1. Correct Answer: B. A curvilinear probe with low frequency (3.5-5.0 MHz)

Rationale: A lower frequency probe with a curvilinear array is typically used for all hepatobiliary imaging. The curvilinear alignment of the crystals allows a fanning out of the beam, which allows visualization of a much wider area than the probe’s footprint. The low frequency also allows better tissue penetration, which may be necessary for obese patients, in whom gallstone disease is typically more common. Phased array probes offer a variety of imaging options, but generally contain fewer crystals, thus fewer scan lines and less spatial resolution.

1. Fentress M. Does the patient have cholelithiasis or cholecystitis?. In: Bornemann P, ed. Ultrasound for Primary Care. Wolters Kluwer; 2021:151-157.

2. Izadifar Z, Izadifar Z, Chapman D, Babyn P. An introduction to high intensity focused ultrasound: systematic review on principles, devices, and clinical applications. J Clin Med. 2020 Feb;9(2):pii: E460.

2. Correct Answer: C. Add color flow Doppler

Rationale/Critique: The addition of color flow Doppler allows identification of vascular structures, as blood flow will display flow velocity within the portal vein and hepatic arteries, but not in the CBD. The CBD also typically lies anterior and to the right of the portal vein, while the hepatic artery commonly lies anterior to the portal vein and toward the midline (left). Adjusting the depth, focal zone, and gain may all help improve visualization of the CBD, but are less helpful for its identification. (See also Figure 61.21.)

1. Gubernick JA, Rosenberg HK, Ilaslan H, Kessler A. US approach to jaundice in infants and children. Radiographics. 2000 Jan-Feb;20(1):173-195.

3. Correct Answer: D. Move the probe to another location

Rationale: The gallbladder is best visualized using a curvilinear probe in the right subcostal area. This should be done in both a longitudinal and transverse axis, to fully study the organ. When excess bowel gas obscures the gallbladder, or in obese patients with high riding livers, imaging through the rib spaces may be beneficial. Rib shadowing may obscure visualization, which can be improved by aligning the imaging plane with the intercostal space. The probe can be angled obliquely or slid anteriorly or laterally until the gallbladder is fully seen. Increasing the depth or using a higher frequency or phased array probe would not improve attenuation of the US signal or the quality of the image.

1. Lee JM, Boll DT. Disease of the gallbladder and biliary tree. In: Hodler J, Kubik-Huch RA, von Schulthess GK, eds. Diseases of the Abdomen and Pelvis 2018-2021: Diagnostic Imaging – IDKD Book [Internet]. Springer; 2018:Chapter 5.

4. Correct Answer: A. The normal appearance of the CBD, portal vein, and hepatic artery seen on their short axis

Rationale/Critique: Viewing the porta hepatis in its short axis demonstrates the three structures in a “Mickey Mouse” head configuration, with the portal vein representing the head, the CBD the right ear, and hepatic artery the left. (See Figure 61.22.)

1. Izadifar Z, Izadifar Z, Chapman D, Babyn P. An introduction to high intensity focused ultrasound: systematic review on principles, devices, and clinical applications. J Clin Med. 2020 Feb 7;9(2):pii: E460.

2. Xiang H, Han J, Ridley WE, Ridley LJ. Mickey mouse signs. J Med Imaging Radiat Oncol. 2018 Oct;62 suppl 1:92. doi:10.1111/1754-9485.39_12784.

5. Correct Answer: B. Tenderness in the right upper quadrant when pressure is applied while the US probe is over the gallbladder

Rationale: Murphy’s sign refers to tenderness of the right upper quadrant on palpation during inspiration. The pain is severe enough to arrest deep inspiration. A “sonographic Murphy’s sign” is similar to the Murphy’s sign elicited during abdominal palpation, except that the positive response is observed during palpation with the US transducer. This is more accurate than hand palpation because it can confirm that it is indeed the gallbladder that is being pressed by the imaging transducer. Sonographic findings of cholecystitis include gallstones, sonographic Murphy’s sign, gallbladder distension, pericholecystic fluid, and gallbladder wall thickening. The presence of cholelithiasis combined with a positive sonographic Murphy’s sign is the most specific sonographic finding in acute cholecystitis. Gallbladder distension (>4 cm transverse and 10 cm in length) and an impacted stone in the gallbladder neck or cystic duct are suggestive findings. Gallbladder wall thickening measuring >3 mm and pericholecystic fluid are additional findings that can be seen; however, they are less specific than the signs previously described.

