Resistive indices in the evaluation of infants with obstructive and nonobstructive pyelocaliectasis.

Abstract

onography plays an important role in the identification of the dilated renal collecting system in the infant. Gray scale sonography accurately identifies abnormal dilation of the renal collecting system; however, its value is limited in differentiating obstructive from reflux uropathy.Studies of the pathophysiology of obstruction have shown that obstruction causes an increase in vascular resistance and a subsequent decrease in renal blood flow. 1-3 Platt and coworkers suggested that the decrease in renal blood flow secondary to obstruction could be measured by the RI ([peak systolic velocity -end diastolic velocity]/peak systolic velocity) and provide an accurate, noninvasive method for diagnosing obstructive uropathy. 4 Platt and coworkers noted that when the DRI between the two kidneys is also taken into consideration in the evaluation of unilateral pyelocaliectasis, the accuracy of Doppler sonography in detecting obstructive hydronephrosis is increased. 4 Conclusions regarding the accuracy of the RI using a threshold value of 0.7 and a DRI of 0.08 or greater in the identification of obstructive uropathy in adults have been mixed. [4][5][6][7] Renal RIs are normally higher in children compared to adults up to the age of 10 years, with the highest values in infants under the age of 1 year. [8][9][10][11][12] Received October 17, 1998, from Loyola University Medical Center Diagnosing obstructive uropathy by renal resistive indices calculated from duplex Doppler sonographic waveforms has been supported as well as challenged in the radiology literature relating to adults. Despite reports of normally higher resistive indices in children as compared to adults, two studies have documented high sensitivity and specificity of renal Doppler sonography in the diagnosis of obstructive uropathy in children, using the same discriminatory criterion of a resistive index of 0.7 or greater as used in adults. We evaluated 43 infants with significant or bilateral pyelocaliectasis secondary to both obstructive and unobstructive uropathy and found no significant difference in the mean resistive indices or the mean difference in resistive indices of two kidneys in one patient. We conclude that Doppler sonography in infants has no value in differentiating obstructive from nonobstructive pyelocaliectasis.

The Accuracy of Doppler Ultrasonography in the Followup of Pyeloplasty for Congenital Pelviureteric Junction Obstruction

“…11 In unilateral hydronephrosis, an RIR of > 1.1 indicates obstruction. In the present study, RIR showed better sensitivity than RRI in detecting obstruction.…”