Laboratory Studies
No laboratory studies are specific for the diagnosis of a choledochal cyst.
Complete blood cell count
An elevated white blood cell count with increased numbers of neutrophils and immature neutrophil forms may be observed in the presence of cholangitis.
Liver function studies
Liver function tests may be useful in narrowing the differential diagnosis. Hepatocellular enzyme and alkaline phosphatase levels may be elevated. None of these tests are specific for the diagnosis of a choledochal cyst.
Serum amylase and lipase concentrations may be increased in the presence of pancreatitis. Serum amylase concentrations also may be elevated in biliary obstruction and cholangitis.
Chemistry panel
Results of serum chemistry may be abnormal if the patient is vomiting. One might expect to see a hypochloremic, hypokalemic metabolic alkalosis in this clinical picture.
Imaging Studies
Ultrasonography
Abdominal ultrasonography is the test of choice for the diagnosis of a choledochal cyst. Ultrasonography is useful in the antenatal period as well and can demonstrate a choledochal cyst in a fetus as early as the beginning of the second trimester. [1, 25] Caroli disease has also been detected antenatally with ultrasound by Sgro and colleagues. [2] (See image below.)
Diagnostic ultrasonogram demonstrating a type I choledochal cyst in a 4-month-old child presenting with hyperbilirubinemia and transaminase elevations.
Endoscopic ultrasonography (EUS) appears to have the potential to differentiate between choledochal and pancreatic cysts, particularly in patients with type II choledochal cysts. [26] It is not limited by bowel gas, intraabdominal structures, or body habitus compared to abdominal ultrasonography. In a retrospective review (2010-2014) of 4 women with either type II cysts, equivocal for choledochal cyst on magnetic resonance imaging (MRI), or the possibility of branch-duct intraductal papillary mucinous neoplasm of the pancreas on computed tomography (CT) scan, EUS was able to demonstrate no communication in all cases between the choledochal structure and the common bile duct. [26] Moreover, EUS-guided fluid aspiration could be used for further testing to differentiate between biliary cysts and other cystic structures. [26]
CT scanning and MRI
Abdominal CT scanning and MRI help to delineate the anatomy of the lesion and the surrounding structures. These tests also can assist in defining the presence and extent of intrahepatic ductal involvement. Yu and associates published a series of 64 patients in whom magnetic resonance cholangiopancreatography (MRCP) was particularly valuable in defining anomalous pancreaticobiliary junctions. [3] (See the images below.)
Computed tomography (CT) scan of a choledochal cyst demonstrating intrahepatic extension involving the main left hepatic duct.
Computed tomography (CT) scan of a choledochal cyst involving the common hepatic duct.
Computed tomography (CT) scan demonstrating a large choledochal cyst and the adjacent gall bladder.
Magnetic resonance cholangiopancreatography
Fitoz and colleagues described the use of MRCP in 17 children with pancreatobiliary anomalies. [4] The reported diagnostic accuracy of magnetic resonance cholangiopancreatography (MRCP) in choledochal cysts in this series was 100%.
Hepatobiliary scintigraphy
Hepatic iminodiacetic acid (HIDA) scintigraphy is a nuclear medicine examination that uses a radiolabeled bile salt (technetium-99m) that is given intravenously and is then taken up by the hepatocytes and excreted in the bile.
Invasive diagnostic studies
When noninvasive measures (eg, ultrasonography, CT scanning, MRI) fail to sufficiently delineate the anatomy, they should be supplemented by the addition of percutaneous transhepatic cholangiography (PTC) or endoscopic retrograde cholangiopancreatography (ERCP) which may have a sensitivity up to 100%. As reported by Nagi and coworkers, these studies are particularly helpful in demonstrating the presence of an anomalous pancreatobiliary junction and in delineating associated extrahepatic or intrahepatic strictures and stones. [27]
Histologic Findings
Evidence of chronic inflammation is typically observed in the cyst wall. The cyst wall is thin, fibrous, and frequently devoid of a true epithelial surface, although it can be lined by a low columnar epithelium. Note that infants can develop complete obstruction of the distal common bile duct secondary to acute and chronic inflammatory changes. In the liver, ductal fibrosis and portal edema may be present. Changes consistent with biliary cirrhosis may be observed in adults with long-standing disease. The most feared histologic abnormality is the presence of cholangiocarcinoma.
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Operative specimen of a type I choledochal cyst.
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Type I choledochal cyst.
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Type II choledochal cyst.
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Type III choledochal cyst (choledochocele).
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Type IV choledochal cyst (extrahepatic and intrahepatic disease).
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Type V choledochal cyst (intrahepatic, Caroli disease).
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Nuclear medicine scan of a choledochal cyst.
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Nuclear medicine scan of a choledochal cyst.
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Computed tomography (CT) scan of a choledochal cyst demonstrating intrahepatic extension involving the main left hepatic duct.
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Computed tomography (CT) scan of a choledochal cyst involving the common hepatic duct.
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Computed tomography (CT) scan demonstrating a large choledochal cyst and the adjacent gall bladder.
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Computed tomography (CT) scan of a large, saccular type I choledochal cyst.
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Diagnostic ultrasonogram demonstrating a type I choledochal cyst in a 4-month-old child presenting with hyperbilirubinemia and transaminase elevations.
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Intraoperative cholangiogram of a type I choledochal cyst.
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Intraoperative image of a Roux-en-Y hepaticojejunostomy to restore biliary-enteric continuity following resection of a choledochal cyst.
