792 Table 2 The incidence of anas- tomotic leakage stratified for the performed operations “Other” contained eight anasto- moses without resection when, intraoperatively, the tumor appeared to have progressed to far and one resection of trans- verse and descending colon Analysis of the anastomotic leakage rate per operation showed a significant trend (p= 0.019), regarding the expected increase in leakage rate going from top to bottom in the table (the group “other” was not in- cluded in this calculation). Performed operations Procedure (Neo)-ileocecal resection Resection transverse colon (Extended) Hemicolectomy right Subtotal colectomy Hemicolectomy left Resection sigmoid Rectosigmoid resection LAR/TME Other Total Overall, the median duration of anesthesia was 217 min (range 75–630 min) and the median duration of operation was 162 min (range 49–497 min). A total of 633 (86%) patients were operated upon during-hours, which was defined as the hours in which a new elective procedure was allowed to start (i.e., between 7.45 h and 15.30 h). This means that generally, the elective program ended around 17.30 h–18.00 h. A total of 106 patients (14%) were operated upon after-hours, which was defined as the period in which patients were operated upon by the operating team that is on call (i.e., between 15.30 h and 7.45 h). A total of 156 (21%) patients were operated upon in an emergency setting, 583 (79%) patients were operated upon in elective setting. The median hospital stay after the operation was 13 days (range 1–180 days) and the median stay on ICU was 0 days (range 0–72 days). The overall in hospital mortality rate was 4.7%. Incidence of anastomotic leakage Anastomotic leakage was diagnosed in 64 (8.7%) patients, of which nine patients (14%) died due to consequences of anastomotic leakage (AL). As depicted in Table 2, the highest incidence of AL occurred after resection of the rectosigmoid (17%), fol- lowed by resection of the transverse colon (15%) and low anterior resection (13%). The median interval between operation and diagnosis of anastomotic leakage was 8 days (range 2–61 days). Risk factor analysis Analysis of the anastomotic leakage rate per operation showed a significant trend, indicating that higher leakage rates occurred as the anastomosis was constructed further downstream (p = 0.019; Table 2). Other potential risk factors for anastomotic leakage that reached significance in the 86 (96%) 23 (85%) 235 (94%) 26 (87%) 56 (88%) 142 (92%) 15 (83%) 83 (87%) 9 (100%) 675 (91.3%) Int J Colorectal Dis (2009) 24:789–795 4 (4%) 4 (15%) 15 (6%) 4 (13%) 8 (12%) 13 (8%) 3 (17%) 13 (13%) 0 (0%) 64 (8.7%) 90 27 250 30 64 155 18 96 9 739 No anastomotic leakage Anastomotic leakage Total univariate analysis were BMI (p = 0.001), PD (p = 0.006), time of surgery (p = 0.029), duration of operation and anesthesia (p = 0.038, p = 0.012; Table 1). Multivariate analysis showed body mass index (BMI) and time of surgery, classified in “during-” and “after hours”, to be independent risk factors (Table 3). Prophy- lactic drainage was significantly associated with anasto- motic leakage as well (Table 3). Adjusted for these factors, no relation was found between leakage rate and the level of anastomosis. Patient outcome Mortality rate amongst the patients with anastomotic leakage (14.1%) was significantly higher than amongst the Table 3 Significant results of multivariate analysis Multivariate analysis Factor BMI (kg/m2) Time of surgery Prophylactic drainage <25 25–30 >30 During-hoursa After-hours No Yes OR 1 0.6 2.6 1 2.2 1 2.8 95% CI – 0.3–1.14 1.3–5.2 – 1.1–4.5 – 1.5–5.1 p value – 0.115 0.006 – 0.030 – 0.001 The group “other” was excluded for the risk factor analysis; therefore, the total number of patients included is 730. Reference categories are indicated by OR=1 OR Odds Ratio, CI Confidence interval a Time of surgery is defined as the hours in which a new elective procedure was allowed to start (i.e. between 7.45 h and 15.30 h). After-hours is defined as the period in which patients were operated upon by the operating team that is on call (i.e., between 15.30 h and 7.45 h).