ATS SEMINARS Intensive Care Ultrasound Series Editor: Gregory A. Schmidt, M.D.
Intensive Care Ultrasound: IV. Abdominal Ultrasound in Critical Care Keith S. Boniface1 and Kathleen Y. Calabrese1 1
Department of Emergency Medicine, George Washington University Medical Center, Washington, DC
Ultrasound in critical care is distinct from ultrasound performed in radiology. Radiology-performed ultrasound is a comprehensive, anatomical examination that seeks to fully describe the area undergoing investigation. Clinicianperformed ultrasound performed at the bedside of the critically ill patient aims to answer a focused clinical question: Is the systolic function of the heart normal? Is there a deep vein thrombosis? Is there a pneumothorax? As a result, the learning curve for performance of these focused evaluations is much shorter and steeper than it is for more comprehensive examinations (1–3). Intensivistperformed abdominal ultrasound focuses on detecting the presence of intraabdominal fluid, obstructive changes of the kidneys and bladder, acute pathology of the gallbladder, and intraabdominal catastrophes. The examinations that follow use a low frequency (1–5 MHz) curvilinear or phased array transducer, with the orientation mark to the left side of the screen.
pericardial spaces. The use of ultrasound in trauma evaluation dates back over 40 years in Europe and Asia (4), became widely adopted in the United States throughout the 1990s, and has become a standard part of the evaluation of the traumatized patient (5). The extended FAST examination, or “eFAST,” includes views of the thorax to evaluate for pleural fluid, discussed below, and the anterior pleural– pleural interface to assess for pneumothorax (6–8), discussed elsewhere in this series of articles. Its use has expanded beyond the trauma bay, however, and the FAST examination is now an integral part of
many different ultrasound protocols that aim to identify the cause of shock in hypotensive patients (9–12). In a randomized, prospective trial, the immediate use of an ultrasound protocol including FAST examination, focused echocardiography, and views of the inferior vena cava led to a shorter list of potential diagnoses and a higher likelihood at the bedside of a hypotensive patient of selecting the correct diagnosis from this list, compared with delayed ultrasound (13). The FAST examination can show signs of aneurysm rupture, bleeding from ectopic pregnancy, postoperative complications, hollow viscus perforation,
Focused Assessment with Sonography for Trauma The Focused Assessment with Sonography for Trauma, or FAST examination, is a protocolized examination that seeks to identify fluid in the peritoneal and
Figure 1. Normal right upper quadrant. In this image, the probe marker is seen on the left side oriented cephalad. Note the hyperechoic curved diaphragm (arrow), the relatively homogenous appearance of the liver (L), then the hypoechoic kidney (K) toward the right of the screen (caudad).
(Received in original form September 25, 2013; accepted in final form November 1, 2013 ) This article has associated videos, which are accessible at www.atsjournals.org/doi/full/10.1513/AnnalsATS.201306-324OT. If you cannot view Flash videos on your device, please access original videos at www.atsjournals.org/doi/suppl/10.1513/AnnalsATS.201306-324OT. Correspondence and requests for reprints should be addressed to Keith S. Boniface, 2120 L Street NW, Suite 450, Washington, DC 20037. E-mail: [email protected] Ann Am Thorac Soc Vol 10, No 6, pp 713–724, Dec 2013 Copyright © 2013 by the American Thoracic Society Originally published in Press as DOI: 10.1513/AnnalsATS.201309-324OT Internet address: www.atsjournals.org
ATS Seminars
713
ATS SEMINARS
Figure 2. Free fluid (FF) in the right upper quadrant. Note the curved diaphragm (arrow) to the left of the liver (L); caudal (right) to the liver and superficial to the kidney (K) there is an anechoic, triangular collection of fluid.
and inflammatory processes, all of which can cause intraabdominal free fluid in the absence of trauma. The FAST examination is composed of four views. The first three views use acoustic windows in the right upper quadrant (RUQ), left upper quadrant (LUQ), and suprapubic regions (liver, spleen, and bladder). These windows serve to conduct the sound wave to the three most dependent areas of the peritoneal cavity in the supine patient as well as to the costophrenic angles bilaterally of the pleural space when performing the eFAST.
The fourth view provides a view of the pericardium, typically obtained from the subxiphoid approach. The order of obtaining these views is not as important as systematically evaluating each quadrant for pathology.
Technique Right Upper Quadrant
The abdominal examination presets are chosen on the ultrasound machine for this examination. The external landmark
Figure 3. Free fluid (FF) in the right upper quadrant. At times, fluid collects only near the inferior pole of the right kidney (K), necessitating a full interrogation not only of Morison’s pouch at the juncture of the liver and kidney but also a caudal evaluation including the paracolic gutter at the lower pole (lp) of the right kidney (K).
714
for probe placement to obtain the two upper quadrant views is the xiphoid process (14). If a horizontal line is drawn at the level of the xiphoid, the probe can then be placed at the point where that horizontal subxiphoid line intersects with the right midaxillary line, with the index mark on the probe oriented toward the patient’s head and the probe aimed slightly posteriorly. This will provide a coronal view of the liver, the right kidney, the potential space of Morison’s pouch, the diaphragm, and a small area cephalad to the diaphragm (Figure 1). Fluid in the RUQ typically shows up as a hypoechoic band of black that tracks between the kidney and the liver (Figure 2). Continuing to scan a rib space or two inferiorly to visualize the lower pole of the kidney is recommended, to assess for more subtle fluid collections that do not track between the kidney and the liver. (Figure 3 and Video 1).
Left Upper Quadrant
In the left upper quadrant, the spleen provides the acoustic window and is smaller and more posteriorly located than the liver in the RUQ. To obtain the LUQ view, the probe is placed at the intersection of the horizontal subxiphoid line and the posterior axillary line, with the index mark on the probe oriented toward the patient’s head and the probe aimed slightly posteriorly. This provides a coronal view of the spleen, the left kidney, the potential space between spleen and kidney, the diaphragm, and a small area cephalad to the diaphragm (Figure 4). It can be helpful to rotate the probe obliquely, given that the kidneys lie in an oblique orientation to the coronal plane. Fluid in the LUQ does not necessarily confine itself to the splenorenal space but can be found in the subphrenic region as well as laterally to the spleen, so it is essential to scan through the entire LUQ by “fanning” anteriorly and posteriorly as well as from the interface between diaphragm and spleen to the inferior pole of the kidney (Figure 5 and Video 2). Troubleshooting of image acquisition for the upper quadrant view is guided by the structures that are visualized—if spleen or liver is seen but not the kidney, the
AnnalsATS Volume 10 Number 6 | December 2013
ATS SEMINARS
Figure 4. Normal left upper quadrant. As in the right upper quadrant, the probe marker is oriented cephalad. The diaphragm (arrow) is hyperechoic, the spleen (S) is relatively homogenous, and the kidney (K) lies more posteriorly and superiorly than the right kidney.
beam can be angled posteriorly to identify the kidney, located retroperitoneally. If only the lower pole of the kidney is seen, then sliding the probe an interspace or two toward the patient’s head will allow for identification of the spleen/kidney or liver/kidney interface. Mirror Image
The LUQ and RUQ views should include a view of the diaphragm. The lung lies just above and adjacent to the diaphragm, and in the normal patient, due to the highly
reflective diaphragm and the air-filled lung, this area just cephalad to the diaphragm will take on the appearance of the spleen or liver—the “mirror-image artifact” (Figure 6 and Video 3). This artifact serves to rule out fluid in the pleural space. Pleural fluid (whether effusion or blood) will appear as an anechoic triangle cephalad to the diaphragm (Figure 7 and Video 4). Pelvic View
The third view of the FAST examination is the pelvic view. To obtain this view,
Figure 5. Free fluid (FF) in the left upper quadrant (LUQ). Free fluid can be found anywhere in the LUQ, including between the diaphragm (arrow) and the spleen (S), as well as between the spleen and kidney (K), as in this case.
ATS Seminars
the probe is placed in the midline just superior to the pubic symphysis. Long axis views can be obtained by placing the index mark toward the patient’s head, and short axis views are obtained with the index mark toward the patient’s right side. The gain may need to be decreased because of the fluid-filled bladder’s increased through-transmission of ultrasound; otherwise, the bright reflections from behind the bladder could mask small pockets of fluid. Depth should be adjusted such that the bladder, seen as the central ovoid hypoechoic structure, occupies less than one-half of the screen depth, to allow for the identification of free fluid deep to the bladder and deep to the uterus posterior to the bladder in women (pouch of Douglas). Fluid can be also found lateral to the bladder wall, where it can be readily identified when the hyperechoic bladder wall is sandwiched between anechoic urine inside and anechoic free fluid outside of the bladder (Figure 8).
