A 5-day-old infant presents with bilious vomiting. An upper gastrointestinal series shows the duodenojejunal junction displaced to the right of the spine. This condition is caused by abnormal fixation of the primary intestinal loop, resulting in fibrous bands called:

Ladd's bands are the correct answer because they are the abnormal peritoneal fibrous bands that form when the midgut loop fails to complete normal rotation and fixation, crossing the duodenum and causing the obstruction seen in intestinal malrotation.

Why Ladd's bands fit the clinical picture exactly

The infant in the stem has bilious vomiting at 5 days of age, which is the classic presentation of proximal intestinal obstruction in the newborn period. The upper gastrointestinal series finding, displacement of the duodenojejunal junction to the right of the spine, is the radiographic hallmark of intestinal malrotation. In normal anatomy, the duodenojejunal flexure lies to the left of the spine at the level of the duodenal bulb, suspended by the ligament of Treitz. When the midgut loop fails to complete its 270 degree counterclockwise rotation and subsequent fixation to the posterior abdominal wall, the cecum and appendix remain in the upper abdomen, and fibrous peritoneal bands extend from the malpositioned cecum across the second and third parts of the duodenum to the retroperitoneum. These bands are Ladd's bands. They compress the duodenum externally, producing the bilious vomiting described. The condition is surgical, not medical, because the obstruction is mechanical and the malrotated bowel is at risk for midgut volvulus around the narrow mesenteric base, a true surgical emergency that can cause intestinal ischemia and necrosis within hours. The combination of bilious vomiting plus a duodenojejunal junction displaced to the right of the spine is pathognomonic for malrotation with Ladd's bands, making option D the only answer that accounts for both the clinical and radiographic findings.

Embryology of midgut rotation and where it fails

The midgut, supplied by the superior mesenteric artery, elongates rapidly during the sixth week of gestation and herniates through the umbilical ring into the extraembryonic coelom because the abdominal cavity is too small to accommodate it. While in the umbilical cord, the midgut loop rotates 270 degrees counterclockwise around the axis of the superior mesenteric artery. The prearterial limb (which becomes the small intestine) rotates first, passing posterior to the artery, and the postarterial limb (which becomes the ascending and transverse colon) rotates second, passing anterior to the artery. Between the tenth and twelfth weeks, the herniated bowel returns to the abdominal cavity. The duodenojejunal junction should fix to the left of the spine, and the cecum should descend to the right lower quadrant. When this rotation and fixation sequence fails, the cecum remains in the upper abdomen, usually near the midline or left upper quadrant, and the mesentery has a narrow attachment that permits the entire midgut to twist around the superior mesenteric artery, producing midgut volvulus. Ladd's bands are the peritoneal folds that form between the malpositioned cecum and the liver, gallbladder, or retroperitoneum, crossing the duodenum and causing extrinsic compression. The bands are not congenital malformations in the sense of a developmental field defect; they are acquired peritoneal adhesions that form because the cecum is in the wrong position. This distinction matters because it explains why the bands can be divided surgically without resecting bowel, which is the basis of the Ladd procedure.

Clinical presentation, diagnosis, and surgical management

Intestinal malrotation presents most commonly in the first month of life, with bilious vomiting as the cardinal symptom. The vomitus is bilious because the obstruction is distal to the ampulla of Vater. The infant may appear well initially, which can delay diagnosis, but the window for intervention is narrow because midgut volvulus can supervene at any time. The diagnostic study of choice is the upper gastrointestinal series, not abdominal ultrasound, although the ultrasound finding of an inverted relationship between the superior mesenteric vein and superior mesenteric artery (vein to the left of the artery instead of to the right) supports the diagnosis. The upper GI series shows the duodenojejunal junction displaced to the right of the spine, a corkscrew appearance of the duodenum and proximal jejunum if volvulus is present, and delayed passage of contrast through the obstructed segment. The Ladd procedure, described by William Ladd in 1936, involves counterclockwise detorsion of the volvulus if present, division of Ladd's bands, broadening of the mesenteric base, appendectomy, and placement of the small intestine on the right side and the colon on the left side. Appendectomy is performed because the cecum remains on the right side after the procedure, and future appendicitis would present atypically. The procedure does not correct the malrotation anatomically; it prevents volvulus by fixing the bowel in a nonrotated position. Mortality is low when performed before intestinal necrosis occurs, but rises sharply if the bowel has infarcted.

