Intestinal malrotation is a congenital anomaly resulting from the failure of the intestine to correctly position itself during fetal development. This condition is most often recognized as a serious medical emergency in infants, with over 90% of symptomatic cases diagnosed within the first year of life. A small number of individuals reach adulthood without a diagnosis, often because the condition has remained asymptomatic or caused only vague symptoms. When discovered in an adult, malrotation presents a unique clinical challenge due to its rarity and non-specific symptoms. The condition stems from an error in the complex, 270-degree counterclockwise rotation and fixation of the midgut around the superior mesenteric vessels, which typically occurs during the tenth week of gestation.
Prevalence and Underlying Causes
Intestinal malrotation in adults is extremely rare, with reported incidence rates estimated between 0.00001% and 0.5% of the adult population. The true incidence is difficult to determine because many adults with this anatomical variation remain completely asymptomatic. Diagnosis is often made incidentally when imaging or surgery is performed for an unrelated reason, such as an appendectomy or a workup for chronic abdominal issues. The defect often remains quiescent until adulthood because the malrotation is typically incomplete or a non-rotation. This anatomical arrangement is stable until a triggering event occurs.
Triggers for symptoms can include the formation of abnormal fibrous attachments, known as Ladd’s bands, which cross and obstruct the duodenum. Other factors include unrelated abdominal surgery, trauma, or pregnancy. The primary danger of malrotation is the narrow stalk of the mesentery supporting the small intestine, which makes the bowel susceptible to twisting on itself, a condition called midgut volvulus.
Clinical Presentation in Adulthood
Adult symptoms of malrotation differ significantly from the acute, life-threatening presentations seen in newborns. Symptoms tend to be chronic, intermittent, and non-specific, often leading to delayed diagnosis. The most common complaint is recurrent, severe abdominal pain, which is frequently post-prandial (occurring after eating). This pain is thought to be caused by intermittent partial obstruction of the duodenum by constricting Ladd’s bands.
Patients also report episodes of unexplained nausea and vomiting, which is typically non-bilious, unlike the bile-stained vomiting characteristic of infants. Other complaints include chronic bloating, early satiety, and alternating constipation and diarrhea. These non-specific symptoms often cause the condition to be misdiagnosed as more common disorders, such as Irritable Bowel Syndrome (IBS) or functional dyspepsia. In rare cases, adults may present acutely with a sudden onset of severe symptoms due to a midgut volvulus, which constitutes a surgical emergency.
Diagnostic Pathway
Diagnosing intestinal malrotation requires a high index of suspicion due to the non-specific symptoms and the condition’s rarity. The initial workup often begins with cross-sectional imaging, such as a Computed Tomography (CT) scan. However, the primary diagnostic tool remains the Upper Gastrointestinal (UGI) series, often called a barium swallow, which visualizes the abnormal positioning of the duodenojejunal junction.
Imaging Findings
The UGI series visualizes the abnormal positioning of the duodenojejunal junction, which normally crosses the midline to the left of the spine. A definitive finding on a CT scan suggesting malrotation is the abnormal relationship between the superior mesenteric artery and vein. Normally, the vein is positioned to the right of the artery, but in malrotation, this relationship is often reversed or the vessels are positioned vertically. The location of the small bowel predominantly on the right side of the abdomen is another anatomical distortion noted on imaging. In cases complicated by an acute volvulus, the CT scan may reveal a characteristic “whirlpool sign,” which represents the spiraling of the superior mesenteric vessels and the bowel around the axis of the twist.
Management and Treatment Options
Once malrotation is confirmed, management centers on preventing midgut volvulus. The standard surgical treatment is the Ladd’s procedure, performed for both acute and chronic symptoms. This operation involves untwisting the bowel, dividing the obstructing Ladd’s bands, and widening the base of the small bowel mesentery to reduce the risk of future twisting.
The surgical team repositions the small intestine on the right side of the abdomen and the large intestine on the left, a configuration that provides stability. A prophylactic appendectomy is typically performed to prevent future diagnostic confusion, as the appendix will be in an unusual location. For truly asymptomatic adults, the decision for prophylactic surgery is controversial, weighing the risk of volvulus against the risks of a major operation. However, due to the unpredictable and life-threatening nature of midgut volvulus, many surgeons recommend the Ladd’s procedure for all confirmed cases.