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MALROTATION AND MIDGUT VOLVULUS

Eleanor J. Rutherford, MD

 

A number of rotational abnormalities have been described which correlate with abnormal embryologic development of the midgut. Intestinal rotation during embryologic development of the bowel was described by Mall in 1898. In 1911, Waugh first described clinical symptoms associated with abnormalities of intestinal rotation and fixation. In 1936, the classic paper by Ladd reported 21 cases of malrotation giving the classical description of surgical treatment.

The incidence of malrotation is 1 in 500 live births. Twenty-five to 40% of patients with symptomatic malrotation present within the first week of life, 50% present within the first month, 75% present prior to 1 year of age, and the remaining 25% present after 1 year of age with equal occurrence in males and females. There is a 2:1 male predominance in cases presenting in the neonatal period. Infants and children with displaced viscera as a result of other developmental abnormalities such as gastroschisis,  omphalocele, or congenital diaphragmatic hernia always have rotational abnormalities owing to lack of fixation. Malrotation has also been associated with small bowel atresia, Meckel's diverticulum, intussusception, Hirschsprung's disease, GER, gastric volvulus, persistent cloaca, and extrahepatic biliary anomalies.

Embryology

Extracoelomic development of the fetal intestine occurs between the 4th and 12th weeks. Initially, development of the midgut occurs with rapid elongation of the primary intestinal loop. The superior mesenteric artery (SMA), supplying the small bowel and proximal colon, acts as the primary blood supply to these segments and the axis of their subsequent rotation. In understanding the normal and abnormal events of embryologic bowel development, it is helpful to divide the process into stages, and to imagine the segments of bowel supplied by the SMA as two joined segments: the proximal portion (duodenojejunal segment) and the distal portion (ileocolic segment).

Following extracoelomic elongation, the proximal portion or duodenal loop begins its counterclockwise 270 rotation around the SMA while returning to the abdomen, passing initially to the right, then below, and finally to the left of the SMA where it becomes fixed, forming the ligament of Treitz and the normal duodenal C-shaped extension leftwards across the midline. Concomitantly, the distal portion, or cecocolic loop, begins its rotation below the SMA, rotating first to the left, then above, and finally to the right of the SMA. The cecum, located at this stage in the right upper quadrant, finally descends into the right lower quadrant.

When the duodenal loop remains on the right side of the abdomen, and the cecocolic loop remains on the left with respect to the SMA, the anatomy is termed nonrotated. Nonrotation, in and of itself, is not a pathologic entity and does not require surgery. Malrotation occurs as a result of an interruption in normal bowel rotation during the second stage of development. Typically, the duodenal loop lacks 90 of its normal 270 rotation, and the cecocolic loop lacks 180 of its normal rotation.

Pathology

Lack of fixation of the small bowel results in obstructing, peritoneal adhesive bands (Ladd's bands) forming between the cecum and the right lateral abdominal wall causing compression of the duodenum and mechanical obstruction. Furthermore, the small bowel becomes suspended from a narrow pedicle (containing the SMA) like a bell clapper. As a result, the small bowel may then twist, in a clockwise direction, about this narrow axis resulting in midgut volvulus (MGV) and ischemia. This is the most catastrophic consequence of malrotation. Volvulus occurs in 68% to 71% of neonates with malrotation and up to 41% in older children.

Clinical Presentation

History

Malrotation typically presents in the first month of life with bilious vomiting and a sudden onset of abdominal pain in an otherwise healthy infant. In infants of this age, this presentation should be considered malrotation with MGV until proven otherwise and immediate surgical consultation is necessary. In older children, symptoms are more vague and may include chronic, intermittent vomiting and crampy abdominal pain, failure to thrive, constipation, bloody diarrhea, and hematemesis.

Physical Examination

Torres, in a review of 22 patients undergoing surgery for malrotation, reported a normal abdominal examination in 50%. Another 32% had abdominal distension without tenderness. Because the obstruction is very proximal, abdominal distension is usually not present. In MGV, as intestinal ischemia progresses to gangrene, bowel distension from gas-producing organisms within the intestine results. At this stage, virtually all patients will develop abdominal pain and peritonitis. The patient with gangrene is usually tachycardic and hypovolemic. Passage of blood or sloughed mucosal tissue may be noted as vascular compromise progresses. As ischemia progresses to infarction and necrosis, fever, peritonitis, abdominal distension, profound dehydration, and vascular collapse worsen.

