[Establishment of a nomogram predicting risk factors of postoperative perineal wound complications after abdominoperineal resection for rectal cancer].

To investigate the risk factors of perineal incision complications after abdominoperineal resection (APR) for rectal cancer, and to establish a nomogram model to predict the complications of perineal incision. A case-control study was conducted to retrospectively collect the medical records of 213 patients with colorectal cancer who underwent APR at the First Affiliated Hospital of Nanjing Medical University from January 2010 to December 2016. The complications of perineal incision after APR were classified according to the modified Clavien-Dindo classification of surgical complications (Version 2019), and the complications of grade II and above were defined as "clinically significant complications" .Twenty-two factors related to complication of perineal incision, such as gender, age, surgical procedure, surgical approach, perineal repair, placement of drainage tube, skin position of drainage tube, operation time, intraoperative blood loss, preoperative radiotherapy and chemotherapy, intraoperative local perfusion chemotherapy, tumor classification, pathological grade, tumor T stage, tumor TNM stage and so on, were analyzed by chi-square test for univariate risk factor of complication in all variables, and variables with <0.2 in univariate analysis were further included in multivariate analysis. Logistic regression analysis was used to screen out independent risk factors. R software (R 3.3.2) was introduced. The rms software package was used to construct a nomogram prediction model. The C-index was calculated (higher meaning better consistency with actual risk) to evaluate the discriminant degree of the model. The Bootstrap method was used to repeat the sampling for internal verification. A total of 42 patients with colorectal cancer who underwent APR from January 2017 to December 2017 at the First Affiliated Hospital of Nanjing Medical University were externally validated, and the corrected C-index was calculated. The model conformity was determined by comparing the C-index calibration difference between the predicted and actual risks. Of the 213 patients with colorectal cancer, 131 were male and 82 were female, with mean age of (59.6±11.6) years. The incidence of postoperative perineal incision complications was 20.2% (43/213), including 27 cases of Clavien-Dindo II and above complications. Univariate analysis showed that the Eastern Cancer Cooperative Group (ECOG) score, preoperative albumin, skin position of drainage tube, intraoperative blood loss, preoperative radiotherapy and chemotherapy were associated with complications of postoperative perineal incision (All <0.05) . Multivariate analysis showed that preoperative albumin levels ≤38 g/L (OR=105.261, 95% CI: 7.781 to 1423.998, <0.001), perinead drainage (OR=11.493, 95% CI: 1.379 to 95.767, =0.024), intraoperative blood loss >110 ml (OR=6.476, 95% CI: 1.505 to 27.863, =0.012) and preoperative radiotherapy and chemotherapy (OR=7.479, 95% CI: 1.887 to 29.640, =0.004) were postoperative clinically significant independent risk factors for perineal incision complications. The nomogram model was established. Preoperative albumin level <38 g/L was for 100 points, the preoperative chemoradiotherapy was for 52.5 points, the intraoperative blood loss >110 ml was for 28.5 points, and the perineal drainage was for 17.5 points. Adding all the points was the total score, and the complication rate corresponding to the total score was the predicted rate of the model. The model had a C-index of 0.863. After internal verification, the C-index dropped by 0.005. External verification showed a C-index of 0.841. Preoperative nutritional status, skin position of drainage tube, intraoperative blood loss and preoperative radiotherapy and chemotherapy may affect the occurrence of perineal wound complications after APR for rectal cancer. The nomogram model constructed in this study is helpful for predicting the probability of clinically significant complications after APR.