Anastomotic leak after lower gastrointestinal surgery is a complication with potential for high morbidity, mortality, and increased costs. A single-institution retrospective chart review was performed on all patients who underwent lower gastrointestinal surgery between June 2009 and June 2013. Fifty-seven variables were included in our analysis and their association with postoperative anastomotic leak was examined. Nine hundred fifty-two patients underwent 983 lower gastrointestinal anastomoses with an overall leak rate in this series of 6 per cent. Type of intestinal anastomosis created (P < 0.00005), operative indication (P < 0.015), operation performed (P < 0.014), intraoperative blood transfusion (P < 0.017), and intraoperative surgical drain placement (P < 0.022) were all predictive of anastomotic leak. Anastomotic leak rate increased by 1.3 times for every additional hour in the operating room after three hours. Both increasing operation time and intraoperative blood transfusions were associated with an increased rate of anastomotic leak. When operative time extends beyond three hours or in those cases were blood transfusions are given, surgeons should consider taking steps to minimize the risks of a potential anastomotic leak.