Previous studies have reported overlap of overactive bladder syndrome (OAB) and bowel dysfunction, including Irritable Bowel Syndrome (IBS) and constipation, suggesting a common aspect of pathophysiology. Prior studies however have focused on the presence/absence of symptoms rather than on severity of symptoms. The aim of this study was to determine if women with OAB and bowel dysfunction report more severe lower urinary tract symptoms than those without bowel dysfunction.

After obtaining institutional review board approval, we recruited 99 adult women with idiopathic OAB from the Urology clinic and through advertisement, using a score of >= 4 on the OABq-V3 to confirm the diagnosis. Participants completed questionnaires detailing demographic and clinical history as well as urinary symptoms (i.e. OAB questionnaire, ICIQ- Female LUTS) and bowel function (i.e. Rome III questionnaire). For the primary exposure, we categorized women into three groups based on bowel dysfunction, as determined by Rome criteria: none (No BD), functional constipation (FC), and IBS.  For the primary analyses, we compared the differences in the summary scores of the OABq and the ICIQ-FLUTS, in addition to individual symptoms, across the primary exposure groups. We also analyzed the associations between OAB symptoms and constipation severity, as measured by the constipation severity score derived from the Rome questionnaire. Statistical tests included chi square analyses and linear regression, with a significance level of 0.05.

Of the 99 women, 58 (59%) reported no bowel dysfunction, 28 (28%) had functional constipation, and 13 (13%) qualified as IBS. Of those with IBS, 9 (69%) had constipation-only or -predominant IBS. Ages, BMI, and the use of anticholinergic, narcotic, anxiety or other pain medications did not differ significantly across the groups (Table 1). OABq symptom scores were significantly higher for both FC and IBS compared to no BD, although not statistically different from each other, even though there was a trend for higher OABq for women with IBS. (Table 2) OAB HRQL was significantly lower for both groups compared to no BD group, and significantly lower for IBS vs. FC. ICIQ FLUTS scores were also significantly higher for IBS compared to FC and no BD.  Constipation severity score was also increased for FC and IBS compared to no BD, but not different from each other. We found a significant association with increased OABq symptom score and increased CSS (beta 1.85, SE .54, p=.001), even with adjustment for age, BMI and medication use.

Women with OAB and either functional constipation or IBS appear to have more severe OAB symptoms than those without bowel dysfunction.  Women with OAB and IBS appear to have more non-OAB and more severe LUTS than those with functional constipation or no bowel dysfunction. There appears to be a positive association between OAB symptom severity and constipation severity.

Severity of concomitant bowel and bladder symptoms may not only have implications for OAB patients, but also may suggest underlying pathophysiologic mechanisms