Scintillation camera renography with 99mTc-DTPA and 131I-Hippuran

Comparison of methods for determination of glomerular filtration rate: low and high-dose Tc-99m-DTPA renography, predicted creatinine clearance method, and plasma sample method

The gamma camera uptake method with Tc-99m-DTPA (diethylenetriaminepentaacetic acid) is a simple method for determination of glomerular filtration rate (GFR), and is less time-consuming than other methods, but its diagnostic accuracy is debated. Gate's method (low-dose; LD), the high-dose method (HD), the predicted-clearance method, and the plasma-clearance method with Tc-99m-DTPA are compared in this study. We also performed GFR measurement and diuretic renography simultaneously. Tc-99m DTPA renography was performed in 36 patients aged 18-72 years with a wide range of renal function (serum creatinine 1.37 +/- 0.49 mg/dl). GFR was determined by four methods: the gamma camera uptake method with low-dose Tc-99m DTPA (Gates, LD); the gamma camera uptake method with high-dose Tc-99m DTPA (HD); the predicted creatinine clearance method (Cockcroft-Gualt, CG); and the plasma sample clearance (PSC) method using a mono-exponential curve. The PSC method was chosen as reference. The regression equations for the CG, Gates (low-dose), and HD methods against the PSC method were 28.68 + 0.80X (r = 0.72; P value < 0.0001, RMSE = 21.65 ml/min/1.73 m(2)), 6.19 + 0.79X (r = 0.90; P value < 0.0001, RMSE = 10.64 ml/min/1.73 m(2)), and 6.53 + 0.88X (r = 0.93; P value < 0.0001, RMSE = 9.35 ml/min/1.73 m(2)), respectively. In comparison with determination of GFR by the PSC method, the CG method tended to overestimate GFR while, perversely, the LD and HD methods tended to underestimate GFR. The three methods were in agreement with the PSC method but the high-dose GFR method resulted in less error in estimation of GFR. Furthermore, GFR measurement and diuretic renography could be performed at the same time when the high-dose method was used. Because of the low cost and negligible radiation burden, this method might be preferred for routine practice in nuclear medicine.

International Scientific Committee of Radionuclides in Nephrourology (ISCORN) consensus on renal transit time measurements

This report is the conclusion of the international consensus committee on renal transit time (subcommittee of the International Scientific Committee of Radionuclides in Nephrourology) and provides recommendations on measurement, normal values, and analysis of clinical utility. Transit time is the time that a tracer remains within the kidney or within a part of the kidney (eg, parenchymal transit time). It can be obtained from a dynamic renogram and a vascular input acquired in standardized conditions by a deconvolution process. Alternatively to transit time measurement, simpler indices were proposed, such as time of maximum, normalized residual activity or renal output efficiency. Transit time has been mainly used in urinary obstruction, renal artery stenosis, or renovascular hypertension and renal transplant. Despite a large amount of published data on obstruction, only the value of normal transit is established. The value of delayed transit remains controversial, probably due to lack of a gold standard for obstruction. Transit time measurements are useful to diagnose renovascular hypertension, as are some of the simpler indices. The committee recommends further collaborative trials.

Determination of glomerular filtration rate using a dual-detector gamma camera and the geometric mean of renal activity: correlation with the Tc-99m DTPA plasma clearance method

PURPOSE

In this study, the authors studied the use of a dual-detector gamma camera to measure the glomerular filtration rate (GFR).

METHODS

Thirty-three patients with a wide range of renal function participated in this study. The GFR was measured using a dual-detector gamma camera by calculating the geometric mean of activity from each kidney and using an outline background. These results were compared with the GFR estimates obtained from Tc-99m DTPA plasma clearance using a multiple blood sample method.

RESULTS

Correlation was excellent between GFR estimated using the dual-detector gamma camera and GFR measured using the plasma clearance of Tc-99m DTPA with multiple blood samples (r = 0.89). The correlation was especially strong in children younger than 13 years (r = 0.94).

CONCLUSION

Measuring the GFR using a dual-detector gamma camera and calculating the geometric mean of renal activity yields relatively accurate results.

