Technetium-99m DTPA renal flow studies in Goldblatt hypertension

Computer-assisted dynamic renal studies were performed on a group of 14 mongrel dogs before and after the induction of unilateral renal artery stenosis. Ninety-second technetium-99m diethylenetriaminepentaacetic acid ( [99mTc]DTPA), 15-min [99mTc]DTPA, and 30-min iodine-131 orthoiodohippurate ( [131I]hippuran) time-activity curves were analyzed and correlated with reduction of renal blood flow as measured by electromagnetic flow probe and PAH clearance techniques. Parameters of the 90-sec [99mTc]DTPA curves found to be significantly different for the same kidney before and after stenosis were: upslope, curve width at 75% maximum, maximum activity value, and differential (stenotic/contralateral) maximum activity ratio. For blood flow reductions greater than 33%, the [99mTc]DTPA studies were judged diagnostic of unilateral renal artery stenosis in all cases, whereas the [131I]hippuran time-activity curves were indicative of stenosis in only six of ten studies. Thus, in this model we find the computer-assisted 90-sec [99mTc]DTPA renal flow study to be superior to conventional [131I]hippuran renography in the diagnosis of moderate-to-severe unilateral renal artery stenosis.     

346例上尿路结石患者99Tcm-DTPA肾动态显像结果分析

目的 探讨99Tcm-二亚乙基三胺五乙酸(99Tcm-DTPA)肾动态显像在上尿路结石患者肾功能评价中的临床价值.方法 回顾性分析了346例上尿路结石患者的核素肾动态显像、静脉肾盂造影(IVP)和血尿素氮(BUN)、血清肌酐(SCr)值,并依据总肾肾小球滤过率(GFR)将BUN和SCr结果分成4组进行分析.结果 ①346例肾动态显像患者,总肾GFR与BUN、SCr水平呈明显负相关(r=-0.458,P=0.000;r=-0.542,P=0.000).②4组之间比较,BUN和SCr均存在统计学差异(F=49.23,P=0.000;F=80.66,P=0.000);经最小显著差别法分析,组1与组2之间比较,BUN和SCr均无统计学差异(P=0.119和P=0.088);而其余各组之间比较,BUN和SCr均存在统计学差异(P均＜0.05).③IVP不显影的43只患肾中,经99Tcm-DTPA肾动态显像提示有18只(41.9%)有残余肾功能(GFR≥10 ml/min),平均GFR为(21.89±12.81)ml/min.结论 99Tcm-DTPA肾动态显像能早期评价肾功能,特别是对IVP不显影的患肾功能的评价具有重要临床价值.     

A comparison of the renal handling of 99Tcm-DTPA and 99Tcm-MAG3 in hypertensive patients using an uptake technique.

The renal uptake and outflow of 99Tcm-DTPA and 99Tcm-MAG3 were compared by analysing renal studies performed in two different departments, but with analysis techniques and computer programs using algorithms that were almost identical. Comparison was performed by a retrospective review of results from patients who were referred for renal investigations because of hypertension but who had apparently normal kidneys. The analysis of tracer outflow rates in the form of whole-kidney transit times and renal cortical transit times showed no significant difference between the two tracers. The fractional uptake rate of tracer for each patient (both kidneys) indicated that MAG3 was extracted from the blood 3.3 times faster than DTPA in patients aged 20-69 years, with a lower ratio above the age of 70. When used to measure relative renal function, there was no overall difference between the two tracers. The fractional uptake rates were also converted to flow rates, producing values of 95.8 +/- 28.0 ml.min(-1).1.73 m-2 for DTPA and 320 +/- 75 ml.min(-1).1.73 m-2 for MAG3, in hypertensive patients aged 20-40 years. These values showed a good correlation with other published GFR and MAG3 clearance rates (obtained using blood sampling methods) in normal patients of similar ages.     

Quantification of renal perfusion abnormalities using an intravascular contrast agent (part 2): results in animals and humans with renal artery stenosis.

