Nephrology Dialysis Transplantation, Vol 12, Issue 10 2081-2086, Copyright © 1997 by Oxford University Press
D Roccatello and G Picciotto
Purpose and design of study: Asymmetric-induced
changes of the renogram under angiotensin-converting enzyme inhibition
(ACE-I), i.e. lateralization, is probably the most distinctive finding for
the detection of haemodynamically significant renal artery stenosis (RAS)
in compensated kidney, since bilateral and symmetric patterns are
non-specific. In the Consensus statement of diagnostic criteria of
renovascular hypertension with captopril renography (Am J
Hypertens 1991; 4: 749-755S) ACE-I-induced asymmetry of
renograms for the left and right kidney was viewed as vitally
important. However, detection of change in split function is a
reliable parameter only when using a glomerular tracer, i.e.
99mTc-DTPA. No indication regarding a more widely
used tubular tracer such as
99mTc-mercaptoacetyltriglycine
(99mTc-MAG3) has been given. Methods and
results: the theoretical contralateral curve, called 'expected
renogram', was calculated frame by frame from renal curves obtained under
ACE-I and one of two baseline curves. The expected renogram was compared
with the recorded ipsilateral curve. More than ±2 SD difference
between expected and recorded renograms was assumed as suggestive of
monolateral or bilateral RAS. Twenty-nine patients with angiographically
proven RAS (bilateral in 12) and 20 patients without arteriographic
evidence of stenosis were evaluated by post-captopril/baseline
99mTc-MAG3 renography results obtained with the
expected renogram analysis were compared with those obtained by standard
criteria which included: improvement of peak time underbase-line
conditions, wash-out (75%) time, and monolateral or bilateral residual
cortical activity >10%, but asymmetrical, i.e. with >5%
change in split function. Compared to the standard evaluation, the use of
the expected renogram for the diagnosis of RAS improved the specificity
from 70 to 95% (P<0.03) without loss of sensitivity (79.3%).
Follow-up data after revascularization were available in 18
scintigraphically positive and six scintigraphically negative patients with
RAS. The sensitivity of the expected renogram method referring to
short-term (1 month) patient outcome following revascularization was 88.8%.
The beneficial effects on blood pressure response persisted in 77% of these
patients at 18 months. Notably, four of six scintigraphically negative
patients with RAS did not show any short-term benefit from
revascularization and the improvement in blood pressure values lasted for
18 months in only one case. Conclusions: The high
specificity of the expected renogram method reduces the number of
unnecessary invasive procedures. This is a critical point for a
low-prevalence disease such as renovascular hypertension.
Keywords: captopril-enhanced scintigraphy; expected
renogram, renal vascular stenosis; renovascular hypertension
ORIGINAL ARTICLES
Captopril-enhanced scintigraphy using the method of the expected renogram: improved detection of patients with renin-dependent hypertension due to functionally significant renal artery stenosis
Fisiopatologia Clinica Nefrologica, Divisone di Nefrologia e Dialisi, e Centro di Immunopatologia (CMID), USL 4, e Servizio di Medicina Nucleare, Ospedale San Giovanni Battista e della Citta di Torino, Italy; Corresponding author
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