Resistive index in renal colic: the effect of nonsteroidal anti-inflammatory drugs.

Abstract

To investigate the effect of nonsteroidal anti-inflammatory drugs (NSAIDs) on the findings of Doppler ultrasonography (DU) in patients with acute unilateral renal obstruction. The study included 60 patients (120 kidneys) with unilateral loin pain suspected to be of renal origin. All patients were evaluated using renal ultrasonography (US) and intravenous urography (IVU) during the attack of loin pain and before giving any medication. Then the patients were given 75 mg diclofenac sodium and DU studies were repeated at 6 and 12 h. In 10 patients with acute renal colic, DU was possible 12-24 h after the relief of ureteric obstruction. The mean resistive index (RI) and DeltaRI at baseline were compared with the mean values 6 and 12 h after giving diclofenac. The RI and DeltaRI were considered positive at values >/=0.70 and >/=0.06, respectively. The sensitivity, specificity and overall accuracy of RI and DeltaRI values before and after giving diclofenac were calculated using IVU as the reference standard. IVU showed that both kidneys were normal in 20 patients that 40 had unilateral obstruction. At baseline, the mean (sd) RI was 0.72 (0.06) in the 40 obstructed kidneys, significantly higher than the RI of 0.60 (0.06) for the 60 normal kidneys (P<0. 001). Six hours after giving diclofenac, the mean RI of normal kidneys remained stable and that of the obstructed kidneys decreased significantly to 0.67 (0.06) (P<0.001) and was almost stable at 12 h. Nevertheless, the mean RI of the obstructed kidneys remained significantly higher than that of the normal kidneys at 6 and 12 h after diclofenac. The mean DeltaRI decreased significantly from 0.11 (0.04) at baseline to 0.06 (0.04) at 6 h after diclofenac (P<0.001) and remained almost stable at 12 h. In the 10 patients undergoing DU after the relief of obstruction, the mean RI returned to normal. At baseline, RI was sensitive in 70% and specific in 98%, while DeltaRI was sensitive in 88% and specific in all cases. Six hours after diclofenac, the specificity of RI and DeltaRI remained stable while the sensitivity decreased significantly to 50% and 68%, respectively. NSAIDs significantly decrease the RI of acutely obstructed kidneys, causing a significant reduction in the sensitivity of DU values identifying acute renal obstruction. To evaluate acute loin pain, DU should be carried out while the patient is in pain and before giving NSAIDs.