The true incidence of intestinal malrotation is unknown ( Fig. 29.2 ). but the most commonly understood rates are reported in the literature to range from 1 in 6000 to 1 in 50 live births. One of the earliest estimates of the incidence of malrotation reported by Collins in 1963 reviewed 71,000 pathologic appendiceal specimens, finding that the cecum was left-sided—suggesting midgut malrotation—in 0.024% of all patients. More contemporary imaging-based estimates of malrotation suggest that it is more common, occurring in from 0.2% to 2.4% of all patients studied, whether in a series of barium enemas or a study of abdominal US for pyloric stenosis, respectively.

Classic malrotation.

Failure of the complete 270° counterclockwise rotation of the midgut and hindgut has resulted in malrotation with Ladd bands crossing over the duodenum from the cecum to the retroperitoneum, increasing the risk of volvulus.

Malrotation is commonly diagnosed early in life, with up to 80% presenting within the first month, and nearly 90% within the first year. However, symptoms of malrotation can present at any stage of life and often the diagnosis can be more difficult to make outside of infancy. ^, A number of database studies and large institutional reviews suggest that malrotation may be more common in older children and adults than previously thought, with the diagnosis occurring after 1 year of age in 28%–69% of all patients with intestinal malrotation. This difference may be accounted for by the variation in presentation of malrotation outside of the infant period. Rather than the classic symptoms of sudden-onset bilious emesis and feeding intolerance, older children and adults present with abdominal pain, recurrent symptoms, nonbilious emesis, diarrhea, or even absence of symptoms in 36%. ^,

Additional congenital anomalies can contribute to an increased rate of intestinal malrotation as 30%–60% of patients with malrotation have associated anomalies ( Table 29.1 ). ^, , Most commonly giant omphalocele, gastroschisis, or congenital diaphragmatic hernia are highly associated with rotational anomalies as they intrinsically develop abnormal rotation in utero due to the lack of constraints in the abdominal space. ^, Of all children with malrotation, 27% have an associated congenital cardiac defect, commonly including tetralogy of Fallot (18%), hypoplastic left heart syndrome (8%), or atrioventricular septal defects (8%). Lastly, one of the more common anomalies associated with rotational disorders is heterotaxy. As a midline congenital anomaly, heterotaxy commonly results in malrotation, occurring in 27%–89% of these children.

The first description of the embryologic rotation of the intestines was written by Mall in 1898 but it was not until 1923 that these findings were translated into the clinical realm by Dott. ^, Many additional reports of intestinal malrotation and volvulus were reported in this period but it was not until the seminal description by William Ladd in 1932 of ten cases of malrotation and the recommendation for counterclockwise detorsion that his technique became the standard of treatment. Describing a simple solution to a complex problem in his follow-up paper he detailed the straightforward six-step procedure that remains the standard of care almost 100 years later: (1) eviscerate the abdominal contents, (2) detorse the intestine through counterclockwise rotation, (3) divide congenital bands in the right upper quadrant over the duodenum, (4) appendectomy, (5) broaden the base of the mesentery, and (6) reduce the abdominal contents by placing the intestine in a nonrotated configuration with the colon in the left abdomen and small intestine in the right abdomen.

Radiographic evaluation to confirm normal intestinal rotation is critical in the workup of suspected malrotation. Prenatal diagnosis of an intestinal rotational anomaly is uncommon but increasing use and quality of fetal ultrasonography and magnetic resonance imaging (MRI) may make prenatal diagnosis more commonplace. ^, Fetal MRI specifically, has increased prenatal identification of associated anomalies such as gastroschisis, omphalocele, or heterotaxy—which is associated with a 33% incidence of intestinal malrotation. Primary evaluation of suspected malrotation often begins with a plain radiograph ( Fig. 29.5 ). Although this can be helpful to differentiate any number of causes of neonatal obstruction, radiographic findings of volvulus can be nonspecific. Isolated gastric distention, multiple dilated loops, gasless abdomen, or an entirely normal radiograph can be common ( Fig. 29.6 ).

Upright plain film demonstrates air–fluid levels with proximal intestinal dilation and minimal distal gas. This infant has midgut volvulus.

