IS Case 368: Choledochal cyst
2009 URMC Imaging Sciences
Publication Date: 2010-03-02
Patient is a 48-year-old female with abdominal pain for more than 6 months. She was referred for definitive treatment to a tertiary care hospital. Other symptoms included, GERD, bloating, epigastric pain and shortness of breath, as well as alternating diarrhea and constipation. The patient had no symptoms of cholangitis or jaundice. The initial work-up at an outside institution involved multi-modality imaging, including: computed tomography (CT), followed by ultrasound (US), then magnetic resonance retrograde cholangiography (MRCP), and finally endoscopic retrograde pancreatic cholangiography (ERCP). Presumptive diagnosis was a type I choledochal cyst. Cyst resection with hepaticojejunostomy was being considered.
Imaging Findings: Non-contrast CT findings: A low attenuation, 3 cm, well-circumscribed structure is visualized in the porta hepatis, isodense (HU 15) to bile. The gallbladder is distinctly visualized as a separate structure. Other low attenuation lesions are also visualized in the bilateral hepatic lobes.
Abdominal US findings: An anechoic structure corresponds to the porta hepatis lesion seen on axial non-contrast CT. A duct extends from this structure, likely representing a draining biliary duct. There is no corresponding flow within this lesion. A second lesion, which was a right hepatic lobe low attenuation lesion on CT, is hyperechoic and therefore not indicative of a biliary cyst. There is a minimal rim of vascularity.
MR and MRCP findings: A choledochal cyst is hyperintense on T2-weighting and hypointense on T1-weighting. 3D MIP reformats show a normal, patent right hepatic duct. The saccular cystic structure (arrow) appears to incorporate the left hepatic duct, though a connection with the common hepatic duct cannot be entirely excluded. There is no evidence of obstruction or additional intrahepatic cysts. A second lesion in the right hepatic lobe is less hyperintense on T2 than the choledochal cyst. Multiphase MR contrast imaging was also performed (not shown). Combined with US and CT findings, this second lesion is compatible with a hemangioma.
ERCP findings: Contrast fills a saccular structure (arrow) at the bifurcation of the common hepatic duct. The right hepatic duct appears intact, while the distal portion of the left hepatic duct is obscured by the cyst. The common bile duct is normal.
Type I choledochal cyst: most common type accounting for 80-90%; seen as a fusiform or saccular dilatation of the common bile duct. Subtype Ia is saccular dilatation of the common bile duct. Subtype Ibi s focal, segmental dilatation of the common bile duct. Subtype Ic is fusiform dilatation of the common hepatic and common bile duct.
Type III choledochal cyst: represent 1-5% and occur as choledochoceles within the duodenal wall.
Type IV choledochal cyst: represent approximately 10% of cysts and are multiple intra- and extrahepatic cysts. Subtype IVA: usually an extrahepatic cyst with multiple intrahepatic cysts Subtype IVB: multiple extrahepatic cysts.
Type V choledochal cysts: a classification including other types of cysts; this is termed Caroli’s disease when there are multiple intrahepatic cysts; dilation of multiple intrahepatic radicles, but can be single; can be unilobar on the left.
Guntz, et al.  described 4 types of unilobar Caroli’s disease:
I, racemose biliary dilatation;
II, digitform biliary dilatation;
Classification is important since Type I, II, and IV are treated with complete excision with biliary-enteric anastomosis. Type III are treated with de-roofing only, since there is no increased risk of biliary malignancy.
In adults, the most common complaint is abdominal pain. Epigastric pain is also described. These complaints are non-specific and correspond with the patient’s complaints. Children are more apt to present with more severe symptoms, including jaundice, and may be associated with other biliary anomalies. The classic triad in children is seen in 30-60% of cases and include: right upper quadrant pain, intermittent jaundice, and palpable right upper quadrant mass. In adults the classic triad is seen in 20%.
The etiology of choledochal cysts may be reflux of pancreatic enzymes into the biliary ducts due to a relatively higher pressure within the pancreatic ductal system. Demographics include: 3:1 female to male ratio; 60% present before age 10.
Complications of choledochal cysts include: rupture with peritonitis; cholangitis; biliary cirrhosis; and portal hypertension; stone formation; portal vein thrombosis; liver abscess; hemorrhage; malignant transformation into cholangiocarcinoma. Complications of Caroli’s disease include: stone formation (95%), within the dilated intrahepatic ducts; recurrent cholangitis; liver abscess; and a 100-fold increase in biliary ductal carcinoma (7% of patients).
Nuclear medicine hepatobiliary imaging can be useful in differentiating hepatic cysts, pancreatic pseudocysts, and enteric duplication from choledochal cysts, as the tracer (e.g., Tc99m-mebrofenin) will exhibit filling and stasis within the true choledochal cyst. Another differential consideration on CT is hydatid cyst.
In this patient, the diagnosis is not compatible with a strict definition of a Type I cyst, but could be classified under the catch-all definition of Type V biliary duct cyst. However, it may be better simply to describe the findings as an unclassified type.
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