Objective: To determine the diagnostic utility of intrarenal arterial Doppler study in ureteric obstruction. To compare intrarenal arterial doppler in patients with obstructed and non obstructed kidneys.

Materials & Methods: Study included prospective inclusion of 63 patients presenting within 24 hrs of the onset of symptoms of unilateral acute renal colic. The case group included kidney with the obstruction side and the opposite side healthy kidney considered as the control. All patients underwent USG and Doppler scan using 2-5 MHz convex probe and will be assessed for the presence or absence of pelvicalyceal system dilatation on the gray-scale images. Minimum three Doppler spectra will be obtained from interlobar arteries along the border of the medullary pyramids, and their mean RI calculated. RI of 0.70 remains the upper limit of average intrarenal resistance. CT scan will be done if ultrasonography is equivocal. If the site of obstruction is up to or proximal to L3 vertebral level, it is considered as proximal obstruction and distal if it is beyond L3 vertebral level.

Results: Resistivity Index (RI) in segmental renal arteries of all the 63 patients was significantly higher in the obstructed kidney than in unobstructed kidney (0.7 vs 0.56; p<0.001) with a sensitivity of 87.3% and specificity of 90%.

Conclusions: Doppler ultrasound is a useful diagnostic tool in the diagnosis of acute ureteric obstruction, thus preventing unnecessary CT and minimizing radiation exposure to patients. RI value > 0.7 have a very high level of specificity and sensitivity for acute ureteric obstruction.

Keywords: Intrarenal arterial Doppler; Acute renal colic; Acute ureteric obstruction; RI value.

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Dr Supriya Pakalapati

Post Graduate, Dept of Radiology, Maharajah’s Institute of Medical Sciences