Surgical Conditions of the Small Intestine in Infants and Children

Malrotation

Intestinal malrotation represents one of the most common congenital anomalies of the gastrointestinal tract encountered by surgeons. Although 90% of cases manifest during the first year of life (with 50% to 75% presenting within the first month of life), patients may present with midgut volvulus and/or obstruction at any age, making an understanding of the embryology, diagnosis, and treatment of malrotation essential for all abdominal surgeons.

The embryologic steps of intestinal rotation have been well described ( Fig. 83.1 ). At gestational week 5, the midgut herniates out of the abdomen into the umbilicus and rotates 90 degrees counterclockwise around the axis of its primary blood supply, the superior mesenteric artery (SMA). At week 10, the midgut returns to the abdomen, rotating another 180 degrees counterclockwise. Ultimately, the duodenum passes under the SMA and crosses over the spine such that the duodenojejunal junction is anchored in the left upper abdomen, while the cecum is fixed in the right lower quadrant. As a result, the mesentery of the small intestine runs obliquely across the long axis of the abdomen from the ligament of Treitz to the right paracolic gutter; this broad fixation anchors the small bowel and prevents it from volvulizing. The right and left colons are anchored to the posterior abdominal wall by mesenteric attachments. Those anchoring the right colon—Ladd bands—attach to the cecum regardless of the cecum's position.

Classic malrotation, also known as nonrotation, is the most common form. Complete nonrotation implies both duodenojejunal malrotation (the duodenojejunal junction does not cross the spine to lay left of midline) and cecocolic malrotation (the cecum is found in the midabdomen, rather than in the right lower quadrant) and results in suspension of the small intestine on a narrow mesentery that is prone to volvulize ( Fig. 83.2A ). Isolated duodenojejunal malrotation (see Fig. 83.2B ) may present with duodenal obstruction secondary to Ladd bands. In isolated cecocolic malrotation, the cecum is extremely mobile and prone to cecal volvulus (see Fig. 83.2C ). In addition, Ladd bands extending from the right paracolic region to the malpositioned cecum may obstruct the duodenum. Reverse rotation, in which the duodenum and SMA are antecolic, rather than retrocolic, may present with transverse colon obstruction (see Fig. 83.2D ).

In 30% to 60% of patients with malrotation, additional congenital anomalies, such as duodenal atresia, imperforate anus, Meckel diverticulum, annular pancreas, preduodenal portal vein, biliary atresia, cardiac anomalies, heterotaxia, trisomy 21, and 16q24 chromosomal deletion syndrome, are seen. Because the pancreas and hepatobiliary tract develop concurrently with intestinal rotation, the association of malrotation with annular pancreas and/or persistent preduodenal portal vein is unsurprising. Congenital diaphragmatic hernias and abdominal wall defects (omphaloceles and gastroschisis) interfere with or abrogate normal rotation before the 10th week of gestation; as such, infants with these conditions are malrotated by definition.

The hallmark of malrotation with midgut volvulus is an infant with bilious emesis. Forty to 60% of neonatal bilious emesis is attributable to surgical bowel obstructions, of which malrotation is the most common cause. As ischemia progresses in midgut volvulus, the infant may develop abdominal distention, hematemesis, hematochezia, peritonitis, and shock. However, it should be noted that volvulized patients may never develop abdominal distention because the point of obstruction may be as proximal as the ligament of Treitz. Malrotation without volvulus may manifest as chronic abdominal pain and/or failure to thrive. It may also be completely asymptomatic and found incidentally during work-up for an unrelated condition.

Early diagnosis of malrotation with volvulus is paramount to prevent potentially life-threatening bowel ischemia. Children with suspected midgut volvulus who show signs of bowel ischemia should undergo emergent surgical exploration without radiologic evaluation. If the child is clinically stable, imaging should be obtained. There are no plain film findings that are pathognomonic for malrotation with volvulus; x-rays may demonstrate a gasless abdomen, a high-grade bowel obstruction, or an essentially normal bowel gas pattern. Ultrasound has gained some degree of acceptance as a screening tool for malrotation. Reversal of the normal anatomic relationship between the SMA and superior mesenteric vein (SMV) is suggestive of malrotation. An ultrasonographic whirlpool sign is consistent with midgut volvulus. However, caution is warranted because false-positive rates of up to 21% are reported with ultrasonographic diagnoses. Therefore, if an ultrasound demonstrates SMA/SMV reversal, malrotation should be confirmed with an upper gastrointestinal contrast study (UGI). UGI remains the criterion standard test for the diagnosis of malrotation. On a normal UGI, the duodenum should cross to the left of the vertebral column and posterior to the stomach. With duodenojejunal malrotation, the duodenum remains to the right of the spine ( Fig. 83.3 ). In midgut volvulus, the small intestine assumes a corkscrew configuration ( Fig. 83.4 ). Contrast enema is rarely used in the work-up for malrotation because the presence of a normally located cecum in the right lower quadrant does not exclude duodenojejunal malrotation and infants often have mobile cecum that may result in false-positive results. Computed tomography (CT) scans may demonstrate twisting of the mesenteric vessels, bowel obstruction, and malposition of the ligament of Treitz and/or cecum. However, the radiation exposure that CT engenders is not without risk. A high-quality UGI conducted by an experienced pediatric radiologist may obviate the need for cross-sectional imaging altogether.

