**Question:** A 2-day-old female infant with fever is examined by the pediatric team. Imaging reveals malrotation of the small intestine without fixation of the mesenteries. The vessels around the duodenojejunal junction are obstructed and the intestine is at risk of becoming gangrenous. Which of the following has occurred to cause the obstruction?

A. Ladd's procedure
B. Volvulus
C. Meckel's diverticulum
D. Congenital hypothyroidism

**Core Concept:** Malrotation of the small intestine is a congenital anomaly where the bowel fails to rotate during the embryonic period. This leads to an abnormal arrangement of the mesenteric attachments and increases the risk of bowel obstruction.

**Why the Correct Answer is Right:** The correct answer is **B. Volvulus**. During normal fetal development, the small intestine rotates and fixates to the posterior abdominal wall and the liver. Malrotation occurs when this process is incomplete, leading to volvulus. In this case, the obstruction occurs due to twisting of the mesenteric vessels around the duodenojejunal junction, causing ischemia and gangrene if not promptly addressed.

**Why Each Wrong Option is Incorrect:**

A. Ladd's procedure: This is a surgical intervention used to correct malrotation after the onset of symptoms. It is not the cause of malrotation but a treatment for it.

C. Meckel's diverticulum: Meckel's diverticulum is a congenital accessory pocket in the intestine that does not affect the bowel rotation and is not the cause of the obstruction in this case.

D. Congenital hypothyroidism: This is a thyroid hormone deficiency and unrelated to bowel rotation anomalies. It is a separate endocrine disorder.

**Core Concept:** Volvulus is a type of bowel obstruction caused by the twisting of the mesentery around the bowel, leading to reduced blood supply and potential gangrene. Malrotation is a congenital anomaly that predisposes to volvulus.

**Why Each Wrong Option is Incorrect:**

A. Ladd's procedure: This is a surgical intervention for treating malrotation-related volvulus, not a cause of malrotation.

C. Meckel's diverticulum: Meckel's diverticulum is a congenital accessory pocket in the intestine and is unrelated to bowel rotation anomalies and does not cause volvulus.

D. Congenital hypothyroidism: This is an endocrine disorder unrelated to malrotation or volvulus.

**Core Concept:** Malrotation and volvulus are congenital anomalies affecting the gastrointestinal tract, specifically concerning the rotation and fixation of the small intestine.

**Why Each Wrong Option is Incorrect:**

A. Ladd's procedure: This is a surgical intervention used to treat malrotation-related volvulus, not a cause of malrotation or volvulus.

C. Meckel's divertic