Nephrogenic adenoma of the urinary bladder. Clinical features, long-term follow-up and recurrence predictors.

Objectives: To review the clinical features of nephrogenic adenoma (NA) of the urinary bladder and assess the long-term recurrence rates.

Material and methods: A retrospective analysis of all diagnosed NA of the urinary bladder between 2000 and 2023 was done. All patients' demographics, symptoms, history of previous bladder surgeries, macroscopic and microscopic features of NA and coincidental pathology were reviewed. The long-term recurrence rate including malignant recurrence was assessed. Univariate and multivariate analysis of predictor of recurrence was performed.

Results: We identified 24 patients diagnosed with NA with a mean (SD, range) age of 56 (16, 15-73) years. Eighteen (75%) patients had previous history of bladder surgeries. Macroscopic appearance on cystoscopy looked polypoidal, flat velvety, papillary and nodular in eight, seven, five, and four patients, respectively. At a median (range) follow-up of 35 (18-145) months, 15 (63%) patients developed one recurrence including NA, non-specific cystitis and urothelial carcinoma (UC) in nine, three and three patients, respectively. Of them, five had a second recurrence, and one patient had a third recurrence. Patients with malignant recurrence had previous history of UC and two of them required radical cystectomy and urinary diversion. Previous TURBT was the only independent predictor for recurrence [OR (95% CI) = 28 (2-37), p = 0.01].

Conclusion: Nephrogenic adenoma is a benign disease that mimics malignant lesion clinically. It is associated with high recurrence rate. Previous resection of bladder lesion is the independent predictor of the recurrence.