Subxiphoid
The fourth and final view of the FAST examination is the subxiphoid view of the heart. Using the abdominal presets, the index mark is placed toward the patient’s right side and the probe is held in an overhand grip and angled under the xiphoid process and pointed toward the patient’s head. The probe needs to be held quite flat to aim the beam up underneath the sternum and obtain a coronal view of the heart. The right ventricle forms the majority of the heart’s border with the liver. The normal heart will have the brightly echogenic pericardium directly adjacent to the less echogenic myocardium (Figure 9 and Video 5). Pericardial fluid will be demonstrated as a hypoechoic to anechoic stripe of fluid between the white pericardium and the gray myocardium (Figure 10 and Video 6). If adequate images are difficult to obtain, the acoustic window can often be improved by a combination of three maneuvers: (1) having the patient take a deep breath, to use the diaphragm to pull the heart closer to the probe; (2) sliding the probe to the patient’s right side along the costal margin by the distance of one or two probe widths, to use a larger wedge of 715
ATS SEMINARS Ascites and Paracentesis
Figure 6. Mirror-image artifact. Note the similar appearance of the liver (L) both above and below the diaphragm. This is due to the highly reflective diaphragm (arrow), with a wall of air-filled lungs behind. The presence of the mirror image artifact (mirror) serves to rule out a pleural fluid collection. In this image, there is also free fluid (FF) between the kidney and spleen.
liver as an acoustic window and to avoid the air-filled gastric bubble; and (3) bending the patient’s legs, to relax abdominal wall musculature. Limitations
The main limitation to the FAST examination is the fact that a very small amount of intraabdominal bleeding may not be demonstrated on ultrasound examination. As a result, providers should have a very low threshold to repeat an initially negative FAST examination,
especially if the patient’s clinical status deteriorates. Placing the patient in Trendelenburg position may increase the sensitivity of the FAST examination in the RUQ view (15). There are many fewer false-positive examinations, but it should be mentioned that intraabdominal blood can look identical to ascites or even urine (in the setting of intraperitoneal bladder rupture), and if there is diagnostic uncertainty about what type of fluid is causing a positive FAST examination, a small-volume diagnostic paracentesis can be helpful.
Paracentesis is an important tool in the evaluation of the patient with liver disease. Although paracentesis is not a high-morbidity procedure, there is evidence supporting a decrease in complications as well as overall cost with the use of ultrasound guidance (16). Ultrasound confirms the clinical suspicion that intraabdominal fluid exists and facilitates aspiration of fluid while avoiding nearby structures, such as bowel, or vasculature, such as the inferior epigastric artery and vein (Figure 11 and Video 7). If there is suspicion of ascites but the clinical examination is not definitive, the FAST examination of the supine patient is ideal for the confirmation of peritoneal fluid. If fluid is identified, the needle can be guided to the deepest pocket; if no fluid is seen, an unnecessary procedure can be avoided. If using ultrasound to guide the needle in real time, a high-frequency linear transducer is ideal. In a randomized trial of landmark compared with ultrasoundguided paracentesis, 95% of patients with ascites were successfully drained under ultrasound guidance. Twenty-five percent of the patients randomized to ultrasound-guided paracentesis were ultimately spared the procedure due to lack of aspirable fluid. Furthermore, landmark-based paracentesis failed in 39% of patients, and 76% of patients with these failed procedures subsequently had a successful paracentesis using ultrasound (17).
Kidney and Bladder Ultrasound
Figure 7. Pleural fluid. In this right upper quadrant view, the curved hyperechoic diaphragm (arrow) is seen along with liver (L) and kidney (K), but black anechoic fluid is now seen where the mirror image artifact is expected, indicating a pleural effusion (Eff ).
716
The renal system is well visualized with ultrasound, and renal sonography can be used in a number of scenarios, from troubleshooting urinary catheter problems to identifying hydronephrosis. These questions can be answered quickly at the bedside of the patient, enabling the critical care practitioner to mobilize appropriate interventional strategies to improve patient outcomes. In the patient with decreased urine output through their urinary catheter, the central question is whether the bladder is empty (renal problem) or full (catheter
AnnalsATS Volume 10 Number 6 | December 2013
ATS SEMINARS Technique
Figure 8. Free fluid in the pelvis. In the sagittal view of the pelvis, free fluid (FF) can be found adjacent to the bladder (B), as seen in this image as an anechoic triangle, or it can also be seen in retrovesicular space (RvS).
problem). The empty bladder with functioning catheter is difficult to visualize, and the anechoic fluid-filled balloon is the only portion visible (Figure 12). In the patient with decreased urine output due to catheter malfunction, a distended anechoic bladder will be visualized (Figure 13). Most point-of-care ultrasound machines have calculation packages to estimate bladder volume, although this degree of precision is not often necessary.
In the patient with acute renal failure, a point-of-care ultrasound can serve to eliminate obstructive postrenal causes of renal failure. The normal kidney has a hyperechoic medulla and relatively hypoechoic cortex. With increasing degrees of obstruction, the collecting system will begin to dilate, extending up into the minor and major calyces and eventually thinning the cortex of the kidney. This can be graded from mild (Figure 14) to severe (Figure 15).
Figure 9. Normal subxiphoid view. In this view, the liver functions as the acoustic window—note its location at the top of the image. The hyperechoic pericardium (Pc) abuts against the grayish myocardium (Mc) of the right ventricle (RV), and the potential pericardial space lies between these two structures. In addition, the left ventricle (LV), left atrium (LA), and right atrium (RA) are visualized.
ATS Seminars
Renal ultrasound should include transverse and longitudinal views of both kidneys as well as the bladder (18). A low-frequency abdominal transducer should be used with either abdominal or the renal presets. The external landmarks for scanning the kidneys are similar to those for the FAST examination described above, or a rib interspace or two caudad, and the liver and spleen are again used as acoustic windows. Care should be taken to fan the probe anteriorly and posteriorly through each kidney, assessing for dilation of the collecting system. If any anechoic areas are noted, color Doppler should be applied to ensure that it is not a vascular structure—hydronephrosis should not enhance with color Doppler. The probe is then rotated 90 degrees counterclockwise, and another fanning sweep is completed from the superior to the inferior poles. Finally, longitudinal and transverse sweeps through the bladder are performed.
Abdominal Aortic Ultrasound Every critical care practitioner should also be facile with ultrasound evaluation of the abdominal aorta, as a ruptured abdominal aortic aneurysm (AAA) can be catastrophic. Its evaluation should be considered in the undifferentiated hypotensive patient (19) and may be considered in the patient with unilateral hydronephrosis, back pain, or abdominal pain. The risk of rupture of AAA is directly correlated with diameter of the aorta. The normal aorta is less than 3 cm, and the 1-year risk of rupture if the aorta is less than 4 cm is vanishingly small and can be removed from the differential diagnosis of the patient in shock; as the aorta increases in size to greater than 5.5 cm, risk of rupture rises rapidly (20). Studies show that ultrasound is sensitive and specific for the diagnosis of AAA, although it has poor sensitivity for detecting the (typically retroperitoneal) blood that accompanies a ruptured AAA (21–23). Technique
The goal of abdominal aortic ultrasound is to visualize the entire structure and 717
ATS SEMINARS
Figure 10. Subxiphoid view of pericardial effusion. The hyperechoic pericardium (Pc) is separated from the grayish myocardium (Mc) by an anechoic pericardial effusion (*), adjacent to the right ventricle (RV ). In addition, the left ventricle (LV), left atrium (LA), and right atrium (RA) are visualized.
the splenic artery to the patient’s left (Figure 16). Measure the aorta from outer wall to outer wall to capture any wall thickening or mural hematoma. Slide caudally, carefully noting the left and right renal arteries (Figure 17), and then measure the mid aorta. Recalling that most abdominal aneurysms are infrarenal (24) (Figure 18 and Video 8), slide more caudally until the bifurcation of the aorta into the left and right iliacs (Figure 19 and Video 9). Measure just proximal to the bifurcation to complete the distal aortic measurement. If the iliacs are prominent and larger in size than the parent aorta, care should be taken in their measurement as well. Finally, return to the proximal aorta with the probe marker cephalad and interrogate the aorta in long axis for aneurysmal dilations.
