Int J Colorectal Dis (2009) 24:789–795 DOI 10.1007/s00384-009-0692-4 ORIGINAL ARTICLE After-hours colorectal surgery: a risk factor for anastomotic leakage Niels Komen & Jan-Willem Dijk & Zarina Lalmahomed & Karel Klop & Wim Hop & Gert-Jan Kleinrensink & Hans Jeekel & W. Ruud Schouten & Johan F. Lange Accepted: 26 February 2009 / Published online: 21 March 2009 # The Author(s) 2009. This article is published with open access at Springerlink.com Abstract Purpose This study aims to increase knowledge of colorectal anastomotic leakage by performing an incidence study and risk factor analysis with new potential risk factors in a Dutch tertiary referral center. Methods All patients whom received a primary colorectal anastomosis between 1997 and 2007 were selected by means of operation codes. Patient records were studied for population description and risk factor analysis. Results In total 739 patients were included. Anastomotic leakage (AL) occurred in 64 (8.7%) patients of whom nine (14.1%) died. Median interval between operation and This work was presented at the Dutch Surgical Days, May 22nd 2008, Veldhoven, the Netherlands. N. Komen (*) Department of Surgery, ZNA Middelheim, Lindendreef 1, 2020 Antwerp, Belgium e-mail: nielskomen@hotmail.com N. Komen : J.-W. Dijk : Z. Lalmahomed : K. Klop : H. Jeekel : W. Ruud Schouten : J. F. Lange Department of Surgery, University Medical Center Rotterdam, Erasmus MC, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands G.-J. Kleinrensink Department of Neurosciences and Anatomy, University Medical Center Rotterdam, Erasmus MC, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands W. Hop Department of Epidemiology and Biostatistics, University Medical Center Rotterdam, Erasmus MC, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands diagnosis was 8 days. The risk for AL was higher as the anastomoses were constructed more distally (p = 0.019). Univariate analysis showed duration of surgery (p = 0.038), BMI (p = 0.001), time of surgery (p = 0.029), prophylactic drainage (p = 0.006) and time under anesthesia (p = 0.012) to be associated to AL. Multivariate analysis showed BMI greater than 30 kg/m2 (p = 0.006; OR 2.6 CI 1.3–5.2) and “after hours” construction of an anastomosis (p = 0.030; OR 2.2 CI 1.1–4.5) to be independent risk factors. Conclusion BMI greater than 30 kg/m2 and “after hours” construction of an anastomosis were independent risk factors for colorectal anastomotic leakage. Keywords After-hours . Colorectal surgery . Anastomotic leakage . Body mass index Introduction Anastomotic leakage (AL) is the major complication after colorectal surgery. It is poorly understood as illustrated by the vast body of confirming and contradicting publications on virtually every known potential risk factor. The great variation of reported incidences of AL, between 3% and 19% [1, 2], illustrates this as well. The poor understanding of AL may be due to its multifactorial aspect. In addition, studies on potential risk factors are performed in different populations throughout the world and, therefore, show many different independent risk factors for anastomotic leakage, varying from divertic- ular disease [3] and rectal resection [4] to weight loss [5], urgent operation [6], smoking [7] and BMI [8]. The factor “surgeon” is important as well since it is shown that leakage risk is lower when patients are operated upon by a high-volume surgeon [9].