1. Oppenheimer DC, Rubens DJ. Sonography of acute cholecystitis and its mimics. Radiol Clin North Am. 2019 May;57(3):535-548. doi:10.1016/j.rcl.2019.01.002. Epub 2019 Feb 10.

2. Ralls PW, Colletti PM, Lapin SA, et al. Real-time sonography in suspected acute cholecystitis. Prospective evaluation of primary and secondary signs. Radiology. 1985 Jun;155(3):767-771. doi:10.1148/radiology.155.3.3890007.

3. Simeone JF, Brink JA, Mueller PR, et al. The sonographic diagnosis of acute gangrenous cholecystitis: importance of the Murphy sign. AJR Am J Roentgenol. 1989 Feb;152(2):289-290.

6. Correct Answer: A. Symptomatic cholelithiasis

Rationale: The US (Figure 61.1) demonstrates a large dependent stone in the gallbladder neck with posterior shadowing, suggestive of cholelithiasis. The gallbladder wall does not appear thickened or distended, and there is no pericholecystic edema, making cholecystitis unlikely. While pain unrelated to her gallbladder remains possible, the US findings, onset with fatty food, and quick resolution suggest that symptomatic cholelithiasis without cholecystitis is the most likely explanation.

1. Murphy MC, Gibney B, Gillespie C, Hynes J, Bolster F. Gallstones top to toe: what the radiologist needs to know. Insights Imaging. 2020 Feb;11(1):13. doi:10.1186/s13244-019-0825-4.

2. Ross M, Brown M, McLaughlin K, et al. Emergency physician-performed ultrasound to diagnose cholelithiasis: a systematic review. Acad Emerg Med. 2011 Mar;18(3):227-235.

7. Correct Answer: C. Acalculous cholecystitis

Rationale/Critique: The US (Figure 61.2) demonstrates a thickened, distended gallbladder with pericholecystic fluid but no stones. These findings, along with the clinical presentation, are highly suggestive of acalculous cholecystitis. This is a fairly common condition in the ICU. Prolonged fasting, TPN, prolonged mechanical ventilation, polytrauma, sepsis, shock, extensive burns, multiple transfusions, and medications (sedatives, vasopressors, opiates) have all been identified as risk factors for the development of acalculous cholecystitis, although the condition is not uncommon in the outpatient population. Common sonographic findings include a typically thickened gallbladder wall (>3.5 mm), distended gallbladder, and pericholecystic fluid (hypoechoic halo). Given the typically high acuity of ICU patients with acalculous cholecystitis, management revolves around minimally invasive (percutaneous) drainage of the gallbladder. When the patient recovers from critical illness, an elective cholecystectomy can be considered.

1. Yokoe M, Hata J, Takada T, et al. Tokyo guidelines 2018: diagnostic criteria and severity grading of acute cholecystitis. J Hepatobiliary Pancreat Sci. 2018 Jan;25(1):41-54.

8. Correct Answer: B. Acute cholecystitis

Rationale/Critique: The US (Figure 61.3) demonstrates a thickened gallbladder with stones and pericholecystic edema. These findings, along with the clinical presentation, are suggestive of acute calculous cholecystitis. US findings are the same as in acalculous cholecystitis (see the previous vignette), with the presence of obvious stones (hyperechoic masses inside the gallbladder that create acoustic shadowing). The normal LFTs suggest that there is no biliary tract obstruction, and the pathology is isolated distal to the cystic duct. Depending on the patient’s overall clinical condition, this may be addressed with cholecystectomy or percutaneous cholecystostomy.

1. Oppenheimer DC, Rubens DJ. Sonography of acute cholecystitis and its mimics. Radiol Clin North Am. 2019 May;57(3):535-548.

9. Correct Answer: D. Chronic cholecystitis

Rationale: The US (Figure 61.4) demonstrates a thickened gallbladder with dependent stones present, but no pericholecystic edema. This, along with the clinical presentation, is suggestive of chronic cholecystitis, likely the result of multiple subclinical episodes of biliary colic and chronic low-grade inflammation, secondary to chronic gallstone disease. The normal LFTs argue against obstructive biliary disease. Chronic cholecystitis that is an incidental imaging finding may be addressed on an outpatient basis.

1. Oppenheimer DC, Rubens DJ. Sonography of acute cholecystitis and its mimics. Radiol Clin North Am. 2019 May;57(3):535-548.

10. Correct Answer: B. Emphysematous cholecystitis

Rationale/Critique: Emphysematous cholecystitis is a rare subtype of acute cholecystitis caused by gas-forming bacteria. It typically presents in elderly, debilitated patients and poorly controlled diabetes is a common risk factor. The diagnosis is suggested by the presence of bright gas locules in the gallbladder wall, ring-down artifacts, and mobile gaseous echoes within the gallbladder lumen. Figure 61.5 demonstrates such gaseous locules within the gallbladder wall. (See Figure 61.23.)

