EXPERIMENTAL STUDIES ON OBSTRUCTIVE NEPHROPATHY

Abstract

Quantitative studies of separate renal function during and after unilateral partial ureteral obstruction were performed in eleven female mongrel dogs.
In the experiments, the dogs underwent a left cutaneous ureterostomy using a vaginal cuff for protection of the ureteral stoma to facilitate repeated separate urine collection for a considerable long period. Then, a partial ureteral obstruction was created at the lower part of the right ureter by a silk knot. The obstruction was kept for five weeks, then the ureteral silk was deligated, and the dogs were followed for 5 more weeks after release of ureteral obstruction.
Split renal function studies were carried out at 1, 3, 5 weeks during obstruction, and 1, 3, 5 weeks after release. Clearance study was performed under constant diuresis to exclude the possible influences of hydronephrosis. The following values were obtained in each renal function studies: Glomerular filtration rate (GFR), creatinine excretion rate (ER_cr), sodium clearance (C_Na), fraction of filtered sodium excreted (FE_Na), potassium clearance (C_k), fraction of filtered potassium excreted (FE_k), osmolar clearance (C_osm), osmolar clearance as percent of GFR (C_osm/GFR), and free water clearance (CH₂O).
Then, each ratios were calculated from the value of obstruction side divided by that of normal side. Regarding free water clearance, the difference was calculated from normal kidney value minus obstructed kidney value. These ratios and difference were compared with GFR recovery ratio 5 weeks after relief of obstruction in the same dog. The results were as follows:
1) GFR and EF_cr of partially obstructed kidney decreased during obstruction and their recovery after relief of obstruction paralleled the degree of their decrease during obstruction. Statistically, GFR ratio had a highly significant correlation with ER_cr ratio through the period (p<0.001).
2) Absolute rate of sodium excretion was less in the partially obstructed kidney and C_Na ratio showed no significant correlation with GFR ratio at any time. FE_Na was uniformly greater on the side with partially obstructed kidney than on the control side after relief of obstruction.
3) Absolute rates of potassium and solute excretion were always lower on the side with partially obstructed kidney than on the control side during and following obstruction.
4) CH₂O was higher on the obstructed side after relief of obstruction.
5) GFR ratio 5 weeks after relief of obstruction had a significant correlation to each value at 5 weeks of obstruction; ER_cr ratio (p<0.001, correlation coefficent: r=0.918), C_Na ratio (p<0.001, r=0.878), FE_Na ratio (p<0.01, r=-0.761), C_k ratio (p<0.001, r=0.944), FE_k ratio (p<0.001, r=-0.929), C_osm ratio (p<0.01, r=0.860), C_osm/GFR ratio (p<0.01, r=-0.800) and CH₂O difference (p<0.001, r=-0.909).