Right Upper Quadrant Ultrasound ensure its diameter is less than 3 cm as it tapers down through the abdomen toward the bifurcation. Interrogation of the aorta begins in the epigastrium, just below the xiphoid process, with the probe marker to the patient’s right and the probe perpendicular to the abdominal wall.
Firm downward pressure should be used to displace any bowel gas and see the abdominal aorta just superficial and to the patient’s left side of the lumbar spine. At this level, the celiac trunk can be identified as it bifurcates into the hepatic artery toward the patient’s right side and
Biliary tract disease remains an important etiology of illness for critical care patients, and ultrasound is the primary modality for diagnosing gall bladder disease. Sonographic signs of cholecystitis and choledocholithiasis are demonstrable by point-of-care ultrasound. Technique
Figure 11. Lower abdominal wall. With the linear probe held transversely in the right lower quadrant, perpendicular to the skin, note subcutaneous tissue (Sc) and rectus muscle (M), below which course the inferior epigastric artery (EpA) and vein (EpV). Deep to these, anechoic ascitic (Asc) fluid and floating loops of bowel (B) can be seen. Identification of the inferior epigastric artery and vein using color Doppler ensures their avoidance and safer needle placement during paracentesis.
718
Ultrasonography of the gall bladder should include a longitudinal as well as a transverse sweep through the gall bladder, with a focus of identifying three main pathologies: cholelithiasis, gall bladder wall thickening, and pericholecystic fluid. Eliciting a sonographic Murphy’s sign (pain elicited after localization of the gallbladder using ultrasound and then pressing directly on the gallbladder) in the alert and cooperative patient can also be useful from a diagnostic standpoint. Patients are typically imaged in the supine position using the abdominal presets and curvilinear probe. Beginning just inferior to the costal margin, the probe is placed just inferior to the xiphoid process with the index marker aimed cephalad and the ultrasound beam directed into the parenchyma of the liver. Slide the probe laterally, remaining under the costal margin, until the anechoic gall bladder is visualized. Alternatively, one
AnnalsATS Volume 10 Number 6 | December 2013
ATS SEMINARS Ultrasound can serve a useful role in diagnosing the etiology of abdominal pain, and identification of gallbladder disease may help expedite source control in the septic patient.
Pneumoperitoneum
Figure 12. Empty bladder with Foley catheter balloon. An empty bladder can be challenging to locate; however, the fluid inside the catheter balloon (Fol) enables the sonographer to locate the catheter tip.
may use the RUQ window of the FAST examination and aim the ultrasound beam anteriorly, toward the xiphoid process, rather than retroperitoneally, as in the FAST examination. When the gall bladder is located, small adjustments of rotation and fanning will allow the intensivist-sonographer to interrogate the gall bladder in both the transverse and longitudinal lies. In addition, identify the common bile duct with the aid of color Doppler as an anechoic tubular
structure with no flow, located just anterior to the portal vein. After identifying the gallbladder and common bile duct, evaluate for pathology: Are there stones (Figure 20 and Video 10) or sludge (Figure 21) in the gall bladder? Is there thickening of the anterior gall bladder wall (.3 mm) (Figure 22) or pericholecystic fluid (Figure 23) that can be found in association with cholecystitis? Is the common bile duct dilated (.4 mm) (Figure 24)?
Free air within the peritoneal cavity is expected in patients who have recently undergone intraabdominal instrumentation (which may last up to 3 wk) (25) as well as those on peritoneal dialysis (26). In critically ill patients not fitting into these categories, pneumoperitoneum is an ominous sign requiring rapid intervention. Although large trials have not been performed evaluating ultrasound as a diagnostic tool for detecting pneumoperitoneum, certain artifacts are associated with free intraperitoneal air, such as ring down artifact that changes with patient movement, enhancement of the peritoneal stripe, and echogenic free peritoneal air (27). In addition, perforation of a hollow viscus is frequently accompanied by free intraperitoneal fluid more echogenic than typically found on FAST scans of trauma patients, due to the spilled enteric contents. Particularly pertinent for the critically ill and hemodynamically unstable patient, ultrasound identification of free air will facilitate appropriate intervention, such as broad-spectrum antibiotics, fluid resuscitation, and expediting of operative care, as in several cases of perforated ulcers (27). Before identifying pathologic collections of intraperitoneal air, however, the critical care sonographer must also understand the appearance of normal collections of air, such as the lung, stomach, and bowel at baseline (28). Technique
Figure 13. Full bladder (B) with malfunctioning Foley catheter (Fol). This image demonstrates a grossly distended bladder with anechoic urine outlining the catheter balloon.
ATS Seminars
Ultrasonographic identification of free air requires close attention to minor abnormalities that may be seen on other abdominal examinations, including aortic, FAST, and gallbladder. Characteristic appearance of pathologic air within the peritoneum provides key clues to guide management of critically ill patients. These collections of air are often very superficial, and so a linear highfrequency probe can be used. In the 719
ATS SEMINARS between the liver and the abdominal wall minimizes the confounder of bowel loops and makes identification of this enhancement easier (Figure 26). In addition, a positive FAST examination with echogenic free fluid should raise the concern of hollow viscus rupture (Figure 27). Being able to identify pathologic collections of free intraperitoneal air can expedite definitive care of these critically ill patients.
Conclusions
Figure 14. Mild hydronephrosis. In mild hydronephrosis, there is some dilation of the renal pelvis (RP); however, the architecture of the kidney remains relatively undistorted such that the calyces (C) and pyramids (P) are still visualized.
supine patient, free air against the peritoneal lining will “enhance” the brightness of the peritoneal stripe, and reverberation artifact can be seen ringing
down from the peritoneal lining (Figure 25 and Video 11). Care must be taken to distinguish between air in the bowel lumen and free air. Looking
Figure 15. Severe hydronephrosis. In severe hydronephrosis, the normal renal architecture is obliterated by the massive dilation of the renal pelvis (RP) and resulting cortical (Ctx) thinning.
720
The usefulness of clinician-performed abdominal ultrasound in the critical care environment is clear (29, 30). From diagnosing intraabdominal trauma to urinary catheter malfunction, from ruling out obstructive causes of acute renal failure to evaluating the gallbladder, from evaluating the abdominal aorta to detecting pneumoperitoneum, abdominal ultrasound is a skill that can help critical care patients in a broad range of clinical scenarios. n Author disclosures are available with the text of this article at www.atsjournals.org.
Figure 16. Normal proximal transverse aorta. Note the anechoic circle of the aorta (Ao), the teardrop-shaped vena cava (IVC), and the inverted “U” of the spine shadow (SS). The celiac trunk (Cel ) bifurcating into hepatic (HA) and splenic arteries (SA) can be seen superficial to the aorta.
AnnalsATS Volume 10 Number 6 | December 2013
ATS SEMINARS
Figure 17. Normal mid aorta. The renal arteries (RA) can be seen originating from the sides of the aorta (Ao), which lies just anterior to the spine shadow (SS).
Figure 20. Cholelithiasis. Gallstones (GS) vary in size and shape and should be seen as hyperechoic material within the gallbladder (GB), with a resultant hypoechoic or anechoic shadow (Sh) below them. Gall stones may be confused with bowel gas, as it also tends to cause hyperechoic reflections to return to the probe; however, shadowing beneath bowel gas is heterogenous and of varying shades of gray. Scanning the gallbladder in both long and short axis can help prevent this error.
Figure 18. Infrarenal aortic aneurysm. This is a transverse view of an 8.5cm aorta (Ao) with a small amount of mural thrombus. SS = spine shadow.
Figure 21. Gallbladder sludge (Sludge) is hyperechoic sediment within the gallbladder. Can be seen as echogenic debris within the gallbladder or may layer in a fluid-fluid level in some cases.
Figure 19. Normal aortic bifurcation. The aortic bifurcation (Bif ) into the iliac arteries (IA) occurs approximately at the level of the umbilicus, just anterior to the spine shadow (SS).
ATS Seminars
721
ATS SEMINARS
Figure 22. Gallbladder wall thickening. The anterior gallbladder wall (GBW) should measure 3 mm or less. Thickening of the anterior gallbladder wall, taken with the clinical context of the patient, may be indicative of acute cholecystitis but may be present in other edematous states. GB = gallbladder.