In Figure 61.24, the US demonstrates the “champagne sign” or “effervescent gallbladder.” This is a term used to describe the hyperechoic appearance of air bubbles secondary to gas formation in the gallbladder lumen. On US, the air in the gallbladder lumen appears highly echogenic with low-level posterior shadowing and reverberation artifacts due to the gas within the lumen of the gallbladder. A less common appearance consists of tiny hyperechoic foci within the lumen released from gas-producing bacteria. These hyperechoic foci are reminiscent of champagne bubbles rising inside a flute of champagne.

1. Minault Q, Gaiddon C, Veillon F, Venkatasamy A. The champagne sign. Abdom Radiol (NY). 2018 Oct;43(10):2888-2889. doi:10.1007/s00261-018-1544-x.

2. Oppenheimer DC, Rubens DJ. Sonography of acute cholecystitis and its mimics. Radiol Clin North Am. 2019 May;57(3):535-548.

11. Correct Answer: A. Gangrenous cholecystitis

Rationale: Gangrenous cholecystitis is a severe, highly morbid complication of acute cholecystitis, in which portions of the gallbladder wall have become ischemic and necrosed. This is manifested sonographically by sloughed mucosal membranes (sometimes visualized as small hyperechoic foci in the gallbladder lumen—as in Figure 61.6), focal wall bulge, ulceration, and disruption of the gallbladder wall (as shown in Figure 61.6). When perforation has occurred, a pericholecystic abscess may be noted, as is seen in the above images. Immunosuppression is a common risk factor, as minimally perceived pain enables the infection to progress before medical attention is sought. Free fluid may or may not be adjacent to the gallbladder, depending on whether the perforation took place on the hepatic or peritoneal surface of the gallbladder.

1. Oppenheimer DC, Rubens DJ. Sonography of acute cholecystitis and its mimics. Radiol Clin North Am. 2019 May;57(3):535-548.

12. Correct Answer: C. Cholangitis

Rationale: The patient presents with the typical Charcot’s triad of leukocytosis, jaundice (or elevated bilirubin), and right upper quadrant pain, which suggests ascending cholangitis. The US (Figure 61.7) demonstrates a dilated common bile duct (CBD). This is suggestive of distal biliary obstruction, commonly from a stone at the sphincter of Oddi, which can lead to a potentially lethal infection. The size of the CBD ranges by patient size and weight, but as a rule of thumb, its size increases by 1 mm for every decade of life over the age of 60. In younger patients, it is approximately 4 to 5 mm, but may increase to 10 mm in diameter after cholecystectomy.

1. Oppenheimer DC, Rubens DJ. Sonography of acute cholecystitis and its mimics. Radiol Clin North Am. 2019 May;57(3):535-548.

13. Correct Answer: C. Portal venous gas

Rationale: The US (Figure 61.8) demonstrates discrete hyperechoic foci that move with blood flow, consistent with gas in the portal vein. In smaller, more peripheral branches of the portal venous system, these may extend into the hepatic parenchyma toward the periphery and be confused with parenchymal pathology. Doppler may demonstrate disruption of the monophasic flow of the portal vein. Portal venous gas should be distinguished from pneumobilia, in which the hyperechoic foci that represent gas are typically seen within the liver parenchyma, entirely outside the vascular system. Common causes of portal venous gas include intestinal ischemia, pneumatosis coli, abdominal sepsis, and severe abdominal inflammation (e.g., complicated diverticulitis). Findings suggestive of acute hepatitis include hepatomegaly (most sensitive sign), gallbladder wall thickening, accentuated brightness of portal vein radicle walls, and overall decreased echodensity. Cirrhosis generally appears with surface nodularity or an overall coarse and heterogeneous echotexture, reduced size, or signs of portal hypertension. (See also Figure 61.25.)

1. Connor-Schuler R, Binz S, Clark C. Portal venous gas on point-of-care ultrasound in a case of cecal ischemia. J Emerg Med. 2020 Mar;58(3):e117-e120. doi:10.1016/j.jemermed.2019.10.033. Epub 2019 Dec 13.

2. Liang KW, Huang HH, Tyan YS, Tsao TF. Hepatic portal venous gas: review of ultrasonographic findings and the use of the “meteor shower” sign to diagnose it. Ultrasound Q. 2018 Dec;34(4):268-271.

14. Correct Answer: B. Pneumobilia