Summation model of pelvic pain in interstitial cystitis.

Many patients with interstitial cystitis (IC) find that particular foods exacerbate disease symptoms. These patients may modify their diet to manage symptoms, but the mechanism by which dietary modification benefits patients with IC is unclear. We hypothesize that integration of neural signals from pelvic organs mediates the effects of diet on symptoms of IC. In animal models, pelvic inflammation is subject to crosstalk, so an inflammatory stimulus in one pelvic organ evokes a response in an independent organ. Recent data show that the colon can modulate bladder-associated pelvic pain in mice. As pelvic organs are innervated through shared circuitry, perceived pelvic pain might occur when spatial summation of individual pelvic inputs exceeds a threshold. Through this mechanism, a noxious dietary stimulus, which otherwise does not exceed the pain threshold in a normal individual, may substantially exacerbate pain in a patient with bladder symptoms. Repeated painful stimuli over time further contribute to symptoms by a process of temporal summation, resulting in enhanced responsiveness through central sensitization. Thus, pelvic organ crosstalk might modulate symptoms of pelvic pain by spatial and temporal summation, suggesting a mechanism for the benefits of dietary modification in patients with IC, as well as therapeutic opportunities.