Prompt surgical exploration should be undertaken if midgut volvulus is suspected. In 1936 William Ladd described the surgical procedure for correction of malrotation and midgut volvulus that continues to be used currently. The Ladd procedure is usually done through a right upper quadrant transverse incision in infants and a midline laparotomy in older children and adults. The bowel is inspected and, if volvulized, detorsed in a counterclockwise direction (one may remember to “turn back the hands of time”) ( Fig. 83.5C ). Ladd bands (peritoneal bands crossing from the right paracolic gutter over the duodenum) are lysed (see Fig. 83.5D ), and the base of the mesentery is widened. The bowel is replaced in the abdomen with the small bowel in the right abdomen and the cecum in the left upper abdomen (see Fig. 83.5E ). An incidental appendectomy is usually performed. If ischemic bowel is encountered, its viability should be assessed after a period of observation. Small areas of frankly necrotic bowel should be resected with or without primary anastomosis. Bowel with marginal viability should be left and allowed to declare itself; a second-look procedure should be performed 24 to 36 hours later. The American Pediatric Surgical Association recommends that younger asymptomatic children found incidentally to have malrotation undergo Ladd procedure whereas older ones may be observed. If an operation is electively pursued, it may be approached laparoscopically; the steps of the operation are the same.

After the Ladd procedure, patients should be decompressed with nasogastric tubes (and possibly receive total parenteral nutrition) until their bowel function returns. The mortality from midgut volvulus with severe bowel compromise may exceed 30%. Long-term complications include adhesive small bowel obstruction (10%), recurrent volvulus, and, if significant bowel loss has been sustained, short gut syndrome.

Intestinal Atresia and Duplication Cysts

Duodenal Atresia

Duodenal atresia occurs in 1 in 6000 to 10,000 births. It arises from a recanalization error; the gut tube fails to obliterate its lumen in the sixth week of gestation. The vast majority (92%) are classified as type I: an obstructing septum or web is formed by either the mucosa or submucosa without a corresponding defect in the muscularis or the mesentery ( Fig. 83.6A ). Type II atresias, which comprise only 1% of all duodenal atresias, consist of two blind ends of duodenum connected by a short fibrous cord (see Fig. 83.6B ). Type III atresias, with two blind ends of duodenum that are completely disconnected but overlie a V -shaped mesenteric defect (see Fig. 83.6C ), occur in 7%. Eighty-five percent of duodenal atresias are located at the junction of the first and second portions of the duodenum. Commonly, the distal common bile duct traverses the medial septum, to which the ampulla is proximal. Rarely, a bifid common bile duct with both proximal and distal ampullae is found.

The presentation of duodenal atresia is variable. Polyhydramnios may be detected on prenatal ultrasound in 30% to 65% of cases. Neonates will demonstrate bilious emesis. Upper abdominal fullness may be appreciated on exam. A double bubble sign , representing the stomach and the obstructed duodenum, on radiography of the abdomen is pathognomonic for the diagnosis ( Fig. 83.7 ); however, distal gas may be seen in patients with incomplete obstructions or bifid common bile ducts. Type I duodenal atresias may be incompletely obstructing and therefore remain undetected until solid foods are introduced. UGI may reveal a rounded end representing the windsocking web.

If duodenal atresia is suspected or diagnosed, the stomach should be decompressed and the infant resuscitated. A work-up should be undertaken to look for associated anomalies: 28% have Down syndrome, 23% annular pancreas, 23% congenital heart disease, and 20% malrotation. After the patient is stable, operative repair may be attempted. Thin webs may be excised through a longitudinal duodenotomy that is started near the point of obstruction, carried proximally over the web, and later closed transversely. The base of these lesions is typically found in the second portion of the duodenum, although it may balloon (“windsock”) distally; caution is advised in placing the duodenotomy because it may be difficult to reach the proximal origin of the web if the bowel is opened at the point of the externally apparent obstruction. Two blind ends may be reapproximated with a diamond-shaped anastomosis, in which the proximal end is opened transversely and the distal longitudinally ( Fig. 83.8 ). Alternatively, duodenojejunostomy or gastrojejunostomy may be performed, although the latter carries the risks of marginal ulceration and blind loop syndrome. When performed open, a catheter should be passed distally to ensure there are no distal atresias; however, this occurrence is rare. In fact, when performed laparoscopically, this step is skipped.