Conversion rates in laparoscopic colorectal surgery: A predictive model with 1253 patients

Background: This study aimed all develop a mathematical model for predicting the conversion rate for patients undergoing laparoscopic colorectal surgery. Method: This descriptive single-center study used routinely collected clinical data from 1,253 patients undergoing laparoscopic surgery between November 1991 and April 2003. A two-level hierarchical regression model was used to identify patient, surgeon, and procedure-related factors associated with conversion of laparoscopic to open surgery. The model was internally validated and tested using measures of discrimination and calibration. Exclusion criteria for laparoscopic colectomy included a body mass greater than 50, lesion diameter exceeding 15 cm, and multiple prior major laparotomies (exclusive of appendectomy, hysterectomy, and cholecystectomy). Results: The average conversion rate for the study population was 10.0% (95% confidence interval [CI], 8.3-11.7%). The independent predictors of conversion of laparoscopic to open surgery were the body mass index (odds ratio [OR], 2.1 per 10 Americans Society of Anesthesiology units increase), (ASA) grade 3 or 4, 1 or 2 (OR, 3.2, 5.8), type of resection (low rectal, left colorectal, right colonic vs small/other bowel procedures; OR, 8.82, 4.76, 2.98), presence of intraoperative abscess (OR, 3.60) or fistula (OR, 4.73), and surgeon seniority (junior vs senior staff OR, 1.56). The model offered adequate discrimination (area under receiver operator characteristic curve, 0.74) and excellent agreement (p = 0.384) between observed and model-predicted conversion rates (range of calibration, 3-32% conversion rate). Conclusions: Laparoscopic conversion rates are dependent on a multitude of factors that require appropriate adjustment for case mix before comparisons are made between or within centers. The Cleveland Clinic Foundation (CCF) laparoscopic conversion rate model is a simple additive score that can be used in everyday practice to evaluate outcomes for laparoscopic colorectal surgery.