A 2-day-old term infant with bilious emesis and midgut malrotation and volvulus. Frontal supine radiograph of the abdomen reveals a gas-distended stomach ( black solid arrow ) and tiny volumes of gas distal to the first portion of the duodenum. Findings on this frontal radiograph are nonspecific for volvulus, but subsequent upper gastrointestinal series confirmed volvulus.

The diagnostic gold standard to rule out malrotation remains the upper gastrointestinal (UGI) series. A normal UGI has three necessary findings to rule out malrotation: (1) the duodenum is confirmed as retroperitoneal and posterior; (2) contrast in the third portion of the duodenum crosses midline to the left of the vertebral bodies; and (3) the DJJ rises to the level of the pylorus left of the spinal pedicles. These findings confirm normal intestinal rotation and rule out malrotation with 91%–100% sensitivity. ^, While a normal UGI can rule out malrotation, it does not rule out volvulus as segmental volvulus can exist in the setting of normal intestinal fixation. However, findings of midgut volvulus can be seen on UGI with sensitivity of 54%. Obstruction can present with a “corkscrew” or “coil-spring” sign on UGI where contrast progresses through the volvulized intestine. In complete obstruction, a classic “bird’s beak” appearance is seen in the duodenum ( Fig. 29.7 ).

The same 2-day-old term infant with bilious emesis as prior with midgut malrotation and volvulus. Frontal (A) and lateral (B) views of the stomach and bowel at the time of upper gastrointestinal series show a dilated proximal duodenum tapering to a point ( white arrow ), and coiled spring appearance of the bowel in the central lower abdomen. The duodenum does not cross to the left side of the spine and ascend to the level of the duodenal bulb, diagnostic of malrotation with volvulus in this case.

Quality, availability, and accuracy of ultrasound (US) to diagnose intestinal rotational anomalies have been increasing since it was first introduced in 1987. Early adoption of US to diagnose malrotation suggested that inversion of the SMA anterior to the superior mesenteric vein (SMV) was consistent with an intestinal rotational anomaly and could be used in place of an UGI as diagnostic of malrotation. ^, However, application of this technique without a confirmatory UGI has been limited likely due to the high false-negative rate (30%) of sonographic SMV/SMA inversion to predict malrotation. Additional findings on US, such as a “whirlpool” sign demonstrating mesenteric twisting, have been predictive of volvulus with 92% sensitivity. ^, Nevertheless, robust prospective data demonstrating that US could replace UGI for definitive diagnosis of malrotation have been lacking. Accordingly, an evidence-based practice committee with the American Pediatric Surgical Association (APSA) conducted a systematic review in 2015 leading to the recommendation that while UGI remains the diagnostic test of choice for malrotation, “US may be useful, especially in the evaluation of the asymptomatic patient where a positive result may indicate a need for a confirmatory UGI.” More recent data, however, continue to support the use of US as a sole diagnostic study. In addition to SMV/SMA inversion and the use of a “whirlpool” sign, identification of the retroperitoneal portion of the duodenum (D3) between the mesenteric vessels and the aorta has demonstrated considerable specificity for malrotation ^, ( Fig. 29.8 ). A study of 539 children evaluated for malrotation reported 100% sensitivity and specificity using a graded approach with US as the initial evaluation and UGI reserved for equivocal sonographic findings. Importantly, a water contrast technique was used to visualize D3 in a retroperitoneal position, which has subsequently been shown to have a specificity of 98% for malrotation. As familiarity with this technique grows, contemporary studies continue to demonstrate its reliability in the diagnosis of intestinal rotational anomalies. A notable metaanalysis of US evaluation in 2257 children reported an aggregate sensitivity of 94% in diagnosing malrotation, which was not statistically different than the sensitivity of UGI in the same group, although US did demonstrate a better specificity of 100%. With increasing accuracy, many hospital systems have adopted US as the first-line diagnostic study for malrotation. However, broader familiarity with the technique and lack of prospective implementation studies limit its widespread acceptance.

Malrotation and midgut volvulus identified on ultrasound.

