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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.

Background: Radiotherapy (RT) after surgery is a treatment option in the management of parotid adenocarcinoma, and the role of adjuvant RT for parotid adenocarcinoma remains to be clarified. The survival benefit of postoperative radiotherapy (PORT) based on prognostic risk factors needs further determination.Materials and methods: In this retrospective cohort study using SEER data, patients were divided into surgery+RT (RT group) and surgery alone (non-RT group). A prognostic risk model was constructed to stratify patients based on the survival rate. We performed a Cox regression analysis with propensity score weighting to evaluate survival benefit between the two groups. Results: We identified 2223 eligible patients with parotid adenocarcinoma, 1449 (65.2%) in the RT group and 774 (34.8%) in the non-RT group. Overall, 674 cancer-specific deaths occurred over a median follow-up of 141 months, the overall survival (OS) of RT group was better than that of non-RT group in the weighted analysis (HR=0.656, 95% CI=0.487-0.882, P=0.005). Significant survival improvements in the RT group compared with the non-RT group were only observed in patients with high risk (HR=0.647, 95% CI=0.426-0.983, P=0.041). The survival benefit of RT was significantly correlated with prognostic risk stratification (PConclusion: In this population-based study, the patient prognostic risk stratification for parotid adenocarcinoma is associated with the magnitude of survival improvement by RT after surgery, suggesting that this risk model could provide decision guidance on comprehensive treatment strategy.