Consensus report on quality control of quantitative measurements of renal function obtained from the renogram: International Consensus Committee from the Scientific Committee of Radionuclides in Nephrourology

Among all the physiological indices that can be quantified using renography, measurement of renal function is the most basic. These measurements are used to make critical clinical management decisions and, as such, their reliability needs to be quality assured. This article seeks to address each aspect of the renography procedure, with particular emphasis on the effect on measurement of relative renal function. Estimation of individual kidney function is mentioned, but only briefly. A consensus approach was adopted, overseen, and directed by a chairman appointed by the Scientific Committee of the International Radionuclides in Nephro-Urology Group. The chairman selected the panel of experts from eight different countries based on their practical experience in the field. Where evidence exists to support the various recommendations it is given. Otherwise, the stated guidance represents the considered opinion of a body of experts, based on long experience and unpublished data. Some necessary compromises were made to account for the fact that renography is seldom performed solely with the purpose of measuring relative renal function. The technicalities of renography have always been a source of debate in nuclear medicine, which is reflected by the fact that a consensus could simply not be reached on a small number of issues. The structure of the report ensures that these are clearly indicated. This should serve to highlight gaps in our current knowledge, thus helping to direct future research. It is envisaged that the recommendations will be revised on a 2-year cycle to ensure that they remain up to date. An "open" process will be used to encourage participation and ownership. It is hoped that promotion of these guidelines, suitably complemented by audit processes, will raise standards in the practice of gamma camera renography.

Renal function up to 16 years after conduit (refluxing or anti-reflux anastomosis) or continent urinary diversion. 1. Glomerular filtration rate and patency of uretero-intestinal anastomosis

OBJECTIVE

To evaluate the glomerular filtration rate (GFR) and incidence of anastomotic stenosis in patients with urinary diversion by ileal or colonic conduit (refluxing or anti-reflux uretero-intestinal anastomosis) or with a continent caecal reservoir.

PATIENTS AND METHODS

All conduit urinary diversions performed from 1977 to 1984 were randomized by type (ileal or colonic) and by the method of ureteric implantation (with or without anti-reflux technique). In continent caecal reservoirs anti-reflux implantation was used for both ureters. Total and separate GFR were measured pre-operatively and after a mean follow-up of 123 months (range 36-198) with 51Cr-EDTA and scintillation renography.

RESULTS

Of the 56 evaluable patients, 18 had an ileal and 20 a colonic conduit, and 18 had a continent reservoir. The total mean GFR fell from 88 to 71 mL/min in the ileal group, from 84 to 65 mL/min in the colonic group and from 100 to 85 mL/min in the reservoir group. Separate GFR did not differ significantly between kidneys with and without reflux protection in the patients with a conduit diversion. Strictures occurred in 15 uretero-intestinal anastomoses and were unrelated to the mode of ureteric implantation (in the conduit groups). Renal function improved after ureteric reimplantation in six of seven kidneys, but after balloon dilatation in only one of five.

CONCLUSION

GFR fell moderately in all three groups, with no significant intergroup difference, and the continent caecal reservoir compared favourably with conduit diversion. The fall in separate GFR did not differ significantly between kidneys with and without reflux protection. Surgical exploration of uretero-intestinal stenosis is recommended if renal function is threatened.

Role of the captopril test in renovascular hypertension: a case report

This article reports the case of a rapidly severe stenosis of the right renal artery, causing uncontrolled hypertension. After failure of a percutaneous transluminal renal angioplasty, which provoked the thrombosis of the vessel, a surgical revascularization was performed after +/- eighteen hours of renal ischemia. Blood pressure, blood urea nitrogen and serum creatinine returned to normal values. A dramatic improvement of the right renal function was attested at the hippuran scintigraphy after a dose test of captopril. The results of renographic studies obtained in this clinical case underline the role of the captopril radionuclide test in detection and follow-up after treatment of renovascular hypertension.

Renal parenchymal function evaluated by scintillation camera renography before and after pyeloplasty for hydronephrosis

Scintillation camera renography with Tc-DTPA was performed before and after pyeloplasty on 16 kidneys with urographic signs of pelviureteric obstruction causing hydronephrosis. Regional parenchymal renograms were generated, and the passage of Tc-DTPA through the parenchyma was measured and correlated to the change in separate glomerular filtration rate. Preoperative parenchymal passage of DTPA was significantly slower (p = 0.02) in kidneys with improved glomerular filtration rate after pyeloplasty than in those without such improvement. Postoperative passage of DTPA in parenchyma was almost identical with that in a reference series. This method seems to be clinically useful for evaluating cases of hydronephrosis and for predicting the outcome of pyeloplasty.

