**Question:** Double bubble sign is seen in:-

A. Abdominal wall hernia
B. Intestinal obstruction
C. Biliary atresia
D. Meckel's diverticulum

**Core Concept:** The double bubble sign is a clinical sign described during a physical examination, typically in infants, which suggests the presence of two gas-filled structures within the abdomen. These structures could indicate either hernias or gastrointestinal obstructions.

**Why the Correct Answer is Right:** The correct answer, D. Meckel's diverticulum, is a type of congenital gastrointestinal abnormality. Meckel's diverticulum is a vestigial remnant of the omphalomesenteric duct, which is a structure present during embryonic development but involutes in most individuals. In some cases, it can lead to complications such as bleeding, obstruction, or neoplasia. A double bubble sign can occur when Meckel's diverticulum causes obstruction, leading to the presence of two gas-filled structures in the abdomen.

**Why Each Wrong Option is Incorrect:**

A. Abdominal wall hernia: A hernia occurs when internal organs protrude through a weakness in the abdominal wall. A double bubble sign would indicate the presence of two gas-filled structures, but hernias typically only present with a single bubble due to the herniated organ.

B. Intestinal obstruction: While intestinal obstruction can present with a double bubble sign, the correct answer (Meckel's diverticulum) is a specific cause of obstruction. Options A, C, and E do not specifically address the unique cause of the double bubble sign (Meckel's diverticulum).

C. Biliary atresia: Biliary atresia is a liver disease causing obstruction of the biliary tree, leading to cholestasis and jaundice. The double bubble sign is not a characteristic presentation of biliary atresia.

**Clinical Pearl:** The double bubble sign is a clue for the presence of Meckel's diverticulum during physical examination in infants, particularly when associated with other clinical findings like bilious vomiting or signs of bowel obstruction. A thorough understanding of the underlying cause is essential to differentiate between potential diagnoses like hernias, intestinal obstructions, or other conditions like biliary atresia.