Diagnostic Studies

A high index of suspicion of malrotation in the neonate with bilious vomiting must be maintained to prevent the devastating consequences of intestinal necrosis. Laboratory blood work has no place in the diagnostic evaluation of patients with suspected malrotation and MGV and should not delay immediate surgical consultation and operation when the diagnosis is suspected. Plain radiographs may show gastric or proximal duodenal dilatation, with or without distal bowel gas.

The choice between upper and lower gastrointestinal contrast studies is often debated. In stable patients, our diagnostic study of choice is a UGI series. Normal rotation is present when the duodenal C-sweep crosses the midline placing the duodenojejunal junction to the left of the spine at a level greater than or equal to the pyloric channel. Malrotation with midgut volvulus is suspected when the duodenojejunal junction is in an abnormal location and/or there is an abrupt ending or corkscrew tapering of contrast (proximal intestinal obstruction). The specificity of UGI studies in detecting malrotation is 100% but the sensitivity for detecting MGV is only 54%, illustrating the importance of clinical judgment in diagnosis. Although a lower gastrointestinal (LGI) contrast study may be used to identify malrotation in patients with equivocal UGI studies, it is not reliable if there is an MGV. As a primary diagnostic test in patients with bilious emesis and a low suspicion of malrotation and MGV clinically, LGI may be used to rule out colonic obstruction (atresia, Hirschsprung's disease, meconium ileus/plug) and may prove therapeutic as well. Contrast from an LGI is evacuated or can be cleared with enemas quickly such that subsequent UGI studies can be carried out and interpreted without the presence of obscuring residual contrast. Findings on LGI include demonstration of the cecum and proximal colon in the left flank. Failure of recognition of malrotation can also occur with LGI studies in 5% to 20% of patients with a normally located cecum.

Treatment

Rapid fluid resuscitation and immediate laparotomy is required in patients suspected of having MGV. In the emergency room, a nasogastric tube is placed and broad-spectrum antibiotics are administered. At operation, the MGV is untwisted in a counterclockwise direction and bowel viability is assessed. Necrotic bowel, if present, is resected. A Ladd's procedure (appendectomy, division of mesenteric bands, and placement of the small intestine on the right and the colon on the left side of the abdomen) is performed.

Intravenous parenteral nutrition is begun in patients having had a significant length of bowel resected. Postoperatively, aggressive fluid resuscitation is continued and intravenous (IV) antibiotics are given. Patients with questionable viability of a significant length of unresected bowel after the initial operation may undergo a second look laparotomy 24 hours later after optimization of the patient's hemodynamic status.

If, at the initial or second look operation, the entire bowel appears necrotic, the surgeon is faced with the difficult decision to either close, allowing the patient to die, or resect leaving the patient with short gut syndrome and consigned to a lifetime of parenteral nutrition with its attendant morbidity. Although small bowel transplantation is performed for infants with short gut syndrome, long-term survival is less than with solid organ transplants. Improvements in immunosuppression strategies as well as better management of functional and infectious problems will be required to increase its practicality.

To avoid potentially devastating complications, we electively operate for malrotation incidentally discovered in asymptomatic infants or in older symptomatic children.

Complications and Outcome

The most serious complication of malrotation is MGV with necrosis of the entire midgut. Mortality in infants with malrotation ranges between 2.5% and 24%, and is significantly influenced by:

  1. the presence of necrotic bowel at laparotomy (25X risk);
  2. the presence of associated anomalies (22X risk); and
  3. younger patient age.

Delay between presentation and operation is associated with a trend towards higher mortality as well. In patients with bowel necrosis, the length of bowel resected also determines survival. Messineo et al in a study of 182 patients undergoing laparotomy for malrotation, found a 0.999 estimated probability of survival in patients with 10% bowel necrosis, 0.920 with 50% necrosis, and 0.351 with 75% necrosis.

In general, the lower acceptable limit of bowel length is considered 25 cm with an intact ileocecal valve, and 42 cm without an ileocecal valve. Though survivors with less bowel have been reported, short gut syndrome, with its inherent complications of long-term parenteral nutrition (growth retardation, line sepsis, hepatobiliary dysfunction) is associated with significant morbidity and mortality.

In summary, unexplained bilious vomiting in an otherwise healthy infant must be considered a surgical emergency and should be considered malrotation with midgut volvulus until proven otherwise.