Glomerular filtration rate up to 10 years after urinary diversion of different types. A comparative study of ileal and colonic conduit, refluxing and antirefluxing ureteral anastomosis and continent caecal reservoir

To evaluate the influence of conduit type (ileal or colonic) and method of ureterointestinal anastomosis (refluxing or antirefluxing) on renal function in patients with urinary diversion, a prospective randomized trial was conducted in 1977-1984. During these years urinary diversion via a continent caecal reservoir emerged as an alternative to conduit diversion at our hospital, and these patients with continent reservoir were also included in the study. Total and separate glomerular filtration rate (GFR) were measured, the latter with scintillation camera renography, preoperatively and at follow-up in 70 patients. Measurements 2-10 years postoperatively showed slight to moderate decrease of GFR in all groups, with no significant difference between values according to conduit type or caecal reservoir or between refluxing and antirefluxing ureterointestinal anastomosis. Almost all of the anastomotic strictures involved the ureter that had been brought beneath the sigmoid mesentery, indicating that ischemia secondary to extensive ureteral mobilization is a likely cause of stricture in these cases.

The benefits of combining early radionuclide renal scintigraphy with routine bone scans in patients with prostate cancer

Based upon the rapid early renal excretion of bone imaging radiopharmaceuticals, we performed a prospective study to determine the use of combining renal evaluation with routine bone scans in 79 consecutive patients with prostate cancer. The radionuclide renal scintigraphy consisted of a 1-minute sequence of 2.5-second frames with a bolus injection of 99mtechnetium-methylene diphosphonate followed by a series of 2-minute images for 24 minutes. Whole body bone scans were performed after a 3-hour delay. All patients had at least 1 confirmatory study with excretory urography (62), ultrasonography (49) or computerized tomography (30). Results were interpreted independently and compared. Ten studies were normal. Radionuclide renal scintigraphy was able to identify 45 of 49 cortical abnormalities (90 per cent) with a false positive rate of 4 per cent. Accuracy of renal cyst detection was only 47 per cent (15 of 32 cases). All acutely obstructed kidneys were identified correctly by radionuclide renal scintigraphy (5 of 5 cases). Of 12 chronically obstructed kidneys 8 (67 per cent) were identified correctly. The 4 missed kidneys were small and nonfunctioning, and they were diagnosed correctly as such but obstruction as the etiology of nonfunction was unidentifiable by radionuclide renal scintigraphy. The false positive rate of obstructive diagnosis by radionuclide renal scintigraphy was 24 per cent (4 of 17 cases). These findings demonstrate that renal evaluation combined with routine bone scanning is an effective screening procedure for renal complications of prostate cancer; no significant abnormalities were missed. The procedure is entirely free of morbidity and does not add to the radiation dose from the bone scan. Furthermore, it is cost-effective, since it avoids the routine need for 2 separate procedures at followup of patients with prostate cancer.

Radionuclide evaluation of renal transplants

In this review article, the following topics are treated: the radiopharmaceuticals 99mTc-diethylenetriaminepentaacetic acid (DTPA), 131I-orthoiodohippurate (OIH), 99mTc-mercaptoacetyltriglycine (MAG3), 67Ga-citrate, radioiodinated fibrinogen, 99mTc-sulfur colloid, 111In-labelled white cells and platelets; gamma camera methods based on images, on first pass and on tubular transit; blood clearance methods; and the diagnosis of surgical complications, acute rejection (AR), acute tubular necrosis (ATN), chronic rejection (CR), and cyclosporine-A (CYA) toxicity.

Acute unilateral obstruction of ureter. Disparity in divided renal function calculated from 131I-hippuran and 99mTc-DTPA renography

Fifteen patients with acute unilateral obstruction of ureter and 30 control patients were studied with simultaneous 131I-Hippuran and 99mTc-DTPA gamma camera renography. In severe outflow obstruction the relative function of the obstructed kidney was higher when calculated with Hippuran than with DTPA. No difference was found in the control subjects. This means that the glomerular filtration rate of an obstructed kidney may be relatively more reduced than the renal blood flow. Therefore, measurement of the single kidney fraction of total glomerular filtration rate has to be calculated with a glomerular filtered tracer, e.g., 99mTc-DTPA.

