Accuracy of Duplex Sonography After Renal Stenting

Accuracy of Duplex Sonography after Renal Stenting
Reports of duplex sonography criteria for recurrent renal arterial (RA) stenosis after endoluminal stenting have suggested that criteria for native arteries may over estimate recurrent disease.
Purpose:
To determine the accuracy of renal duplex sonography (RDS) to define the presence or absence of significant (i.e. greater than or equal to 60% diameter reducing) renal artery stenosis (RAS) after percutaneous angioplasty and endoluminal stenting (PTRAS) for RA atherosclerosis.
Methods:
Demographic, duplex, and angiographic data were reviewed and compared. RDS was obtained after overnight fast. Peak systolic velocities (PSV) were obtained from multiple sites along the main renal artery from both anterior and flank approaches. Comparable images from digital subtraction angiography were independently examined for stenosis. Percent diameter RAS was determined from the site of maximal stenosis compared with the normal renal artery distal to the RA stent. Sensitivity and specificity were estimated and 95% confidence intervals (CI) were computed after adjusting for within patient "clustering" of observations applying native renal artery RDS criteria using angiography as the gold standard. Receiver operating characteristic (ROC) curves were used to estimate the optimal RDS values (ie the maximum sum of sensitivity and specificity) for recurrent stenosis,
Results:
From 10/2003 to 6/2009, 49 patients had angiographic imaging after PTRAS. 30 patients (18 women, 12 men; mean age: 71±9 years) provided technically adequate paired angiographic and RDS assessment after PTRAS for 66 RAs. Paired analysis was performed for 23 RAs after primary PTRAS and 43 RAs after secondary treatment. The prevalence of significant RAS was 35 % (23 of 66 RAs). RAs with greater than 60% diameter stenosis had higher PSV compared to those without (2.48±1.15m/s vs 1.44± 0.58 m/s. ; P<0.001). Compared to angiography, RA-PSV > 1.8 m/s with distal renal artery turbulence demonstrated a sensitivity of 73% [95% CI (54%, 91%)], specificity of 80% [95% CI (67%, 93%)], and an overall accuracy of 77% [95% CI (67%, 88%)] with a positive predictive value of 64% [95% CI (46%,82%)]. RA-PSV > 2.0 m/s demonstrated a sensitivity of 68% [95% CI (51%, 85%)], specificity of 80% [95% CI (67%, 93%)], an accuracy of 76% [95% CI (66%, 85%)], and a positive predictive value of 63% [95% CI (45%, 80%)].Optimal RDS value estimated by ROC curve resulted in RA-PSV of 2.5 m/s which was associated with a sensitivity of 59% [95% CI (36%, 82%)], specificity of 95% [95% CI (89%, 100%)], an accuracy of 83% [95% CI (74%, 92%)], and a positive predictive value of 87% [95% CI (68%, 100%)].
Conclusion:
Renal duplex sonography is useful to detect significant stenosis after PTRAS. RDS criteria for significant native renal artery stenosis compare favorably with optimal RDS criteria estimated by ROC curves.