Intestinal malrotation is a congenital anatomical anomaly that results from an abnormal rotation of the gut as it returns to the abdominal cavity during embryogenesis.
Although some individuals live their entire life with malrotated bowel without symptoms, the abnormality does predispose to midgut volvulus and internal hernias, with the potential for life-threatening complications.
Intestinal malrotation is a congenital abnormality seen in up to 1:6000 live births 5. It is also frequently (~50%) associated with other abdominal anomalies, some of which are causative and others merely associated 5:
- duodenal atresia, stenosis or web
- congenital diaphragmatic herniation
- gastroschisis and omphalocele: always associated with a degree of malrotation
- heterotaxy: 70% of individuals will have a malrotation
- choanal atresia
The clinical presentation of malrotation often correlates with the age of onset 5.
In the older child or even adult presentation is more frequently intermittent with episodes of spontaneously resolving duodenal obstruction. This is thought to be due to kinking of the duodenum by Ladd bands rather than a volvulus 5. Internal hernias are also encountered.
In some individuals, the presentation is very non-specific with episodes of abdominal pain, weight loss, melaena, or even chronic pancreatitis 5.
During normal embryogenesis, the bowel herniates into the base of the umbilical cord and rapidly elongates. As it returns to the abdominal cavity, it undergoes complex ~270 degrees counter clockwise rotation resulting in the duodenojejunal (D-J) flexure typically located to the left of the midline, at the level of L1 vertebral body and the terminal ileum located in the right iliac fossa. This results in a broad mesentery running obliquely down from the DJ flexure to the caecum and prevents rotation around the superior mesenteric artery (SMA) 1-6.
In malrotation, this does not occur and, as a result, the mesentery has a short root, which allows it to act as a pedicle (through which the SMA and SMV pass) around which volvulus can occur.
Intestinal nonrotation is a subtype of malrotation in which the small bowel is mainly located in the right hemiabdomen and the caecum in the left hemiabdomen.
Abdominal radiographs, in the absence of midgut volvulus, are neither specific nor sensitive 2. They may show:
- right sided jejunal markings
- absence of stool filled colon in the right lower quadrant
May show an inversion in the SMA/SMV relationship with the SMA on the right and the SMV on the left.
- may again show abnormal SMA (smaller and more circular)/SMV relationship
- large bowel predominantly on left and small bowel predominantly on the right
A paediatric upper gastrointestinal contrast study is the examination of choice when the diagnosis is suspected. The key findings of malrotation is an abnormal duodenojejunal (DJ) junction location:
- frontal view
- DJ junction fails to cross the midline to the left of the left-sided vertebral body pedicle
- DJ junction lies inferior to the duodenal bulb
- lateral view
- second and third duodenum not located posteriorly in a retroperitoneal position
Although not specific criteria of malrotation, the jejunum is commonly located to the left of the spine.
Contrast enema has historically also been used, the theory being that in malrotation the large bowel will also be malrotated. Unfortunately, in ~25% (range 20-30%) of cases with malrotation, the caecum is normally located. The converse is also true, with the position of the caecum in normal individuals being variable 4. Very rarely, the caecum may be malrotated and the small bowel in a normal position.
Treatment and prognosis
Due to the potential for life-threatening midgut volvulus and ischaemic bowel, once discovered malrotation is corrected surgically. The general principles of treatment are:
- mobilisation of the bowel including untwisting any volvulus present
- division of abnormal peritoneal bands (Ladd bands)
- widening of the mesenteric base
- fixation of the duodenum and caecum to the retroperitoneum (pexy) is not universally performed 5-6
It should be noted that normal anatomical positioning is not achieved; the duodenum and small bowel remain on the right, and the caecum and colon are on the left side of the abdomen 5-6.
A rate of 15% false positive has been reported in the diagnosis of malrotation using barium meal 7. Hence, differential diagnoses must be kept in mind, including:
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