Effect of repeated instillation of interstitial cystitis urine on the rabbit urinary bladder

One theory for the etiology of interstitial cystitis (IC) proposes toxic substances in the urine. This hypothesis was tested in our laboratory by infusing urine into the bladders of rabbits twice weekly for six weeks. For the first study rabbits were treated by one-hour biweekly intravesical exposure to urine from a symptomatic interstitial cystitis patient, a normal volunteer, or physiologic saline. For the second study, animals were exposed to both a high and a low molecular weight fraction of urine pooled from 7 interstitial cystitis patients, 7 normal female volunteers, and physiologic saline. At the end of six weeks the animals were cystoscoped and the bladder was removed the following day for histologic and contractile studies. Post-distention glomerulations were observed in 3 of the 4 whole IC urine-treated animals and an ulcer identical to the classic "Hunner's ulcer" was seen in one of these animals. Post-distention petechial hemorrhages were also noted in all 5 of the high molecular weight IC urine-treated animals but in none of the others, suggesting a difference between IC and normal urine. These IC urine-treated groups also showed the greatest degree of histologic changes including edema and plasma cell infiltrates in the lamina propria, submucosa and perivascular tissue. However, there was no statistically significant difference in bladder capacity, micturition patterns, or contractile response of bladder strips. These results indicate that there are substances with nominal molecular weight greater than 10 kD in interstitial cystitis urine that induce changes in the rabbit bladder that resemble bladders of interstitial cystitis patients.