Impact of obesity on the cost of major colorectal surgery.

Background: The incidence of obesity is increasing in New Zealand. The aim of the study was to determine whether obesity impacts on the cost of treating patients undergoing major colorectal surgery.

Methods: Between 1 February 2008 and 31 July 2009, consecutive patients undergoing major colorectal surgery at Christchurch Hospital, New Zealand, were enrolled in the study. Body mass index (BMI) and waist-to-hip ratios were assessed using standardized techniques. Patients with a high surgical risk were identified using established criteria and all patients were assessed using the Portsmouth modification of the Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (P-POSSUM). Cost analysis was performed using a structured query language database. Patients were analysed using accepted groupings for BMI, waist circumference and waist-to-hip ratio.

Results: A total of 372 patients were enrolled in the study, of whom 345 were included in the analysis. The incidence of diabetes was significantly higher with increased BMI (P = 0·002), whereas all other co-morbidities, and P-POSSUM values, did not differ between BMI groups. The groups were similar in terms of case mix. Treatment of obese patients (BMI at least 30 kg/m(2)) was significantly more expensive than that of normal weight patients (BMI 20-24·9 kg/m(2)): €10,036 versus €7390 (P = 0·005). Treatment costs for patients with a BMI of 25-29·9 kg/m(2) were next highest (€9048) followed by those for patients whose BMI was less than 20 kg/m(2) (€8884). Patients with a waist circumference above recognized standards for men and women also cost significantly more to treat (€10,063 versus €7836; P = 0·014).

Conclusion: Excess body fat was associated with higher costs of major colorectal surgery.