Figure 23. Pericholecystic fluid (PcF). Collection of fluid around the gallbladder (GB) suggests either intraabdominal ascites, which can be verified by a Focused Assessment with Sonography for Trauma examination, or may be suggestive of gallbladder pathology, as seen in this image. A triangular, anechoic fluid collection lies just superficial to the gallbladder, which has a shadowing (Sh) stone (GS) lodged in the neck.
722
Figure 24. Dilated common bile duct (CBD). This transverse view of the portal vein with color Doppler shows flow in the portal vein and hepatic artery but not in the dilated common bile duct.
Figure 25. Free intraperitoneal air. Enhancement of the peritoneal stripe and reverberation artifact deep to the enhancement characterize free intraperitoneal air.
AnnalsATS Volume 10 Number 6 | December 2013
ATS SEMINARS
Figure 27. Echogenic free fluid (FF). Note the free fluid in Morison’s pouch with increased echogenicity of the fluid, suggestive of hollow viscus rupture. K = kidney; L = liver. Figure 26. Free intraperitoneal air between liver and abdominal wall. On left of image, the bright horizontal line of the enhanced peritoneal stripe is air collecting on the inside of the peritoneum, creating reverberation artifact. To the right of the image is the unenhanced peritoneal lining and the edge of the liver.
References 1 Thomas B, Falcone RE, Vasquez D, Santanello S, Townsend M, Hockenberry S, Innes J, Wanamaker S. Ultrasound evaluation of blunt abdominal trauma: program implementation, initial experience, and learning curve. J Trauma 1997;42:384–388, discussion 388–390. 2 Ma OJ, Gaddis G, Norvell JG, Subramanian S. How fast is the focused assessment with sonography for trauma examination learning curve? Emerg Med Australas 2008;20:32–37. 3 Jang T, Kryder G, Sineff S, Naunheim R, Aubin C, Kaji AH. The technical errors of physicians learning to perform focused assessment with sonography in trauma. Acad Emerg Med 2012;19: 98–101. 4 Kristensen JK, Buemann B, Kuhl ¨ E. Ultrasonic scanning in the diagnosis of splenic haematomas. Acta Chir Scand 1971;137: 653–657. 5 American College of Surgeons Committee on Trauma. Advanced Trauma Life Support for Doctors, 8th ed. Chicago: American College of Surgeons; 2008. p. 117. 6 Wilkerson RG, Stone MB. Sensitivity of bedside ultrasound and supine anteroposterior chest radiographs for the identification of pneumothorax after blunt trauma. Acad Emerg Med 2010;17:11–17. 7 Nandipati KC, Allamaneni S, Kakarla R, Wong A, Richards N, Satterfield J, Turner JW, Sung KJ. Extended focused assessment with sonography for trauma (EFAST) in the diagnosis of pneumothorax: experience at a community based level I trauma center. Injury 2011;42:511–514. 8 Kirkpatrick AW, Sirois M, Laupland KB, Liu D, Rowan K, Ball CG, Hameed SM, Brown R, Simons R, Dulchavsky SA, et al. Hand-held thoracic sonography for detecting post-traumatic pneumothoraces: the Extended Focused Assessment with Sonography for Trauma (EFAST). J Trauma 2004;57:288–295.
ATS Seminars
9 Rose JS, Bair AE, Mandavia D, Kinser DJ. The UHP ultrasound protocol: a novel ultrasound approach to the empiric evaluation of the undifferentiated hypotensive patient. Am J Emerg Med 2001;19: 299–302. 10 Bahner DP. Trinity: a hypotensive ultrasound protocol. J Diagn Med Sonogr 2002;18:193–198. 11 Atkinson PRT, McAuley DJ, Kendall RJ, Abeyakoon O, Reid CG, Connolly J, Lewis D. Abdominal and Cardiac Evaluation with Sonography in Shock (ACES): an approach by emergency physicians for the use of ultrasound in patients with undifferentiated hypotension. Emerg Med J 2009;26:87–91. 12 Perera P, Mailhot T, Riley D, Mandavia D. The RUSH exam: Rapid Ultrasound in SHock in the evaluation of the critically ill. Emerg Med Clin North Am 2010;28:29–56, vii. 13 Jones AE, Tayal VS, Sullivan DM, Kline JA. Randomized, controlled trial of immediate versus delayed goal-directed ultrasound to identify the cause of nontraumatic hypotension in emergency department patients. Crit Care Med 2004;32:1703–1708. 14 Shokoohi H, Boniface KS, Siegel A. Horizontal subxiphoid landmark optimizes probe placement during the Focused Assessment with Sonography for Trauma ultrasound exam. Eur J Emerg Med 2012; 19:333–337. 15 Abrams BJ, Sukumvanich P, Seibel R, Moscati R, Jehle D. Ultrasound for the detection of intraperitoneal fluid: the role of Trendelenburg positioning. Am J Emerg Med 1999;17:117–120. 16 Patel PA, Ernst FR, Gunnarsson CL. Evaluation of hospital complications and costs associated with using ultrasound guidance during abdominal paracentesis procedures. J Media Econ 2012;15:1–7. 17 Nazeer SR, Dewbre H, Miller AH. Ultrasound-assisted paracentesis performed by emergency physicians vs the traditional technique: a prospective, randomized study. Am J Emerg Med 2005;23: 363–367.
723
ATS SEMINARS 18 American Institute of Ultrasound in Medicine. AIUM practice guideline for the performance of an ultrasound examination of the abdomen and/or retroperitoneum. J Ultrasound Med 2008;27:319–326. 19 Perera P, Mailhot T, Riley D, Mandavia D. The RUSH exam 2012: rapid ultrasound in shock in the evaluation of the critically ill patient. Ultrasound Clin 2012;7:255–278. 20 Brewster DC, Cronenwett JL, Hallett JW Jr, Johnston KW, Krupski WC, Matsumura JS; Joint Council of the American Association for Vascular Surgery and Society for Vascular Surgery. Guidelines for the treatment of abdominal aortic aneurysms. Report of a subcommittee of the Joint Council of the American Association for Vascular Surgery and Society for Vascular Surgery. J Vasc Surg 2003;37:1106–1117. 21 Rubano E, Mehta N, Caputo W, Paladino L, Sinert R. Systematic review: emergency department bedside ultrasonography for diagnosing suspected abdominal aortic aneurysm. Acad Emerg Med 2013;20:128–138. 22 Shuman WP, Hastrup WH Jr, Kohler TR, Nyberg DA, Wang KY, Vincent LM, Mack LA. Suspected leaking abdominal aortic aneurysm: use of sonography in the emergency room. Radiology 1988;168:117–119. 23 Tayal VS, Graf CD, Gibbs MA. Prospective study of accuracy and outcome of emergency ultrasound for abdominal
724
24 25
26. 27
28
29 30
aortic aneurysm over two years. Acad Emerg Med 2003;10: 867–871. Barkin AZ, Rosen CL. Ultrasound detection of abdominal aortic aneurysm. Emerg Med Clin North Am 2004;22:675–682. Gayer G, Hertz M, Zissin R. Postoperative pneumoperitoneum: prevalence, duration, and possible significance. Semin Ultrasound CT MR 2004;25:286–289. Chang JJ, Yeun JY, Hasbargen JA. Pneumoperitoneum in peritoneal dialysis patients. Am J Kidney Dis 1995;25:299–301. Jones R. Recognition of pneumoperitoneum using bedside ultrasound in critically ill patients presenting with acute abdominal pain. Am J Emerg Med 2007;25:838–841. Hoffmann B, Nurnberg ¨ D, Westergaard MC. Focus on abnormal air: diagnostic ultrasonography for the acute abdomen. Eur J Emerg Med 2012;19:284–291. Neri L, Storti E, Lichtenstein D. Toward an ultrasound curriculum for critical care medicine. Crit Care Med 2007;35:S290–304. Mayo PH, Beaulieu Y, Doelken P, Feller-Kopman D, Harrod C, Kaplan A, Oropello J, Vieillard-Baron A, Axler O, Lichtenstein D, et al. American College of Chest Physicians/La Societ ´ e´ de Reanimation ´ de Langue Française statement on competence in critical care ultrasonography. Chest 2009;135:1050–1060.
