Indigocarmine as a quantitative indicator of urothelial integrity

There is increasing evidence that the urothelium of the bladder mucosa prevents the penetration of solutes from the urine into the bladder wall. In the current study, in vivo treatments of rabbit urinary bladder with DMSO, acetone and overdistension resulted in damage to the physical integrity of the bladder mucosa as quantitated by the penetration of the dye indigocarmine (1% in saline) into submucosal tissues. Penetration of the dye can be quantitated, because the dye can be extracted from the tissue and measured spectrophotometrically. Indigocarmine does not penetrate normal, control, bladder mucosae. Bladders treated with gentle 20, 30 and 50% acetone washes for one minute permit dye penetration which is proportional to the acetone concentration utilized. Intravesical 50% DMSO ("RIMSO 50") administration permits modest dye penetration. Distension by slow filling with saline to volumes 90% of capacity and greater causes a marked increase in dye penetration which is proportional to the magnitude of overdistension. Although pretreatment of the bladder with heparin did not reduce the dye penetration following acetone administration, it completely abolished penetration of the dye following overdistension. Indigocarmine is potentially useful as both a quantitative and qualitative indicator of bladder mucosal integrity.