The Impact of Obesity on Outcomes Following Major Colorectal Surgery
Introduction Obesity is a major health problem in western society with rapidly increasing prevalence in most countries. The healthcare burden of obesity is far reaching but many of the consequences are yet to be fully understood. While there is a perception that obesity negatively impacts on outcomes following colorectal surgery there is conflicting evidence for this. Aims To assess the perception of New Zealand General Surgeons of the impact of obesity on outcomes following major colorectal surgery and to compare this to the current literature. To determine whether obesity impacts on the outcomes following major colorectal surgery. To determine whether obesity impacts on the cost of treating patients undergoing major colorectal surgery. Methods Members of the New Zealand Association of General Surgeons were surveyed by mail. Surgeons were asked to respond to statements provided regarding the impact of obesity on outcomes following major colorectal surgery. The surgeon’s responses were compared with recent literature. Between February 1st, 2008 and July 31st, 2009, patients undergoing major colorectal surgery at public and private hospitals in Christchurch and Invercargill, New Zealand were enrolled. Following informed consent, BMI, waist circumference, and waist-hip ratios were assessed. High risk patients were identified using established criteria as well as ASA and P-POSSUM. Complications were identified according to established criteria. Patients were grouped according to BMI categories and recognised cut-offs for waist measurement and waist-hip ratios. Using the database described above a Cost analysis was performed on all patients treated at Christchurch public hospital using a SQL database. The cost of treatment was analysed with respect to the same BMI, waist circumference and waist-hip ratio cut-offs. Results More than 90% of surgeons agreed or strongly agreed that obese patients are at greater risk of wound infection, cardiac, pulmonary, and thrombo-embolic risk, as well as overall morbidity, mortality and hospital cost. A literature review found evidence of increased risk of wound infection, anastomotic leak, and pulmonary and thrombo-embolic risk. There was mixed evidence or no evidence that obesity increases cardiac risk, sepsis, overall morbidity and mortality or overall cost. A cohort of 415 patients was enrolled and following exclusions 388 were analysed. Diabetes was more common with increased BMI (p=0.004). Other categories of operative risk were not different. ASA and P-POSSUM mortality scores were greater in the underweight group (p=0.026 and p=0.016). There was no difference in overall morbidity (p=0.095) however there were higher rates of more severe morbidity in the obese groups defined by BMI and waist circumference (p=0.049 and p=0.009). 372 patients were enrolled in the costing study and following exclusions 345 were analysed. The incidence of diabetes was significantly higher with increased BMI (p=0.002) however all other comorbidities were not different. Obese patients were more expensive than normal weight patients ($20,072 versus $14,780(p<0.05)). Obese patients defined by waist circumference also cost significantly more ($20,126 versus $15,672 (p=0.014)). Conclusion The survey found that surgeons believe that obese patients are at increased risk of mortality, increased cost of treatment and all complications except anastomotic leak. Those views are not always supported by current evidence. This study demonstrates that obesity, measured by BMI and waist circumference, is not associated with increased overall morbidity but is associated with more severe morbidity. I have also demonstrated that excess body fat as measured by BMI is associated with a significantly increased cost of treatment (36%) for patients undergoing major colorectal surgery.
Advisor: Frizelle, Frank
Degree Name: Master of Medical Science
Degree Discipline: Christchurch School of Medicine
Publisher: University of Otago
Keywords: Obesity; Colorectal; Outcomes; BMI; Surgery
Research Type: Thesis