Hypotensive response to captopril: a potential pitfall of scintigraphic assessment for renal artery stenosis.
A characteristic pattern seen on captopril renography is described that is due to systemic hypotensive response. Most patients with these findings on captopril renography do not receive renal artery angiograms in our clinic because it is usually recognized. However, this pattern has received little attention in the medical literature and may be misinterpreted as being due to physiologically significant renal artery hypertension. METHODS: Over the last 3 y, renal artery angiograms were performed on three patients with systemic hypotensive response pattern on captopril renography. This allowed a unique opportunity to correlate the results of the captopril renogram with the renal artery angiograms in this patient population. Captopril renography was performed with a glomerular filtration agent, diethylenetriamine pentaacetic acid (DTPA), and a tubular agent, o-iodohipurate (OIH). RESULTS: Renal artery angiograms showed no evidence of renal artery stenosis in three patients with systemic hypotensive response pattern on captopril renography. Systemic hypotension on captopril renograms results in preserved uptake of both DTPA and OIH and hyperconcentration in the cortex and collecting system. CONCLUSION: The systemic hypotensive response pattern seen on captopril renography is a distinctive pattern that does not represent physiologically significant renal artery stenosis. (+info)
Value of captopril renal scintigraphy in hypertensive patients with renal failure.
The aims of this study were to show the value of captopril renal scintigraphy for detecting a renovascular cause in hypertensive patients with renal failure and to assess the ability to predict the beneficial effect of revascularization on renal function. METHODS: Thirty-eight patients with renal failure (mean glomerular filtration rate = 35 mL/min) underwent renal scintigraphy after injection of 99mTc-mercaptoacetyltriglycine. Baseline scintigraphy was performed, and the test was repeated 24 h later after oral administration of 50 mg captopril given 60 min before the test. RESULTS: In 5 of 6 patients with a renovascular cause for renal failure, and 2 of 3 patients with a probable arterial pathology, scintigraphy had a high probability. The result was indeterminate in the other 2 patients. In 5 of 11 patients with negative arteriography and 14 of 18 patients with probable absence of renovascular pathology, we found a low probability of functional renal artery stenosis. Six revascularization procedures were performed and were predictive of a beneficial effect in 5 patients. Time of peak activity was an effective predictor in each case. CONCLUSION: In hypertensive patients with renal failure, captopril renal scintigraphy can detect hemodynamic dysfunction downstream from a renal artery stenosis and can predict the beneficial effect of revascularization in some cases. (+info)
Prospective validation of single plasma sample 99mTc-ethylenedicysteine clearance in adults.
99mTc-L,L-ethylene, L, dicysteine (EC) clearance shows strong correlation with orthoiodohippurate clearance, and it is possible to estimate effective renal plasma flow from 99mTc-EC clearance. In routine clinical studies, it is practical to use the one or two plasma sample method instead of multiple plasma samples for clearance determination. A single-sample technique was developed for 99mTc-EC, and a regression formula was generated. A prospective study tested the validity of this regression formula. METHODS: The study population was composed of 26 patients with a wide range of renal function. Multiple plasma sample 99mTc-EC clearances were calculated from all patients using the open two-compartment model. Single plasma sample clearances were also determined from the 54-min plasma sample using the regression formula published previously. RESULTS: The multiple-sample plasma clearance of 99mTc-EC ranged from 46 to 668 mL/min with a mean of 300.76 +/- 150.73 mL/min. The clearances obtained from the 54-min plasma sample ranged from 49 to 699 mL/min, with a mean of 297.39 +/- 152.23 mL/min. There was an excellent correlation between the clearances obtained by the two techniques (r = 0.99, slope = 0.9911). The standard error of estimation was found to be 25.9 mL/min. CONCLUSION: This study suggests that 99mTc-EC clearance can be estimated from 54-min plasma samples with an acceptable error of estimation for most routine clinical studies. (+info)
Evaluation of renal function from 99mTc-MAG3 renography without blood sampling.
To develop a camera-based method for evaluating renal function with 99mTc-mercaptoacetyltriglycine (MAG3), we examined the relationship between various renogram parameters and 99mTc-MAG3 clearance. METHODS: Twenty-one patients underwent renal scintigraphy with 99mTc-MAG3. Eighty 3-s frames were obtained after the bolus injection of 250 MBq tracer, followed by the collection of 52 30-s frames. Regions of interest were drawn for the kidneys, perirenal background areas and subrenal background areas, and background-subtracted renograms were generated. Renal accumulation at 0.5-1.5, 0.5-2, 1-2, 1-2.5 and 1.5-2.5 min after tracer arrival in the kidney was calculated as area under the background-subtracted renogram, and percent renal uptake was obtained after correction for soft-tissue attenuation and injected dose. The slope of the renogram was determined for the same segments used in calculating area under the renogram, and slope index was computed as slope corrected for attenuation and injected dose. Percent renal uptakes and slope indices were correlated by linear regression analysis with 99mTc-MAG3 clearance measured using a single blood sampling method. RESULTS: Among the values of percent renal uptake, the value obtained at 1.5-2.5 min using the perirenal background correlated best with 99mTc-MAG3 clearance. The slope index at 0.5-1.5 or 0.5-2 min using the subrenal background provided better accuracy than percent renal uptake for predicting clearance. There were no substantial differences in the relative function of the right kidney between the methods using percent renal uptake and slope index. CONCLUSION: 99mTc-MAG3 clearance can be assessed with acceptable accuracy by a camera-based method. The method based on the slope of the renogram may replace the one based on the area under the renogram in evaluating renal function from 99mTc-MAG3 renograms. (+info)
Quantitative SPECT of 99mTc-DMSA uptake in kidneys of infants with unilateral ureteropelvic junction obstruction: assessment of structural and functional abnormalities.
