1  Answers:

1:A. Common hepatic duct

2:E. Proper hepatic artery

3:B. Main portal vein

This is the classic “Mickey Mouse” configuration of the structures demonstrated on abdominal ultrasound that make up the portal triad. This relationship is found in the porta hepatis at the margin of the hepatoduodenal ligament. The corresponding color Doppler image is shown below. The larger vessel is the portal vein (PV). In normal patients, the two “ears” representing the bile duct (BD) and the proper hepatic artery (HA) on the left are similar in size. With biliary obstruction, the dilated duct enlarges the right “ear.”

The extrahepatic common duct is normally ≤6 mm diameter (measured from inner wall to inner wall) in patients 60 years or younger, with an additional 1 mm caliber increase acceptable for each additional decade up to 10 mm. After cholecystectomy, patients are also allowed up to 10 mm. These measurements are guidelines and should be correlated with ancillary imaging findings as well as the clinical scenario to help determine if biliary obstruction is likely.

References: Brant WE. Chapter 36: Abdominal ultrasound. In: Brant WE, Helms CA (eds). Fundamentals of diagnostic radiology, 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2007:927–953.

Tirumani SH, Shanbhogue AK, Vikram R, et al. Imaging of the porta hepatis: spectrum of disease. Radiographics 2014;34(1):73–92.

2  Answer C.Coronal and axial T2W images from an MRCP demonstrate two dark filling focal defects in a mildly prominent common bile duct. The axial image shows dependent location of the filling defect. Findings are consistent with choledocholithiasis. There is also cholelithiasis, with a stone seen in the gallbladder.

Up to one-third of patients with gallstones develop symptoms, which may include biliary colic, cholecystitis, cholangitis, or pancreatitis. Ultrasound is usually the initial imaging modality performed in patients with right upper quadrant pain and suspected biliary pathology. Choledocholithiasis accounts for the majority of cases of biliary obstruction, most often migrating from the gallbladder. Patients with suspected choledocholithiasis without direct visualization of a ductal stone on ultrasound may proceed to MRCP or ERCP for further evaluation.

MRCP has a high sensitivity of about 90% for choledocholithiasis, compared to 20% to 60% for ultrasound. The stones are visualized as dark filling defects surrounded by bright bile on the heavily T2W images of MRCP. The stones may be round or have a faceted appearance with angular margins. Stones impacted in the ampulla may be missed or misdiagnosed as ampullary lesions due to the lack of surrounding fluid. Tiny stones ≤3 mm may still be hard to detect even on thin-slice MRCP images, and patients may ultimately require ERCP for diagnosis and treatment.

Pneumobilia would appear as a ventral (nondependent) hypointensity with air–fluid level on axial images, highlighting the importance of careful correlation with axial images to make the distinction with choledocholithiasis. Cholangiocarcinoma or ampullary carcinoma may present as a soft tissue mass or a stricture. With ascariasis, the parasites can be seen in the bile duct as a linear filling defect.

References: Irie H, Honda H, Kuroiwa T, et al. Pitfalls in MR cholangiopancreatographic interpretation. Radiographics 2001;21(1):23–37.

Yeh BM, Liu PS, Soto JA, et al. MR imaging and CT of the biliary tract. Radiographics 2009;29(6):1669–1688.

3  Answer A.This patient has a constellation of findings consistent with acute (calculous) cholecystitis as follows:

• Sonographic Murphy sign is positive, with maximum tenderness during compression with the transducer over the gallbladder.
  
• The gallbladder is distended with shadowing gallstones (long black arrow) as well as sludge.
  
• The gallbladder wall is edematous with a striated appearance and measures >3 mm in thickness as delineated by the calipers.
  
• The gallbladder wall is hypervascular (short white arrows) on the color Doppler image, indicating inflammation.
  
• Pericholecystic fluid is identified (long white arrow).

Although the individual imaging features of acute cholecystitis (AC) on ultrasound are nonspecific, identification of multiple features increases diagnostic confidence. Meta-analyses reveal overall excellent (>80%) sensitivity and specificity of ultrasound for AC. A sonographic Murphy sign may be the most sensitive feature for AC, but specificity is relatively low. A positive Murphy sign in combination with cholelithiasis has been found to have a positive predictive value of about 90%, but it is not always possible to adequately assess for the Murphy sign in patients who have taken pain medication or have been sedated. Among the answer choices, acute hepatitis and adenomyomatosis can also cause gallbladder wall thickening, but they are less likely choices given this constellation of findings. Adenomyomatosis is usually an asymptomatic incidental finding. Other causes of diffuse gallbladder wall thickening are listed in the table below.

Patients with AC may present with right upper quadrant pain, fever, and leukocytosis. A gallstone that is persistently impacted in the cystic duct or gallbladder neck causes gallbladder obstruction and distention. Subsequently, inflammation of the gallbladder wall is induced by the accumulated bile salts or superinfection. AC can progress to life-threatening complications which are best evaluated by CT, including gas formation, gangrene, hemorrhage, and perforation. Definitive treatment for AC is cholecystectomy.

References: ACR Appropriateness Criteria: right upper quadrant pain. American College of Radiology website. http://www.acr.org/~/media/ACR/Documents/AppCriteria/Diagnostic/RightUpperQuadrantPain.pdf. Published 1996. Updated 2013. Accessed August 2, 2015.

Hanbidge AE, Buckler PM, O’Malley ME, et al. From the RSNA refresher courses: imaging evaluation for acute pain in the right upper quadrant. Radiographics 2004;24(4):1117–1135.

O’Connor OJ, Maher MM. Imaging of cholecystitis. AJR Am J Roentgenol 2011;196(4):W367–W374.

