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Caroli Disease: Imaging

Author: William J Romano, MD, FRCPC, Director, Interventional Radiology Research, Department of Radiology, William Beaumont Hospital; Clinical Assistant Professor, Department of Radiology, Wayne State University School of Medicine
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Updated: Apr 6, 2009

Radiography

Findings

Plain abdominal radiographs are not helpful unless hepatic calculi are found. Barium examinations are not indicated. Traditional IV or oral cholangiography is not beneficial. However, ERCP is helpful.

Degree of Confidence

Confidence is poor because these are not appropriate studies.

Computed Tomography

Findings

Dilated segmental intrahepatic biliary radicles are present without involvement of the extrahepatic biliary tree. Preinfused scans may show hyper-attenuating sludge and stones or debris.

Hypoattenuating, tubular branching structures are identified; these communicate and extend from the porta hepatis toward the periphery. CT scan with IV contrast enhancement can show tiny dots, representing intraluminal portal veins, within the dilated intrahepatic bile ducts. This is termed the central dot sign. Take 3D images with or without the CT cholangiographic technique to help prove the relationship of the dilated structure to the ductal system, although this is better accomplished with MRCP (see below). CT can help depict abscesses and guide percutaneous drainage.

Complications such as cholangitis, choledocholithiasis, or cholangiocarcinoma may be present and can be identified with CT imaging. Portal hypertension can be present and result in hepatosplenomegaly with varices. Contrast-enhanced images obtained through the kidneys can show associated multiple renal cysts.

Degree of Confidence

The diagnosis can be made confidently if irregular cystic lesions communicate with the dilated biliary tree. No obstruction is present without the usual peripheral tapering of intrahepatic ducts on the opposite side that extend from dilated central ducts and the dilated extrahepatic biliary tree. Liver cysts are round.

False Positives/Negatives

False-positive findings are unusual. Bilobar dilatation of the intrahepatic ducts from causes other than Caroli disease mimics obstruction and does not have the superior liver predominance characteristic of Caroli disease. Artifact can cause false-negative findings.

Magnetic Resonance Imaging

Findings

Dilated segmental intrahepatic biliary radicles can be identified with MRI, as with CT and ultrasonography. MRCP reveals similar findings and allows better review of the results, especially with a computer workstation. This noninvasive 3D technique is a good alternative to ERCP or direct cholangiography. This can confidently show the communication of the multiple cysts, which is mandatory for the differential diagnosis with cystic disease of the liver and multiple abscesses. In polycystic liver disease, the hepatic cysts rarely  communicate with the bile ducts and the bile ducts typically are intrinsically normal.² Complications of Caroli disease also can be identified with MRI.

Degree of Confidence

The confidence level is very high. MRI can be used to distinguish other forms of cystlike liver diseases. MRI plus MRCP has been proposed as the study of choice.^7,8

False Positives/Negatives

False-positive findings can occur with other cystic or cystlike lesions. Artifact can limit the evaluation and cause false-negative results.

Ultrasonography

Findings

Ultrasonography is currently the examination of choice. Dilated segmental intrahepatic biliary radicles are easily detected. No obstruction is present. The cystlike tubular anechoic spaces converge toward the porta hepatis. They are largest in the superior part of the liver. The intraluminal portal vein sign is related to the protrusion of the portal vein branches into the cyst wall. Color flow Doppler ultrasonography is helpful in showing blood flow in these branches but no flow is present in the bile-containing spaces. Portal branches bridge the cyst walls.

Ultrasonography can also help in the diagnosis of complications and in the follow-up of patients with Caroli disease. Intraductal calculi are echogenic with acoustic shadowing.

Ultrasonography-guided needle aspiration of bile from the cystlike lesions may be beneficial in the diagnosis of cholangitis and in confirming that the cysts communicate with the biliary tree. Congenital hepatic fibrosis in Caroli syndrome may be diagnosed with sonograms that show abnormal liver echogenicity. Ultrasonography-guided core biopsy may be performed, if necessary, to obtain liver samples for histologic evaluation to confirm this condition. In addition, polycystic renal disease, which is associated with Caroli disease, can be confirmed with sonography.

Degree of Confidence

Ultrasonography is an excellent tool. A positive result has good predictive value and permits diagnosis with a high level of confidence. Caroli disease is the only condition in which dilated ducts surround the portal radicles; this finding at ultrasonography may obviate other invasive diagnostic techniques.

False Positives/Negatives

Few variants affect diagnosis with ultrasonography. Choledochal cyst or other cystic diseases, including congenital or acquired cystic masses, may cause false-positive findings. These structures do not communicate with the biliary tree. False-negative results occur if the liver is not fully evaluated.

Nuclear Imaging

Findings

Hepatobiliary scintigraphy with technetium-99m iminodiacetic acid (^99mTc IDA) agents reveals large, irregular, multifocal collections of the radiotracer in the liver. A beaded appearance in the dilated ducts, if present, is somewhat pathognomonic. These collections correspond to the segmental dilatations, and no extrahepatic obstruction is present, although bile stasis and stone formation may result in atypical obstruction.

On early images, if the ducts are dilated enough, they appear as photopenic branching areas within the liver. Single photon emission computed tomography (SPECT) may better outline the ductal pattern but it is most helpful in the evaluation of focal disease.

Degree of Confidence

The confidence level is moderate to high when focal or segmental involvement is present in the large intrahepatic branches without obstruction. Overall, scintigraphy is not helpful compared with cross-sectional imaging techniques.

False Positives/Negatives

False-positive findings may be related to other cystic lesions of the biliary tree. False-negative findings are related to problems with the technique. Cholangitis can impair hepatic uptake of radiotracers. Obstruction related to stones or debris from the ducts may cause misdiagnosis.

Angiography

Findings

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