The true prevalence of malrotation in both the pediatric and adult population is unknown due to the unclear number of asymptomatic patients. Adult presentation is rare and estimated to account for only 0.2–0.5% of cases . The current literature suggests that presentation varies by age [4, 6, 7]. Malrotation in adults tends to either be found incidentally when a patient undergoes imaging or requires a laparotomy, or present as chronic, non-specific gastrointestinal symptoms such as intermittent crampy abdominal pain, bloating, weight loss, and nausea/vomiting. Right paraduodenal hernias are caused by abnormal rotation of the midgut during embryogenesis, secondary to failure of the pre-arterial limb to complete the 270º counterclockwise rotation [8, 9]. We present a rare case of a healthy 84-year-old with no previous gastrointestinal symptoms who was only diagnosed with malrotation when he presented acutely with bowel ischemia secondary to a paraduodenal hernia.
There are several findings on CT that are individually non-specific but, when taken together, are highly suggestive of intestinal malrotation. Firstly, the relationship of the SMA and SMV is abnormal. The SMA is normally to the left of the SMV. This relationship was found in 79% of normal individuals but only 29% of individuals with malrotation . Secondly, the location of the third portion of the duodenum (D3) is abnormal. D3 should be retroperitoneal, coursing horizontally from right-to-left posteroinferior to the superior mesenteric artery and eventually terminating at the duodenojejunal flexure in the left upper quadrant. This course was identified in 100% of normal individuals but only 2.5% of individuals with malrotation  Thirdly, the location of the proximal small bowel is atypical. After the duodenal sweep, the jejunum is normally in the left mid-abdomen coursing toward the ileum in the right lower quadrant. Yet, 91% of patients with malrotation were found to have proximal small bowel predominantly in the right hemiabdomen . Our patient demonstrated all three of these findings, thus there was a high radiological suspicion for malrotation.
There is a notable lack of quality data on screening for malrotation in asymptomatic patients. The current evidence is focused on patient populations that have a higher prevalence of malrotation including those with congenital heart disease such as heterotaxy syndrome  and abdominal wall defects . An APSA systematic review on screening concluded that there is minimal Level 4 evidence to support screening in these high-risk groups, resulting in a Grade D recommendation . This recommendation was based on several studies noting a poor distinction in what constituted normal anatomy in upper gastrointestinal contrast studies (UGI). Similarly, using an UGI for screening in the general population is not well established and has been associated with a 15% false positive  and 6% false negative rate . Higher quality evidence is needed to produce a recommendation for screening in asymptomatic children and adults.
Moreover, there are no clear guidelines on the management of older asymptomatic patients with malrotation as the literature regarding the benefit of surgical intervention is varied. The traditional rationale to not offer surgery to older asymptomatic children and adults is based on the reported declining risk of presenting with volvulus with advancing age . A systematic review comparing observation versus prophylactic Ladd’s procedure in patients with heterotaxy syndrome and asymptomatic malrotation found a 14% rate of post-operative complications in those who underwent a Ladd’s, including a 3% rate of peri-operative mortality, 10% rate of small bowel obstruction, and 21% long-term mortality rate (mostly due to heart failure) . The authors concluded that they could not ascertain whether the risk of death from a prophylactic Ladd’s or the risk of missed midgut volvulus in patients who are observed was greater. Proponents of a prophylactic Ladd’s procedure to reduce future complications cite the lower peri-operative risks associated with an elective surgery. A retrospective study of 33 patients, ranging in age between 11 and 83 years, revealed that post-operative complications occurred significantly more frequently in patients operated on emergently versus electively (60 vs 22%) .
With our patient, we opted to perform an open Ladd’s procedure due to the acuity of his presentation, the extremely dilated stomach and duodenum, and the questionable etiology of his bowel ischemia given how rarely malrotation is diagnosed in his age group. The open approach is preferred in patients with confirmed or suspected midgut volvulus . However, a Ladd’s procedure is often performed laparoscopically in the absence of bowel ischemia. There is evidence of an increased risk of volvulus recurrence with the laparoscopic approach in children due to the decreased formation of post-operative adhesions . It is difficult to know whether malrotation caused or contributed to our patient’s bowel ischemia, or was an incidental finding in the setting of a paraduodenal hernia.
In conclusion, bowel ischemia secondary to a paraduodenal hernia in the setting of malrotation in a previously asymptomatic older adult is rarely encountered. While guidelines for screening and intervention in asymptomatic patients remain unclear, it is critical to keep malrotation on the differential in acutely ill patients with concerning presentations across pediatric and adult age groups. The prompt recognition and appropriate management of this potentially devastating condition will ultimately enhance patient outcomes.
The patient was surprised to learn about what had caused his acute presentation to the hospital, especially as he had been very healthy his entire life. The patient’s family was curious whether there was a genetic component to malrotation, and they were counseled that it is not typically thought of as a hereditary disease. The patient was thankful that no bowel had to be resected, and that the problem was solved during a single operation. He had been counselled that he may become quite ill post-operatively given his multi-organ dysfunction on presentation. However, on post-operative day #1 he already felt very well, and overall felt like his recovery was quite smooth.