Effect of the NSAID diclofenac on 99mTc-MAG3 and 99mTc-DTPA renography.

UNLABELLED: Renal function and disease are commonly evaluated by radionuclide studies. The choice of radiopharmaceutical agent for various studies is crucial for proper interpretation. (99m)Tc-mercaptoacetyltriglycine ((99m)Tc-MAG3) is excreted almost exclusively by the renal tubules, whereas (99m)Tc-diethylenetriamine pentaacetic acid ((99m)Tc-DTPA) is predominantly excreted by glomerular filtration. The present study compared the effect of the nonsteroidal antiinflammatory drug (NSAID) diclofenac, which is the most commonly used drug to relieve kidney pain, on the kinetic behavior of administered (99m)Tc-MAG3 and (99m)Tc-DTPA in experimental animals. METHODS: Two groups of 12 New Zealand White rabbits ((99m)Tc-MAG3 and (99m)Tc-DTPA) were used for the renography. Each rabbit served as its own control. The animals were given 60 mL of saline intravenously 30 min before each renographic study. A baseline study (control) was done by injecting 48 MBq (1.3 mCi) of (99m)Tc-MAG3, and renography was performed. Two days later, a single intravenous dose of diclofenac (2 mg/kg) (treated animals) was given, and after 20 min, (99m)Tc-MAG3 renography was performed. This procedure was repeated for the (99m)Tc-DTPA group after administration of 96 MBq (2.6 mCi) of the tracer. Dynamic images (as 2-s frames for the first minute and 30-s frames for the next 30 min on a 64 × 64 matrix) were acquired using a γ-camera equipped with a low-energy high-resolution collimator interfaced with a computer. Regions of interest were drawn over the whole kidneys. Time-activity curves were generated from the region of interest. Time to peak activity (T(max)), time from peak to 50% activity (T(1/2)), and the uptake slope of each kidney were calculated from the renograms for control and treated rabbits. RESULTS: Administration of diclofenac shifted the experimental renogram curves to the right, compared with the control curves, indicating that there was a delayed renal uptake of the 2 tracers and clearance of the radioactivity. The calculated average values of T(max) for control and treated rabbits using (99m)Tc-MAG3 were 1.8 ± 0.5 and 6.35 ± 0.4 min, respectively, whereas those of (99m)Tc-DTPA were 3.4 ± 0.4 and 18.2 ± 2 min, respectively. The T1/2 for control and treated rabbits for (99m)Tc-MAG3 were 3.2 ± 0.07 and 6.6 ± 0.07 min, respectively, whereas those for (99m)Tc-DTPA were 10.1 ± 1 and 35 ± 4 min, respectively. The differences were statistically significant (P < 0.05). CONCLUSION: This study showed that diclofenac delayed both T(max) and T1/2. The NSAID-induced kinetic changes were considerably greater for (99m)Tc-DTPA than for (99m)Tc-MAG3. On the basis of these findings, it is suggested that (99m)Tc-MAG3 be used to perform renography for studies involving the use of NSAID administration to decrease any change that may occur due to the type of tracer and not to the condition of the kidney.

Optimal scintigraphic evaluation of a hydronephrotic horseshoe kidney.

A 25-y-old man with horseshoe kidney was referred for diuretic-augmented renal scintigraphy. Single-detector dynamic posterior imaging was performed and revealed asymmetric retention of radiotracer in the left collecting system. Renal scintigraphy was repeated with a modified protocol. Dynamic imaging was performed this time using dual-detector acquisition of both anterior and posterior data. Thereafter, pregravity and subsequently postgravity static images were obtained in both anterior and posterior projections. This second study showed near-complete emptying of the left collecting system. This case illustrates the utility of using simultaneous anterior and posterior imaging and geometric mean calculations for functional analysis and also highlights the value of physiologic maneuvers to augment the traditional diuretic challenge.

Congenital solitary kidney with renovascular hypertension diagnosed by means of captopril-enhanced renography and magnetic resonance angiography.

A 24 year-old woman had a congenital solitary kidney with renovascular hypertension due to fibromuscular dysplasia. She had been treated as having essential hypertension until she developed preeclampsia and HELLP (hemolysis, elevated liver enzymes, and low platelet count) syndrome at 28 weeks of gestation. Plasma renin activity and captopril test results did not indicate any abnormalities. However, renography revealed captopril-induced deterioration. Magnetic resonance angiography was also useful to detect renal artery stenosis. These findings were confirmed by renal angiography. After successful percutaneous transluminal renal angioplasty, her blood pressure and the pattern of captopril renography normalized.

Reliability of captopril renography in patients under chronic therapy with angiotensin II (AT1) receptor antagonists.

