[Bladder nephrogenic metaplasia: circumstances of discovery, predisposing factors, and clinical course in 7 cases diagnosed between 1988 and 2000].

Introduction: Nephrogenic adenoma (NA) or nephrogenic metaplasia is a rare, benign urothelial tumour.
Material and Methods: This retrospective study evaluated the circumstances of discovery, predisposing factors, and clinical course of seven patients with nephrogenic adenoma diagnosed between 1988 and 2000. The mean age of these patients was 55.7 years (range: 16 to 88 years). The mean follow-up was 24 months (range: 4 to 108 months).
Results: There are no specific endoscopic findings and the lesion was sometimes flat or papillary with an appearance that can be identical to that of bladder tumour. The diagnosis was always based on histological findings. Suggestive clinical signs were nonspecific and comprised: haematuria, dysuria, or urgency. Treatment was surgical with transurethral resection or electrocoagulation of the lesion, combined with elimination of the factors irritating the urothelial mucosa. In our experience, recurrences were observed in 28.5% of patients and occurred during the year following the initial treatment.
Conclusion: Nephrogenic adenoma is a rare, benign urothelial tumour most frequently situated in the bladder. The presenting clinical signs are completely nonspecific and usually related to predisposing factors (infections, inflammation, bladder tumour). Only histological examination can provide the essential proof of the benign nature of this lesion. Endoscopic resection therefore has two objectives: diagnostic and therapeutic. The clinical course is characterized by recurrences.