AnnalsATS Volume 10 Number 6 | December 2013
Intensive Care Ultrasound: IV. Abdominal Ultrasound in Critical Care Keith S. Boniface1 and Kathleen Y. Calabrese1 1
Department of Emergency Medicine, George Washington University Medical Center, Washington, DC
Ultrasound in critical care is distinct from ultrasound performed in radiology. Radiology-performed ultrasound is a comprehensive, anatomical examination that seeks to fully describe the area undergoing investigation. Clinicianperformed ultrasound performed at the bedside of the critically ill patient aims to answer a focused clinical question: Is the systolic function of the heart normal? Is there a deep vein thrombosis? Is there a pneumothorax? As a result, the learning curve for performance of these focused evaluations is much shorter and steeper than it is for more comprehensive examinations (1–3). Intensivistperformed abdominal ultrasound focuses on detecting the presence of intraabdominal fluid, obstructive changes of the kidneys and bladder, acute pathology of the gallbladder, and intraabdominal catastrophes. The examinations that follow use a low frequency (1–5 MHz) curvilinear or phased array transducer, with the orientation mark to the left side of the screen.
pericardial spaces. The use of ultrasound in trauma evaluation dates back over 40 years in Europe and Asia (4), became widely adopted in the United States throughout the 1990s, and has become a standard part of the evaluation of the traumatized patient (5). The extended FAST examination, or “eFAST,” includes views of the thorax to evaluate for pleural fluid, discussed below, and the anterior pleural– pleural interface to assess for pneumothorax (6–8), discussed elsewhere in this series of articles. Its use has expanded beyond the trauma bay, however, and the FAST examination is now an integral part of
many different ultrasound protocols that aim to identify the cause of shock in hypotensive patients (9–12). In a randomized, prospective trial, the immediate use of an ultrasound protocol including FAST examination, focused echocardiography, and views of the inferior vena cava led to a shorter list of potential diagnoses and a higher likelihood at the bedside of a hypotensive patient of selecting the correct diagnosis from this list, compared with delayed ultrasound (13). The FAST examination can show signs of aneurysm rupture, bleeding from ectopic pregnancy, postoperative complications, hollow viscus perforation,
Focused Assessment with Sonography for Trauma The Focused Assessment with Sonography for Trauma, or FAST examination, is a protocolized examination that seeks to identify fluid in the peritoneal and
Figure 1. Normal right upper quadrant. In this image, the probe marker is seen on the left side oriented cephalad. Note the hyperechoic curved diaphragm (arrow), the relatively homogenous appearance of the liver (L), then the hypoechoic kidney (K) toward the right of the screen (caudad).
(Received in original form September 25, 2013; accepted in final form November 1, 2013 ) This article has associated videos, which are accessible at www.atsjournals.org/doi/full/10.1513/AnnalsATS.201306-324OT. If you cannot view Flash videos on your device, please access original videos at www.atsjournals.org/doi/suppl/10.1513/AnnalsATS.201306-324OT. Correspondence and requests for reprints should be addressed to Keith S. Boniface, 2120 L Street NW, Suite 450, Washington, DC 20037. E-mail: [email protected] Ann Am Thorac Soc Vol 10, No 6, pp 713–724, Dec 2013 Copyright © 2013 by the American Thoracic Society Originally published in Press as DOI: 10.1513/AnnalsATS.201309-324OT Internet address: www.atsjournals.org
ATS Seminars
713
ATS SEMINARS
Figure 2. Free fluid (FF) in the right upper quadrant. Note the curved diaphragm (arrow) to the left of the liver (L); caudal (right) to the liver and superficial to the kidney (K) there is an anechoic, triangular collection of fluid.
and inflammatory processes, all of which can cause intraabdominal free fluid in the absence of trauma. The FAST examination is composed of four views. The first three views use acoustic windows in the right upper quadrant (RUQ), left upper quadrant (LUQ), and suprapubic regions (liver, spleen, and bladder). These windows serve to conduct the sound wave to the three most dependent areas of the peritoneal cavity in the supine patient as well as to the costophrenic angles bilaterally of the pleural space when performing the eFAST.
The fourth view provides a view of the pericardium, typically obtained from the subxiphoid approach. The order of obtaining these views is not as important as systematically evaluating each quadrant for pathology.
Technique Right Upper Quadrant
The abdominal examination presets are chosen on the ultrasound machine for this examination. The external landmark
Figure 3. Free fluid (FF) in the right upper quadrant. At times, fluid collects only near the inferior pole of the right kidney (K), necessitating a full interrogation not only of Morison’s pouch at the juncture of the liver and kidney but also a caudal evaluation including the paracolic gutter at the lower pole (lp) of the right kidney (K).
714
for probe placement to obtain the two upper quadrant views is the xiphoid process (14). If a horizontal line is drawn at the level of the xiphoid, the probe can then be placed at the point where that horizontal subxiphoid line intersects with the right midaxillary line, with the index mark on the probe oriented toward the patient’s head and the probe aimed slightly posteriorly. This will provide a coronal view of the liver, the right kidney, the potential space of Morison’s pouch, the diaphragm, and a small area cephalad to the diaphragm (Figure 1). Fluid in the RUQ typically shows up as a hypoechoic band of black that tracks between the kidney and the liver (Figure 2). Continuing to scan a rib space or two inferiorly to visualize the lower pole of the kidney is recommended, to assess for more subtle fluid collections that do not track between the kidney and the liver. (Figure 3 and Video 1).
Left Upper Quadrant
In the left upper quadrant, the spleen provides the acoustic window and is smaller and more posteriorly located than the liver in the RUQ. To obtain the LUQ view, the probe is placed at the intersection of the horizontal subxiphoid line and the posterior axillary line, with the index mark on the probe oriented toward the patient’s head and the probe aimed slightly posteriorly. This provides a coronal view of the spleen, the left kidney, the potential space between spleen and kidney, the diaphragm, and a small area cephalad to the diaphragm (Figure 4). It can be helpful to rotate the probe obliquely, given that the kidneys lie in an oblique orientation to the coronal plane. Fluid in the LUQ does not necessarily confine itself to the splenorenal space but can be found in the subphrenic region as well as laterally to the spleen, so it is essential to scan through the entire LUQ by “fanning” anteriorly and posteriorly as well as from the interface between diaphragm and spleen to the inferior pole of the kidney (Figure 5 and Video 2). Troubleshooting of image acquisition for the upper quadrant view is guided by the structures that are visualized—if spleen or liver is seen but not the kidney, the
AnnalsATS Volume 10 Number 6 | December 2013
ATS SEMINARS
Figure 4. Normal left upper quadrant. As in the right upper quadrant, the probe marker is oriented cephalad. The diaphragm (arrow) is hyperechoic, the spleen (S) is relatively homogenous, and the kidney (K) lies more posteriorly and superiorly than the right kidney.
beam can be angled posteriorly to identify the kidney, located retroperitoneally. If only the lower pole of the kidney is seen, then sliding the probe an interspace or two toward the patient’s head will allow for identification of the spleen/kidney or liver/kidney interface. Mirror Image
The LUQ and RUQ views should include a view of the diaphragm. The lung lies just above and adjacent to the diaphragm, and in the normal patient, due to the highly
reflective diaphragm and the air-filled lung, this area just cephalad to the diaphragm will take on the appearance of the spleen or liver—the “mirror-image artifact” (Figure 6 and Video 3). This artifact serves to rule out fluid in the pleural space. Pleural fluid (whether effusion or blood) will appear as an anechoic triangle cephalad to the diaphragm (Figure 7 and Video 4). Pelvic View
The third view of the FAST examination is the pelvic view. To obtain this view,
Figure 5. Free fluid (FF) in the left upper quadrant (LUQ). Free fluid can be found anywhere in the LUQ, including between the diaphragm (arrow) and the spleen (S), as well as between the spleen and kidney (K), as in this case.
ATS Seminars
the probe is placed in the midline just superior to the pubic symphysis. Long axis views can be obtained by placing the index mark toward the patient’s head, and short axis views are obtained with the index mark toward the patient’s right side. The gain may need to be decreased because of the fluid-filled bladder’s increased through-transmission of ultrasound; otherwise, the bright reflections from behind the bladder could mask small pockets of fluid. Depth should be adjusted such that the bladder, seen as the central ovoid hypoechoic structure, occupies less than one-half of the screen depth, to allow for the identification of free fluid deep to the bladder and deep to the uterus posterior to the bladder in women (pouch of Douglas). Fluid can be also found lateral to the bladder wall, where it can be readily identified when the hyperechoic bladder wall is sandwiched between anechoic urine inside and anechoic free fluid outside of the bladder (Figure 8).
