American Journal of Roentgenology, Vol 165, 405-408, Copyright © 1995 by American Roentgen Ray Society
Sonographic measurement of renal enlargement in children with acute pyelonephritis and time needed for resolution: implications for renal growth assessment
FE Pickworth, JB Carlin, MR Ditchfield, MP de Campo, JF de Campo, DJ Cook, T Nolan, HR Powell, R Sloane and K Grimwood
Department of Radiology, Royal Children's Hospital, Melbourne, Victoria, Australia.
OBJECTIVE. Failure of a kidney to grow satisfactorily in childhood is
evidence of renal disease. Because kidneys may enlarge during an episode of
acute pyelonephritis, concomitant renal length measurements cannot be used
as baselines for growth assessment. This study was designed to determine
the degree of renal enlargement in children with acute pyelonephritis and
the time the enlargement takes to resolve after treatment is started to
find the optimum time for obtaining baseline measurements. SUBJECTS AND
METHODS. In a cohort study, 180 children younger than 5 years old with
their first proven acute urinary tract infection, with or without
pyelonephritis, had renal scintigraphy and sonography within 15 days of
starting treatment. The presence of cortical defects on scintigrams
indicated pyelonephritis. The lengths of kidneys with and without
scintigraphic defects (i.e., with and without pyelonephritis) were
compared, adjusting for age and sex, and the length of kidneys with defects
was related to time elapsed between the start of treatment and sonography.
RESULTS. Ninety-nine kidneys (28%) in 77 children (43%) had scintigraphic
defects. Kidneys with defects were an average of 3.2 mm longer than kidneys
without defects. Length and time interval between treatment and sonography
in kidneys with defects correlated negatively, with mean length approaching
that of kidneys without defects by 10-11 days. CONCLUSION. Kidneys with
acute pyelonephritis initially 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 renal disease, sonography should be delayed or repeated at
least 2 weeks after the start of treatment to determine the length of the
uninflamed kidney.