Renal functional reserve in children with a solitary functioning kidney and chronic kidney disease

Abstract

Objective – To examine renal functional reserve (RFR) and blood pressure (BP) in children with a solitary functioning kidney (SFK) and stage 1-3 chronic kidney disease (CKD).

Method – RFR was measured in 48 children with SFK and in 10 healthy children, as the difference between unstimulated and stimulated clearance of endogenous creatinine by a meat-free oral protein load (OPL). Cimetidine was given 48 h prior to the measurement when the study subjects were on a diet free of meat, fish and poultry. Serum cystatin C and urinary protein (UPRT)/urinary creatinine (UCr) were examined before and 2 hours after OPL. BP was determined by office and by 24-h ambulatory BP monitoring (ABPM).

Results – The majority of the patients (79.6%) had congenital SFK, while the remaining had acquired SFK due to unilateral nephrectomy. Sixteen patients had CKD1, 19 patients had CKD2 and 13 had CKD3. The patients and controls did not differ in terms of age, gender, body size, office and 24-h blood pressure readings and basal GFR. Kidney size was greater and serum cystatin C was higher in patients than in controls. Increased proteinuria and arterial hypertension were found in 24.3% and 18.9% of the patients, respectively. Nocturnal hypertension was more common than that during the daytime. After OPL, GFR significantly increased, more in controls than in patients. Among the patients, the RFR was the highest in the CKD3 group.

Conclusion – OPL induced an increase in GFR above its basal value. This response was higher in healthy children than in those with SFK. The positive relationship between RFR and CKD stage and the highest RFR in CKD3 patients suggests well preserved renal functional reserve in patients with moderate renal failure. ABPM is necessary for BP evaluation in children with SFK.