**Question:** Chain of lakes appearance on ERCP is seen in:

A. Choledocholithiasis
B. Cholangitis
C. Choledochal cyst
D. Hepatolithiasis

**Core Concept:** ERCP (Endoscopic Retrograde Cholangiopancreatography) is an endoscopic procedure used to visualize bile and pancreatic ducts. Chain of lakes appearance is a specific radiographic sign seen in certain conditions affecting the biliary tract.

**Why the Correct Answer is Right:** The correct answer, Choledocholithiasis (gallstone in the common bile duct), presents with a "chain of lakes" appearance on ERCP. This refers to the radiopaque (opaque on imaging) gallstones obstructing multiple branches of the common bile duct, resulting in the appearance of multiple radiopaque "lakes" within the obstructed ducts.

**Why Each Wrong Option is Incorrect:**

A. Choledocholithiasis: While gallstones can cause the chain of lakes appearance, it is not the only condition.
B. Cholangitis (inflammation of the bile ducts) does not present with a chain of lakes appearance.
C. Choledochal cyst is a congenital cystic dilatation of the bile ducts, not associated with the chain of lakes appearance.
D. Hepatolithiasis (gallstones in the liver) is not associated with the chain of lakes appearance on ERCP.

**Clinical Pearl:** ERCP can help diagnose and treat various biliary tract diseases, including choledocholithiasis. However, the chain of lakes appearance is a specific radiographic sign in choledocholithiasis, which should be recognized for accurate diagnosis and treatment planning.