Subxiphoid
The fourth and final view of the FAST examination is the subxiphoid view of the heart. Using the abdominal presets, the index mark is placed toward the patient’s right side and the probe is held in an overhand grip and angled under the xiphoid process and pointed toward the patient’s head. The probe needs to be held quite flat to aim the beam up underneath the sternum and obtain a coronal view of the heart. The right ventricle forms the majority of the heart’s border with the liver. The normal heart will have the brightly echogenic pericardium directly adjacent to the less echogenic myocardium (Figure 9 and Video 5). Pericardial fluid will be demonstrated as a hypoechoic to anechoic stripe of fluid between the white pericardium and the gray myocardium (Figure 10 and Video 6). If adequate images are difficult to obtain, the acoustic window can often be improved by a combination of three maneuvers: (1) having the patient take a deep breath, to use the diaphragm to pull the heart closer to the probe; (2) sliding the probe to the patient’s right side along the costal margin by the distance of one or two probe widths, to use a larger wedge of 715
ATS SEMINARS Ascites and Paracentesis
Figure 6. Mirror-image artifact. Note the similar appearance of the liver (L) both above and below the diaphragm. This is due to the highly reflective diaphragm (arrow), with a wall of air-filled lungs behind. The presence of the mirror image artifact (mirror) serves to rule out a pleural fluid collection. In this image, there is also free fluid (FF) between the kidney and spleen.
liver as an acoustic window and to avoid the air-filled gastric bubble; and (3) bending the patient’s legs, to relax abdominal wall musculature. Limitations
The main limitation to the FAST examination is the fact that a very small amount of intraabdominal bleeding may not be demonstrated on ultrasound examination. As a result, providers should have a very low threshold to repeat an initially negative FAST examination,
especially if the patient’s clinical status deteriorates. Placing the patient in Trendelenburg position may increase the sensitivity of the FAST examination in the RUQ view (15). There are many fewer false-positive examinations, but it should be mentioned that intraabdominal blood can look identical to ascites or even urine (in the setting of intraperitoneal bladder rupture), and if there is diagnostic uncertainty about what type of fluid is causing a positive FAST examination, a small-volume diagnostic paracentesis can be helpful.
Paracentesis is an important tool in the evaluation of the patient with liver disease. Although paracentesis is not a high-morbidity procedure, there is evidence supporting a decrease in complications as well as overall cost with the use of ultrasound guidance (16). Ultrasound confirms the clinical suspicion that intraabdominal fluid exists and facilitates aspiration of fluid while avoiding nearby structures, such as bowel, or vasculature, such as the inferior epigastric artery and vein (Figure 11 and Video 7). If there is suspicion of ascites but the clinical examination is not definitive, the FAST examination of the supine patient is ideal for the confirmation of peritoneal fluid. If fluid is identified, the needle can be guided to the deepest pocket; if no fluid is seen, an unnecessary procedure can be avoided. If using ultrasound to guide the needle in real time, a high-frequency linear transducer is ideal. In a randomized trial of landmark compared with ultrasoundguided paracentesis, 95% of patients with ascites were successfully drained under ultrasound guidance. Twenty-five percent of the patients randomized to ultrasound-guided paracentesis were ultimately spared the procedure due to lack of aspirable fluid. Furthermore, landmark-based paracentesis failed in 39% of patients, and 76% of patients with these failed procedures subsequently had a successful paracentesis using ultrasound (17).
Kidney and Bladder Ultrasound
Figure 7. Pleural fluid. In this right upper quadrant view, the curved hyperechoic diaphragm (arrow) is seen along with liver (L) and kidney (K), but black anechoic fluid is now seen where the mirror image artifact is expected, indicating a pleural effusion (Eff ).
716
The renal system is well visualized with ultrasound, and renal sonography can be used in a number of scenarios, from troubleshooting urinary catheter problems to identifying hydronephrosis. These questions can be answered quickly at the bedside of the patient, enabling the critical care practitioner to mobilize appropriate interventional strategies to improve patient outcomes. In the patient with decreased urine output through their urinary catheter, the central question is whether the bladder is empty (renal problem) or full (catheter
AnnalsATS Volume 10 Number 6 | December 2013
ATS SEMINARS Technique
Figure 8. Free fluid in the pelvis. In the sagittal view of the pelvis, free fluid (FF) can be found adjacent to the bladder (B), as seen in this image as an anechoic triangle, or it can also be seen in retrovesicular space (RvS).
problem). The empty bladder with functioning catheter is difficult to visualize, and the anechoic fluid-filled balloon is the only portion visible (Figure 12). In the patient with decreased urine output due to catheter malfunction, a distended anechoic bladder will be visualized (Figure 13). Most point-of-care ultrasound machines have calculation packages to estimate bladder volume, although this degree of precision is not often necessary.
In the patient with acute renal failure, a point-of-care ultrasound can serve to eliminate obstructive postrenal causes of renal failure. The normal kidney has a hyperechoic medulla and relatively hypoechoic cortex. With increasing degrees of obstruction, the collecting system will begin to dilate, extending up into the minor and major calyces and eventually thinning the cortex of the kidney. This can be graded from mild (Figure 14) to severe (Figure 15).
Figure 9. Normal subxiphoid view. In this view, the liver functions as the acoustic window—note its location at the top of the image. The hyperechoic pericardium (Pc) abuts against the grayish myocardium (Mc) of the right ventricle (RV), and the potential pericardial space lies between these two structures. In addition, the left ventricle (LV), left atrium (LA), and right atrium (RA) are visualized.
ATS Seminars
Renal ultrasound should include transverse and longitudinal views of both kidneys as well as the bladder (18). A low-frequency abdominal transducer should be used with either abdominal or the renal presets. The external landmarks for scanning the kidneys are similar to those for the FAST examination described above, or a rib interspace or two caudad, and the liver and spleen are again used as acoustic windows. Care should be taken to fan the probe anteriorly and posteriorly through each kidney, assessing for dilation of the collecting system. If any anechoic areas are noted, color Doppler should be applied to ensure that it is not a vascular structure—hydronephrosis should not enhance with color Doppler. The probe is then rotated 90 degrees counterclockwise, and another fanning sweep is completed from the superior to the inferior poles. Finally, longitudinal and transverse sweeps through the bladder are performed.
Abdominal Aortic Ultrasound Every critical care practitioner should also be facile with ultrasound evaluation of the abdominal aorta, as a ruptured abdominal aortic aneurysm (AAA) can be catastrophic. Its evaluation should be considered in the undifferentiated hypotensive patient (19) and may be considered in the patient with unilateral hydronephrosis, back pain, or abdominal pain. The risk of rupture of AAA is directly correlated with diameter of the aorta. The normal aorta is less than 3 cm, and the 1-year risk of rupture if the aorta is less than 4 cm is vanishingly small and can be removed from the differential diagnosis of the patient in shock; as the aorta increases in size to greater than 5.5 cm, risk of rupture rises rapidly (20). Studies show that ultrasound is sensitive and specific for the diagnosis of AAA, although it has poor sensitivity for detecting the (typically retroperitoneal) blood that accompanies a ruptured AAA (21–23). Technique
The goal of abdominal aortic ultrasound is to visualize the entire structure and 717
ATS SEMINARS
Figure 10. Subxiphoid view of pericardial effusion. The hyperechoic pericardium (Pc) is separated from the grayish myocardium (Mc) by an anechoic pericardial effusion (*), adjacent to the right ventricle (RV ). In addition, the left ventricle (LV), left atrium (LA), and right atrium (RA) are visualized.
the splenic artery to the patient’s left (Figure 16). Measure the aorta from outer wall to outer wall to capture any wall thickening or mural hematoma. Slide caudally, carefully noting the left and right renal arteries (Figure 17), and then measure the mid aorta. Recalling that most abdominal aneurysms are infrarenal (24) (Figure 18 and Video 8), slide more caudally until the bifurcation of the aorta into the left and right iliacs (Figure 19 and Video 9). Measure just proximal to the bifurcation to complete the distal aortic measurement. If the iliacs are prominent and larger in size than the parent aorta, care should be taken in their measurement as well. Finally, return to the proximal aorta with the probe marker cephalad and interrogate the aorta in long axis for aneurysmal dilations.
