Surgical Site Infections and Cost in Obese Patients Undergoing Colorectal Surgery

May 17, 2011

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In a study published in the May online version of Archives of Surgery, researchers from Johns Hopkins University measured the effect of obesity on surgical site infection (SSI) rates and the associated costs of SSIs for patients having colorectal surgery.

The study was retrospective using administrative claims data obtained from Blue Cross and Blue Shield insurance claims database.

The study quantified the rate of SSIs in obese and nonobese patients who underwent colectomy procedures.  The researchers identified 7020 patients in the data set.  Patients with a body mass index greater than or equal to 30 were defined as obese.  A total of 1243 patients met the criteria for being obese.  The subject patients were those having a total or segmental colectomy for colon cancer, diverticulitis, or inflammatory bowel disease.  Data from January 2002 to December 2008 were included.

The 30-day SSI rates among obese patients as compared to those who were nonobese were reviewed.  Total costs from all health care claims for 90 days following surgery were also determined.  Additionally, the study researchers performed a multivariate logistic regression to identify SSI risk factors.

The findings revealed that obese patients had an increased rate of SSIs (14.5%) as compared with nonobese patients (9.5%). Independent risk factors for surgical infection were obesity and open surgical operations as compared with a laparoscopic procedure.

Patients with surgical site infections incurred higher healthcare costs.  The mean total cost for patients with SSIs was $31,933 compared to $14,608 for patients without infections.

The researchers also found that the total length of hospital stay was longer for patients with an infection.  The mean length of stay for patients with SSIs  was 9.5 days as compared to 8.1 days for those without infection.  Probability of readmission to the hospital was also higher (27.8% as compared to 6.8%).

The authors conclude that the risk of having an SSI after a colectomy is increased in obese patients by 60%.  Open procedures had a higher risk of SSI.   Additionally, the presence of the infection itself increased the cost of a colectomy by a mean of $17,324.  If a readmission of the patient occurred, the median length of the readmission stay was longer for those patients experiencing an SSI as compared to those who did not.  Much of the increased cost was associated with the increase rate of hospital readmission.

Based on the study findings, the authors noted  “pay-for-performance programs will unfairly penalize hospitals and health care providers who disproportionately care for obese and other high-risk patients.”  Because of the prevalence of obesity in certain population subgroups, such as black women, the researchers “warn of the discriminatory implications of unadjusted pay-for-performance policies.”

The authors conclude by making an extremely important statement, one that is certain to influence policy related to pay-for-performance schemes related to healthcare-associated infections:

“We conclude that patients undergoing colorectal surgery who develop SSIs, many of whom are obese, tax the health care system. Pay-for-performance policies in surgery should account for the increased risk of infection and cost of caring for this population. Failure to consider these differences could lead to perverse incentives that may penalize surgeons who care for obese patients and may even affect obese patients’ access to colorectal surgery.”

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Reference:  Wick, E.C., Hirose, K., Shore, A.D., Clark, J.M., Gearhart, S.L., Efron, J., and Makary, M.A.  (2011).  Surgical Site Infections and Cost in Obese Patients Undergoing Colorectal surgery. Archives of Surgery.  Published online May 16, 2011.  Available at:

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