The interrelation between the morphologic degree of renal artery stenosis and changes in parenchymal perfusion is assessed using an intravascular contrast agent. In seven adult foxhounds, different degrees of renal artery stenosis were created with an inflatable clamp implanted around the renal artery. Dynamic susceptibility-weighted gradient-echo imaging was used to measure signal-time curves in the renal artery and the renal parenchyma during administration of 1.5 mg/kg BW of an intravascular ultrasmall particle iron oxide (USPIO) contrast agent. From the dynamic series, regional renal blood volume (rRBV), regional renal blood flow (rRBF), and mean transit time (MTT) were calculated. The morphologic degree of stenosis was measured in the steady state using a high-resolution 3D contrast-enhanced (CE) MR angiography (MRA) sequence (voxel size = 0.7 x 0.7 x 1 mm(3)). Five patients with renoparenchymal damage due to long-standing renal artery stenosis were evaluated. In the animal stenosis model, cortical perfusion remained unchanged for degrees of renal artery stenosis up to 80%. With degrees of stenoses > 80%, cortical perfusion dropped to 151 +/- 54 ml/100 g of tissue per minute as compared to a baseline of 513 +/- 76 ml/100 g/min. In the patients, a substantial difference in the cortical perfusion of more than 200 +/- 40 ml/100 g/min between the normal and the ischemic kidneys was found. The results show that quantitative renal perfusion measurements in combination with 3D-CE-MRA allow the functional significance of a renal artery stenosis to be determined in a single MR exam. Differentiation between renovascular and renoparenchymal disease thus becomes feasible.     

单侧肾功能严重受损者99Tcm-二亚乙基三胺五乙酸肾动态显像测定对侧肾肾小球滤过率的临床意义

目的 探讨99Tcm-二亚乙基三胺五乙酸(99Tcm-DTPA)肾动态显像在单侧肾脏功能严重受损患者中的应用.方法 应用99Tcm-DTPA肾动态显像,测定82例单侧肾脏功能严重受损患者的对侧肾脏肾小球滤过率(GFR),并将其与血清肌酐(SCr)值进行相关性分析,同时对对侧肾脏功能受损的病因进行分析.结果 对侧肾GFR与SCr值呈负相关(r=-0.643,P<0.001);在一侧肾脏功能严重受损患者中,肾结石和泌尿系移行细胞肿瘤患者的对侧肾脏易受损害.结论 单侧肾脏功能严重受损患者有必要通过99Tcm-DTPA肾动态显像密切观察对侧肾脏情况,以便及时治疗,防止对侧肾功能的衰竭.     

A comprehensive analysis of renal DTPA studies. III. Renal artery stenosis

Renal DTPA studies were analysed to produce numerical data of renal function (blood flow, glomerular filtration, and excretion), and this was used as an adjunct to the routine imaging information in a study of renal artery stenosis (RAS). The results show an overall accuracy of 81%, with a sensitivity of 96% and a specificity of 61%. In patients with RAS, beta-blocking drugs reduced the difference between the two kidneys. ACE-inhibiting drugs appeared to preserve renal blood flow but also to cause a deterioration in the glomerular filtration rate of kidneys with RAS. An explanation is proposed, in which renal capillary pressure is more important for function than is renal blood flow.     

99Tcm-p-aminohippuric acid as a new renal agent

99Tcm-p-aminohippuric acid (99Tcm-PAH) is a new renal radiopharmaceutical prepared from a lyophilized kit by the addition of sodium pertechnetate (Na99TcmO4). Each vial contains PAH, the calcium trisodium salt of diethylenetriamine pentaacetic acid (CaNa3DTPA) and stannous chloride (SnCl2.2H2O) in an inert atmosphere. It is a stable radiopharmaceutical with high radiochemical purity (> 95%). Its protein binding is very similar to that of 131I-OIH, but it is hydrophilic in character. Animal studies using 99Tcm-PAH have indicated that it provides renal images of satisfactory quality with no external background. Despite its almost identical radiochemical purity and HPLC analysis results to 99Tcm-DTPA, 99Tcm-PAH is rapidly secreted by the kidneys in a manner consistent with tubular secretion, as confirmed by rat probenecid studies, whereas 99Tcm-DTPA is excreted by glomerular filtration. The pharmacokinetic parameters of 99Tcm-PAH (t1/2(alpha)) = 2.5 min, t1/2(beta) = 41.7 min, Cl = 5.22 ml.min-1, Kel = 5.1 x 10(-4) min-1) differ from those of 99Tcm-DTPA. Evaluation of 99Tcm-PAH in two human volunteers confirmed its good renal characteristics: rapid disappearance from the vascular system, high uptake in kidneys followed by its very fast elimination, and low residual activity 20 min after its intravenous administration.     

