Captopril renography and the relevance of abnormal but bilateral identical curves in the diagnosis of renal artery stenosis

Impact of renin-angiotensin system polymorphisms on renal haemodynamic responsiveness to acute angiotensin-converting enzyme inhibition in type 2 diabetes mellitus

Introduction.The aim of this study was to document the impact of renin-angiotensin system (RAS) polymorphisms on renal haemodynamics and renal hormones in type 2 diabetes mellitus. Materials and methods. Fifty-nine adult patients were studied. Renal haemodynamics were evaluated using 99mTc-MAG3 clearance (MAG3 Cle) using Bubeck's method and captopril renogram. RAS hormones and angiotensin-converting enzyme (ACE) levels were measured before and after captopril.ACE, angiotensin II type 1 receptor and angiotensinogen gene polymorphisms were analysed. Results. Post-captopril MAG3Cle values were significantly lower in patients with microalbuminuria compared to nonproteinuric patients. Statistically significant negative correlation was found between clearance percentage change values and HbA1c levels (r: —0.42, p=0.009). MAG3Cle was relatively lower following captopril administration in DD patients, while a relative increment was observed in I allele carriers (p=0.02).TheAC-CC group had significantly higher mean post-captopril clearance value compared to the AA genotype (480.9±56.1 ml/min/1.73 m2 vs. 428.4±74.8 ml/min/1.73 m2, p=0.022). Conclusions. Our data indicate that the heterogeneity of patients' response to ACE inhibition is, at least partly, genetically determined, and the genetic polymorphisms in RAS might predict the acute responsiveness to ACE inhibitors.

Interobserver Reproducibility in the Interpretation of Captopril Renograms From Patients Suspected of Having Renovascular Hypertension

This work was undertaken to identify, in hypertensive patients suspected of having renovascular hypertension (RVH), scintigraphic images and curves whose interpretation could be difficult. The baseline and postcaptopril Tc-99m MAG 3 images and curves from 10 patients clinically suspected of having RVH were retrospectively selected to have a wide sample of images and curves. The data and a multiple-choice questionnaire were presented as a PowerPoint file, which was sent electronically to Belgian nuclear medicine physicians; they had to answer if the images and curves were or were not suggestive of the diagnosis of RVH or if it was impossible to answer. There was near-complete interobserver agreement for normal baseline and postcaptopril data, for unilateral postcaptopril delayed transit and/or impaired uptake. Agreement was not as good for bilateral and symmetrical changes, for mild changes, or in cases of impaired function. This study shows that the analysis by the Internet of interobserver agreement is an easy and rapid method allowing one to identify difficult to interpret pre- and postcaptopril renographic data.

Calcium channel blockers: a potential cause of false-positive captopril renography

PURPOSE

The purpose of the study was to review the causes of false-positive and false-negative captopril Tc-99m MAG3 renograms performed to evaluate renovascular hypertension at the authors' institution.

METHODS

From May 2000 to January 2002, 77 patients were referred for evaluation of possible renovascular hypertension with captopril Tc-99m MAG3 renography. If the findings of the captopril study were abnormal, a baseline study was performed 3 days later. The captopril studies were retrospectively reviewed and correlated with available renal arteriography, magnetic resonance angiography, and duplex Doppler sonography studies and clinical follow-up. Renal artery stenosis greater than 70% on an arteriogram and 60% on Doppler studies or magnetic resonance angiography was considered positive for renovascular hypertension.

RESULTS

There were five false-negative and four false-positive studies. The five patients who had the false-negative captopril studies underwent arteriography, which showed renal artery stenosis, and a stent was placed in two of them. The four false-positive captopril studies were proved by negative arteriograms in three and negative magnetic resonance angiography in one. Three patients with false-positive studies had bilateral renal function impairment after captopril and were taking calcium channel blockers at the time of the captopril study. One patient had a left nephrectomy and was also taking calcium channel blockers.

CONCLUSION

Chronic intake of calcium channels blockers is a potential cause of bilateral symmetric false-positive captopril renography.