Collagen polyp of the urinary tract: A report of two cases

Injection of collagen into the urethral or bladder wall has gained populari ty as an effective way to control urinary stress incontinence. The same tec hnique has recently been used to improve function of urinary pouches surgic ally created from intestinal segments. We report the first two cases of a p olypoid lesion in these structures, both of which were composed of injected collagen. The first lesion occurred in the deal urinary pouch of a 41-year -old paraplegic man who had cystoprostatectomy for severe spasm and repeate d infection of the bladder. The pouch, removed for repeated infection, show ed a 2.5-cm submucosal polyp. The second lesion was in the urethra of a 71- year-old man who underwent radical retropubic prostatectomy for prostatic c arcinoma, followed by artificial urethral sphincter placement. Follow-up cy stoscopy revealed a proximal urethral polyp that was biopsied. In both case s, collagen was injected into these structures for controlling urinary inco ntinence. Histologically, the polyps were caused by submucosal accumulation of injected collagen with pathognomonic features (i.e., eosinophilic, homo geneous, and poorly cellular material that was faintly positive by the peri odic acid-Schiff and strongly positive by the trichome stain). These two ca ses expand the list of differential diagnoses for a polypoid lesion in the intestinal and urinary tracts and illustrate the morphology of injected col lagen. A familiarity with these changes is diagnostically helpful because a n increasing number of specimens removed for therapeutic failure of injecte d collagen are expected.