ABSTRACTS PRESENTADOS AL 11th INTERNATIONAL SYMPOSIUM "RADIONUCLIDES IN NEPHRO-UROLOGY", REALIZADO EN MONTEREY, CALIFORNIA, 13-17 MAYO 2001.
13. ANALYSIS OF FALSE POSITIVE AND FALSE NEGATIVE CAPTOPRIL RENOGRAMS FOR DETECTION OF RENAL ARTERY STENOSIS.
Göran Granerus and Jan Ohlsson. Departments of Clinical Physiology University Hospital. Linköping and County Hospital Ryhov. Jönköping. Sweden.
The Swedish Captopril Renographic Project has since its beginning in 1997 to present collected 170 complete studies from ten different hospitals. All the tests have been performed according to a strictly standardized protocol. MAG3 was exclusively used as the indicator. 25 mg captopril was given orally and current anti-hypertensive medication was maintained (including ACE/AII-blockers). 108 patients were treated with ß-blockers, 54 with ACE-inhibitors, 10 with AII-inhibitors, 85 with diuretics and 13 with prostaglandin synthesis inhibitors. No patients were excluded due to renal insufficiency or other reasons.
There
were 64 high probability, 27 indeterminate and 79 low probability
captopril renograms. The test had a sensitivity of 72% and specificity
of 98% for the detection of a renal artery stenosis >50%. For renal
artery stenosis of 70-90%, the corresponding figures were 82% and
98%. Adding the 27 indeterminate cases increased sensitivity to 76%
and decreased specificity to 84%. Surprisingly, the sensitivity and
specificity was the same in patients maintaining current treatment
with ACE or AII-blockers, 71% and 95% compared to patients without
such drugs, 72% and 100%.
There was only one false positive test, probably due to low urine flow rate and hydronephrosis. On the other hand, there were 25 false negative tests, in most cases probably due to either the presence of a moderate degree of stenosis (15 cases) or a branch stenosis (9 cases). Bilateral stenosis (8 cases) or occlusion with established collateral circulation was of the same order in the false negative and true positive groups. An analysis of the renograms indicated that side differences in parenchymal transit time (PTT) or pelvic appearance time (PAT) were the most reliable parameters for the diagnosis of significant stenosis, except for branch stenosis where the 20minute ratio seemed more useful. Bilateral stenosis could rarely be diagnosed with this test.
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