Renal scintigraphic captopril test in the diagnosis of renovascular hypertension

Angiotensin converting enzyme (ACE) inhibitor-induced renal failure has been reported in bilateral renal artery stenosis and in stenosis in solitary kidneys, but not in unilateral renal artery stenosis. In these patients, however, a functional impairment of the kidney ipsilateral to the stenosis can often be detected after ACE inhibition by scintigraphic techniques employing glomerular radionuclide tracers like 99mTc-diethylenetriamine pentaacetic acid (DTPA). Dynamic renal scintigraphy with 99mTc-DTPA before and 1 hour after administration of captopril, 25 mg (renal scintigraphic captopril test; RSCT), was performed in a selected series of 39 hypertensive subjects with suspected renovascular hypertension. Changes in glomerular filtration rate induced by captopril on the individual kidney were estimated by assessing the early (120-180 seconds) DTPA uptake by the kidney. Values were expressed as the ratio between the kidney with the lower uptake and the contralateral one in 34 patients and as the ratio of the kidney counts to the injected dose in five patients with solitary kidneys, aortic coarctation, or both. Compared with precaptopril values, postcaptopril uptake decreased markedly in 14 subjects (-62.42 +/- 30.94 [SD]%; range, -25 to -100%) and decreased modestly or even increased in the other 25 (+0.57 +/- 9.83%; range, +28 to -13%). Of the 14 subjects considered to be RSCT-positive diagnostic workup revealed either established (10) or strongly suspected (2) renal artery stenosis in 12 and aortic coarctation in 2 subjects. In another patient with established renovascular hypertension, results of the RSCT were negative when performed in the supine position but became positive when repeated in the sitting position.(ABSTRACT TRUNCATED AT 250 WORDS)

Ramipril for hypertension secondary to renal artery stenosis. Changes in blood pressure, the renin-angiotensin system and total and divided renal function

The converting enzyme inhibitor, ramipril, 20 mg once daily, was given to 3 hypertensive patients with unilateral renovascular disease. At 1 month, 24 hours after the last dose of ramipril, blood pressure, plasma angiotensin II and converting enzyme activity remained low, and active renin and angiotensin I high. There was no tendency for converting enzyme inhibition to be overcome during 1 month of ramipril therapy. Ramipril caused slight increases in serum potassium and urea, no change in serum creatinine and no consistent changes in the renal vein renin ratio. Ramipril caused little change in renal plasma flow on the stenotic side, but filtration fraction was reduced in 2 patients. There was no serious deterioration in total or individual glomerular filtration rate during ramipril therapy. The drug was well tolerated and there were no serious side effects. Ramipril, given once daily, is likely to be effective in controlling hypertension with renal artery stenosis.

Evaluation of renal parenchyma in children by DMSA scintigraphy, X-ray computed tomography and intravenous urography

The demonstration of diminished or scarred renal parenchyma in children is often the decisive factor in determining the future management of children with urinary tract malformations. Renal scintigraphy using technetium 99m-labelled dimercaptosuccinic acid (DMSA), computed tomography (CT) and intravenous urography (IU) were used to evaluate the renal parenchyma prior to ureter re-implantation in a series of 13 children. Their ages ranged from 5 months to 3 years 8 months. The indication for operation was ureteric reflux in 8 children and distal ureteric stenosis in 5. CT was performed on a Toshiba TCT-80 scanner. Renal scintigraphy was performed 3 hours after intravenous injection of DMSA. Compared with IU, DMSA imaging gave more information about the renal parenchyma in 6 children, gave equal information in 6 and less in 1. Compared with CT, DMSA imaging gave more information in 2 children, was equally informative in 8 and less so in 3. Accordingly, DMSA imaging was judged to be more sensitive than IU and as sensitive as CT. DMSA imaging can be used both for the initial evaluation and for follow-up assessment of renal parenchymal damage.

Gamma camera renography with 99Tcm-MDP and 131I-Hippuran

Nineteen patients with urologic disorders referred to bone scintigraphy were evaluated with a dual radioisotope technique using simultaneous injection of 99Tcm-MDP and 131I-Hippuran. The MDP and Hippuran renograms showed in general the same pattern and there was no difference between the kidney function determined with the two radionuclides. The peak of the MDP curves occurred later and was less distinct than that of the Hippuran curves. The residual activity of the kidneys 20 min after the injection was higher on the MDP renograms compared with the Hippuran renograms. The early sequential MDP images were superior in quality to the Hippuran images and to the renal images obtained at bone scintigraphy. The early MDP images correlated well with the findings at urography performed in 12 patients, as all cases of radiologically diagnosed hydronephrosis, reduction of renal parenchyma and renal mass lesions became demonstrated. Renal calculi were only diagnosed at urography. In conclusion, MDP cannot replace Hippuran as a renal radionuclide agent, mainly due to its lower extraction ratio and the high bone uptake. However, an increased use of early dynamic renal imaging is recommended in urologic patients referred to bone scintigraphy as valuable information about renal function may be obtained by this procedure.

