There is controversy regarding the role of radiological imaging for
urinary tract infection (UTI). The "gold standard" has been the intravenous pyelogram (IVP). Yet, the IVP has a very limited value with only about 25% of children with
pyelonephritis demonstrating abnormalities. Ultrasound (US) has recently been advocated as a replacement for the poorly sensitive and poorly specific IVP. However, comparative studies between US and IVP indicate only an equivalent sensitivity and specificity. Cortical scintigraphy with Technetium-99m
glucoheptonate (99mTc GH) or
99mTc dimercaptosuccinic acid (
99mTc DMSA) has also been advocated as a means of differentiating parenchymal (
pyelonephritis) from nonparenchymal (lower UTI) involvement in UTI. The clinical presentation may be misleading especially in the infant and child in whom an elevated temperature,
flank pain, shaking
chills, or an elevated sedimentation rate are often lacking. The clinician attempts to localize the site of
infection for it has a direct bearing upon the
therapy. A collecting system
infection can often be eradicated with a single oral dose of an appropriate
antibiotic, whereas renal parenchymal involvement requires IV
therapy for an extended interval. Cortical scintigraphy can localize the site of
infection with a high degree of accuracy. Recent studies report a sensitivity of 86% and specificity of 81% of
pyelonephritis. This is in contrast to the IVP with a sensitivity of only 24% and US with a sensitivity of only 42%. The scintigraphic appearance of parenchymal
infection of the kidney is a spectrum of minimal to gross defects reflecting the degree of histologic involvement that spans from a mild
infection to frank
abscess. Cortical scintigraphy can be used to monitor the evolution of
scarring following
infection. Cortical scintigraphy with
99mTc DMSA or 99mTc GH is the method of choice for the initial evaluation of UTI. Not only does it have a very high sensitivity and specificity for differentiating parenchymal from collecting system disease, but it also provides an accurate quantitative measurement of function and in combination with radioiodinated
orthoiodohippurate renography and
Lasix (
furosemide; Abbott Laboratories, North Chicago) diuresis will also differentiate significant obstruction from stasis. The use of
radionuclide techniques opens new vistas for the investigation of UTI. Cortical scintigraphy should become the gold standard by which other technologies,
therapy, and theoretical considerations of
pyelonephritis are measured.