patients.
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FIG 14. Placenta percreta. (A) Transabdominal ultrasound image shows inferior placenta (*) that covers the internal os. The placentamyometrium interface is not visualized and the placenta extends to the bladder surface (B). (B and C) Sagittal and coronal T2WIs shows the placenta previa extending through the myometrium with loss of normal bladder mucosa (arrow), consistent with placenta percreta. T2WI, T2-weighted image. (Color version of figure is available online.)
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FIG 15. Uterine scar endometriosis. Soft tissue gray scale (A) and color Doppler (B) ultrasound images of the suprapubic region show a heterogeneously echogenic subcutaneous mass with internal vascularity. Postcontrast axial CT (C) and T1W fat saturation images (D) show 2 enhancing nodules (arrows) in the subcutaneous fat overlying the region of the cesarean section wound. (Color version of figure is available online.)
Abdominal wall implantation is estimated to occur in 0.03%-1% of postcesarean-section patients with an approximate delay of symptoms of 3-6 years.20 Clinical presentation is cyclical pain in the region of the cesarean scar, where a palpable mass may be present. Ultrasound is often used as a first-line imaging study to evaluate the palpable subcutaneous mass. Ultrasound demonstrates a round or oval, heterogeneously hypoechoic, vascular lesion along the cesarean-section scar (Fig 15A and B). Small cystic areas may be present owing to blood pooling from recent hemorrhage. Hyperemia may be seen on color Doppler owing to inflammatory changes. CT or MRI is used to evaluate extent of disease. CT scan demonstrates an enhancing soft tissue lesion with or without surrounding inflammatory changes (Fig 15C). MR image demonstrates a soft tissue lesion with variable T1 hyperintense signal related to blood products of varying ages (Fig 15D). Treatment is wide surgical resection of the implants.
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Summary Postpartum or posttermination patients may suffer from complications of various causes, including vascular, infectious, surgical, and neoplastic etiologies and ectopic implantation of placental or endometrial tissue. Diagnosis of common postpartum complications can be challenging because of the variable appearance of the postpartum uterus and variable clinical or surgical history of the patient. The normal postpartum uterus varies in size and orientation, as it undergoes natural involution and physiological changes to return to its pregravid state. The endometrial cavity often contains blood products, debris, or gas during the postpartum or posttermination period, which are normal imaging findings in the absence of clinical symptoms. In patients with clinical symptoms, ultrasound, CT, or MRI can be used for imaging and diagnosis depending on the suspected etiologies. Ultrasound is the first imaging modality of choice in most complications of vascular
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origin, including uterine hemorrhage, RPOC, AVM, pseudoaneurysm, bladder flap, or subfascial hematoma. Neoplastic conditions such as invasive mole and choriocarcinoma, or ectopic or abnormal tissue implantation may also be initially diagnosed on ultrasound. Cross-sectional imaging can be performed for further delineating the anatomy of ultrasound findings and evaluating the extent of disease for treatment planning. CT is used in the diagnosis of infectious or postsurgical complications involving the deep pelvis such as abscess or SPT. Owing to its fast scan time, CT can be helpful in assessing for postsurgical hemorrhage or hematoma in immediate postoperative patients. MRI is useful when delineation of the zonal anatomy is critical for diagnosis, such as uterine wound or scar dehiscence, abnormal placentation, or uterine scar endometriosis. MRI can be used in diagnosing ovarian vein thrombosis in cases of possible SPT, if CT does not visualize the findings and clinical suspicion remains high. Common postpartum complications that are diagnosed clinically include endometritis and superficial wound infection. In these cases, imaging studies may be helpful in excluding associated findings, such as abscess formation or SPT. Identification of postpartum and posttermination complications is essential for minimizing morbidity and mortality in these patients. Recognizing common and uncommon entities is crucial for accurate diagnosis and management.
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