UNLABELLED: Captopril renography is a reliable, widely used test for the functional diagnosis of renovascular hypertension. Well-recognized drawbacks of the procedure include reduced accuracy in patients with bilateral disease or renal impairment as well as the possible interference from concurrent antihypertensive medication (diuretics, beta-blockers, angiotensin-converting enzyme inhibitors, calcium channel blockers). Currently, no data exist regarding the reliability of captopril renography in patients with renovascular hypertension evaluated while they are under chronic treatment with angiotensin II (AT1) receptor antagonists (Sartans). Moreover, the renographic response of the kidney with renal artery stenosis to prolonged therapy with angiotensin II receptor antagonists has not yet been evaluated. METHODS: We investigated the diagnostic effectiveness of (99m)Tc-mercaptoacetyltriglycine captopril renography performed after acute addition of 25 mg of captopril to the daily dose of AT1 receptor antagonist in 13 patients with unilateral renal artery stenosis and subsequent evidence of renovascular hypertension, based on short-term (3 mo) blood pressure outcome after revascularization. The renographic evaluation was first performed after ingestion of the daily therapy of angiotensin II receptor antagonist alone (Sartan renography) and was repeated within 7 d after the acute addition of 25 mg of captopril to chronic treatment with angiotensin II receptor antagonist (captopril-Sartan renography). A cohort of 13 patients with a final diagnosis of essential hypertension was chosen as the control subjects. RESULTS: Twelve of 13 patients were correctly detected by captopril-Sartan renography (92% sensitivity), and 3 subjects were also identified without the addition of captopril. Adding captopril to Sartan therapy resulted in a slight reduction in mean arterial blood pressure, while significant side effects were never observed. No false-positive results were found in the 13 patients with essential hypertension. CONCLUSION: We conclude that performing captopril renography with the acute addition of 25 mg of captopril to the chronic monotherapy with Sartans has the same diagnostic effectiveness as performing captopril renography alone. Interrupting the vasoactive action of angiotensin II alone on the efferent glomerular arteries, which can also be selectively achieved by chronic administration of angiotensin II receptor antagonists, does not fully explain the effectiveness of captopril renography in detecting renovascular hypertensive patients.

Interventions in renal scintirenography.

Nuclear nephrourology continues to develop and expand on traditional provocative physiological maneuvers, such as diuretic and captopril renography. In addition, newer interventions are conceived, such as aspirin renography, which test new and fascinating aspects of renal functional reserve. Since the last review of this topic in 1991, nephrourologic nuclear medicine has made considerable progress in diverse ways. Captopril and diuresis renography have made strides in establishing greater consensus of interpretation and procedure. Commonplace aspirin, the ubiquitous wonder drug, has revealed an unexpected role in renography by way of its inhibition of prostaglandin E2. Finally, further investigations of exercise renography in essential hypertension have deepened the plausibility of a renal role in the etiology of perhaps 50% of affected individuals.

Angiotensin-converting enzyme inhibition-induced changes in hippurate renography and renal function in renovascular hypertension.

UNLABELLED: We studied the mechanism of angiotensin-converting enzyme (ACE) inhibition-induced changes in hippurate renography of the poststenotic kidney. METHODS: Ten male mongrel dogs, six with unilateral and four with bilateral renal artery stenosis, were equipped with renal artery blood flow probes and catheters in the aorta, atrium and both renal veins. RESULTS: Enalaprilat (10 mg intravenously) in conscious dogs with renal artery stenoses produced changes in all stenotic (n = 11) but not in nonstenotic kidney 123I-hippurate renograms (n = 6). Renographic changes correlated significantly with initiation of intrarenal 131I-hippurate retention, a decrease in mean arterial pressure (MAP), renal extraction of 131I-hippurate and 125I-iothalamate (r = 0.68, r = 0.62, r = 0.84, r = 0.83, respectively) but not with renal blood flow changes (r = 0.34). Furthermore, renal uptake of 131I-hippurate and 125I-iothalamate decreased in stenotic kidneys with a grade II renogram (-52 +/- 11% and -79 +/- 6%, respectively). Iodine-125-hippurate autoradiograms of stenotic kidneys during ACE inhibition showed tracer retention mainly in the proximal tubular cells. Results during osmotic diuresis supported our findings. CONCLUSION: Angiotensin-converting enzyme inhibition-induced hippurate retention curves of poststenotic kidneys appear to result from a sequence of events. A decrease in MAP combined with efferent vasodilation leads to a decrease in intraglomerular capillary pressure. This decrease in pressure causes a decrease in glomerular filtration rate and proximal tubular urine flow. This decrease in turn hampers tubular hippurate transit and transport across the luminal membrane, leading to intrarenal hippurate retention and, in more severe cases, decreased renal hippurate uptake.

[Isotopic renogram after captopril administration: clinical experience in the assessment of the hypertensive patient]. / Renograma isotópico después de la administración de captopril: experiencia clínica en la valoración del paciente hipertenso.

BACKGROUND: Isotopic renogram allows renal function to be estimated in both kidneys independently. The glomerular filtrate in ischemic kidneys is largely dependent on the tone of the efferent glomerular arteriolae and therefore on the concentration of circulating angiotensin II. METHODS: In 42 patients with severe high blood pressure in whom renal angiographic study was carried out for suspicion of vasculo-renal hypertension, an isotopic renogram using 99m Tc-DTPA as a tracer was performed in basal conditions and following the administration of 50 mg of oral captopril. RESULTS: In 21 patients both the angiographic examination and the post-captopril renogram were normal. In 16 patients in whom uni or bilateral stenosis higher than 50% of the lumen of renal artery was observed on angiographic examination, the post-captopril renogram showed changes. In 5 patients the angiography was normal while the renogram showed evaluable changes. No false negatives were observed in the post-captopril renogram, however the basal renogram was not demonstrative in 6 patients with stenosis of the renal artery. Sensitivity of the test was thus 100% and specificity 80%. The positive predictive value was 76% and the negative predictive value 100%. CONCLUSIONS: The post-captopril renogram may be a useful test in the functional study of renal behaviour in patients with vasculo-renal hypertension.