Objective: The aim of our study was to assess the role of Doppler ultrasonography (DU) by resistive index (RI) and the difference of the RI (DeltaRI) in patients with acute unilateral renal obstruction.
Patients and methods: We studied 36 consecutive patients (12 female, 24 male; mean age 45.6 +/- 8.4 years) with suspected renal colic by intravenous pyelography (IVP) and DU with determination of the RI and the Delta RI. A RI of >= 0.70 and a DeltaRI of >= 0.06 were considered suggestive of obstruction. IVP was considered as the "gold standard".
Results: In the studied population, RI was 0.664 +/- 0.060 in the affected kidney site of symptoms and 0.614 +/- 0.025 in the contralateral one, with an overall Delta RI of 0.049 +/- 0.062. At IVP, 14 patients resulted within normal range (Group A; 39%), 6 patients showed lithiasis without obstruction (Group B; 17%), 8 patients showed delayed excretion of the contrast medium (Group C; 22%), and 8 patients showed a functional exclusion of the kidney (Group D; 22%). One-way analysis of variance showed the IVP group significantly related to Delta RI with the highest values in Groups C (DeltaRI of 0.093 +/- 0.051; p<0.001) and D (DeltaRI of 0.116 +/-0.030; p<0.001) in comparison with Group A (DeltaRI of 0.001 +/-0.038) and Group B (DeltaRI of 0.015 +/-0.024). No differences were detected between Groups C and D (p=0.223) and between Groups A and B (p-0.472). DeltaRI measurement with DU permitted to predict the renal obstruction with a sensitivity of 93.8%, a specificity of 95.0% and an accuracy of 94.4%.
Conclusions: Intrarenal Doppler ultrasonography represents a sensitive and highly specific test that can significantly contribute to the diagnosis of obstruction in patients with acute renal colic. It should be used as the first line imaging method in suspected acute renal colic, as well as for patients with renal insufficiency, pregnant women or for patients with adverse reactions to contrast media