Absolute renal blood flow quantification by dynamic MRI and Gd-DTPA

The aim of this study was to demonstrate the feasibility of the absolute renal blood flow quantification using MRI and injection of contrast media. Using a T1-weighted fast gradient sequence following an intravenous bolus injection of Gd-DTPA, dynamic images of the kidney were obtained in patients with well-functioning native kidneys (n = 7) or transplant (n = 9), with significant renal artery stenosis (n = 4) and with renal failure (n = 7). After signal intensity calibration, the absolute renal perfusion was equal to the wash-in slope of the renal transit curve divided by the contrast medium concentration at the peak of the bolus in the aorta. The cortical blood flow was 2.54 ± 1.16 ml/min per gram in well-functioning kidneys decreasing to 1.09 ± 0.75 ml/min per gram in case of renal artery stenosis (p = 0.04) and to 0.51 ± 0.34 ml/min per gram in case of renal failure (p < 0.001). These measurements were in agreement with previous results obtained by other methods. A standard MRI imaging sequence and a simple model can provide realistic quantitative data on renal perfusion. This work justifies further studies to compare this model with a gold standard for renal blood flow measurements. Received: 9 September 1999; Revised: 31 January 2000; Accepted: 16 March 2000     

Evaluation of dynamic gadolinium-enhanced breath-hold MR angiography in the diagnosis of renal artery stenosis.

OBJECTIVE: The aim of our study was to evaluate a three-dimensional gadolinium-enhanced breath-hold MR angiography sequence using standard MR gradients in detecting renal artery stenosis. SUBJECTS AND METHODS: Forty-two patients referred for angiography for suspected renal artery stenosis underwent both conventional digital subtraction angiography (DSA) and MR angiography. MR angiography was performed on a 1.5-T scanner with standard gradients. A fast multiplanar spoiled gradient-echo sequence was used with the following parameters: TR/TE, 10.3/1.9; flip angle, 45 degrees; field of view, 36 x 32 cm; matrix size, 256 x 128; one excitation; volume thickness, 70 mm; and partitions, 28. Gadolinium was administered IV as a dynamic bolus of 30-40 ml. Conventional and MR angiographic images were interpreted by two radiologists in consensus. RESULTS: DSA revealed 87 renal arteries, of which 79 were in 35 patients with native kidneys and eight arteries were in seven patients with transplanted kidneys. Gadolinium-enhanced MR angiography showed 85 (98%) of 87 renal arteries. Seventeen patients had 20 significant (>50% stenosis) renal artery stenoses and five patients had five occluded renal arteries revealed by DSA. MR angiography revealed 85 renal arteries (98%), 20 stenoses (100%), and five occlusions (100%). Gadolinium-enhanced MR angiography led to one false-positive interpretation for renal artery stenosis and no false-negative interpretations. Thus, the sensitivity, specificity, and accuracy of MR angiography for renal artery stenosis were 100%, 98%, and 99%, respectively. CONCLUSION: The MR angiography pulse sequence we used was an effective and reliable technique for the diagnosis of renal artery stenosis. The sequence can be performed on widely available MR equipment that does not require fast gradient hardware.     

Assessment of split renal function before and after angioplasty or bypass grafting in the patients with renovascular hypertension

Two different methods to assess the change of split renal function following angioplasty or bypass grafting were studied in a total of 12 patients with renovascular hypertension. The studies were performed before and within seven days after the therapeutic intervention. Split effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) after injections of I-131 hippuran and Tc-99m DTPA were measured using kidney counting corrected for depth and dose, described by Schlegel and Gates. In six of 10 patients with unilateral renal artery stenosis and in two patients with bilateral renal artery stenoses (two of 4 affected kidneys), the split renal function was improved after the therapeutic intervention, in accordance with the drop in blood pressure and the reduction of plasma renin activity. The improvement in ERPF and GFR was more likely in the patients without severely reduced renal function. In such patients, the improvement in ERPF was more pronounced than that in GFR. And in two patients with functional improvement, the Captopril-induced reduction of split GFR in the affected kidney was disappeared after the intervention. Moreover, in the long-term follow-up of three patients with functional improvement, one patient showed the deterioration of split renal function suggesting the relapse of renal artery stenosis. These results suggest that the combined studies of split ERPF and GFR determinations can be useful to evaluate the therapeutic effect as well as the presence or absence of functional improvement after the intervention.     

The angiographic incidence of renal artery stenosis in the arteriosclerotic population

The incidence of renal artery stenosis was evaluated with intra-arterial digital subtraction angiography in 100 consecutive patients referred for peripheral arteriopathy. Fifty-seven patients were normotensive, 43 were hypertensive. In the normotensive group, renal artery stenosis was found in ten patients (17.5%). In the hypertensive group renal artery stenosis was found in twelve patients (28%). It is concluded that the incidence of renal artery stenosis is high in an arteriosclerotic population both in normotensive and hypertensive patients.     

