Persistent descending mesocolon as a vital risk factor for anastomotic failure and prolonged operative time for sigmoid colon and rectal cancers

Background: The diagnostic criteria and effect of persistent descending mesocolon (PDM) on sigmoid and rectal cancers (SRCs) remain controversial. This study aims to clarify PDM patients' radiological features and short-term surgical results. Method: From January 2020 to December 2021, radiological imaging data from 845 consecutive patients were retrospectively analyzed using multiplanar reconstruction (MRP) and maximum intensity projection (MIP). PDM is defined as the condition wherein the right margin of the descending colon is located medially to the left renal hilum; this is usually proved intraoperatively. The anatomical features and surgical results of PDM patients were compared with those of non-PDM patients. Results: The frequency of PDM was 3.8%. The lengths from the inferior mesenteric artery (IMA) to the inferior mesenteric vein (1.6 vs. 2.5 cm, p＜0.001), IMA to marginal artery arch (2.7 vs. 8.4 cm, p＜0.001), and IMA to the colon (3.5 vs. 9.8 cm, p＜0.001) were significantly shorter in the PDM group than those in the non-PDM group. The conversion to open surgery (12.5% vs. 1.2%, p=0.001), operative time (207.5 vs. 156 min, p=0.001), intraoperative blood loss (p＜0.001), marginal arch injury (15.6% vs. 1.1%, p＜0.001), splenic flexure free (21.9% vs. 3.3%, p＜0.001), and Hartmann procedure (15.6% vs. 0.1%, p＜0.001) were significantly higher in the PDM group. Moreover, PDM was an independent risk factor for prolonged operative time (OR=3.205, p=0.004) and anastomotic failure (OR=7.601, p=0.003). Conclusion: PDM was an independent risk factor for prolonged operative time and anastomotic failure in SRC surgery. Preoperative radiological evaluation using MRP and MIP can help surgeons better handle this rare congenital variant.