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)
Reproducibility of single-sample clearance of 99mTc-mercaptoacetyltriglycine and 131I-orthoiodohippurate.
Recent literature has questioned whether 99mTc-mercaptoacetyltriglycine (MAG3) clearance measurements are reproducible enough for routine clinical monitoring of renal function. For many years, we have routinely followed the renal function of patients with spinal cord injuries using a combination of radionuclide imaging and clearance measurement. METHODS: In this study, we retrospectively review 1626 effective renal plasma flow (ERPF) measurements in 197 patients with paraplegia or quadriplegia performed over a 21-y period, using 131I-orthoiodohippurate (OIH) through 1990 and MAG3 since 1991. MAG3 clearance was divided by 0.53 to convert it to ERPF. Reproducibility was measured as pooled SD from the single-patient linear regression lines of ERPF versus time. RESULTS AND CONCLUSION: There was no significant difference between MAG3 (SD = 46 mL/min, n = 907) and OIH (SD = 52 mL/min, n = 719). The data were therefore combined to obtain the SD for a single ERPF measurement, which was 49 mL/min. The corresponding coefficient of variation was 8.5% of the mean value of 581 mL/min. In our experience, this is adequate for monitoring the renal function of these patients. (+info)
Use of radionuclide imaging in the early diagnosis and treatment of renal allograft rejection.
Data are presented on the clinical application of radionuclide imaging to evaluate changes in cadaver transplant function in the immediate postoperative period. The method uses orthoiodohippuric acid (hippuran) administered IV, with scintillation imaging, and curve analysis by a digital computer. An initial study is always obtained 24 hours after transplantation. Serial studies are then obtained, as needed, to interpret the clinical course. Selected cases are presented which illustrate the use of this protocol in various clinical settings. In the oliguric patient serial studies have been of particular value. They have identified ATN so that over-enthusiastic treatment for rejection could be avoided. They have also identified acute rejection complicating ATN so that high dose steroid therapy could be administered appropriately. In the non-oliguric patient they have frequently contributed to the early diagnosis of acute rejection, and they have been useful in monitoring the effect and duration of treatment for severe rejection crisis. It is concluded that radionuclide imaging studies, when carefully applied and interpreted, are a valuable adjunct to the management of patients in this complex clinical setting. (+info)
Prediction of renal transplant survival from early postoperative radioisotope studies.
It has been routine at the University of Alabama Medical Center to obtain a radionuclide renal function study immediately after transplantation (usually within 3 d) that includes estimation of effective renal plasma flow (ERPF) from a single plasma sample in addition to imaging. We present here the correlation between baseline measurements and the 1-y graft survival. METHODS: Two cohort years were reviewed: 1988, when 131I-orthoiodohippurate (OIH) was used; and 1995, when 99mTc-mercaptoacetyltriglycine (MAG3) was used. ERPF was measured concurrently with gamma-camera imaging by previously published single-injection, single-sample methods (converting MAG3 clearance to ERPF by means of a correction factor). RESULTS: Graft survival during the first postoperative year improved significantly in the interval between cohort years, from 74% of 147 cadaver (CD) grafts in 1988 to 91% of 200 CD grafts in 1995 (log rank test, P < 0.05). In contrast, for living related donor (LRD) grafts there was no significant change, from 91% of 66 in 1988 to 91% of 83 in 1995. The baseline ERPF was a significant predictor of graft survival in both 1988 and 1995 (Wilcoxon test, P > 0.05). For LRD grafts the association was not significant in either year. Using MAG3 (1995), the peak time and the ratio of counting rate (R) at 20 min to that at 3 min (R20:3) were also significant predictors for CD graft survival. Using OIH (1988 cohort), the correlation with peak time did not reach significance, and the R20:3 measurement was not available. Although multivariate combinations (Cox proportional hazards model) did not have significantly more predictive value at the 95% confidence level than ERPF or R20:3 alone, some statisticians suggest a 75% confidence level for adding an additional covariate to a multivariate model. Use of this level led to a model including both ERPF and R20:3. CONCLUSION: Single-sample ERPF measured in the immediate post-transplant period, whether from OIH clearance or MAG3 clearance, was a statistical predictor of graft survival for CD transplants. For MAG3, the peak time and R20:3 were also significant predictors. These associations held only for CD transplants and not for LRD transplants. (+info)
Scintiphotography in diagnosis of urinary fistula after renal transplantation.
Scintiphotographic studies in six patients with ureteral fistula following renal transplantation are presented. Images were obtained using 99m-Tc-Sn-DTPA or 131-I-orthoiodohippurate. Urinary leakage was accurately detected in each case but the pattern of extravasation is highly variable. When carefully performed, radionuclide scintiphotography is a safe and effective method for detecting urinary leakage after renal transplantation. (+info)
How gender and age affect iodine-131-OIH and technetium-99m-MAG3 clearance.
OBJECTIVE: The relationship between age and effective renal plasma flow (ERPF) results, as measured in nuclear medicine, is well known. This paper explores the relationships among gender, age, and ERPF measurements. After reading this paper, the nuclear medicine technologist should be able to: (a) discuss the importance of establishing normal range values for ERPF that include age and gender variables; (b) state how age affects ERPF results; and (c) state how gender affects ERPF results. (+info)
Parenchymal mean transit time analysis of 99mTc-DTPA captopril renography.
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.
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)