Clinical History
Vomiting, pale diarrhea and dehydration associated to abdominal distension and intraperitoneal free liquid collections, a surgical emergency, needing peroperative imaging.
Imaging Findings
Patient admitted for vomiting, pale diarrhea and a weight loss of of 120 grams in 24 hours. Her general state was diminished with discrete signs of dehydration. Abdominal distension was noted with rare peristaltic noises. Abdominal ultrasonography showed free liquid collection in hepato-renal and Douglas recesses. Contrast enema was unrelevant.
Explorative laparotomy and peroperative retrograde cholangiography (fig 1 and 2) showed a type I 4 cm ruptured choledochal cyst.
Discussion
By definition a choledochal cyst relates to an intra or/and extra-hepatic biliary tree dilatation . It is rare condition which is most often diagnosed before the age of 10 (1,2). However few cases of elderly patients have been reported (2).
Classification
Todani and al (3) described six different type of cysts. Type I is the most frequent type (80-90%) and consists in a fusiform dilation of the choledochal duct. Type II is an eccentric diverticulum of the common bile duct. Type III is a dilation involving the intraduodenal portion of the choledochal duct, corresponding to the choledocele. Type IVA consists in multiple extra-hepatic dilatation associated with intra-hepatic dilations involving one or more segments of the biliary tree. Type B in multiple dilations of the extra-hepatic biliary tree, the intra-hepatic one being normal. Type V involves only the intra-hepatic biliary tree and relates to Caroli disease.
Pathogenesis
Choledochal cysts aetiology has been widely discussed. The theory involving an epithelial proliferation of embryonic common bile duct has recently been supplanted by the common channel theory proposed by Babbit et al (4). In this theory, a faulty budding (proximal to gallbladder) of the primitive ventral pancreatic duct is responsible for a long common channel draining both the biliary tree and the pancreatic duct (2). As no sphincter is present at the junction between the biliary tract and the pancreatic tree, there will be a free passage of bile and pancreatic juices. Since the pressure in pancreatic duct is higher than the pressure in the common bile duct (2), a chronic reflux of pancreatic juice into the biliary tree will occur. It has been actually shown that choledochal cysts contain high levels of amylases and in an experimental model, dilation of the common bile duct was induced by prolonged exposure to pancreatic juice (5).
Clinical signs
The most frequent clinical signs are abdominal pain, jaundice, fever, pale stool, but mass are more commonly seen in children than in the adult population (1). Clinically, in newborns, choledochal cysts may mimic biliary atresia and Tc-99m disofenin scintigraphy or CT- or RM-cholangiography may help to asses the diagnose.
Different complications may occur such as recurrent pancreatitis, spontaneous or traumatic cystic rupture, lithiasis, cholangitis, progressive biliary cirrhosis, and portal hypertension due either to the compression exerced by the cyst on the portal vein, or to the cirrhosis. The occurrence of carcinoma has been found to be 2,5 to 26 times higher than in the normal population (1). The risk of malignant transformation increases with age. The highest incidence of cancer belong to Type I cyst followed by IV and III (3).
Imaging features
Abdominal plain films show displacement of normal anatomic structures by a soft tissue density mass (2). Ultrasonography (US)and CT scan provide essentials information’s about the location, size, and associated dilation of the intra-hepatic biliary tree (2). The evidence of a non peristaltic cyst extending into the hepatic parenchyma, between the right and left lobes, is diagnostic of type I choledochal cyst, differentiating it from other abdominal cystic lesion such as duodenal duplication (2). CT and US show the internal content of choledochal cyst, which can relates to stones or rarely to carcinoma (2). US may underestimated the extend of biliary tree dilation (1). CT scan is more accurate to demonstrate intra-hepatic biliary tree and the distal choledochal duct, which may be obscured by bowel gas on US (2).
CT- or RM-cholangiography demonstrate the entire biliary tree with less invasive manipulation than percutanous transhepatic cholangiography or endoscopic retrograde cholangiopancreatography (ERCP).
Hepatobiliary scintigraphy with Tc-99m disofenin shows accumulation and stasis of the radionuclide into the dilated biliary ducts followed by bowel excretion (2).
Surgical management
Cyst excision has supplanted simple drainage because of the risk of cholangiocarcinoma and the risk of pancreatitis following the percutaneous procedure. Surgical techniques differes according to the cyst type (1). Type I is managed with surgical excision and hepaticojejunostomy. Type II is managed with a simple cyst excision. Type III don’t need any surgical approach and is simply managed by sphincterotomy during ERCP. Type IV are managed with a total excision of the extrahepatic cyst and type IVA with an associated hepatic lobectomy when intra-hepatic cysts are confined to only one lobe. Caroli’s disease can be treated by partial hepatectomy when feasible, or, in the diffuse form, by medical management of symptoms associated with permanent external drainage. In this last situation transplantation may be considered.
Differential Diagnosis List
