EVALUATION OF AUTOLOGOUS FAT IMPLANTATION IN THE RAT URINARY-BLADDER SUBMUCOSA

Objectives. Autologous fat has been used as a bulking implant material for stress urinary incontinence. There is considerable controversy as to the ultimate fate of the grafted fat. This study was conducted to determine the fate of autogenous fat implanted into the bladder of rat s. Methods. Two groups of adult female rats were studied. In the test animals (group 1, n = 20), mesenteric adipose tissue (1 mt) was harves ted and homogenized with an equal weight of sterile saline. Using a 25 -gauge needle, 0.5 g of saline-fat mixture was injected into the dorsa l bladder neck submucosa. Control animals (group 2, n = 12) were injec ted with sterile saline only.,A subset of animals from each group were killed after 7, 35, 105, and 150 days, and the bladder and urethra we re fixed. The fixed tissue was examined microscopically and photograph ed at each follow-up period. Results. Seven days after injection of fa t, there was a pronounced acute inflammatory reaction with numerous po lymorphonuclear leukocytes and macrophages at the site of fat injectio n. There was minimal inflammatory reaction at the site of saline injec tion. By day 35, most of the fat had been eliminated by these phagocyt es because of severe acute and chronic inflammation. By day 105, the s ubmucosa tissue of the experimental rats had returned to normal visual ly and to a flat surface, lacking the appearance of a sizable ''bulge' ' as shown at days 0 and 7. Histopathologic findings were also similar to the control rats. Inflammatory cells were no longer present by day 105. Conclusions. The implantation of homogenized, autologous fat in the rat urinary bladder submucosa causes acute and chronic inflammatio n and fat necrosis. The severe phagocytosis at the implant sites elimi nates the vast majority of the devitalized implanted fat during the fi rst month. (C) 1998, Elsevier Science Inc. All rights reserved.