62 Malrotation

Clinical Presentation

A 3-week-old boy presents with sudden-onset bilious vomiting.

Figure 62A

Radiologic Findings

Upper gastrointestinal (GI) study (Fig. 62A) demonstrates an abnormally low position of the duodenojejunal junction (DJJ) (arrow), below the level of the duodenal bulb.

Figure 62B Abdominal x-ray of a 5-month-old girl presenting in hypovolemic shock. Thickened bowel loops secondary to ischemia are seen in the left upper quadrant.

Diagnosis

Malrotation

Differential Diagnosis

Displacement of the DJJ by distended bowel loops or intra-abdominal masses
Nonrotation (duodenal loop and small bowel to the right of the midline with the entire colon on the left. May be considered a subset of malrotation, but only rarely associated with volvulus)

Discussion

Background

Malrotation and midgut volvulus is potentially one of the most serious pediatric surgical emergencies, and the role of radiology in its diagnosis is critical. Delay in diagnosis carries the risk of infarctive necrosis of the entire small bowel and is potentially fatal.

Etiology/Embryology

Around the sixth week of gestation, the duodenojejunal and ileocolic segments of the primitive gut herniate into the extraembryonic coelom in the umbilical cord. Both loops elongate and rotate 270 degrees anticlockwise around the axis of the superior mesenteric artery. The bowel loops return to their final positions within the abdominal cavity by the 11th week, and their mesenteries become fixed to the parietal peritoneum.

The duodenal loop is fixed with the DJJ in the left upper quadrant at the ligament of Treitz. The ileocecal junction is fixed in the right lower quadrant. The normal small bowel mesentery therefore has a broad diagonal base across the abdomen.

Any arrest in this 270-degree anticlockwise rotation during physiologic umbilical herniation results in malrotation and malfixation of the small bowel. The DJJ is displaced medially and inferiorly and/or the cecum medially and superiorly. The small bowel mesentery is therefore shortened and the risk of the entire small bowel twisting on its narrow pedicle increased (volvulus).

Midgut volvulus leads to small bowel obstruction, occlusion of the superior mesenteric vessels, ischemia, and, if there is delay in diagnosis and treatment, complete small bowel infarction.

Abnormal peritoneal bands—Ladd’s bands—are often found in association with malrotation, passing from the cecum to the right lateral abdominal wall, crossing the duodenum. They may contribute to duodenal obstruction but are rarely the sole cause.

Figure 62C Signs of volvulus on upper GI study include the classic “corkscrew” appearance (1) and almost complete obstruction of the third part of the duodenum (2).

Clinical Findings

Eighty to 90% of children present with bilious vomiting at <1 year of age, 65 to 75% within the first month of life. However, volvulus can occur at any age, including adulthood, and the diagnosis should always be considered. Late presentation can result in a hypovolemic, shocked patient.

In older children, intermittent obstruction can cause chronic or recurrent abdominal pain, vomiting, and failure to thrive. Rarely, a malabsorption syndrome results from chronic venous and lymphatic obstruction. Melena due to bleeding from mesenteric and intramural varices secondary to chronic venous obstruction has been described.