OBJECTIVES: Historically, complication rates following colorectal surgery were stratified by disease process, type of operation, or anesthesia risk derived after an intensive review of the medical record. Newer computer applications purport to shorten this process and predict the probability of postoperative complications by distinguishing them from comorbidities that are co-mingled on uniform discharge codes. We analyzed CaduCIS software (CareScience, Inc., Philadelphia, PA) which uses discharge codes to see if its predictions of comorbidity and complications accurately track the medical record. METHODS: Two-hundred and seventy patients were analyzed using principal and secondary diagnoses coded on discharge. Coding inaccuracies of clinical occurrences were identified by physician review of each medical record. The actual incidences of 17 common preoperative comorbidities and 11 postoperative complications were compared to computerized predictions by applying standard statistical tests. RESULTS: The overall incidence of complications obtained by physician (actual) review was 47%, compared to 46% by computer. The computerized predicted distribution of comorbidities was similar to the actual occurrences in 15 of 17 categories. Analysis showed a statistical difference between the computer-predicted and "actual" complication rates in 5 of the 11 categories; however these differences (underestimates) were due to charting and coding inaccuracies, not to computerized errors. The most common preoperative comorbidities and complications were cardiopulmonary (47% and 28%, respectively). CONCLUSIONS: The computer-system's accurate measurement of the overall complication rate supports the claim that aggregate complication estimates derived from readily available administrative data are sufficient for across-the-board comparisons among hospitals. The computerized system can generate such measurements in a fraction of the time is takes to manually review the medical records. As uniform discharge coding of co-mingled comorbidity and complications are increasingly used to rapidly compute surgical outcomes, colon and rectal surgeons need to ensure compatibility of the actual and coded medical record.