How this topic appears on postgraduate entrance examinations

Examiners test malrotation in three predictable ways. First, they present a neonate with bilious vomiting and ask for the diagnosis, which is malrotation until proven otherwise. Second, they describe the upper GI series finding of a duodenojejunal junction displaced to the right of the spine and ask what structure causes the obstruction, which is Ladd's bands. Third, they ask about the embryologic mechanism, which is failure of the 270 degree counterclockwise rotation of the midgut loop. The distractors are always remnants of other embryologic structures: the urachus, the vitelline duct, and the notochord. The urachus connects the bladder to the umbilicus and causes a urinary discharge from the umbilicus when patent. The vitelline duct connects the midgut to the yolk sac and causes a Meckel's diverticulum when its proximal portion persists. The notochord induces neural tube formation and its remnants are not related to intestinal obstruction. A table comparing these structures is provided below. Examiners may also ask about the surgical procedure, the Ladd procedure, and specifically why appendectomy is performed, which is to prevent diagnostic confusion from future appendicitis in an abnormally positioned cecum. The most dangerous trap is confusing malrotation with duodenal atresia, which also causes bilious vomiting but shows the double bubble sign on plain radiograph without distal gas, whereas malrotation shows a normal or near normal gas pattern with the upper GI series revealing the displaced duodenojejunal junction.

Why the other options fail

One-glance recall table

Mnemonics

What the exam actually asks

• Bilious vomiting in a neonate is malrotation with midgut volvulus until proven otherwise. Do not choose duodenal atresia unless the stem gives the double bubble sign with no distal gas.
• The upper GI series, not ultrasound, is the gold standard for diagnosing malrotation. The displaced duodenojejunal junction to the right of the spine is the key finding.
• Ladd's bands are peritoneal folds from the malpositioned cecum to the retroperitoneum. They are not a separate embryologic structure but a consequence of failed fixation.
• The Ladd procedure includes division of bands, detorsion, broadening of the mesentery, and appendectomy. Appendectomy is done to avoid future diagnostic confusion.
• Midgut volvulus is a surgical emergency. The narrow mesenteric base in malrotation permits the entire small bowel to twist around the superior mesenteric artery, causing ischemia within hours.

Traps that cost marks

• Choosing vitelline ligament because the vitelline duct is a midgut structure. The vitelline duct causes Meckel's diverticulum, not duodenal obstruction from fibrous bands.
• Choosing urachus because it is a fibrous remnant. The urachus is a bladder-to-umbilicus structure and causes umbilical discharge, not bilious vomiting.
• Confusing malrotation with duodenal atresia. Both cause bilious vomiting, but duodenal atresia shows the double bubble sign on plain film with no distal gas, and the duodenojejunal junction is normally positioned.
• Assuming the upper GI series finding of a displaced DJ junction is diagnostic of volvulus. The displaced DJ junction indicates malrotation; the corkscrew sign indicates volvulus.

Frequently asked

What is the difference between malrotation and volvulus?

Malrotation is the anatomic abnormality in which the midgut loop fails to complete its normal 270 degree counterclockwise rotation and fixation, leaving the cecum in the upper abdomen and the mesentery with a narrow base. Volvulus is the twisting of the midgut around the superior mesenteric artery that occurs as a complication of malrotation. Malrotation is the underlying condition; volvulus is the acute emergency that can cause intestinal ischemia and necrosis. Not all patients with malrotation develop volvulus, but all patients with midgut volvulus have malrotation.

Why is appendectomy performed during the Ladd procedure?

Appendectomy is performed because after the Ladd procedure, the cecum remains on the right side of the abdomen but the small intestine is placed on the right and the colon on the left, creating a nonanatomic arrangement. If the patient later develops appendicitis, the pain would present atypically, potentially delaying diagnosis. Removing the appendix during the initial procedure eliminates this future diagnostic confusion. The appendix itself is not involved in the obstruction.

Can malrotation present in older children or adults?

Yes, although the classic presentation is in the first month of life, malrotation can present in older children or even adults with chronic intermittent vomiting, abdominal pain, malabsorption, or acute volvulus. The diagnosis is made by upper gastrointestinal series showing the displaced duodenojejunal junction. The Ladd procedure is performed regardless of age when malrotation is diagnosed, because the risk of volvulus persists throughout life.

References

• Gray's Anatomy, 42nd. Chapter on embryology of the gastrointestinal tract, midgut rotation and fixation
• Bailey and Love's Short Practice of Surgery, 28th. Chapter on neonatal intestinal obstruction, malrotation and the Ladd procedure
• Robbins and Cotran Pathologic Basis of Disease, 10th. Chapter on congenital anomalies of the gastrointestinal tract