Collagen polyp of the urinary tract: a report of two cases.

Injection of collagen into the urethral or bladder wall has gained popularity as an effective way to control urinary stress incontinence. The same technique has recently been used to improve function of urinary pouches surgically created from intestinal segments. We report the first two cases of a polypoid lesion in these structures, both of which were composed of injected collagen. The first lesion occurred in the ileal urinary pouch of a 41-year-old paraplegic man who had cystoprostatectomy for severe spasm and repeated infection of the bladder. The pouch, removed for repeated infection, showed 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 carcinoma, followed by artificial urethral sphincter placement. Follow-up cystoscopy revealed a proximal urethral polyp that was biopsied. In both cases, collagen was injected into these structures for controlling urinary incontinence. Histologically, the polyps were caused by submucosal accumulation of injected collagen with pathognomonic features (i.e., eosinophilic, homogeneous, and poorly cellular material that was faintly positive by the periodic acid-Schiff and strongly positive by the trichome stain). These two cases expand the list of differential diagnoses for a polypoid lesion in the intestinal and urinary tracts and illustrate the morphology of injected collagen. A familiarity with these changes is diagnostically helpful because an increasing number of specimens removed for therapeutic failure of injected collagen are expected.