IS Case 172: Malrotation
Imaging Sciences URMC 2008
Publication Date: 2009-05-21
Intestinal malrotation is a defect that occurs at the 10th week of gestation. During this stage of development, the intestines normally migrate back into the abdominal cavity following a brief period where they are temporarily located at the base of the umbilical cord. As the intestine returns to the abdomen, it makes two rotations and becomes fixed into its normal position, with the small bowel centrally located in the abdomen and the colon (large intestine) draping around the top and sides of the small intestine. When rotation is incomplete and intestinal fixation does not occur, this creates a defect known as intestinal malrotation.
With intestinal malrotation, the small intestine is located in the right side of the abdomen, while the large intestine is on the left of the abdomen. The cecum and the appendix, which are normally attached to the right lower abdominal wall, are unattached and variably located. In many cases, abnormal tissue referred to as Ladd's bands attaches the cecum to the duodenum and may create a blockage in the duodenum. On cross-sectional imaging the bowel can be seen to have a swirling pattern around the superior mesenteric vessels.
Since the intestine is not properly fixated, the bowel may twist on its own blood supply which can lead to volvulus. When volvulus involves the entire small bowel, it is referred to as mid-gut volvulus. This can result in the loss of most of the intestine. In some case, it may also result in death.
A number of other acute and chronic signs of disease are related to intestinal malrotation and lack of fixation. These include chronic abdominal pain, malabsorption and malnutrition, and subsequent growth disturbance.
Intestinal malrotation occurs in 1 of every 500 live births in the United States. Up to 40% of patients with malrotation show signs of the disease within the first week of life. By 1 month of age, 50 to 60% are diagnosed. Seventy-five to 90% of patients are diagnosed by age 1. The remaining cases are diagnosed after age 1 and into adulthood.
Malrotation of the intestine is usually not evident until the intestine becomes twisted or obstructed by Ladd's bands, resulting in symptoms. Since all of the functional intestine can die with a volvulus, this is considered life threatening.
Children are started on intravenous fluids to prevent dehydration, and antibiotics are administered to prevent infection. A nasogastric tube is placed from the nose into the stomach to prevent gas buildup in the stomach.
Surgical repair is performed as soon as possible. The bowel is untwisted and checked carefully for damage. Ideally, circulation to the intestine is restored after it is untwisted, allowing it to regain its pink coloration. If the intestine is healthy, an operation called the Ladd's procedure is performed to repair the malrotation. Since the appendix is not in the correct location, and it would be difficult to diagnose a future appendicitis, it is usually removed at this time.
If the blood supply to the intestine remains in question after untwisting, another operation is usually performed within 24 to 48 hours to re-evaluate it and determine the extent of bowel necrosis. If it appears that a section of intestine is severely damaged beyond recovery, this damaged portion is removed.
Mortality rates substantially increase with the presence of necrotic bowel at surgery and the presence of other co-existing abnormalities. However, they decrease with age, with the average mortality in infants varying from 5 to 10%.
- Donnelly LF. Fundamentals of Pediatric Radiology. Saunders, 2001:100-103.