Discussion

Intestinal malrotation is a congenital anomaly which is predominantly diagnosed within the first year of life. Adults and adolescents with this condition represent only 0.2%–0.5% of the cases [6]. Most patients are asymptomatic, with an incidental discovery of this condition during surgical intervention or pre-operative workup as in our case [7].

Normal midgut rotation involves a 270° counterclockwise rotation around the SMA [8] (Fig. 7a). In nonrotation, this process is incomplete, resulting in a left-sided colon and right-sided small bowel (Fig. 7d). Unlike classic malrotation, nonrotation typically results in a wide mesenteric base, which reduces the risk of volvulus. Consequently, many individuals remain asymptomatic and the anomaly is discovered incidentally, as in this patient [8].

Figure 7: (a) Normal intestinal rotation, (b) malrotation without volvulus, (c) malrotation with volvulus, (d) nonrotation [8].

In surgical cases involving major abdominal surgery with incidental nonrotation, preoperative imaging is crucial in identifying the abnormal orientation of vasculature. Ultrasounds, computed tomography scans, magnetic resonance imaging, and even mesenteric arteriography can be used to diagnose midgut malrotation [9, 10]. The preoperative CTA revealed inversion of the SMA and SMV as well as the abnormal location of the small and large intestines which allowed our surgical team to anticipate the abnormal vasculature and structures and perform careful dissection for vessel preservation.

FAP is a high penetrance autosomal dominant disease characterized by development of colorectal adenomas that starts in childhood and will progress inevitably to colorectal cancer by the fourth or fifth decade of life [11]. In patients with FAP, the surgical options for the patients include colectomy with ileorectal anastomosis or proctocolectomy with either permanent ileostomy or ileal pouch-anal anastomosis [12]. This is determined by factors such as age, sex, family history, acceptance of a stoma, the rectal polyp burden, concern for infertility and sexual dysfunction, ability to follow-up with endoscopic surveillance, and many other factors [13]. Ileorectal anastomosis was chosen for this patient due to his young age, male sex, and low rectal polyp burden (<20 polyps), thus allowing for preserved rectal function.

This case emphasizes the importance of recognizing congenital anomalies that alter normal anatomy during preoperative assessment. Imaging is crucial in informing the surgical team of variations in vasculature location, thus preventing intraoperative complications.

In conclusion, this case underscores the importance of recognizing incidental intestinal nonrotation when planning major abdominal surgery. Although largely asymptomatic, nonrotation can cause significant changes in the location of vasculature and structures, in turn leading to intraoperative complications if such anomalies are not anticipated. This rare coexistence of FAP and nonrotation highlights the need for individualized surgical planning.