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MALROTATION MIDGUT VOLVULUS IN NEWBORN
Category: Child Health
Abstract : Malrotation and volvulus : Because of the potential for midgut volvulus and loss of the entire small bowel, malrotation represents perhaps the most feared cause for proximal small-bowel obstruction. Midgut volvulus from malrotation is a life-threatening surgical emergency in the newborn. Remember that malrotation is not synonymous with volvulus. Malrotation occurs in approximately 1 in 6000 newbor
Malrotation and volvulus : Because of the potential for midgut volvulus and loss of the entire small bowel, malrotation represents perhaps the most feared cause for proximal small-bowel obstruction. Midgut volvulus from malrotation is a life-threatening surgical emergency in the newborn. Remember that malrotation is not synonymous with volvulus.
Malrotation occurs in approximately 1 in 6000 newborns; rotational abnormalities may be present in as many as 1% of the population. Volvulus represents the acute twisting of the intestines upon their mesentery and can occur in a patient with malrotation due to the lack of normal fixation of the bowel to the retroperitoneum. Patients who develop obstructive symptoms of malrotation usually present in the first month of life. Of those who are eventually symptomatic, 90% present in the first year of life. Associated anomalies include duodenal or jejunoileal atresia, Hirschsprung disease, and, rarely, mesenteric cysts.
Malrotation results from a failure of the GI tract to complete its normal rotation as it returns to the abdominal cavity at 8-10 weeks' gestation. The bowel develops outside of the abdominal cavity as a single long loop of bowel based on the pedicle of the superior mesenteric vessels. As the bowel returns to the abdomen, the proximal small bowel returns first and the duodenum rotates underneath the superior mesenteric vessels to assume a retroperitoneal position. Rotation continues as the large bowel returns to the peritoneal cavity, rotating over the vascular pedicle to place the ileocecal valve in the right lower quadrant and establishing the hepatic and splenic flexures.
Fixation points develop in the peritoneum at the duodenum, ligament of Treitz, ileocecal valve, and right and left paracolic gutters. This arrangement results in a broad fixed base of the small-bowel mesentery by 10 weeks' gestation. If the rotation of the bowel is incomplete or does not occur, normal mesenteric attachments are absent and abnormal peritoneal bands may develop. These bands may obstruct the duodenum and are known as Ladd bands. Most worrisome in malrotation is the lack of peritoneal attachments of the bowel. The unfixed bowel may twist around itself and compromise the blood supply of the superior mesenteric pedicle.
The initial presentation of a newborn with volvulus of the midgut may be bilious vomiting. The abdomen is initially soft and scaphoid and may or may not be tender on physical examination. As the obstruction progresses, the volvulus compromises flow in the superior mesenteric pedicle and the ischemic bowel becomes dilated, distended, and firm. The child may become hypotensive from sequestration of fluid within the obstructed bowel; peritonitis and shock may develop. Metabolic acidosis on laboratory evaluation may indicate bowel compromise. Prompt surgical intervention is required.
Some patients with malrotation present with a more indolent course of long-standing partial obstructive symptoms, constipation, and associated intestinal dysmotility. A history of chronic intermittent abdominal pain may also be associated with malrotation, presumably from intermittent partial volvulus.
Radiographic imaging that exhibits a characteristic pattern can confirm a diagnosis of malrotation in a stable patient. An upper GI series usually shows incomplete obstruction with extrinsic compression of the duodenum and torsion of the small bowel. The ligament of Treitz may be found in an abnormal position to the right of the midline or below the level of the pylorus. Obstructive bands may partially block the duodenum. The position of the splenic and hepatic flexure as well as the cecum may not
demonstrate the normal fixation pattern to the right and left paracolic gutters. Ultrasonography may also be helpful in confirming the diagnosis. Normally, the superior mesenteric artery (SMA) lies to the left of the superior mesenteric vein (SMV). An SMA that lies to the right or anterior to the SMV suggests malrotation. Contrast enema may demonstrate the abnormal position of the cecum but is no longer considered the best study to establish the diagnosis of malrotation.
Malrotation with midgut volvulus is a true surgical emergency in the newborn. Delay in operation may result in catastrophic loss of a large portion of the small bowel. In patients with severe midgut volvulus, the entire midgut is necrotic and the child cannot survive. Surgical treatment for malrotation is the Ladd procedure. A Ladd procedure includes evisceration of the midgut and immediate counterclockwise derotation of the gut to release the volvulus and reestablish flow of blood to the bowel. Obstructing Ladd bands from the colon to the duodenum are released.
The position of the mesentery does not allow the bowel to be placed in a normal position within the abdomen; therefore, the bowel is returned to the abdomen in a manner that spreads out the mesentery as much as possible. The duodenum and small bowel are placed on the right side of the abdomen, and the colon is placed on the left, with the cecum in the left lower quadrant. Because the ileocecal valve now is on the left side of the abdomen, the appendix is removed. Development of new postoperative adhesions may secure the bowel in this new configuration to avoid recurrent volvulus.
Morbidity and mortality from malrotation and volvulus are directly related to the extent of bowel necrosis. The mortality rate may be as high as 65% if more than 75% of the small bowel is necrotic at the time of laparotomy. Survivors may develop short bowel syndrome, with its associated complications of malabsorption and malnutrition. The Ladd procedure does not address the intestinal dysmotility associated with malrotation but rather prevents the risk of midgut volvulus. Thus, patients with constipation and motility problems from malrotation may not note improvement in their symptoms following the Ladd procedure.
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