Excretion of Fluorescein in the Urine of Women With Interstitial Cystitis

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Abstract
Altered bladder permeability may have a role in the pathogenesis of interstitial cystitis. Fluorescein, a fluorescent dye of molecular weight 325, has been used to assess membrane permeability. Orally ingested fluorescein normally is rapidly conjugated to glucuronate by the liver and excreted in the urine. To test its use as a marker of bladder permeability, we administered fluorescein orally to 6 patients with interstitial cystitis who satisfied National Institutes of Health, National Institute for Diabetes and Digestive and Kidney Diseases criteria and to 6 normal female control subjects. After emptying the bladder and collection of a baseline blood sample, fasted subjects ingested 20 mg. fluorescein and blood samples were collected 1, 2, 3, 4 and 24 hours later. Urine was collected during each of the first 4 hours, and then from 4 to 10, 10 to 16 and 16 to 24 hours. Urine volume was measured, and all plasma and urine samples were analyzed for fluorescein. Plasma fluorescein concentrations (ng./ml.) were significantly (p < 0.05) higher in interstitial cystitis patients than in control subjects at 1 and 2 hours after fluorescein ingestion. Urine fluorescein excretion (mg.) was significantly (p < 0.05) lower in interstitial cystitis patients than in control subjects at 4 to 10 hours after fluorescein ingestion, and for the entire 24 hours. The increased fluorescein concentration in the plasma and decreased excretion in the urine of interstitial cystitis patients suggest that fluorescein may be a useful marker of altered membrane permeability.