Transverse sonogram of the upper abdomen shows dilation of the duodenum (outlined in gray dashed line ) that tapers abruptly to a point anterior to and between the superior mesenteric artery (SMA, red arrow ) and superior mesenteric vein (SMV, blue arrow ). The SMV is abnormally to the left of the SMA in this image, suggestive of malrotation. SMV/SMA inversion, along with absence of a retroperitoneal duodenum—posterior to the mesenteric vessels—is diagnostic of volvulus in this patient. Additionally, the SMV lumen was compressed as it swirled around the SMA on adjacent images, while the SMA remained patent and distal branches of the SMV were dilated due to proximal SMV compression. Aorta: red arrow . Vertebral body: white arch .

While not recommended as the first-line imaging study to rule out malrotation in infants, computed tomography (CT) is increasingly used, especially among older children and adults with abdominal pain. Studies reporting the sensitivity of CT to diagnosis congenital intestinal rotational anomalies are lacking, but review of SMV/SMA position on CT demonstrates only a 71% sensitivity to diagnose malrotation. Alternatively, identification of a “swirl” or “whirl” sign on CT, where the mesenteric vessels twist around each other, has been shown to be very specific for volvulus, with or without the presence of malrotation ^, ( Fig. 29.9 ).

Computed tomography findings of midgut volvulus.

Coronal IV contrast-enhanced CT (A) shows swirl sign in the central mesentery ( yellow arrow ), large volume ascites ( green asterisks ), and mural nonenhancement of the multiple dilated bowel loops. 3D surface renderings (B) show abrupt nonenhancement and tapering of the SMA ( red arrow ) and SMV near its confluence with the splenic vein ( blue arrow ) and the right image shows the coiled appearance of the volvulized bowel ( yellow arrow ). SMA , Superior mesenteric artery; SMV , superior mesenteric vein.

One of the more common scenarios that a pediatric surgeon may find themself in is commenting on the management of asymptomatic malrotation—when an intestinal rotational anomaly is found incidentally. Screening employs a diagnostic test to identify a medical problem before symptoms exist and although widespread screening for intestinal malrotation is not recommended, there are a number of high-risk groups in whom a missed diagnosis could be dire. Children with congenital heart disease—in particular heterotaxy—abdominal wall defects, and congenital diaphragmatic hernia constitute such groups with increased risk of rotational anomalies. A high prevalence of malrotation in these groups might suggest that screening would be of value, but reports of volvulus in CDH, gastroschisis, or omphalocele are exceedingly rare. Among children with heterotaxy, the incidence of malrotation is 27%–89%. Notably, the rate of nonrotation or atypical rotation with a broad mesentery among children with heterotaxy accounts for 57% of malrotation in this group, leading to an inherently lower risk for true midgut volvulus. While volvulus in this group could be catastrophic, actual reported rates are low but complications after Ladd’s procedure have been reported to be exceedingly high, leading many to recommend against routine screening in these groups. ^,

While there are certainly concomitant diagnoses that make the likelihood of malrotation much higher, not all radiographic rotational anomalies have the same rate of volvulus. Classic malrotation with a narrow mesenteric base and a right-sided or absent LOT carries the highest risk of volvulus. Other variations including nonrotation or atypical malrotation with a wide mesenteric base are not at significant risk for volvulus. These groups should inherently be managed differently and evidence would suggest that laparoscopy to define the width of the mesenteric base in nonrotation or atypical rotation, without completion of Ladd’s procedure, is well-tolerated without subsequent morbidity. ^,

Children with heterotaxy are inherently at high risk for rotational anomalies and deserve separate consideration in regard to screening and management of potential malrotation. While the presence of heterotaxy is associated with a higher rate of intestinal malrotation, only 43% of these children are known to have a narrow mesenteric base, placing them at the highest risk for volvulus. The incidence of volvulus among children with heterotaxy is 1%–6%, ^{, ,} but complications from Ladd’s procedure are considerably higher (14%–57%), ^, leaving many to state that there is little evidence to support screening in asymptomatic children with heterotaxy. ^{, ,}

Others have supported a more nuanced approach to malrotation in heterotaxy patients. Hill et al. suggest that right atrial isomerism may result in a narrow mesenteric base (72% with true malrotation) whereas left atrial isomerism (86% nonrotated) could be managed expectantly. In a prospective study of expectant management by Collins et al., at 5-year follow-up there was no mortality from untreated malrotation and an 11% incidence of symptomatic malrotation requiring Ladd’s procedure.