**Question:** Double-Bubble" sign in X-ray is seen in

A. Obstructive jaundice
B. Choledochal cyst
C. Cystic fibrosis
D. Inflammatory bowel disease

**Correct Answer:** B. Choledochal cyst

**Core Concept:** The "Double-Bubble" sign in X-ray is a radiological sign that is associated with conditions involving the biliary tract and the stomach. It is named so because it presents as two rounded bubbles in the abdomen, representing the dilated biliary tree (the larger bubble) and the stomach (the smaller bubble).

**Why the Correct Answer is Right:** The correct answer, Choledochal cyst, is a rare congenital abnormality where cystic dilatation of the bile duct is seen. This condition results from a failure of the cystic duct to fuse with the common bile duct during development. The dilated biliary tree (the larger bubble) and the stomach (the smaller bubble) are clearly visible on X-ray, resulting in the characteristic "double-bubble" appearance.

**Why Each Wrong Option is Incorrect:**

A. Obstructive jaundice: This condition results from blockage in the biliary tree and is typically caused by gallstones, choledocholithiasis, or tumors. On X-ray, obstructive jaundice typically presents with dilated biliary tree without a visible stomach bubble.

B. Cystic fibrosis: This genetic disorder affects multiple organs, including the lungs, pancreas, and gastrointestinal tract. The "Double-Bubble" sign is not a feature of cystic fibrosis, which primarily affects the lungs and digestive system.

C. Inflammatory bowel disease: Inflammatory bowel disease (e.g., Crohn's disease) affects the gastrointestinal tract, particularly the terminal ileum and colon. The "Double-Bubble" sign is not seen in inflammatory bowel disease, as it primarily affects the colon and rectum, not the stomach and biliary tree.

**Clinical Pearl:** The "Double-Bubble" sign is an essential clinical clue for the diagnosis of choledochal cyst, a rare congenital abnormality involving the biliary tree. Adequate knowledge of this sign can help guide the physician in differentiating choledochal cyst from other conditions presenting with similar signs and symptoms, ensuring appropriate management and treatment.