Acute childhood pyelonephritis: predictive value of positive sonographic findings in regard to later parenchymal scarring

RATIONALE AND OBJECTIVES: The authors evaluated the importance of positive sonographic findings in acute childhood pyelonephritis. MATERIALS AND METHODS: A total of 290 children (91 boys, 199 girls, aged 4 days to 15 years median, 394 days]) with clinically suspected acute pyelonephritis underwent initial renal gray-scale ultrasound (US) and dimercaptosuccinate scintigraphic examination within 3 days of onset. A total of 173 patients underwent color or energy US examination. One hundred fifteen children with normal scintigraphic or pathologic findings (other than acute pyelonephritis) were excluded from further study; 170 patients with abnormal scintigraphic findings underwent follow-up scintigraphic scanning 60-90 days later. RESULTS: When pathologic structures other than acute pyelonephritis were not considered, the diagnostic value of gray-scale US was poor, with a sensitivity of 45.5%, a specificity of 86.6%, a positive predictive value of 88.8%, and a negative predictive value of only 40.6%. In regard to future renal scarring, gray-scale US had a positive predictive value of 67.7%, a negative predictive value of 40%, and a likelihood ratio of 1.16. Abnormal Doppler findings helped predict future scarring with a positive predictive value of 85.7%, a negative predictive value of 37.2%, a very low sensitivity of 26.9%, a high specificity of 90.6%, and a likelihood ratio of 2.87. CONCLUSION: Positive US Doppler findings in children with clinically suspected acute pyelonephritis indicate the need for immediate treatment. A positive initial gray-scale US examination does not predict future renal scarring, but a positive Doppler examination indicates a high probability of scarring. Negative gray-scale or Doppler US does not exclude a diagnosis of acute pyelonephritis and it cannot predict an absence of future scarring.