High incidence of nephrogenic adenoma of the bladder after renal transplantation

Tumors of the bladder termed nephrogenic adenomas in kidney allograft recipients are believed to develop as urothelial metaplastic proliferations in response to mechanical trauma, chemical noxae, irradiation, and bacterial or viral pathogens. We report on the incidence of nephrogenic adenoma of the bladder in patients who received renal transplants during a period of 7 years and 3 months at the University Hospital of Vienna. Diagnosis was obtained by cystoscopy and histological analysis. Nephrogenic adenoma was treated by transurethral electroresection and administration of antibiotics in case of urinary tract infections. Follow-up consisted of cytological controls of urine and bladder irrigation fluid as well as of cystoscopy every 3 months. In 7 of 1328 renal allograft recipients, nephrogenic adenoma could be detected after 7 to 60 months following renal transplantation. In five patients, recurrence was detected 9 to 23 months after diagnosis of the initial lesion. No evidence of malignant degeneration was observed in any patient. Nephrogenic adenoma was not related to immunosuppressive therapy, cytomegalovirus disease, or gancyclovir therapy. We suggest that after successful transurethral electroresection of nephrogenic adenomas, cytological controls are adequate every 3 months. Only in renal transplant patients with recurrence of voiding disturbances, macrohematuria, or urinary tract infection are cystoscopy and biopsy indicated in the routine follow-up regimen.