Radermacher J, Vitzthum A, Stoess B, Olbricht CJ et al
Resistive index and improvement of renal function after
correction of renal artery stenosis
Am Soc Nephrol
J Am Soc Nephrol (abstract)
(Sep) 7:1554 1996
Bilateral renal artery stenosis (RAS) is believed to be the cause of
ESRD in approx. 10% of patients older than 50 years. In some cases,
renal failure is reversible by angioplasty or surgery; however,
prediction of renal functional improvement after renal
revascularization is difficult. Procedures used to predict renal
viability, including renal size and function and renal biopsy, are
insensitive or invasive.
In this prospective study, the diagnostic value of color
duplex sonography (CDS) was compared to angiography for detection of
RAS in 73 patients with renal insufficiency (Cr > 130 umol/l or
1.47 mg/dl). Average resistance index (RI: 1 - (minimum diastolic
flow/maximum systolic flow) was determined in three segmental renal
arteries.
CDS was 95% sensitive and 87% specific for the detection of RAS, with
a positive predictive value of 96% and a negative predictive value of
87%. 37 patients with RAS > 50% (diameter reduction) underwent
successful (RAS after intervention < 30%) angioplasty or surgery.
25/28 patients with a RI < 0.8 (n=28) experienced a fall in serum
creatinine with revascularization. No patient with RI values > 0.8
(n=9) showed benefit. Renal segmental artery resistive indices may
prove to be a reliable and safe way to determine whether
revascularization will be beneficial in patients with RAS and impaired
renal function.
Comment: There is much current interest in non-invasive
diagnosis of renovascular disease. Although CDS in experienced hands
is a reliable test for the detection of RAS, it has not been clear
whether it can predict the physiologic rather than just the anatomic
significance of a lesion. These findings support the contention that
CDS can indeed predict clinical outcome of revascularization.
An article on diagnosis of renovascular disease by intra-and
extrarenal Doppler scanning was recently published
(Kidney Int
1996; 50: 1288-92). In this study, severity of stenoses was
inversely
correlated with RI (i.e., the greater the stenosis, the lower the RI).
Side-to-side difference of RI (delta RI) was also greatest in patients
with high-grade unilateral RAS. However, delta RI did not correlate
with reduction of BP after revascularization.
In short, more information is needed before the role of CDS in the
detection and management of renovascular disease can be determined.
(David J. Leehey, M.D., Loyola University at Chicago)
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Am Soc Nephrol
H: Special problems :
Renovascular hypertension