Normal midgut herniation, rotation, and fixation occur from 6 to 12 weeks of gestation. (a) Physiologic herniation of the intestine occurs at 6 weeks with a cephalad duodenojejunal limb and a caudal cecocolic limb in relation to the superior mesenteric artery (SMA). (b–e) The midgut undergoes a 270° counterclockwise rotation (from the viewer’s perspective) around the SMA, resulting in a left-sided ligament of Treitz and fixation of the cecum in the right lower quadrant.
Malrotation occurs in approximately 1 out of every 500 births . Symptomatic malrotation is estimated to be far less frequent, becoming clinically evident in only 1 out of every 6000 births . The overarching concern with malrotation is the risk of midgut volvulus , wherein the narrow mesenteric pedicle becomes acutely torsed and may result in long-segment bowel ischemia from the jejunum to the distal transverse colon.
In classic malrotation , the duodenojejunal limb rotation arrests early and becomes positioned to the right of the midline. Partial rotation of the cecocolic limb displaces the cecum in the epigastrium in close approximation to the duodenojejunal junction, creating a narrow mesenteric pedicle that is susceptible to volvulus (Fig. 28.2a). This configuration also frequently results in congenital bands known as Ladd’s bands, which extend from the cecum and terminal ileum over the surface of the second portion of the duodenum and can cause symptoms of duodenal obstruction by extrinsic compression. Atypical malrotation , also known as malrotation variant, duodenal malposition, or low-lying ligament of Treitz, is a more recently recognized abnormality of intestinal rotation in which the ligament of Treitz lies to the left of the midline but remains suboptimally positioned. Patients with atypical malrotation have a lower risk of volvulus, and they are more likely to have persistent obstructive symptoms following operative intervention .
Key components of the laparoscopic Ladd’s procedure. (a) Upon entry into the abdominal cavity, the upper intestinal anatomy should be defined. Nonrotation featuring a right-sided ligament of Treitz is depicted in the illustration. (b) Paraduodenal Ladd’s bands extending from the cecum are sharply divided. (c) The ileocecal mesentery is widened by incising the anterior mesenteric leaflet. (d) Intracorporeal or extracorporeal appendectomy may then be performed. The small intestine is positioned to the right of the abdomen and the colon positioned to the left
Newborns and infants with malrotation most commonly present with new onset bilious emesis . Somnolence, lethargy, hematemesis, melena, and hematochezia are symptoms that may portend underlying vascular compromise and should prompt rapid resuscitation and emergent open exploration without further radiographic evaluation. Volvulus is less common in older children, who have more variable symptoms with abdominal pain being the most common complaint . Patients may also present with nonspecific findings including chronic abdominal pain, intermittent episodes of emesis, early satiety, weight loss, failure to thrive, malabsorption, and diarrhea .
Abdominal distension is the most common sign in neonates and infants with midgut volvulus , but a normal abdominal examination has been reported in up to 60 % of patients . The onset of compromised intestinal blood flow may be heralded by the development of peritoneal signs.
Laboratory values can be normal in asymptomatic malrotation and symptomatic disease with intermittent volvulus. Hypochloremia may be seen with severe dehydration. Leukocytosis or leukopenia and lactic acidosis suggest compromised intestinal blood flow.
Only stable patients with concern for malrotation and no evidence of intestinal ischemia should undergo further radiographic evaluation. Abdominal radiographs may demonstrate proximal gastric or duodenal intestinal obstruction, but a nonspecific bowel gas pattern does not rule out rotational anomalies or volvulus. The upper gastrointestinal contrast study is the gold standard for diagnosis of malrotation . With malrotation , the key finding is an abnormal duodenojejunal junction, which is normally located to the left midline and at the level of the pylorus or gastric antrum. This may be demonstrated by a duodenum that does not cross the midline or a low-lying ligament of Treitz. The second and third portions of the duodenum may be positioned outside of their normal posterior and retroperitoneal locations, and with follow through, the small bowel can be noted to be predominately located to the right of the midline with the large bowel to the left. A corkscrew-shaped duodenum is a common sign of midgut volvulus , while a z-shaped configuration of the duodenum may be seen with obstructing Ladd’s bands . Ultrasonography, which can define the relationships of the SMA, superior mesenteric vein (SMV) , and duodenum, has gained popularity in the evaluation of malrotation , but its role remains disputed. Left-sided or anterior SMV (in relation to the SMA) and absence of the duodenum behind the SMA are the predominant radiographic features of rotational anomalies. These findings are sometimes incidentally demonstrated on cross-sectional imaging, such as computed tomography .
Immediate operative exploration is the standard of care for the treatment of acute midgut volvulus . Urgent or elective exploration is recommended for children with symptomatic obstructive symptoms and radiographic evidence of malrotation . Controversy exists regarding the optimal management of asymptomatic patients with radiographic evidence of rotational anomalies. Distended stomach and bowel may cause inferior displacement of the ligament of Treitz giving a false impression of atypical malrotation on the anteroposterior (AP) view. Repeat imaging may be warranted when the bowel is less dilated . Exploration can be considered in asymptomatic patients who are younger in age, while observation may be appropriate in older children and adults with appropriate counseling and education concerning the potential risks and benefits .
The laparoscopic Ladd’s procedure has a controversial, but increasingly recognized role in both the diagnosis and treatment of anomalies of intestinal rotation. Laparoscopic exploration permits direct visualization of the ligament of Treitz and cecum to verify or refute preoperative concern for malrotation and allows for correction of these defects without the need for formal laparotomy. Furthermore, internal hernias and congenital bands can be both identified and safely corrected by a laparoscopic approach. Laparoscopy is generally discouraged in the setting of midgut volvulus , as emergent abdominal decompression and intestinal detorsion are needed, and the risk of damage to edematous bowel likely outweighs the potential benefits of laparoscopy. As such, open Ladd’s procedure is generally recommended in the setting of midgut volvulus .