We evaluated individual renal function using quantitative SPECT of dimercaptosuccinic acid (DMSA) uptake by the kidneys (QDMSA) in infants with unilateral ureteropelvic junction (UPJ) obstruction and compared our findings with infants without obstruction. METHODS: QDMSA was performed on 13 infants (mean age of 2.8 +/- 2.8 mo) with unilateral UPJ obstruction and on 15 age-matched controls without obstruction. RESULTS: Control kidneys (n = 30) had a volume of 43.5 +/- 8.8 mL, a percentage injected dose (%ID)/mL 0.62 +/- 0.12 and uptake of 26.1% +/- 3.9%. Kidneys with UPJ obstruction (n = 13) had a volume of 61.2 +/- 19.3 mL, a %ID/mL of 0.42 +/- 0.11 and uptake of 25.4% +/- 8.2%. Contralateral kidneys (n = 13) had a volume of 44.0 +/- 11.9 mL, a %ID/mL of 0.57 +/- 0.16 and uptake of 24.2% +/- 4.6%. The uptake in obstructed kidneys was similar to that observed in contralateral and control kidneys (t = -0.77, P = 0.45; t = -0.37, P = 0.71; respectively). UPJ kidneys had a statistically significant increased volume and decreased %ID/mL, compared with contralateral kidneys (t = 3.35, P < 0.006 and t = 3.75, P < 0.003, respectively) and control kidneys (t = -4.2, P < 0.001 and t = 4.7, P < 0.001, respectively). There was no significant difference between contralateral kidneys and control kidneys regarding volume (t = -0.16, P = 0.87), %ID/mL (t = 0.98, P = 0.33) and uptake (t = -1.41, P = 0.16). Of 13 infants, 11 (85%) showed large kidneys with thinning of the renal cortex. In 1 infant, there was no difference between the obstructed and contralateral kidneys regarding volume, %ID/mL and uptake, and 1 infant showed significant decreased uptake in the UPJ kidney compared with the contralateral kidney. CONCLUSION: Although the overall renal function of the obstructed kidneys remained unchanged, there was a statistically significant decrease in the %ID/mL of renal tissue in UPJ kidneys, which may represent renal dysfunction. Increased functional volume with a thin cortex may represent a compensatory mechanism of the obstructed kidney. Such changes may contribute to the understanding of pathophysiologic mechanisms and may be an early sign of obstruction in infants with hydronephrosis. Further longitudinal studies with an extended number of infants and serial measurements of kidney volumes and %ID/mL are warranted to assess the significance of QDMSA in the management of infants with asymptomatic unilateral renal pelvic dilatation. (+info)
Relative 99mTc-MAG3 renal uptake: reproducibility and accuracy.
The aim of this study was to estimate the reproducibility and accuracy of 99mTc-mercaptoacetyltriglycine (MAG3) relative percentage uptake. METHODS: Reproducibility was evaluated on healthy volunteers who were submitted twice to a 99mTc-MAG3 renographic study, which used different uptake algorithms, different background corrections and different time intervals. Accuracy was evaluated in a group of patients with symmetrical or asymmetrical relative renal function, who underwent both 99mTc-dimercaptosuccinic acid (DMSA) and 99mTc-MAG3 studies, using the DMSA relative percentage uptake as a reference. RESULTS AND CONCLUSION: The methods that combined the best reproducibility and accuracy for estimating 99mTc-MAG3 left-to-right uptake ratio were the integral method, with subrenal or perirenal background correction, and the Patlak-Rutland plot. The use of the integral method without background correction introduced a systematic bias, whereas the slope method resulted in high variability. Therefore these methods cannot be recommended. (+info)
Autotransplantation and stent implantation for bilateral renal artery fibromuscular dysplasia.
A 36-yr-old male was found to have renovascular hypertension due to an occluded right renal artery and 70% stenosis in the left renal artery, caused by fibromuscular dysplasia. The right kidney was supplied by collateral blood flow, and secreted more renin than the left kidney. Two differential therapeutic approaches were taken: autotransplantation for the right kidney and percutaneous transluminal renal angioplasty followed by stent implantation for the left. The renovascular hypertension was treated with these therapies, preserving renal function in this patient. (+info)
A comparison of deconvolution and the Patlak-Rutland plot in renography analysis.
Deconvolution and the Patlak-Rutland plot are two of the most commonly used methods for analyzing dynamic radionuclide renography. Both methods allow estimation of absolute and relative renal uptake of radiopharmaceutical and of its rate of transit through the kidney. METHODS: A theoretical comparison of uptake assessment by both techniques is made and a mathematical derivation of the relationship between mean transit time (MTT) and renal outflow efficiency (ROE) is presented. The validity of these theoretical findings was tested in a series of 120 renograms obtained using 99mTc-mercaptoacetyltriglycine (MAG3). RESULTS: The estimates of renal uptake obtained are theoretically equivalent. The renogram measurements confirmed this, because there was no significant systematic difference in relative counts obtained by the two methods. Absolute counts were significantly higher for the deconvolution measurements, but only by 2.0%. The SDs of the differences between the two techniques, expressed as a percentage of the mean, were 1.7% and 5.4% for relative and absolute counts, respectively. There was an inverse monotonic relationship between MTT and ROE. ROE evaluated at a particular time was shown to depend on absolute renal function. Measured values of MTT and ROE were consistent with the theoretical prediction. CONCLUSION: The two approaches to renogram analysis provide consistent parameters for both uptake and transit evaluation. (+info)