Estimating Postoperative Mortality and Morbidity Risk of Radical Cystectomy With Continent Diversion Using Predictor Equations

Purpose: The POSSUM (Physiological and Operative Severity Score for Enumeration of Mortality and Morbidity) and Portsmouth POSSUM predictor equations are scoring systems validated in the general surgery literature that estimate postoperative morbidity and mortality risk. We tested the validity of POSSUM and Portsmouth POSSUM in patients undergoing radical cystectomy with continent diversion. Materials and Methods: We retrospectively reviewed physiological parameters, operative parameters, and 30-day morbidity and mortality in 102 patients who underwent radical cystectomy with continent orthotopic diversion, as done by a single surgeon. Predicted morbidity and mortality were calculated using the POSSUM and Portsmouth POSSUM equations. Patients were stratified into risk groups, and observed and predicted outcomes were compared. The accuracy of predictions was assessed using binomial and chi-square analysis. Results: Observed mortality and morbidity rates were 2.9% and 34.3%, respectively. Predicted morbidity using POSSUM analysis was 46 compared to the 35 observed in our series (p = 0.01). Compared to 3 observed deaths predicted mortality using POSSUM and Portsmouth POSSUM analysis was 13 and 5 (p = 0.002 and 0.30, respectively). There was a significant lack of fit for the POSSUM model to predict morbidity and mortality (p <0.05). However, the mortality risk estimated by Portsmouth POSSUM was not significantly different from the observed mortality rate in our cohort. Conclusions: In our series the POSSUM equation over predicted morbidity and mortality, and was unsuitable for a comparative audit of patients who underwent radical cystectomy with continent diversion. The Portsmouth POSSUM equation allowed satisfactory prediction of mortality in our cohort and should be evaluated further in larger series.