ObjectiveTo understand the impact of preoperative nutritional status on the postoperative complications for patients with low/ultra-low rectal cancer undergoing extreme sphincter-preserving surgery following neoadjuvant therapy. MethodsThe patients with low/ultra-low rectal cancer who underwent extreme sphincter-preserving surgery following neoadjuvant therapy from January 2009 to December 2020 were retrospectively collected using the Database from Colorectal Cancer (DACCA), and then who were assigned into a nutritional risk group (the score was low than 3 by the Nutrition Risk Screening 2002) and non-nutritional risk group (the score was 3 or more by the Nutrition Risk Screening 2002). The postoperative complications and survival were analyzed for the patients with or without nutritional risk. The postoperative complications were defined as early-term (complications occurring within 30 d after surgery), middle-term (complications occurring during 30–180 d after surgery), and long-term (complications occurring at 180 d and more after surgery). The survival indicators included overall survival and disease-specific survival. ResultsA total of 680 patients who met the inclusion criteria for this study were retrieved from the DACCA database. Among them, there were 500 (73.5%) patients without nutritional risk and 180 (26.5%) patients with nutritional risk. The postoperative follow-up time was 0–152 months (with average 48.9 months). Five hundreds and forty-three survived, including 471 (86.7%) patients with free-tumors survival and 72 (13.3%) patients with tumors survival. There were 137 deaths, including 122 (89.1%) patients with cancer related deaths and 15 (10.9%) patients with non-cancer related deaths. There were 48 (7.1%) cases of early-term postoperative complications, 51 (7.5%) cases of middle-term complications, and 17 (2.5%) cases of long-term complications. There were no statistical differences in the incidence of overall complications between the patients with and without nutritional risk (χ2=3.749, P=0.053; χ2=2.205, P=0.138; χ2=310, P=0.578). The specific complications at different stages after surgery (excluding the anastomotic leakage complications in the patients with nutritional risk was higher in patients without nutritional risk, P=0.034) had no statistical differences between the two groups (P>0.05). The survival curves (overall survival and disease-specific survival) using the Kaplan-Meier method had no statistical differences between the patients with and without nutritional risk (χ2=3.316, P=0.069; χ2=3.712, P=0.054). ConclusionsFrom the analysis results of this study, for the rectal cancer patients who underwent extreme sphincter-preserving surgery following neoadjuvant therapy, the patients with preoperative nutritional risk are more prone to anastomotic leakage within 30 d after surgery. Although other postoperative complications and long-term survival outcomes have no statistical differences between patients with and without nutritional risk, preoperative nutritional management for them cannot be ignored.