4  Answer D.This patient has a sludge-filled gallbladder with no stones identified. There is borderline gallbladder wall thickening. In this critically ill patient, findings could represent acute acalculous cholecystitis (AAC). Cholescintigraphy with HIDA scan augmented with morphine reportedly has a higher sensitivity of 67% for AAC compared to ultrasound, which has sensitivity of 50%. Nevertheless, ultrasound is the most appropriate initial study for suspected acute cholecystitis (both calculous and acalculous) with a rating of 9 out of 10 as noted by the ACR Appropriateness Criteria, compared to 6 out of 10 for cholescintigraphy. The advantages of ultrasound over cholescintigraphy include technical considerations such as greater availability, shorter scan time, and lack of radiation. Ultrasound also has benefits of morphologic evaluation over cholescintigraphy allowing detection of gallstones, assessment of duct caliber, and identification of alternative diagnoses. HIDA scan should be still considered an important ancillary study for the diagnosis of acute cholecystitis in the setting of an equivocal ultrasound.

About 15% of cases of acute cholecystitis represent AAC. Patients are often seriously ill and have been hospitalized in the ICU for a prolonged period of time before the development of AAC. AAC rarely presents de novo in an outpatient setting. The diagnosis of AAC can be problematic and is one of exclusion because fever and leukocytosis are nonspecific signs in the at-risk patient population. These patients frequently have other conditions that can cause gallbladder wall thickening. It may not be possible to assess for a sonographic Murphy sign because of patient intubation and use of analgesics and sedatives.

AAC has a higher morbidity and mortality than conventional acute calculous cholecystitis. Rapid progression to gangrene and perforation contributes to a high mortality of up to 65%. Percutaneous cholecystostomy with drainage catheter placement can be both diagnostic and therapeutic. It is generally safer than performing an emergent cholecystectomy in a critically-ill patient and can be an effective temporizing measure until patients can proceed to cholecystectomy.

References: ACR Appropriateness Criteria: right upper quadrant pain. American College of Radiology website. http://www.acr.org/~/media/ACR/Documents/AppCriteria/Diagnostic/RightUpperQuadrantPain.pdf. Published 1996. Updated 2013. Accessed August 2, 2015.

Bennett GL. Chapter 77: Cholelithiasis, cholecystitis, choledocholithiasis, and hyperplastic cholecystoses. In: Gore RM, Levine MS (eds). Textbook of gastrointestinal radiology, 4th ed. Philadelphia, PA: Elsevier/Saunders, 2015:1348–1391.

5a  Answer A.The patient’s CT and MRCP show a collection of fluid and gas in the cholecystectomy bed. There is no high density or extravasation of IV contrast to suggest pseudoaneurysm or active hemorrhage. A collection in the gallbladder fossa after recent cholecystectomy is not uncommon and may be a postoperative finding that resolves spontaneously. However, in a patient with signs and symptoms of peritonitis, this collection could represent a bile leak or abscess that requires intervention. A gallbladder remnant may be left behind if adhesions or variant anatomy prevents complete removal of the gallbladder but should be small rather than filling the length of the gallbladder fossa. A duplicated (accessory) gallbladder is a very rare congenital anomaly that should not be a primary consideration and presumably would have been recognized and removed at cholecystectomy.

If the diagnosis is unclear, an HIDA scan may be useful to confirm a bile leak. MRCP with a hepatobiliary agent such as gadoxetate disodium (Eovist, Bayer HealthCare Pharmaceuticals) has also been used to help diagnose and localize bile leaks, as 50% of this contrast agent is taken up by hepatocytes and excreted into the biliary system. Extravasation of this contrast outside the biliary tree in the hepatobiliary phase would indicate a bile leak. Treatment of bile leaks may involve a combination of endoscopic, percutaneous, and surgical intervention.

References: Melamud K, LeBedis CA, Anderson SW, et al. Biliary imaging: multimodality approach to imaging of biliary injuries and their complications. Radiographics 2014;34(3):613–623.

Raman SP, Fishman EK, Gayer G. Chapter 81: Postsurgical and traumatic lesions of the biliary tract. In: Gore RM, Levine MS (eds). Textbook of gastrointestinal radiology, 4th ed. Philadelphia, PA: Elsevier/Saunders, 2015:1348–1391.

5b  Answer D.Two months later, the MRCP and the following ERCP show a high-grade obstruction (arrow) at the biliary hilum near the cholecystectomy clips with intrahepatic biliary ductal dilation. There is no surrounding fluid collection on the MR or extravasation on the ERCP to indicate a recurrent bile leak. (The round area of contrast on the ERCP represents contrast in the duodenum.) Given the time course and the preceding events, this is consistent with a benign stricture complicating the recent biliary injury rather than development of cholangiocarcinoma or sclerosing cholangitis.

The most common locations for postcholecystectomy strictures are at the junction of the cystic duct with the common duct and at the biliary hilum. Although these strictures are benign, they can be difficult to manage. Treatment includes ERCP for stent placement, but recurrence is common. Surgical intervention with hepaticojejunostomy may eventually be required.

References: Katabathina VS, Dasyam AK, Dasyam N, et al. Adult bile duct strictures: role of MR imaging and MR cholangiopancreatography in characterization. Radiographics 2014;34(3):565–586.

Raman SP, Fishman EK, Gayer G. Chapter 81: Postsurgical and traumatic lesions of the biliary tract. In: Gore RM, Levine MS (eds). Textbook of gastrointestinal radiology, 4th ed. Philadelphia, PA: Elsevier/Saunders; 2015:1348–1391.