Malrotation and Midgut Volvulus

Sarah Mezban

CLINICAL INFORMATION

Malrotation results when the normal embryologic sequence of bowel development and fixation is interrupted. Malrotation predisposes to two problems: midgut volvulus and small bowel obstruction. Because of the potential for midgut volvulus and infarction of the entire small bowel, malrotation with midgut volvulus is a life-threatening surgical emergency in the newborn.

Embryology.

Normal rotation of the proximal duodenojejunal loop and the distal cecocolic loop takes place around the superior mesenteric artery (SMA) as the axis, and is usually divided into three stages:

Stage I. Physiologic herniation of the gut through the umbilicus at sixth week of gestation is accompanied by a 180-degree counterclockwise rotation of the developing intestine around the SMA. The midgut lengthens along the SMA, and as rotation continues, a very broad pedicle is formed at the base of the mesentery.
Stage II. At the 10th week of gestation the bowel returns to the abdominal cavity. As it returns, the duodenojejunal loop rotates an additional 90 degrees to end at the anatomic left of the SMA. The cecocolic loop turns 180 degrees more as it reenters the abdominal cavity. This turn places it to the anatomic right of the SMA.
Stage III. Occurs from 11 weeks’ gestation until term. It involves the descent of the cecum to the right lower quadrant and fixation of the mesenteries. Normal small bowel mesentery has a broad attachment stretching diagonally from the duodenojejunal junction (DJJ) (in the left upper quadrant) to the cecum (in the right lower quadrant). The point of attachment at the DJJ is referred to as the ligament of Treitz.

Pathophysiology.

The cause of intestinal malrotation is disruption in the normal embryological development of the bowel at any stage.

Nonrotation

Arrest in development at stage I results in nonrotation. Subsequently, the DJJ does not lie inferior and to the left of the SMA, and the cecum does not lie in the right lower quadrant. The mesentery in turn forms a narrow base which is prone to clockwise twisting, leading to midgut volvulus. The width of the base of the mesentery is different in each patient, and not every patient develops midgut volvulus.

Incomplete Rotation

Stage II arrest results in incomplete rotation and is most likely to result in duodenal obstruction. Typically, peritoneal bands running from the misplaced cecum to the mesentery compress the third portion of the duodenum.

Incomplete Fixation

Malrotation is most often associated with malfixation. Potential hernial pouches form when the mesentery of the right and left colon and the duodenum do not become fixed retroperitoneally.

Frequency.

Malrotation frequency is unknown since many asymptomatic patients may never present; it is estimated to occur in 1 in 500 live births.

Age.

In 60% of patients, malrotation presents by age 1 month. Another 20-30% of patients present at age 1-12 months. Malrotation may remain clinically “silent” for some time and can present at any age.

Clinical Presentation.

The typical history of a patient with intestinal malrotation depends on age at presentation and degree of obstruction.