Influence of ureteral obstruction (hydronephrosis) on renal function in man

¹ Departments of Surgery, Urology and Physiology, Karolinska Institutet Medical School, Karolinska sjukhuset, Stockholm, Sweden

Ten cases of pelvic dilatation due to obstruction of urinary flow are presented. They were investigated by means of selective clearances for the separate kidneys. GFR (clearance of inulin), ERPF (clearance of PAH) and maximal tubular excretory capacity (Tm_PAH) were determined, together with the extraction ratio of PAH (E_PAH). In four additional cases the changes in the functional pattern of each kidney were studied after the removal of the existing obstruction to urine outflow. The results indicate that partial obstruction to the urinary flow results in lowered C_In/C_PAH ratios and generally elevated C_PAH/Tm_PAH ratios, indicating ‘relative renal hyperemia.’ The Tm_PAH and E_PAH did not seem to be primarily affected by the obstruction. The lowered C_In/_PAH ratios seemed to be due to diminished GFR or increased ERPF or both. Upon removal of the obstruction the decreased renal activities rapidly recovered simultaneously with a disappearance of the compensatory hyperfunction of the other kidney. The determination of selective clearances offers a possible method for establishing whether or not calculi or strictures obstruct urinary outflow.