Renal dysfunction in recurrent urinary tract infections in childhood.

One hundred children aged 1.5-19.5 years, with recurrent urinary tract infections, at least one of which was febrile (pyelonephritis, PN), were investigated by means of inulin and para-aminohippurate (PAH) clearance tests for the evaluation of glomerular filtration rate (GFR), effective renal plasma flow, and concentrating and diluting capacities. Renal function data were collated with the clinical history and radiological findings. GFR and PAH clearance were found to be reduced compared with controls. Patients whose first PN was diagnosed before the age of 3--particularly those with a history of three or more PN infections--showed the lowest values for GFR and PAH clearance. Furthermore, parenchymally reduced kidneys were found most frequently in this group of patients. Concentrating capacity was decreased in some patients, but a low concentrating capacity did not reveal patients with reduced GFRs. Diluting capacity evaluated as minimal urine osmolality was normal, but was reduced when evaluated as free water clearance in some patients with reduced values for GFR.