Long-term followup of renal morphology and function in children with recurrent pyelonephritis.

Renal morphology and function were evaluated in 161 children with recurrent pyelonephritis with or without vesicoureteral reflux and with or without scarred or small kidneys. The patients were followed for 1 to 21 years. Renal function was determined by glomerular filtration rate and effective renal plasma flow by clearances of inulin and paraaminohippuric acid. Of 105 children with normal kidneys originally small or scarred kidneys developed in 37, of whom 22 had grade III or greater vesicoureteral reflux, while small kidneys developed in 13 of 29 children with renal scarring originally. Of the 37 children with normal kidneys originally renal parenchymal scarring developed in 14 after the age of 4 to 5 years. Glomerular filtration rate was already < -2 standard deviations of that of controls in 51% of the patients at the first and in 53% at the last investigation of renal function. Of these patients with a glomerular filtration rate of < -2 standard deviations 69% had small or parenchymally reduced kidneys most of whom had the first pyelonephritis episode before age 3 years. Patients with small kidneys had a lower glomerular filtration rate than those with normal sized kidneys, whether scarred or not. The low glomerular filtration rate and its subsequent further reduction were related to kidney size and not to the presence or degree of vesicoureteral reflux. However, in individual patients the rate of functional deterioration could not be predicted from the radiological findings. Patients with bilateral small kidneys seemed to show the greatest decrease in glomerular filtration rate during followup as did those with grade III or greater reflux undergoing surgery bilaterally and those patients also had a lower glomerular filtration rate at the last investigation compared to patients not undergoing surgery. In conclusion, renal functional damage seems to occur early in the course of the disease and seems to be related to kidney size but there is a further slow progression with reduction in renal function which occurs, although this is difficult to predict from the radiological changes in individual patients. Therefore, patients with recurrent pyelonephritis should be followed regularly by glomerular filtration rate determination using an accurate method.