During early fetal life, the midgut is attached to the yolk sacand loops outward into the umbilical cord. Beginning ataround 10 weeks’ gestation, the bowel reenters the abdomenand rotates counterclockwise around the superior mesentericartery until the cecum arrives in the right lower quadrant.The duodenum rotates behind the artery and terminates atthe ligament of Treitz in the left upper quadrant. The baseof the mesentery becomes fixed along a broad attachmentposteriorly, running from the cecum to the ligament of Treitz (Fig. 129-1A). When rotation is incomplete or otherwiseabnormal, “malrotation” is present. Incomplete rotationoccurs when the cecum stops near the right upper quadrant, and the duodenum fails to move behind the mesenteric artery; this results in an extremely narrow mesenteric root (see Fig. 129-1B) that makes the child susceptible to mid-gut volvulus, causing intestinal obstruction or mesentericartery occlusion and intestinal infarction (Fig. 129-2). It is also common for abnormal mesenteric attachments (Laddbands) to extend from the cecum across the duodenum,causing partial obstruction.
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About 60% of children with malrotation present withsymptoms of bilious vomiting during the first month of life.The remaining 40% present later in infancy or childhood.The emesis initially may be due to obstruction by Ladd bandswithout volvulus. When midgut volvulus occurs, the venousdrainage of the gut is impaired; congestion results in ischemia, pain, tenderness, and often bloody emesis and stools.The bowel undergoes ischemic necrosis, and the child mayappear septic. Physicians must be alert to the possibility ofvolvulus in patients with vomiting and fussiness or abdominal pain.
Plain abdominal x-rays generally show evidence of obstruction. Abdominal ultrasound may show evidence of malrotation. An upper gastrointestinal (GI) series shows the absence of a typical duodenal “C-loop,” with the duodenum instead remaining on the right side of the abdomen. Abnormal placement of the cecum on follow-through (or by contrast enema) confirms the diagnosis. Laboratory studies are nonspecific, showing evidence of dehydration, electrolyte loss, or evidence
Figure 129-1 A, Normal rotation of the midgut. Note the long axis of mesenteric attachment (line). B, Midgut malrotation. Note the narrow mesentery, which predisposes to volvulus, and the presence of Ladd bands extending across the duodenum from the abnormally elevated cecum. (From Donellan WJ, editor: Abdominal Surgery of Infancy and Childhood, Luxembourg, 1996, Harwood Academic, pp 43/6, 43/8.)
Figure 129-2 Malrotation with volvulus. Midgut is twisted around the mesentery, with an area of darker, ischemic intestine visible.
(Courtesy Robert Soper, MD.) of sepsis. A decreasing platelet count is a common indicator of bowel ischemia.
in position, but postoperative adhesions tend to hold the mesentery in place, resulting in a broad attachment and eliminating the risk of recurrent volvulus. Necrotic bowel is resected and, at times, results in short gut syndrome.
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Congenital partial or complete blockage of the intestine is a developmental defect that occurs in about 1 in 1500 live births. Atresia occurs in several forms (Fig. 129-3). One ormore segments of bowel may be missing completely, theremay be varying degrees of obstruction caused by webs orstenosis, or there may be obliteration of the lumen in cord-like bowel remnants. The end result is obstruction with