Renal colic in pregnant women: Role of renal resistive index

Objectives. To investigate the value of the renal resistive index (RI) in the identification of acute renal obstruction in pregnant women. Methods. The study included 22 pregnant women with acute unilateral ureteral obstruction due to a stone disease (group A), 71 normotensive pregnant patients without loin pain (group B), and 20 nonpregnant women of child-bearing age with both kidneys normal (group C). All patients underwent Doppler ultrasound (DUS) with determination of the Ri and the difference between the RI of the corresponding and contralateral kidney (Delta RI). The RI and Delta RI was considered positive for obstruction with a value of 0.70 or greater and 0.04 or greater, respectively. Ureteral obstruction was confirmed by several clinical, radiologic, and endoscopic findings. The sensitivity, specificity, and overall accuracy of RI and Delta RI for the diagnosis of acute unilateral ureteral obstruction were calculated. Results. in group A, kidneys with ureteral obstruction (n = 22) had a mean RI of 0.69 +/- 0.03; the contralateral normal kidneys (n = 22) had a mean RI of 0.63 +/- 0.03, a significant difference (P < 0.0001). The mean RI of ail kidneys in group B (n = 142) and all kidneys in group C (n = 40) was 0.64 +/- 0.05 and 0.62 +/- 0.04, respectively; the difference was not statistically significant. A comparison between the mean RI of the normal kidneys of group A and ail the kidneys of groups B and C revealed no significant difference. The mean RI of the obstructed kidneys in group A was significantly higher than the mean RI of all the kidneys in groups 5 and C. Similarly, the mean Delta RI of group A was significantly higher than the mean Delta RI of groups B and C (0.06 +/- 0.01 versus 0.006 +/- 0.003 versus 0.006 +/- 0.004, respectively). The RI was sensitive in 45%, specific in 91%, and accurate in 87%. The corresponding values for Delta RI were 95%, 100%, and 99%. Conclusions. The Delta RI is a sensitive and specific test that can replace intravenous urography in the diagnosis of acute unilateral ureteral obstruction in pregnant women. (C) 2000, Elsevier Science Inc.