Purpose. We assessed the value of renal duplex Doppler sonography in d
iagnosing obstruction in patients with acute renal colic. Methods. We
compared the results of renal duplex Doppler sonography with those of
intravenous urography (IVU) in 65 patients presenting with symptoms of
renal colic. The Doppler spectral waveforms were used to calculate th
e resistance index (RI). The difference between the mean Rls (Delta RI
) in the 2 kidneys was calculated for each patient. The sensitivity, s
pecificity, and accuracy of Delta RI for the diagnosis of obstruction
were calculated with several discriminatory thresholds. Results. All p
atients had an obstruction on IVU. When a high Delta RI threshold for
obstruction (Delta RI greater than or equal to 0.1) was applied, the s
ensitivity and specificity of duplex Doppler sonography were 10% and 8
0%, respectively. When the Delta RI threshold was decreased, the sensi
tivity increased but the specificity decreased, and both remained quit
e low. Twelve patients had a lower mean RI in the obstructed kidney th
an in the normal contralateral kidney. Among 14 patients without pyelo
caliceal dilatation, the sensitivity of duplex Doppler sonography was
70% with a Delta RI threshold of 0.03. Conclusions. Duplex Doppler son
ography is not sensitive enough to diagnose obstruction in patients wi
th acute renal colic. (C) 1998 John Wiley & Sons, Inc.