Discussion Author: Timothy Justin Miller
Choledocholithiasis and Gallstone pancreatitis
One of the most common causes of biliary outflow obstruction is common duct stones or choledocholithiasis. It accounts for about 20-50% adult cases of obstructive jaundice. Gallstones are very common in the general population, but they do not always cause pathology. 10 % of the population has gallstones seen on ultrasound examination; however, other causes of CBD obstruction musty be ruled out, especially if CBD dilatiation is seen without identification of an obstructing lesion.
The sensitivity of US for the detection of stones ranges from 20-80%. This sensitivity is improved when the pancreatic head is well visaulized and there is CBD dilatation. CT is similiar to US , while contrast studies and MRCP have the highest sensitivity.
If intrahepatic or extrahepatic dilation is seen, an obstructing lesion must be sought. The upper limits of normal for the CBD are 7 mm. This may increase by one mm for every decade over 60 and it may extend to 10 mm if the patient has had a prior cholecystectomy. Differential considerations for CBD dilatation include choledocholithiasis, tumor, inflammatory stricture, iatrogenic obstruction, autioimmune diseases and certain parasites. The most common causes are benign in nature; however, malignant tumors account for about 25 % of cases. The most common tumors include: pancreatic head tumors, cholangiocarcinoma, to include the Klatskin tumor, ampullary/duodenal carcinoma, metastasis and lymhadenopathy.
As previously discussed, if CBD dilatation is the only thing definitively diagnosed on initial imaging then follow up studies are warreanted to rule out more insidious etiologies.
In this case, the patient fell within the majority, with a simple gallstone pancreaitis. The gallstone and the head of the pancreas was not visualized on initial ultrasound examination, therefore a CT scan, pancreas protocal was ordered to further evaluate.The diagnosis was elucidated on CT and no further imaging was required.
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