SONOGRAPHIC MEASUREMENT OF RENAL ENLARGEMENT IN CHILDREN WITH ACUTE PYELONEPHRITIS AND TIME NEEDED FOR RESOLUTION - IMPLICATIONS FOR RENAL GROWTH ASSESSMENT

OBJECTIVE. Failure of a kidney to grow satisfactorily in childhood is evidence of renal disease, Because kidneys may enlarge during an episo de of acute pyelonephritis, concomitant renal length measurements cann ot be used as baselines for growth assessment, This study was designed to determine the degree of renal enlargement in children with acute p yelonephritis and the time the enlargement takes to resolve after trea tment is started to find the optimum time for obtaining baseline measu rements. SUBJECTS AND METHODS. In a cohort study, 180 children younger than 5 years old with their first proven acute urinary tract infectio n, with or without pyelonephritis, had renal scintigraphy and sonograp hy within 15 days of starting treatment, The presence of cortical defe cts on scintigrams indicated pyelonephritis, The lengths of kidneys wi th and without scintigraphic defects (i.e., with and without pyeloneph ritis) were compared, adjusting for age and sex, and the length of kid neys with defects was related to time elapsed between the start of tre atment and sonography. RESULTS. Ninety-nine kidneys (28%) in 77 childr en (43%) had scintigraphic defects, Kidneys with defects were an avera ge of 3.2 mm longer than kidneys without defects, Length and time inte rval between treatment and sonography in kidneys with defects correlat ed negatively, with mean length approaching that of kidneys without de fects by 10-11 days. CONCLUSION. Kidneys with acute pyelonephritis ini tially increase in length but return to normal on average by the 11th day of treatment. If poor renal growth is used as an indication of ren al disease, sonography should be delayed or repeated at least 2 weeks after the start of treatment to determine the length of the uninflamed kidney.