USE OF INJECTABLE FAT TO OBSTRUCT THE URETHRA IN RABBITS

Bulking agents have been injected to correct urinary incontinence for at least 15 years. The injection seeks to increase bladder outlet resi stance by partially obstructing the urethra and thereby reduce urinary leakage in patients with stress urinary incontinence. Although the im plant is effective and requires a shorter in-hospital stay than more t raditional procedures, no ideal implant substance has been discovered. To assess the effectiveness of injected fat as a bulking agent, we in jected small volumes of perivesical fat into the bladder neck in New Z ealand White (NZW) rabbits and tested the effect on the bladder. In ei ght rabbits, we harvested perivesical fat and partially closed the ure thral lumen with an initial injection. A second injection 1 month late r completely closed the urethral lumen. We injected six other rabbits with similar volumes of saline as controls. Two weeks after the second injection, we measured micturition frequency, bladder weight, respons e to electrical field stimulation, and response to bethanecol in each group. Fat implants were present at the injection site in each case 4 weeks after the first injection. Rabbits receiving fat implants had in creased micturition frequency, increased bladder weight, and increased response to bethanecol acid field stimulation. Previous studies have demonstrated that these changes are characteristic of mild outlet obst ruction in rabbits. Injected fat can be made to close the urethra and create bladder outlet obstruction in rabbits. The short-term success o f fat as a bulking agent in this experiment is encouraging and suggest s the need for longer term studies. (C) 1995 Wiley-Liss, Inc.