Chronic partial ureteral obstruction in the neonatal guinea pig. I. Influence of uninephrectomy on growth and hemodynamics.

Although obstructive nephropathy is a frequent cause of renal insufficiency in infancy, factors influencing adaptation to chronic partial ureteral obstruction (CPUO) are poorly understood. Guinea pigs were subjected to unilateral CPUO within the first 2 days of life (Group I) and microsphere studies were performed at 23 +/- 3 days of age. To also investigate the role of functional renal mass on growth and hemodynamics, contralateral nephrectomy was performed in Group II at the time of ureteral constriction. Compared to sham-operated controls (ureteral diameter = 1 mm) CPUO caused impaired somatic growth in both groups. Resulting hydroureteronephrosis was variable and most severe (ureteral diameter greater than 3 mm) in azotemic animals of Group II, which demonstrated reduced compensatory renal hypertrophy and poorest somatic growth. Mean arterial blood pressure was not affected by CPUO or uninephrectomy. Renal blood flow (RBF) was higher in Group II than Group I, and did not fall significantly with severity of CPUO in Group II, in which number of perfused glomeruli was similar to controls. In contrast, renal vascular resistance (RVR) increased by 172% in animals of Group I with severe CPUO, and was associated with 34% fewer perfused glomeruli than in the hypertrophied contralateral kidney. With increasing severity of CPUO, RBF tended to be distributed to outer cortical regions in the obstructed kidney of Group I, while the shift in RBF distribution was from outer to inner cortex in the remaining kidney of Group II. Filtration fraction fell as a result of CPUO in both groups, such that reduction in the glomerular filtration rate was due in large part to factors other than RBF.(ABSTRACT TRUNCATED AT 250 WORDS)