99Tcm-DTPA法肾小球滤过率在肾癌患者术前肾功能评价中的临床意义

目的 探讨99Tcm-DTPA法肾小球滤过率(GFR)在肾细胞癌(RCC)患者术前肾功能评价中的临床意义.方法　 99例RCC患者,其中行根治性肾切除术(RN)者89例,行保留肾手术(NSS)者10例.术前行99Tcm-二亚乙基三胺五乙酸(99Tcm-DTPA)显像测定GFR.比较RCC患者和对照组(正常供肾者)的GF...     

Reversible diminished renal 99mTc-DMSA uptake during converting-enzyme inhibition in a patient with renal artery stenosis

A patient is described who had accelerated hypertension and unilateral renal artery stenosis, and who developed further deterioration in renal function during treatment with captopril, an angiotension-I (AI) converting-enzyme inhibitor. 99mTc-DMSA uptake was greatly diminished in the stenotic kidney, although renal blood flow and handling of 131I-hippurate was preserved. Uptake of 99mTc-DMSA in the affected kidney returned after substitution of captopril by the vasodilator minoxidil, while a comparable degree of blood pressure control was maintained. Thus, caution must be taken when interpreting results of 99mTc-DMSA scintigraphy in patients with proven or suspected renal artery stenosis treated with an AI converting-enzyme inhibiting drug. Moreover, our finding points to the importance of glomerular filtration in the renal handling of 99mTc-DMSA.     

Renal disease: value of functional magnetic resonance imaging with flow and perfusion measurements

PURPOSE: To differentiate healthy kidneys from diseased kidneys, we propose a combined magnetic resonance (MR) examination that includes measurements of renal arterial blood flow and parenchymal perfusion. MATERIALS AND METHODS: A total of 130 kidneys (patients/healthy volunteers: 83/47) were examined using renal artery MR flow measurements and renal parenchymal perfusion measurements, as well as contrast-enhanced MR angiography. Cine phase-contrast-flow measurements were performed using an ECG-gated fast low angle shot pulse sequence; perfusion was measured with an arterial spin labeling flow-sensitive alternating inversion recovery technique. Contrast-enhanced MR angiography was performed with a fast 3D gradient echo sequence in a single breath hold. For evaluation, kidneys were divided into groups based on nephrologic diagnosis of the patient. Recursive partitioning and Wilcoxon rank-sum tests were used to separate the different groups. RESULTS: Significant differences in mean renal artery flow and parenchymal perfusion were found in kidneys with renal artery stenosis as well as parenchymal disease as compared with healthy kidneys. Using a classification tree derived from the recursive partitioning, a specificity of 99% and sensitivity of 69% with a positive/negative predictive value of 97%/84% was achieved for the separation of healthy kidneys from kidneys with vascular, parenchymal or combined disease. The overall accuracy was 88%. CONCLUSION: The combination of cine PC flow measurements and MR perfusion measurements offers a comprehensive assessment of both renovascular and renoparenchymal disease and provide a noninvasive approach to differentiate between these kidneys and normal kidneys.     

Percutaneous transluminal renal angioplasty: indication for renovascular hypertension associated with renal atrophy

The results of clinical studies indicate that percutaneous transluminal renal angioplasty (PTRA) is an effective means for treating renovascular hypertension resulting from renal artery stenosis. However, the indications for the patients with renal failure or renal atrophy are not established on a firm ground. We attempted PTRAs of ten kidneys in nine patients with hypertension associated with renal atrophy. They were followed for an average of 8 months by the methods including blood pressure, angiography or DSA, blood chemistry, and RI-renogram. We also evaluated enlargement of the renal size on an angiogram or on a plain film at DSA. Angiographic follow-up showed persistent relief of the stenosis in all cases. After PTRA, blood pressure reduced to normal or improved in two thirds of the patients for the follow-up period. In the study of three patients with excellent results for blood pressure, two patients showed the renal length to be increased by 1.0 cm or more, and one patient by 0.5 cm. In the same group, RI-renogram also showed good response. These data indicate that PTRA could improve total perfusion on the affected kidneys. On the other hand, in three patients with no change in blood pressure, there was poor response in both the renal size and the data of RI-renograms. We suggest that the irreversible changes might have occurred in these kidneys. It was difficult to predict cure group from no change group before PTRA.     

Renal arteriovenous transit times of technetium-radiolabeled chelates

A noninvasive method was developed for quantitating the distribution of renal arteriovenous transit times of technetium-99m (99mTc) radiopharmaceuticals. Using this method, the characteristic transit times and amplitudes of the first two components of [99mTC] DTPA or MDP transit through the renal vasculature were calculated. The first component amplitude (A1) was evaluated for its ability to discriminate between 20 hypertensive patients with renovascular disease and 21 normotensive subjects. A1 was compared with three other quantitative indices: the ascending slope of the initial renal time-activity curve, the kidney-to-aorta slope ratio (K/A), and renal size. A1 nearly perfectly separated the hypertensive patients from the normotensive subjects; the ability of A1 to discriminate between these two groups is clearly superior to renal size, the initial renal slope, and K/A. We conclude that measurements of the intrarenal distribution of blood flow have distinct advantages over indices of renal blood flow that have been derived from scintillation camera measurements of 99mTc radiopharmaceuticals.     

