Anomalous pancreaticobiliary junction
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Anomalous pancreaticobiliary junction, also known as pancreaticobiliary maljunction, describes the abnormal junction of the pancreatic duct and common bile duct that occurs outside the duodenal wall to form a long common channel.
The incidence varies from 1.5% to 3.2% 11. The estimated prevalence in Asia is 100 to 1000 times higher than in other parts of the world 6. It is more common in females (F:M=3:1) 7.
It can be divided into 2 types:
with biliary dilatation (~ 80%): 50% diagnosed in children, often associated with stricture of the hilar duct and tends to have a higher incidence of symptoms
without biliary dilatation (~20%): the main symptom is abdominal pain, it is more difficult to diagnose as there is no biliary dilatation
choledochal cyst: the vast majority of patients with Todani type Ia, Ic, and IVa choledochal cysts, in which dilatation involves principally the main bile duct, have an anomalous pancreaticobiliary junction 2
bile duct stricture: affecting the distal duct or hilar duct
synchronous biliary cancer: rare 6,7 with increased incidence on coexistence with biliary dilatation, especially Todani type I
The origin of a long common channel might be formed embryologically with adhesion of the ventral pancreatic duct and the terminal portion of the bile duct 8. It is divided into anomalous pancreaticobiliary junction with biliary dilatation (77%) and without biliary dilatation (23%) 7.
The anomalous pancreaticobiliary junction makes biliary drainage not under the control of sphincter of Oddi, resulting in pancreatic juice reflux into the biliary tract that injures the biliary epithelium 5.
The Japanese Study Group on Pancreaticobiliary Maljunction (JSPBM) proposed the following classification in 2015 9:
type A (stenotic type): dilatation of the common bile duct upstream of a stenotic segment of the distal common bile duct, which joins the common channel
type B (non‐stenotic type): nonstenotic distal common bile duct smoothly joins the common channel; no localized dilatation of the common channel
type C (dilated channel type): narrow distal common bile duct joins dilated common channel
An intrabiliary amylase level more than 8000 UI/L within the bile duct and gallbladder obtained endoscopically (ERCP) or percutaneously suggests reflux of pancreatic juice through an anomalous pancreaticobiliary junction and shows a positive predictive value and a specificity of more than 90 % 6.
In patients with a short common channel, direct cholangiography (e.g. ERCP) can be effective in the assessment of pancreaticobiliary junction incompetence.
It has a limited role in diagnosis, but is a useful noninvasive tool for screening. Careful measurement of the common bile duct and comparison with the normal limits for age helps in early detection. Detection of a dilated common bile duct may be the first clue to suspect pancreaticobiliary maljunction with biliary dilatation. In this case, further MRCP is recommended for biliary junction anatomy. It is also associated with gallbladder wall thickening. However, it is non-specific.
The visualization of pancreaticobiliary junction outside the duodenal wall can be detected at endoscopic ultrasound. It is also helpful in screening and surveillance of biliary cancer after diagnosis of pancreaticobiliary maljunction.
pancreaticobiliary junction outside the duodenal wall
common channel length of ≥8 mm, though some authors suggest a cutoff of >15 mm 5
an abnormal union between the pancreatic and bile ducts
common bile duct dilatation is suggestive of pancreaticobiliary maljunction with biliary dilatation
Drip-infusion cholangiography CT involves the injection of intravenous biliary contrast agent and can well-delineate biliary anatomy and is less invasive than ERCP.
Treatment and prognosis
Once an anomalous pancreaticobiliary junction has been diagnosed, risk-reducing prophylactic surgical correction is recommended to reduce the risk of developing biliary cancer. Follow up of these cases is essential even years after prophylactic surgery as the residual bile ducts still have risk for cancer 5.
For patients without biliary dilatation, prophylactic cholecystectomy is recommended as the gallbladder is the commonest site for cancer development in these patients.
biliary stones: within the bile ducts or gallbladder
History and etymology
Anomalous pancreaticobiliary junction was first described by Arnolds in 1906 in an autopsy case in Germany 10.
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