Captopril-induced changes in MAG3 clearance in patients with renal arterial stenosis and the effect of renal angioplasty.
(17/217)
Angiotensin-converting enzyme inhibition by captopril decreases renal (131)I-o-iodohippurate sodium or iothalamate extraction in patients with renal artery stenosis (RAS). This study investigated the effect of captopril on another renal radiopharmaceutical, (99m)Tc-mercaptoacetyltriglycine (MAG3), in particular its plasma clearance. METHODS: Three groups of patients were studied. Group I contained 22 patients with hypertension but a low likelihood of RAS according to negative captopril renography results, confirmed by angiography in 5. Group II contained 22 hypertensive patients with RAS documented by angiography and positive captopril and plasma renin response. Group III contained 10 patients after successful percutaneous transluminal renal angioplasty (PTRA) with negative captopril renography results. The 60-min, single-sample technique was used for measurement of the plasma clearance of MAG3 during baseline and captopril renography. RESULTS: In 18 of 22 group I patients, clearance increased (P < 0.01) during captopril renography compared with baseline conditions, whereas in 18 of 22 group II patients, clearance decreased (P< 0.01). In group III patients, clearance was not significantly altered. The clearance decrease in group II did not correlate with the blood pressure decrease or plasma renin activity increase during captopril renography. CONCLUSION: Renal function assessed by MAG3 plasma clearance decreases in hypertensive patients with RAS but increases in patients without RAS. MAG3 clearance measurements during baseline and captopril renography can thus serve as additional diagnostic information when investigating patients with hypertension for the possibility of an RAS. (+info)
Evaluation of duplex ultrasound and captopril renography for detection of renovascular hypertension.
(18/217)
BACKGROUND: Renovascular hypertension is the most common form of curable secondary hypertension and, if untreated, may lead to end-stage kidney disease. Given that renal function and hypertension may improve after renal angioplasty, it is pertinent to identify patients with renal artery stenosis. The aim of the present study was to evaluate both duplex ultrasound and captopril renography for detection of renal artery stenosis among hypertensive patients. METHODS: To avoid selection bias, all patients referred to our center for evaluation of renovascular hypertension were asked to participate in the study. Patients were examined by intra-renal duplex ultrasound (N = 121), measuring pulsatility index and acceleration of the blood flow during early systole. In 98 patients, 99mTc-DTPA captopril renography was performed in conjunction with duplex ultrasound. Renal angiography was performed in all patients regardless of the results of the noninvasive tests. RESULTS: The prevalence of renal artery stenosis was 19%. In the 98 patients examined by both duplex ultrasound and captopril renography, sensitivity and positive predictive values for detection of a renal artery stenosis of 50% degree or more were 84 and 76%, respectively, for duplex ultrasound, whereas captopril renography was associated with a sensitivity and positive predictive value of 68% for both (P = NS). Specificity and negative predictive values were 94 and 96%, respectively, for duplex ultrasound, whereas the corresponding values for captopril renography were 92% for both (P = NS). Specificity and negative predictive values were 94 and 96%, respectively, for duplex ultrasound, whereas the corresponding values for captopril renography were 92% for both (P = NS). CONCLUSIONS: Both duplex ultrasound and captopril renography are associated with high specificity and negative predictive values for detection of renal artery stenosis. Sensitivity and positive predictive values are at least as good for duplex ultrasound compared with captopril renography. Given that duplex ultrasound is easier to perform and more cost effective, we propose that it should be the method of first choice when screening for renal artery stenosis in a hypertensive population. (+info)
Aspirin renography and captopril renography in the diagnosis of renal artery stenosis.
(19/217)
Preliminary data suggest that aspirin renography is more sensitive than captopril renography for indicating renal artery stenosis (RAS). Considering that aspirin, compared with captopril, reduces renal blood flow and, thus, tubular tracer delivery in poststenotic kidneys, aspirin renography is expected to be more useful, particularly if tubular tracers are used. METHODS: We prospectively compared aspirin renography (20 mg/kg orally) and captopril renography (25 mg orally) with 99mTc-mercaptoacetyltriglycine in 75 consecutive patients suspected of having RAS. RESULTS: RAS, diagnosed as stenosis of more than 50% on angiography, was found unilaterally in 34 patients and bilaterally in 17 patients. RAS was absent in 24 patients. The sensitivities for unilateral RAS or bilateral RAS (i.e., stenosis that was at least unilateral) were, respectively, 88% and 88% for captopril renography and 82% and 94% for aspirin renography (not significant). The overall specificity was 75% for captopril renography and 83% for aspirin renography (not significant). Tracer uptake ratios, time to peak activity, and percentage of 20-min tracer retention were also not significantly different for captopril and aspirin renography. Subgroup analysis of modest (50-75%) and severe (> or =75%) RAS, or of plasma creatinine greater than 120 micromol/L, also showed no difference between captopril and aspirin renography. CONCLUSION: We conclude that for identification of RAS, the usefulness of aspirin renography equals, but does not surpass, that of captopril renography. (+info)
A simple method for measuring severely reduced glomerular filtration rate.
