Background: The removal of more than one kidney in animals leads to proteinuria and progressive renal failure due to focal segmental glomerulosclerosis. This injury may be the result of chronic glomerular hyperfiltration. The purpose of this study was to determine the effect of a reduction in renal mass of more than 50 percent on residual renal function and morphology in humans.
Methods: We evaluated long-term renal function in 14 patients with a solitary kidney who had undergone partial nephrectomy for renal-cell or transitional-cell carcinoma. In 12, the first kidney had been removed 2 months to 21 years previously for the same type of cancer; in 2, the other kidney was congenitally atrophic. Before surgery, no patient had clinical or histopathological evidence of primary renal disease. All 14 patients underwent partial nephrectomy to remove a localized tumor, with 25 to 75 percent of the solitary kidney being excised. They were evaluated 5 to 17 years after surgery (mean, 7.7).
Results: Twelve patients had stable postoperative renal function, and end-stage renal failure developed in two. There were no changes in blood pressure in any patient during follow-up. Nine patients had proteinuria, which was mild (0.15 to 0.8 g of urinary protein per day) in five. The extent of proteinuria was inversely correlated with the amount of remaining renal tissue (P = 0.0065) and directly correlated with the duration of follow-up (P = 0.0005). Four patients with moderate-to-severe proteinuria had renal biopsies, which revealed focal segmental glomerulosclerosis in three patients and global glomerulosclerosis in one.
Conclusions: Long-term renal function remains stable in most patients with a reduction in renal mass of more than 50 percent. These patients are, however, at increased risk for proteinuria, glomerulopathy, and progressive renal failure.