Clearance Of Contrast Medium Research Articles

Clinical research of CT urography in quantitative assessment of single-kidney glomerular filtration rate in renal tumors and hydronephrosis patients

Objective To evaluate the clinical value of CT urography (CTU) in quantitative analysis of single-kidney renal glomerular filtration rate (GFR) in patients with renal tumor and hydronephrosis. Methods A total of 49 patients with renal tumor or hydronephrosis from January 2018 to September 2018 in the Second Hospital of Tianjin Medical University were prospectively collected. In all cases, the CT urography and 99mTc-DTPA renal dynamic imaging data and related clinical data were collected. All patients were divided into two groups: the experimental group (39 patients with a total of 78 kidneys) and the validation group (10 patients with a total of 20 kidneys). According to the presence or absence of renal diseases, the kidneys of the experimental group and the validation group were further divided into four groups, namely, the single kidney group, the tumor group, the stagnant water group and the healthy group. The CT urography protocol consisted of noncontrast, arterial phase, nephrographic, and excretory phase imaging. The total renal GFR was determined by CT measurement of renal clearance of contrast media (CM), and the total CT-GFR was then split into single-kidney CT-GFR by a left and right kidney proportionality factor. Differences between CT-GFR and SPECT-GFR measurements in each group of the experimental group was compared by paired-sample t test. Correlations between CT-GFR and SPECT-GFR in the experimental group and their correlations with RPV was analyzed by Pearson method. The Bland-Altman mapping method was used to evaluate the consistency between CT-GFR and SPECT-GFR in the experimental group. Results Paired difference between single-kidney CT-GFR (48.76±18.50) ml·min-1·1.73 m-2 and single-kidney SPECT-GFR (45.68±17.95) ml·min-1·1.73 m-2 in the experimental group, P 0.05).Pearson Correlation analysis showed that the correlations between CT-GFR and RPV in all experimental groups were better than the correlation between Gates-GFR and RPV (P<0.05). Conclusions This study demonstrated the feasibility of using CT urography to measure single-kidney GFR, verifying its application value in diseases such as kidney tumors and obstructive hydronephrosis, and proved that the proposed single-kidney CT-GFR correlates better than the SPECT-GFR with RPV. Key words: Kidney neoplasms; CT urography; Glomerular filtration rate; Comparative study

Contrast Layering

Patients with angiographically normal coronary arteries sometimes exhibit delayed clearance of contrast medium. This contrast layering (CL) was tested with intravascular ultrasound (IVUS) and markers of endothelial dysfunction and oxidative stress. The study group (n = 26) consisted of patients with CL and the control group (n = 32) comprised patients with normal coronary arteries despite angina symptoms. The CL was observed in 36 coronary arteries of 26 patients in the study group. Total antioxidant status and nitric oxide levels were significantly lower; total oxidant status, malondialdehyde plasma levels, and oxidative stress index were significantly higher in patients with CL than in controls. The IVUS studies revealed that atherosclerotic plaque burden, fibrous tissue, dense calcific tissue, and necrotic core ratios were significantly higher in the coronary segments with CL compared with adjacent normal segments. These results support the concept of CL as a new angiographic appearance of early atherosclerosis.

Evaluation of pulsed electromagnetic stimulation for the enhancement of femoral fracture healing in dogs

The clinical study was conducted on twelve dogs of either sex having midshaft oblique fracture of right femur and divided into two groups comprising of six animals in each group. Under anaesthetic combination of atropine sulphate, xylazine hydrochloride, diazepam and ketamine hydrochloride, the fractured fragments were reduced and stabilised with stack pinning and two cerclage wiring. Group I animals were treated as control and received only postoperative care and management. Group II animals were treated with pulsed electromagnetic field (PEMF) stimulation of 75 Hz for 20 min daily for 15 days for enhancement of fracture healing along with postoperative care and management. The clinical union of cutaneous wounds were observed on 9th and 7th day in animals of group I and II. Full weight bearing was observed on 50th day and 29th day in Group I and Group II animals respectively. Radiographically there was abundant periosteal callus with persistence of fracture line on 8th postoperative week in animals of group I and complete union of fracture with minimal periosteal callus on 6th postoperative week in animals of group II. Positive osteomedullographic signs and clearance of contrast medium in all the animals of group I and II on 60th postoperative day indicated reestablishment of intraosseous and extraosseous network. Pulsed electromagnetic stimulation was found to be an effective non invasive technique in enhancement of femoral fracture healing without any complication and can be used as an adjunct to internal fixation for fracture treatment