99mTc-DTPA and 99mTc-DMSA renal gamma imaging in the surveillance of patients with conduit urinary diversion

We studied renal anatomy and function using 99mTc-2-3 dimercaptosuccinic acid (DMSA) and 99mTc-diethylenetriaminepentaacetic acid (DTPA) in 27 patients with conduit urinary diversion. In this condition, free ureteral reflux is often associated with bacteriuria, and these factors are thought to precipitate progressive renal deterioration. Gamma-camera images provided valuable information concerning the structure of the renal parenchyma, the function of individual kidneys and possible ureteral obstruction, thus helping us to decide whether or not to instigate further treatment. The information gained using renal gamma imaging with 99mTc-DTPA and 99mTc-DMSA was complementary and partly overlapping. We preferred the use of 99mTc-DTPA because of its ability to visualise the ureters and the region of ureteroconduit anastomosis. Using diuretic medication, we were able to differentiate true ureteral obstruction from atony in 9 patients using 99mTc-DTPA.

Comparative assessment of techniques for estimation of glomerular filtration rate with 99mTc-DTPA

The relative accuracy of five simplified methods of measuring glomerular filtration rate was prospectively assessed using 99mTc-DTPA. The slope of the biological clearance curve, the 3-h volume of dilution and three renal tracer uptake methods (Piepsz, Gates and Nielsen) were concurrently compared with a multiple blood sampling reference method. The volume of dilution method from a single blood sample was markedly superior to the other four simplified methods which all had a similar degree of accuracy.

Kidney scintigraphy after ACE inhibition in the diagnosis of renovascular hypertension

Suppression of the renin-angiotensin system (RAS) by angiotensin converting enzyme (ACE) inhibition may induce renal failure in patients with bilateral renal artery stenosis. Recent scintigraphic studies with the glomerular tracer technetium-99m-diethylenetriaminepenta-acetate (99m-Tc DTPA) indicate that in patients with unilateral renal artery stenosis, glomerular filtration rate (GFR) may be markedly reduced in the affected kidney after inhibition of ACE. This finding reflects the important role of the RAS in maintaining GFR (by increasing postglomerular resistance) in states of low renal perfusion pressure. Preliminary observations suggest that this scintigraphic test might be useful in the detection of renovascular hypertension.

Splint renal function after captopril in unilateral renal artery stenosis

The renal extraction ratios of 131I-sodium iodohippurate (131I-Hippuran) and 125I-thalamate were greatly reduced on the affected side by 50 mg captopril in seven out of 14 patients with unilateral renal artery stenosis. With long term captopril 150 mg daily the uptake of 99mTc-diethylenetriaminepenta-acetic acid by the affected kidney, which was determined by scintillation camera renography, became almost zero in these seven patients, indicating severe reduction of the glomerular filtration rate. Function of the affected kidney returned on discontinuing treatment. The reduced extraction of sodium iodohippurate probably reflected a shortened plasma transit time through the kidney due to intrarenal vasodilatation. The reduced extraction of thalamate reflected a low filtration fraction, suggesting that the vasodilatation was, at least in part, at the level of the postglomerular arterioles. Captopril had little effect on the contralateral kidney and on the kidneys of 17 patients with essential hypertension, and serum creatinine concentrations showed minor changes. Radioisotope renography should be performed after beginning captopril treatment in patients with renal artery stenosis. This is also recommended for patients given captopril as a third line drug when renal artery stenosis has not been excluded. Hypertension is these patients is often severe and difficult to control. Renal artery disease is not rare in this difficult group and finding seriously impaired renal function on one side during captopril treatment may be diagnostic.

