To perform a study to describe the way in which an increasingly obese body mass index (BMI) is associated with urinary tract infection (UTI). The association between UTI and obesity is not well characterized. In fact, previous investigations of this subject have yielded conflicting findings. UTI is increasingly being recognized as a preventable complication, and UTI rates are used to measure quality of surgical care.

We evaluated claims over a 5-year period (2002-2006) in a national private claims database to identify patients diagnosed with UTI or pyelonephritis by ICD-9 coding. Descriptive analyses were performed and odds ratios were calculated.

A total of 95,598 subjects were identified for evaluation. Gender distribution was 42.9% male and 57.1% female. In the overall study cohort, the diagnosis of a UTI or pyelonephritis occurred in 13% and 0.84%, respectively. Women were 4.2 times more likely to be diagnosed with a UTI (19.3% vs 4.6%), and 3.6 times more likely to be diagnosed with pyelonephritis (1.22% vs 0.34%), than were men. At all stratifications of obesity, the obese were significantly more likely to be diagnosed with a UTI or pyelonephritis than nonobese patients.

Elevated BMI appears to be associated with an increased risk for UTI and pyelonephritis. Further study is needed to determine whether this association may be attributed to a cause-and-effect relationship. However, these results may serve to guide clinicians who treat obese patients, because it may be an additional benefit of weight loss.