Internal Jugular Veins Outflow in Patients with Multiple Sclerosis: A Catheter Venography Study

To investigate an examiner-independent catheter venography protocol that could be used to reliably diagnose venous outflow abnormalities in patients with multiple sclerosis (MS) and chronic cerebrospinal venous insufficiency and to determine whether venous angioplasty is effective in the treatment of these abnormalities. A total of 313 patients with MS and 12 patients with end-stage renal disease underwent echo-color Doppler sonography and catheter venography of the internal jugular veins (IJVs) to evaluate contrast medium clearance time. In patients with venous outflow anomalies, balloon angioplasty of the IJVs was performed. A contrast medium clearance time cutoff value of 4 seconds or less provided the maximal combination of sensitivity and specificity for the right IJV (sensitivity, 73.4%; specificity, 100%) and left IJV (sensitivity, 91.4%; specificity, 100%). IJVs with a clearance time between 4.1 and 6 seconds had moderate delayed flow (MDF), and IJVs with a clearance time longer than 6 seconds had severe delayed flow (SDF); 89% of patients showed MDF/SDF through at least one IJV, 79% showed MDF/SDF through both IJVs, and only 5% showed normal flow in both IJVs. Balloon angioplasty was immediately able to improve flow in at least one IJV in 69% of patients, but venous flow was normalized in both veins in only 37% of patients; SDF persisted after angioplasty in 32% of patients. There is a high prevalence of abnormal delayed flow through IJVs in patients with MS. Venous angioplasty was effective in only a minority of patients with SDF.

Measurement of glomerular filtration rate using dynamic magnetic resonance imaging in patients with chronic kidney disease

Determination of glomerular filtration rate (GFR) using plasma disappearance curves requires the injection of a filtration marker and repeated timed blood collections. Gadolinium-containing contrast media are excreted exclusively by glomerular filtration and could provide a novel approach to quantifying GFR using magnetic resonance (MR) imaging. The aim of this study was to demonstrate the feasibility of measuring GFR by the clearance of gadolinium-containing contrast medium in patients with chronic kidney disease (CKD). Informed consent was obtained from stable CKD patients in stages 1, 2 or 3 (n=16; 5 women, 11 men; median age 54 years). GFR was measured after a bolus injection of gadobutrol (4 mL, approximately 0.05 mmol/kg) and calculated from the washout of the signal intensity obtained over the liver. The obtained MR-GFR was compared with simultaneously measured plasma clearance of inulin and gadobutrol. Technical failure occurred in 2 patients. The mean obtained MR-GFR was 71 ± 25 (SD) mL/min per 1.73 m² and agreed well with the mean inulin-GFR (70 ± 24 mL/min per 1.73 m²). Pearson's correlation coefficient was r=0.91. The mean of the paired differences was 1 ± 10 mL/min per 1.73 m² and not significantly different from zero. GFR obtained from gadobutrol plasma clearance also agreed well with inulin-GFR and MR-GFR (r=0.92 and r=0.75, respectively). We describe a novel method of determining GFR from MR imaging using a low dose of gadobutrol in patients with reduced GFR that enables the absolute quantification of GFR after routine contrast-enhanced MR imaging.

Magnetic resonance imaging of hypoxic injury to the murine placenta

We assessed the use of magnetic resonance imaging (MRI) to define placental hypoxic injury associated with fetal growth restriction. On embryonic day 18.5 (E18.5) we utilized dynamic contrast-enhanced (DCE)-MRI on a 4.7-tesla small animal scanner to examine the uptake and distribution of gadolinium-based contrast agent. Quantitative DCE parameter analysis was performed for the placenta and fetal kidneys of three groups of pregnant C57BL/6 mice: 1) mice that were exposed to Fi(O(2)) = 12% between E15.5 and E18.5, 2) mice in normoxia with food restriction similar to the intake of hypoxic mice between E15.5 and E18.5, and 3) mice in normoxia that were fed ad libitum. After imaging, we assessed fetoplacental weight, placental histology, and gene expression. We found that dams exposed to hypoxia exhibited fetal growth restriction (weight reduction by 28% and 14%, respectively, P < 0.05) with an increased placental-to-fetal ratio. By using MRI-based assessment of placental contrast agent kinetics, referenced to maternal paraspinous muscle, we found decreased placental clearance of contrast media in hypoxic mice, compared with either control group (61%, P < 0.05). This was accompanied by diminished contrast accumulation in the hypoxic fetal kidneys (23%, P < 0.05), reflecting reduced transplacental gadolinium transport. These changes were associated with increased expression of placental Phlda2 and Gcm1 transcripts. Exposure to hypoxia near the end of mouse pregnancy reduces placental perfusion and clearance of contrast. MRI-based DCE imaging provides a novel tool for dynamic, in vivo assessment of placental function.