(20/217)
OBJECTIVE: The purpose of this study was to develop a simpler method to measure severely reduced glomerular filtration rate (GFR) for patients with a GFR below 30 mL/min. METHOD: The GFR was measured in 24 patients using both the 51Cr EDTA slope-intercept method (the conventional method) and 99mTc-DTPA with our proposed simpler GFRn method. RESULTS: The correlation coefficient was 0.92 between the 2 methods, with a slope of 0.97 and an intercept of 2 mL/min. CONCLUSION: Our simplified method for measuring GFR is accurate for most patients with severely reduced GFR. Errors are acceptably small in patients with severely reduced GFR when edema or dehydration are present. If extrarenal (liver) clearance is significant, however, a urine sampling method is required for an accurate GFR measurement. (+info)
Urinary extravasation and leakage after renal transplantation: a case report.
(21/217)
OBJECTIVE: This case report illustrates urinary extravasation and leakage after renal transplantation, as documented by nuclear medicine renal imaging. The extravasation and leakage were identified only on images acquired after the patient voided. The surgical wound site dressings were found to contain radioactive contamination as well. (+info)
Functional imaging of intrarenal blood flow using scintillation camera and computer.
(22/217)
In order to obtain spatial distribution of an index for regional blood flow at each element on a scintigraphic image of the kidney, we attempted the construction of the so-called functional image. After injecting a single bolus of 133Xe into a renal artery by means of a catheter, this objective was accomplished using digital computer processing for a sequence of scintillation camera recordings of the following washout process from the kidney. This is expressed in a form of matrix of disappearance rate constant. Calculation for the rate constant, the flow index of the functional image, was done using either the least squares (LS) method or height-over-area (H/A) method. Although the former method was considered to be theoretically suitable without undue participation of background activities, the latter was preferred because of stable results for image construction. On reviewing the functional image thus obtained from 22 patients representing a variety of renal diseases, the H/A gave specific information concerning regional distribution of the perfusion integrity mainly related to the cortical part of the kidney. This is often difficult to accomplish utilizing the conventional method of compartmental analysis of the xenon washout curve or selective renal angiography. (+info)
Parenchymal mean transit time analysis of 99mTc-DTPA captopril renography.
(23/217)
Proposed renal hemodynamic mechanisms of captopril suggest that quantitation of renographic retention parameters should help identify patients suspected of having renovascular disease. The parenchymal mean transit time (MTT) is theoretically superior to other measures of retention, but data supporting its superiority are few. METHODS: Two groups of subjects were studied with diethylenetriamine pentaacetic acid (DTPA) baseline and captopril renography, one (n = 43) with demographically defined essential hypertension (group I) and the other (n = 60) with a high prevalence of renovascular disease (group II). Abnormal parenchymal MTT values were derived from the statistical confidence limits of group I data and then applied to group II subjects for comparison with angiographic results. RESULTS: Depending on the sensitivity of the threshold chosen, specificity varied, but the overall accuracy of baseline parenchymal MTT for renovascular hypertension detection ranged from 54% to 58%. Change in parenchymal MTT (post-captopril - pre-captopril) accuracy was 55%-61% and was not significantly different. Neither method improved on previously reported quantitative or qualitative criteria. Group II subjects had significantly worse renal function than did group I subjects, and 23% had nondiagnostic renograms. CONCLUSION: Parenchymal MTT analysis of DTPA captopril renography is not more accurate and offers no advantages compared with qualitative renography or with more commonly used renographic measures in our subjects. This may relate to the high prevalence of renal dysfunction in our population. In subjects with renal dysfunction, the low sensitivity and the trend toward low specificity of parenchymal MTT do not support its routine use for the evaluation of renovascular disease among patients suspected of having renovascular hypertension. (+info)
Comprehensive evaluation of renal function in the transplanted kidney.
(24/217)
By means of a comprehensive renal function test based on the analysis of orthoidohippurate kinetics carried out 223 times in 86 renal transplatn patients, we have been able to separate clearly five clinical entities: normally functioning transplanted kidneys, acute tubular necrosis, cell-mediated rejection, humoral (chromin) rejection, and postrenal obstruction. Accurate prediction of the fate of the rejecting kidney can be made while still subclinical as much as a week before manifestations by other techniques are evident. Data on 22 donors studied 44 times are also presented. The comprehensive test consists of measurements of effective renal plasma flow (ERPF), sequential scintigraphy, calculations of excretory index (EI) (percent dose actually found in bladder and voided urine as a fraction of the percent dose expected at a given time after injection at the patient's specific ERPF), and residual urine volume. Formulas and regression equations for the calculation of ERPF, EI, residual urine, etc., are presented. (+info)