Intestinal malrotation

Overview
Intestinal malrotation is a congenital anomaly of rotation of the midgut (embryologically, the gut undergoes a complex rotation outside the abdomen). As a result:
 * the small bowel is found predominantly on the right side of the abdomen
 * the cecum is displaced (from its usual position in the right lower quadrant) into the epigastrium - right hypochondrium
 * the ligament of Treitz is displaced inferiorly and rightward
 * fibrous bands (of Ladd) course over the horizontal part of the duodenum (DII), causing intestinal obstruction.
 * the small intestine has an unusually narrow base, and therefore the midgut is prone to volvulus (a twisting that can obstruct the mesenteric blood vessels and cause intestinal ischemia).

Associated conditions
This can lead to a number of disease manifestations such as:
 * acute midgut volvulus
 * chronic midgut volvulus
 * acute duodenal obstruction
 * chronic duodenal obstruction
 * internal herniation

Causes
The exact causes are not known. It is not associated with a particular gene, but there is some evidence of recurrence in families.

Presentation
Patients (often infants) present acutely with midgut volvulus, manifested by bilious vomiting, crampy abdominal pain, abdominal distention, and the passage of blood and mucus in their stool. Patients with chronic, uncorrected malrotation can have recurrent abdominal pain and vomiting.

Malrotation can also be entirely asymptomatic.

Diagnosis
With acutely ill patients, consider emergency surgery laparotomy if there is a high index of suspicion.

Plain radiography may demonstrate signs of duodenal obstruction with dilatation of the proximal duodenum and stomach but it is often non-specific. Upper gastrointestinal series is the modality of choice for the evaluation of malrotation as it will show an abnormal position of the duodeno-jejunal flexure (ligament of Treitz). In cases of malrotation complicated with volvulus, it demonstrates a corkscrew appearance of the distal duodenum and jejunum. In cases of obstructing Ladd bands, it will reveal a duodenal obstruction.

In equivocal cases, contrast enema, may be helpful by showing the caecum at an abnormal location.

It is usually discovered near birth, but in some cases is is not discovered until adulthood. In adults, the "whirlpool sign" of the superior mesenteric artery can be useful in identifying malrotation.

Treatment
Resuscitate the patient with fluids to stabilize them before surgically
 * correcting the malrotation
 * cutting the fibrous bands over the duodenum.

One surgical technique is known as "Ladd's procedure", after Dr. William Ladd.