Quantitative Assessment of Glomerular Filtration Rate with MR Gadolinium Slope Clearance Measurements: A Phase I Trial

To prospectively demonstrate the feasibility of quantifying the glomerular filtration rate (GFR) by assessing the renal clearance of gadolinium-based contrast medium from the extracellular fluid volume in healthy volunteers. The study was approved by the ethics committee and the governmental drug administration department (registration number 4030139, EudraCT number 2004-002969-20, study protocol number 318/2004). Informed consent was obtained from 16 healthy volunteers (six female, 10 male; mean age, 24.5 years +/- 2.8 [standard deviation]). Thirteen volunteers (four women, nine men; mean age, 24.8 years +/- 2.7; range, 23-30 years) successfully contributed to the study. The GFR was assessed by recording the renal clearance of gadobutrol (3.75 mL, approximately 0.05 mmol per kilogram of body weight) at navigator-gated turbo fast low-angle shot magnetic resonance (MR) imaging. Time-signal intensity curves were constructed from manually drawn regions of interest in the liver, spleen, and renal cortex, and the GFR was calculated by using exponential fitting. Simultaneously obtained iopromide clearance measurements were the reference standard. Statistical evaluations included Bland-Altman plotting and analysis of the relative deviation from iopromide clearance. Evaluation of liver regions of interest revealed the lowest mean of paired differences from the iopromide clearance measurements (-5.9 mL/min per 1.73 m(2) +/- 14.6), with a mean GFR of 109.0 mL/min per 1.73 m(2) +/- 17.1 (134.1 mL/min per 1.73 m(2) +/- 35.4 for spleen, 100.7 mL/min per 1.73 m(2) +/- 25.1 for renal cortex) compared with a mean GFR of 103.1 mL/min per 1.73 m(2) +/- 9.4 measured by using iopromide clearance. The maximum deviation of MR-determined gadobutrol clearance values from iopromide clearance values was 29.2%. The mean disposition half-life of gadobutrol measured in the liver was 83.0 minutes +/- 14.2 (72.4 minutes +/- 20.2 in spleen, 92.6 minutes +/- 23.7 in renal cortex). The described MR imaging method enables absolute quantification of the GFR after routine contrast material-enhanced MR imaging.

Contrast media clearance in a single kidney measured on multiphasic helical CT: results in 50 patients without acute renal disorder.

Single kidney contrast media clearance was measured using multiphasic CT in patients without acute renal disorder. The aim of this study was to answer two questions. First, how accurate is CT in measuring contrast media clearance compared with plasma clearance? Second, is the accuracy of CT clearance measurements dependent on the timing of CT scans with respect to the contrast media injection? Fifty adult patients without acute renal disorder were included in this study. Each patient underwent CT for clinical indications. The CT protocol consisted of an unenhanced scan and three contrast-enhanced scans 45, 75, and 105 sec after starting an injection of 120 mL of iopromide using an injection rate of 3 mL/sec. All scans included both kidneys. As a reference, plasma clearance of contrast media was determined as a slope clearance by measuring iodine concentration in eight blood specimens up to 8 hr postinjection. CT clearance was calculated three times for each patient, including early CT clearance, 45-75 sec postinjection; late CT clearance, 75-105 sec postinjection; and overall CT clearance, 45-105 sec postinjection. An overall CT clearance yielded the best correlation with plasma clearance with a correlation coefficient of r = 0.84 and a regression line of y = 7.5 + 0.94x. The mean difference was -3 mL/min (95% confidence interval, -35 to 29 mL/min). CT clearance calculated from data acquired with a minimally modified diagnostic abdominal CT protocol was well correlated with the reference method in determining contrast media clearance for patients without acute renal disorders. The presented method can be used to calculate single kidney contrast media clearance in patients receiving contrast-enhanced abdominal CT for clinical indications.

