Compensatory Glomerular Hypertrophy Is Not a Cause of Supranormal Renographic Differential Renal Function in Patients with Ureteropelvic Junction Obstruction

Ham, Won Sik; Jeong, Hyeon Joo; Han, Sang Won

Abstract

PURPOSE: Increasing clinical importance is being placed on the role of differential renal function (DRF) for the management of congenital ureteropelvic junction obstructions. Supranormal DRF of a hydronephrotic kidney, on a renal scan, is hypothesized to be due to an increase in single nephron filtration or nephron volume. However, the etiology of this paradoxical phenomenon still remains to be elucidated. We studied the histopathological changes of hydronephrotic kidneys with a supranormal DRF.
MATERIALS AND METHODS
35 children with unilateral congenital hydronephrosis and supranormal DRF (>55%), on preoperative renal scans, who had undergone pyeloplasty, were retrospectively evaluated. There were 3 female and 32 male patients. The mean age at the time of the operation was 12.6 months, ranging from 0.1 to 144 months. Needle biopsies, from 3 different sites at the lower pole of the kidney, were performed during surgery. To evaluate the presence of glomerular hypertrophy, the maximal planar area of the glomeruli was measured under light microscopy. Tissue samples were obtained in same manner from kidneys with no history of urinary tract disease on autopsy, and used as controls. The mean glomerular areas of the patient and control groups were plotted according to the patient's age.
RESULTS
The mean glomerular area in the patient group was smaller than in the control group, with the exception of 4 patients. According to the logistical regression, the probability of larger renal glomeruli increased with decreasing DRF (p=0.1155).
CONCLUSIONS
The glomerular area of a hydronephrotic kidney, with a supranormal renal function on a renal scan, was not significantly larger than the normal controls. Therefore, we believe that the theory of increased nephron volume as a cause of a supranormal DRF can be excluded.