**Question:** Most common site of gall stone impaction in Cholecysto Intestinal fistula is

A. Choledochus
B. Cecum
C. Ileum
D. Cecal vault

**Core Concept:** Choledochocele is a rare congenital or acquired cystic dilatation of the common bile duct (CBD), resulting from a communication between the CBD and the intestine. When a gallstone becomes trapped in the fistula, it can lead to complications such as cholangitis, pancreatitis, and obstruction.

**Why the Correct Answer is Right:**

The correct answer is the **D. Cecal vault**. In a choledochocele, the common bile duct (CBD) communicates with the cecum or ascending colon, allowing gallstones to enter the intestinal tract and potentially become trapped. This results in gallstone impaction in the cecal vault.

**Why Each Wrong Option is Incorrect:**

A. Choledochus (CBD) is incorrect because the choledochocele already creates a direct connection between the CBD and cecum, allowing stone entry and impaction.
B. Cecum is partially correct, but the correct site is the cecal vault, which represents the area between the cecum and the ileocecal valve.
C. Ileum is incorrect because the choledochocele and subsequent impaction typically occur in the cecal vault, not within the ileum itself.

**Clinical Pearl:**

Understanding choledochocele and its potential complications is essential for physicians dealing with patients presenting with acute abdomen, pancreatitis, or cholangitis. Prompt diagnosis and appropriate management can prevent severe complications associated with these conditions.