Right Upper Quadrant Ultrasound ensure its diameter is less than 3 cm as it tapers down through the abdomen toward the bifurcation. Interrogation of the aorta begins in the epigastrium, just below the xiphoid process, with the probe marker to the patient’s right and the probe perpendicular to the abdominal wall.
Firm downward pressure should be used to displace any bowel gas and see the abdominal aorta just superficial and to the patient’s left side of the lumbar spine. At this level, the celiac trunk can be identified as it bifurcates into the hepatic artery toward the patient’s right side and
Biliary tract disease remains an important etiology of illness for critical care patients, and ultrasound is the primary modality for diagnosing gall bladder disease. Sonographic signs of cholecystitis and choledocholithiasis are demonstrable by point-of-care ultrasound. Technique
Figure 11. Lower abdominal wall. With the linear probe held transversely in the right lower quadrant, perpendicular to the skin, note subcutaneous tissue (Sc) and rectus muscle (M), below which course the inferior epigastric artery (EpA) and vein (EpV). Deep to these, anechoic ascitic (Asc) fluid and floating loops of bowel (B) can be seen. Identification of the inferior epigastric artery and vein using color Doppler ensures their avoidance and safer needle placement during paracentesis.
718
Ultrasonography of the gall bladder should include a longitudinal as well as a transverse sweep through the gall bladder, with a focus of identifying three main pathologies: cholelithiasis, gall bladder wall thickening, and pericholecystic fluid. Eliciting a sonographic Murphy’s sign (pain elicited after localization of the gallbladder using ultrasound and then pressing directly on the gallbladder) in the alert and cooperative patient can also be useful from a diagnostic standpoint. Patients are typically imaged in the supine position using the abdominal presets and curvilinear probe. Beginning just inferior to the costal margin, the probe is placed just inferior to the xiphoid process with the index marker aimed cephalad and the ultrasound beam directed into the parenchyma of the liver. Slide the probe laterally, remaining under the costal margin, until the anechoic gall bladder is visualized. Alternatively, one
AnnalsATS Volume 10 Number 6 | December 2013
ATS SEMINARS Ultrasound can serve a useful role in diagnosing the etiology of abdominal pain, and identification of gallbladder disease may help expedite source control in the septic patient.
Pneumoperitoneum
Figure 12. Empty bladder with Foley catheter balloon. An empty bladder can be challenging to locate; however, the fluid inside the catheter balloon (Fol) enables the sonographer to locate the catheter tip.
may use the RUQ window of the FAST examination and aim the ultrasound beam anteriorly, toward the xiphoid process, rather than retroperitoneally, as in the FAST examination. When the gall bladder is located, small adjustments of rotation and fanning will allow the intensivist-sonographer to interrogate the gall bladder in both the transverse and longitudinal lies. In addition, identify the common bile duct with the aid of color Doppler as an anechoic tubular
structure with no flow, located just anterior to the portal vein. After identifying the gallbladder and common bile duct, evaluate for pathology: Are there stones (Figure 20 and Video 10) or sludge (Figure 21) in the gall bladder? Is there thickening of the anterior gall bladder wall (.3 mm) (Figure 22) or pericholecystic fluid (Figure 23) that can be found in association with cholecystitis? Is the common bile duct dilated (.4 mm) (Figure 24)?
Free air within the peritoneal cavity is expected in patients who have recently undergone intraabdominal instrumentation (which may last up to 3 wk) (25) as well as those on peritoneal dialysis (26). In critically ill patients not fitting into these categories, pneumoperitoneum is an ominous sign requiring rapid intervention. Although large trials have not been performed evaluating ultrasound as a diagnostic tool for detecting pneumoperitoneum, certain artifacts are associated with free intraperitoneal air, such as ring down artifact that changes with patient movement, enhancement of the peritoneal stripe, and echogenic free peritoneal air (27). In addition, perforation of a hollow viscus is frequently accompanied by free intraperitoneal fluid more echogenic than typically found on FAST scans of trauma patients, due to the spilled enteric contents. Particularly pertinent for the critically ill and hemodynamically unstable patient, ultrasound identification of free air will facilitate appropriate intervention, such as broad-spectrum antibiotics, fluid resuscitation, and expediting of operative care, as in several cases of perforated ulcers (27). Before identifying pathologic collections of intraperitoneal air, however, the critical care sonographer must also understand the appearance of normal collections of air, such as the lung, stomach, and bowel at baseline (28). Technique
Figure 13. Full bladder (B) with malfunctioning Foley catheter (Fol). This image demonstrates a grossly distended bladder with anechoic urine outlining the catheter balloon.
ATS Seminars
Ultrasonographic identification of free air requires close attention to minor abnormalities that may be seen on other abdominal examinations, including aortic, FAST, and gallbladder. Characteristic appearance of pathologic air within the peritoneum provides key clues to guide management of critically ill patients. These collections of air are often very superficial, and so a linear highfrequency probe can be used. In the 719
ATS SEMINARS between the liver and the abdominal wall minimizes the confounder of bowel loops and makes identification of this enhancement easier (Figure 26). In addition, a positive FAST examination with echogenic free fluid should raise the concern of hollow viscus rupture (Figure 27). Being able to identify pathologic collections of free intraperitoneal air can expedite definitive care of these critically ill patients.
Conclusions
Figure 14. Mild hydronephrosis. In mild hydronephrosis, there is some dilation of the renal pelvis (RP); however, the architecture of the kidney remains relatively undistorted such that the calyces (C) and pyramids (P) are still visualized.
supine patient, free air against the peritoneal lining will “enhance” the brightness of the peritoneal stripe, and reverberation artifact can be seen ringing
down from the peritoneal lining (Figure 25 and Video 11). Care must be taken to distinguish between air in the bowel lumen and free air. Looking
Figure 15. Severe hydronephrosis. In severe hydronephrosis, the normal renal architecture is obliterated by the massive dilation of the renal pelvis (RP) and resulting cortical (Ctx) thinning.
720
The usefulness of clinician-performed abdominal ultrasound in the critical care environment is clear (29, 30). From diagnosing intraabdominal trauma to urinary catheter malfunction, from ruling out obstructive causes of acute renal failure to evaluating the gallbladder, from evaluating the abdominal aorta to detecting pneumoperitoneum, abdominal ultrasound is a skill that can help critical care patients in a broad range of clinical scenarios. n Author disclosures are available with the text of this article at www.atsjournals.org.
Figure 16. Normal proximal transverse aorta. Note the anechoic circle of the aorta (Ao), the teardrop-shaped vena cava (IVC), and the inverted “U” of the spine shadow (SS). The celiac trunk (Cel ) bifurcating into hepatic (HA) and splenic arteries (SA) can be seen superficial to the aorta.
AnnalsATS Volume 10 Number 6 | December 2013
ATS SEMINARS
Figure 17. Normal mid aorta. The renal arteries (RA) can be seen originating from the sides of the aorta (Ao), which lies just anterior to the spine shadow (SS).
Figure 20. Cholelithiasis. Gallstones (GS) vary in size and shape and should be seen as hyperechoic material within the gallbladder (GB), with a resultant hypoechoic or anechoic shadow (Sh) below them. Gall stones may be confused with bowel gas, as it also tends to cause hyperechoic reflections to return to the probe; however, shadowing beneath bowel gas is heterogenous and of varying shades of gray. Scanning the gallbladder in both long and short axis can help prevent this error.
Figure 18. Infrarenal aortic aneurysm. This is a transverse view of an 8.5cm aorta (Ao) with a small amount of mural thrombus. SS = spine shadow.
Figure 21. Gallbladder sludge (Sludge) is hyperechoic sediment within the gallbladder. Can be seen as echogenic debris within the gallbladder or may layer in a fluid-fluid level in some cases.
Figure 19. Normal aortic bifurcation. The aortic bifurcation (Bif ) into the iliac arteries (IA) occurs approximately at the level of the umbilicus, just anterior to the spine shadow (SS).
ATS Seminars
721
ATS SEMINARS
Figure 22. Gallbladder wall thickening. The anterior gallbladder wall (GBW) should measure 3 mm or less. Thickening of the anterior gallbladder wall, taken with the clinical context of the patient, may be indicative of acute cholecystitis but may be present in other edematous states. GB = gallbladder.
