A 2-day-old neonate presents with bilious vomiting and abdominal distension. Imaging reveals a 'bird's beak' appearance at the duodenojejunal junction with proximal bowel dilatation. Which is the most common site of intestinal obstruction due to malrotation of the gut?

Explanation

## Most Common Site of Obstruction in Malrotation **Key Point:** The duodenojejunal junction is the most common site of obstruction in malrotation of the gut, accounting for >90% of symptomatic cases. ### Embryological Basis During normal gut rotation (weeks 6–10 of gestation): 1. The midgut herniates out of the coelom and rotates 270° counterclockwise around the superior mesenteric artery (SMA). 2. The duodenojejunal junction normally rotates to the left of the midline and becomes fixed by the ligament of Treitz. 3. In malrotation, this junction fails to rotate properly, remaining on the right side of the midline. ### Why the Duodenojejunal Junction? When malrotation occurs, abnormal peritoneal attachments (Ladd's bands) form across the duodenum at the duodenojejunal junction. These bands: - Compress the duodenum from anterior and lateral aspects - Create the characteristic "bird's beak" appearance on barium studies - Obstruct the passage of chyme, causing bilious vomiting **Clinical Pearl:** The classic presentation is a neonate or young infant with bilious vomiting within the first few days of life. The vomiting is bilious (not bilious-free) because the obstruction is distal to the ampulla of Vater. **High-Yield:** Midgut volvulus (twisting of the entire midgut around the SMA) is the most serious complication of malrotation and can occur with or without Ladd's bands. It presents as an acute surgical emergency with shock and necrotic bowel. ### Comparison with Other Sites | Site | Frequency in Malrotation | Mechanism | |------|--------------------------|----------| | **Duodenojejunal junction** | >90% | Ladd's bands compression | | Ileocecal junction | Rare | Not a typical obstruction site | | Jejunoileal junction | Rare | Not a typical obstruction site | | Cecal region | Rare | Cecum is normally on right; not obstructed | **Mnemonic:** **DJJ** (Duodenojejunal Junction) = **D**uodenal **J**unction = **J**unction of **D**uodenum — the most common site. ### Management Once malrotation with Ladd's bands is diagnosed: - **Surgical correction:** Ladd's procedure (division of Ladd's bands, widening of the mesentery, and repositioning of the cecum to the left). - **Emergency if volvulus present:** Immediate surgical exploration to assess bowel viability. [cite:Langman's Embryology 14e Ch 11]