Renal function after urinary diversion. A study of continent caecal reservoir, ileal conduit and colonic conduit

Total and separate renal function, renal parenchymal thickness and dilatation of the upper urinary tract were studied in 40 patients preoperatively and 24 to 67 months after urinary diversion, using 51Cr-EDTA clearance test, scintillation camera renography and urography. In ten patients a continent caecal reservoir was used for diversion. In the other patients, an ileal or a colonic conduit (15 patients with each method) was used, one ureter being implanted with an anti-reflux method and the other with direct technique. Renal function following urinary diversion showed little or no deterioration in most patients. The functional outcome was not related to the method of diversion or, in the conduit groups, to the mode of ureteral implantation. Serum creatinine tests and urography were not adequate for determining loss of renal function. Radionuclide studies proved to be valuable for assessing renal function after urinary diversion.

Acute effects of full urinary bladder and full caecal urinary reservoir on regional renal function. A study with scintillation camera renography

Scintillation camera renograms were recorded in six patients without a history of bladder function disturbances and in eight patients with caecal urinary reservoir. Each patient was studied once with empty bladder/reservoir and once with full bladder/reservoir. Renograms were obtained from parenchyma, pelvis and whole kidney. Time was measured from injection of isotope to peak of the renogram curve (Tmax) and to the point corresponding to the centre of gravity of the area under the curve (Tg). A full reservoir gave longer Tmax and Tg for both parenchyma and pelvis than an empty reservoir. With full bladder the only significant change was Tg increase for renal pelvis. In the patients with full caecal reservoir, the elimination of radioisotope from the renal pelvis was significantly slower, reflected as longer Tmax and Tg, than in the subjects with full bladder. In comparisons between empty and full bladder/reservoir, Tg permitted clearer separation between the groups than did Tmax. The higher Tmax and Tg values for full than for empty reservoir indicated obstruction to urinary flow and could be ascribed to the high intrareservoir pressure. Regularly occurring pressure waves with amplitudes of 30-65 cm H2O were recorded in the reservoirs, sometimes reflected as transient increases in radioisotope activity in the renograms. In some patients the two kidneys differed considerably in their response to a full urinary bladder or reservoir. The cause may have been difference in the dynamics of the two ureterovesical junctions or of the ureterointestinal anastomoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of renal function parameters with simultaneously administered 99mTc-DTPA and 131I-hippuran

The present study aimed at comparing two renal function tests using 99mTc-DTPA (diethylene triamine penta acetic acid) and 131I-labeled hippuran (o-hippuric acid). A mixture of 80 MBq 99mTc-DTPA and 7.4 MBq 131I-hippuran in a total volume of 1.5 ml or less was injected into an arm-vein. Both radiopharmaceuticals have identical initial distributions in the blood pool when injected in this manner. Seventy-two patients were studied with the present dual radionuclide technique. The following parameters were derived from the renogram: area under curve, uptake ratio, Tmax, decrease ratio, excretion ratio, and rate of decrease. The parameters for 99mTc-DTPA and 131I-hippuran were compared for various kidney groups. Generally the renographic parameters were well correlated. Apart from the systematic differences due to different modes of renal excretion, the curve patterns virtually agreed. The differences that were observed between the two tracers lacked clinical significance.

Renal radiopharmaceuticals--an update

Noninvasive radionuclide procedures in the evaluation of renal disease have been accepted increasingly as effective and valuable alternatives to older clinical methods. The development of suitable radiopharmaceuticals labeled with high photon intensity radionuclides and with 99mTc in particular has stimulated this modality during the last few years. Currently several nearly ideal agents are available for anatomical and functional studies of kidney imparting very low absorbed radiation doses. These include 99mTc-GHA and 99mTc-DMSA for renal morphology and differential function evaluation, 99mTc-DTPA for GFR and 123I orthoiodohippurate for ERPF measurements. A suitable agent as a replacement for the latter labeled with 99mTc is actively being sought. Computer-assisted processing of dynamic renal function studies enables the observer to obtain a wealth of information related to the renal extraction, uptake, parenchymal transit and pelvic transit parameters of the agent administered into the bloodstream. Each of these parameters either globally or differentially contributes to a detailed evaluation of renal disease states. Several of these procedures have been validated against classical techniques clinically but more detailed information is being sought with the recently introduced radiopharmaceuticals. With the detailed validation and increasing recognition of the clinical utility of several of the radionuclidic procedures at many centers, it is hoped that radionuclide assessment of renal disorders ultimately will be made available routinely at all medical facilities.