Figure 23. Pericholecystic fluid (PcF). Collection of fluid around the gallbladder (GB) suggests either intraabdominal ascites, which can be verified by a Focused Assessment with Sonography for Trauma examination, or may be suggestive of gallbladder pathology, as seen in this image. A triangular, anechoic fluid collection lies just superficial to the gallbladder, which has a shadowing (Sh) stone (GS) lodged in the neck.
722
Figure 24. Dilated common bile duct (CBD). This transverse view of the portal vein with color Doppler shows flow in the portal vein and hepatic artery but not in the dilated common bile duct.
Figure 25. Free intraperitoneal air. Enhancement of the peritoneal stripe and reverberation artifact deep to the enhancement characterize free intraperitoneal air.
AnnalsATS Volume 10 Number 6 | December 2013
ATS SEMINARS
Figure 27. Echogenic free fluid (FF). Note the free fluid in Morison’s pouch with increased echogenicity of the fluid, suggestive of hollow viscus rupture. K = kidney; L = liver. Figure 26. Free intraperitoneal air between liver and abdominal wall. On left of image, the bright horizontal line of the enhanced peritoneal stripe is air collecting on the inside of the peritoneum, creating reverberation artifact. To the right of the image is the unenhanced peritoneal lining and the edge of the liver.
References 1 Thomas B, Falcone RE, Vasquez D, Santanello S, Townsend M, Hockenberry S, Innes J, Wanamaker S. Ultrasound evaluation of blunt abdominal trauma: program implementation, initial experience, and learning curve. J Trauma 1997;42:384–388, discussion 388–390. 2 Ma OJ, Gaddis G, Norvell JG, Subramanian S. How fast is the focused assessment with sonography for trauma examination learning curve? Emerg Med Australas 2008;20:32–37. 3 Jang T, Kryder G, Sineff S, Naunheim R, Aubin C, Kaji AH. The technical errors of physicians learning to perform focused assessment with sonography in trauma. Acad Emerg Med 2012;19: 98–101. 4 Kristensen JK, Buemann B, Kuhl ¨ E. Ultrasonic scanning in the diagnosis of splenic haematomas. Acta Chir Scand 1971;137: 653–657. 5 American College of Surgeons Committee on Trauma. Advanced Trauma Life Support for Doctors, 8th ed. Chicago: American College of Surgeons; 2008. p. 117. 6 Wilkerson RG, Stone MB. Sensitivity of bedside ultrasound and supine anteroposterior chest radiographs for the identification of pneumothorax after blunt trauma. Acad Emerg Med 2010;17:11–17. 7 Nandipati KC, Allamaneni S, Kakarla R, Wong A, Richards N, Satterfield J, Turner JW, Sung KJ. Extended focused assessment with sonography for trauma (EFAST) in the diagnosis of pneumothorax: experience at a community based level I trauma center. Injury 2011;42:511–514. 8 Kirkpatrick AW, Sirois M, Laupland KB, Liu D, Rowan K, Ball CG, Hameed SM, Brown R, Simons R, Dulchavsky SA, et al. Hand-held thoracic sonography for detecting post-traumatic pneumothoraces: the Extended Focused Assessment with Sonography for Trauma (EFAST). J Trauma 2004;57:288–295.
ATS Seminars
9 Rose JS, Bair AE, Mandavia D, Kinser DJ. The UHP ultrasound protocol: a novel ultrasound approach to the empiric evaluation of the undifferentiated hypotensive patient. Am J Emerg Med 2001;19: 299–302. 10 Bahner DP. Trinity: a hypotensive ultrasound protocol. J Diagn Med Sonogr 2002;18:193–198. 11 Atkinson PRT, McAuley DJ, Kendall RJ, Abeyakoon O, Reid CG, Connolly J, Lewis D. Abdominal and Cardiac Evaluation with Sonography in Shock (ACES): an approach by emergency physicians for the use of ultrasound in patients with undifferentiated hypotension. Emerg Med J 2009;26:87–91. 12 Perera P, Mailhot T, Riley D, Mandavia D. The RUSH exam: Rapid Ultrasound in SHock in the evaluation of the critically ill. Emerg Med Clin North Am 2010;28:29–56, vii. 13 Jones AE, Tayal VS, Sullivan DM, Kline JA. Randomized, controlled trial of immediate versus delayed goal-directed ultrasound to identify the cause of nontraumatic hypotension in emergency department patients. Crit Care Med 2004;32:1703–1708. 14 Shokoohi H, Boniface KS, Siegel A. Horizontal subxiphoid landmark optimizes probe placement during the Focused Assessment with Sonography for Trauma ultrasound exam. Eur J Emerg Med 2012; 19:333–337. 15 Abrams BJ, Sukumvanich P, Seibel R, Moscati R, Jehle D. Ultrasound for the detection of intraperitoneal fluid: the role of Trendelenburg positioning. Am J Emerg Med 1999;17:117–120. 16 Patel PA, Ernst FR, Gunnarsson CL. Evaluation of hospital complications and costs associated with using ultrasound guidance during abdominal paracentesis procedures. J Media Econ 2012;15:1–7. 17 Nazeer SR, Dewbre H, Miller AH. Ultrasound-assisted paracentesis performed by emergency physicians vs the traditional technique: a prospective, randomized study. Am J Emerg Med 2005;23: 363–367.
723
ATS SEMINARS 18 American Institute of Ultrasound in Medicine. AIUM practice guideline for the performance of an ultrasound examination of the abdomen and/or retroperitoneum. J Ultrasound Med 2008;27:319–326. 19 Perera P, Mailhot T, Riley D, Mandavia D. The RUSH exam 2012: rapid ultrasound in shock in the evaluation of the critically ill patient. Ultrasound Clin 2012;7:255–278. 20 Brewster DC, Cronenwett JL, Hallett JW Jr, Johnston KW, Krupski WC, Matsumura JS; Joint Council of the American Association for Vascular Surgery and Society for Vascular Surgery. Guidelines for the treatment of abdominal aortic aneurysms. Report of a subcommittee of the Joint Council of the American Association for Vascular Surgery and Society for Vascular Surgery. J Vasc Surg 2003;37:1106–1117. 21 Rubano E, Mehta N, Caputo W, Paladino L, Sinert R. Systematic review: emergency department bedside ultrasonography for diagnosing suspected abdominal aortic aneurysm. Acad Emerg Med 2013;20:128–138. 22 Shuman WP, Hastrup WH Jr, Kohler TR, Nyberg DA, Wang KY, Vincent LM, Mack LA. Suspected leaking abdominal aortic aneurysm: use of sonography in the emergency room. Radiology 1988;168:117–119. 23 Tayal VS, Graf CD, Gibbs MA. Prospective study of accuracy and outcome of emergency ultrasound for abdominal
724
24 25
26. 27
28
29 30
aortic aneurysm over two years. Acad Emerg Med 2003;10: 867–871. Barkin AZ, Rosen CL. Ultrasound detection of abdominal aortic aneurysm. Emerg Med Clin North Am 2004;22:675–682. Gayer G, Hertz M, Zissin R. Postoperative pneumoperitoneum: prevalence, duration, and possible significance. Semin Ultrasound CT MR 2004;25:286–289. Chang JJ, Yeun JY, Hasbargen JA. Pneumoperitoneum in peritoneal dialysis patients. Am J Kidney Dis 1995;25:299–301. Jones R. Recognition of pneumoperitoneum using bedside ultrasound in critically ill patients presenting with acute abdominal pain. Am J Emerg Med 2007;25:838–841. Hoffmann B, Nurnberg ¨ D, Westergaard MC. Focus on abnormal air: diagnostic ultrasonography for the acute abdomen. Eur J Emerg Med 2012;19:284–291. Neri L, Storti E, Lichtenstein D. Toward an ultrasound curriculum for critical care medicine. Crit Care Med 2007;35:S290–304. Mayo PH, Beaulieu Y, Doelken P, Feller-Kopman D, Harrod C, Kaplan A, Oropello J, Vieillard-Baron A, Axler O, Lichtenstein D, et al. American College of Chest Physicians/La Societ ´ e´ de Reanimation ´ de Langue Française statement on competence in critical care ultrasonography. Chest 2009;135:1050–1060.
AnnalsATS Volume 10 Number 6 | December 2013