Use of technetium-99m-MAG3 for renal scintigraphy after angiotensin-converting enzyme inhibition.

Technetium-99m-mercaptoacetyltriglycine (99mTc-MAG3) was tested in 82 hypertensive patients submitted to renal scintigraphy 1 hr after oral premedication with 50 mg of Captopril. Baseline studies were obtained only for those patients showing abnormal findings in the provocative study. All patients underwent renal arteriography. Sensitivity and specificity for the detection of renal artery stenosis (RAS) greater than 50% were 89% and 91%, respectively. After Captopril administration, tracer parenchymal transit time increased significantly in ischemic kidneys (334 +/- 93 sec in baseline conditions versus 468 +/- 96 sec after Captopril, p less than 0.001) but not in kidneys with no RAS or RAS less than 50% (243 +/- 46 sec versus 271 +/- 95 sec, p = ns). False-positive responses were mostly bilateral and associated with a marked decrease in blood pressure. Technetium-99m-MAG3 is an effective compound for detecting RAS greater than or equal to 50% with Captopril renal scintigraphy. Performing the provocative test as a first step considerably reduced the number of scintigraphic studies required.     

Increased kidney size following renal angioplasty. A 'new' observation

Percutaneous transluminal renal angioplasty was performed in nine patients (10 kidneys). Immediately following dilatation of the renal artery stenosis, seven of ten kidneys increased in length by at least 0.5 cm (0.5-1.5 cm) indicating improved renal perfusion. This is an observation that does not seem to have been described before. Another, but rare, cause of renal enlargement following angioplasty is hematoma formation which was seen in one of the cases. All of the patients responded well to the treatment and five previously hypertensive patients became normotensive shortly after dilatation.     

99Tcm-DTPA肾动态显像与血清胱抑素C测定法在肾小球功能评价中的对比研究

目的 比较99Tcm-二亚乙基三胺五乙酸(99Tcm-DTPA)肾动态显像和血清胱抑素C测定两种方法在评价肾小球滤过功能中的差别.方法 随机抽取100例患者,其中高血压病患者38例、肾脏病患者35例、动脉硬化性闭塞症患者10例、糖尿病患者9例、其他疾病患者8例.分别通过99Tcm-DTPA肾动态显像法和血清胱抑素C测定法评估肾小球滤过功能.结果 两种方法所测得的肾小球滤过率(GFR)差异无统计学意义(t=1.591,P＞0.05),且呈线性相关(r=0.809,P＜0.01);放射性核素肾动态显像法在测定GFR的同时,还可以获得分肾功能,观察双肾血流灌注和排泄状况.结论 用99Tcm-DTPA肾动态显像与血清胱抑素C测定两种方法评估GFR,结果无显著差异,且相关性很好.前者可以获得分肾功能,对肾功能状态的评估更为全面;而后者测定方法简便、省时,且价廉,更适合于对临床患者肾功能的筛查.     

Transluminal angioplasty in patients with bilateral renal artery stenosis or renal artery stenosis in a solitary functioning kidney

Renal angioplasty in patients with bilateral renal artery stenosis or with renal artery stenosis in a solitary functioning kidney has been thought to be relatively contraindicated. We report the results of renal artery angioplasty in 18 patients, 10 with severe bilateral renal artery stenosis and eight with severe renal artery stenosis in a solitary kidney. Twenty-five (89%) of 28 angioplasties were successful, with a mean improvement of the degree of stenosis from 85% to 18% after angioplasty and a restoration of renal blood flow. A significant drop in mean blood pressure at admission of 187/101 mm Hg to 154/87 mm Hg at discharge, 152/86 mm Hg at 3-month, and 146/82 mm Hg at 1-year follow-up was seen. Because of the decrease in blood pressure, 11 of the patients decreased or stopped taking diuretics and 15 decreased or stopped taking antihypertensive medications. Although no significant change in renal function was found by measuring mean serum creatinine levels over time, no patient had an elevated serum creatinine level at follow-up, indicating preservation of renal function. One major complication, cholesterol embolization to the bowel, was seen. Our results suggest that angioplasty is an acceptable treatment of hypertension in patients with bilateral renal artery stenosis or renal artery stenosis in a single kidney.