An Unexpected Anatomical Trap in Perforated Crohn's Disease

Accurate pre-operative assessment is critical in Crohn's emergencies; intestinal malrotation is an under-recognised anatomical confounder with direct endoscopic and operative implications. We report a 20-year-old man under investigation for terminal ileitis who presented with acute peritonitis. Contrast-enhanced CT demonstrated perforated terminal ileitis and, importantly, features of complete common mesentery: a left-sided colon, right-sided small bowel predominance, and an abnormal superior mesenteric vessel relationship (Figure 1A–C). Emergency laparotomy confirmed perforated Crohn's disease in a non-rotation configuration, with a freely mobile small bowel and left-sided colon, and a Ladd's band requiring division (Figure 1D–E). Although malrotation may be recognised pre-operatively or at laparotomy, it can be overlooked when imaging interpretation focuses primarily on inflammatory or perforation features. Yet simple CT signs (bowel topography and SMA–SMV relationship) are reproducible and should be checked in Crohn's presentations, particularly when operative intervention is likely [1]. The relevance extends beyond operative orientation. In Crohn's disease, unrecognised malrotation may explain unexpectedly difficult colonoscopy, prolonged caecal intubation and failure to intubate the terminal ileum, as previously reported [2]. When endoscopic assessment is technically challenging or non-diagnostic, targeted review of cross-sectional imaging for malrotation may prevent repeated difficult procedures and shorten time to definitive management. For surgeons, complete common mesentery presents specific hazards: abnormal bowel positioning and a shortened mesenteric root may increase the risk of vascular injury during dissection, while a narrow mesenteric base predisposes to midgut volvulus with potentially extensive small bowel ischaemia, particularly consequential in young Crohn's patients where bowel length preservation is critical [3, 4]. Mohamed Hajri: conceptualization, writing – original draft, visualization. Sadok Megdiche: conceptualization, writing – review and editing. Zied Hadrich: data curation, writing – review and editing. Sahar Sellami: writing – review and editing. Abdelwaheb Nakhli: data curation, writing – review and editing. Zeineb Benzarti: writing – original draft. Lassad Gharbi: supervision, writing – review and editing, validation. Dhouha Bacha: supervision, validation. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Written informed consent was obtained from the patient for publication of clinical details and images. The authors declare no conflicts of interest. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.