Measurement of single kidney contrast media clearance by multiphasic spiral computed tomography: preliminary results

Objective. We present preliminary results of a new method (hereinafter called ‘CT-clearance’) to measure single kidney contrast media clearance by performing multiphasic helical CT of the kidneys. CT-clearance was calculated according to an extension of the Patlak–Plot. In contrast to prior investigators, who repeatedly measured a single slice, this method makes it possible to calculate single kidney clearance from at least three spiral CTs, utilizing the whole kidney volume. Methods. Spiral CT of the kidneys was performed unenhanced and about 30 and 100 s after administration of about 120 ml iopromide. Sum-density of the whole kidneys and aortic density was calculated from this data. Using this data, renal clearance of contrast media was calculated by CT-clearance in 29 patients. As reference, Serum-clearance was calculated in 24 patients by application of a modified one-exponential slope model. Information on the relative kidney function was gained by renal scintigraphy with Tc99m-MAG-3 or Tc99m-DMSA in 29 patients. Results. Linear regression analysis revealed a correlation coefficient of CT-clearance with Serum-clearance of r=0.78 with Cl (CT) [ml/min]=22.2+1.03 * Cl (serum), n=24. Linear regression of the relative kidney function (rkf) of the right kidney calculated by CT-clearance compared to scintigraphy results provided a correlation coefficient r=0.89 with rkf(CT)[%]=18.6+0.58 * rkf(scintigraphy), n=29. Conclusion. The obtained results of contrast media clearance measured by CT-clearance are in the physiological range of the parameter. Future studies should be performed to improve the methodology with the aim of higher accuracy. More specifically, better determination of the aortic density curve might improve the accuracy.

Review article: the quantification of renal function with enhanced computed tomography.

The changes with time in renal parenchymal and vascular attenuation following injection of an intravascular contrast medium can be exploited to study renal physiology in several ways. Shortly after injection, both contrast medium clearance and fractional vascular volume per unit volume of kidney can be measured on a regional basis by obtaining sequential CT data from one anatomical level and the application of a graphical analysis to the baseline subtracted CT numbers for tissue and vascular regions of interest: c(t) and b(t), respectively. By plotting the ratio c(t)/b(t) against integral of b(t)dt/b(t), both fractional vascular volume and contrast medium clearance can be estimated graphically. At later time points, a semilogarithmic plot against time of the declining attenuation of vascular or parenchymal regions of interest gives information about overall, as opposed to regional, renal function: the gradient estimates the glomerular filtration rate per unit volume of extracellular fluid. Absolute glomerular filtration rates can also be calculated with blood sampling. Although further experimental evaluation is needed, these techniques have a strong theoretical basis, and experimental work performed so far is encouraging. Possible applications of these techniques are discussed.

Iohexol clearance for renal function measurement in gynaecologic cancer patients.

To determine a valid and practical routine for glomerular filtration rate measurement in gynaecologic cancer patients. The established method, endogenous creatinine clearance, was compared to 51Cr-EDTA clearance and contrast medium clearance in 68 women with various gynaecologic carcinomas. Contrast medium clearance was determined in association with conventional urography (iohexal 300 mg I/ml, 40 ml) for evaluation of urinary tract involvement by the tumour. Automated X-ray fluorescence analysis equipment was used for the plasma analysis of iohexol and clearance calculations. Endogenous creatinine clearance and 51Cr-EDTA clearance were determined according to standard routine procedures. Simultaneous determinations of contrast medium clearance and 51Cr-EDTA clearance (n = 33), contrast medium clearance and endogenous creatinine clearance (n = 50), as well as 51Cr-EDTA clearance and endogenous creatinine clearance (n = 30) were compared. The mean differences were -2.8 (SD 6.6), -1.8 (SD 22.3), and 2.7 (SD 18.3) ml/min/1.73 m2, respectively. It is concluded that contrast medium clearance is as adequate as 51Cr-EDTA clearance for glomerular filtration rate measurement. We suggest that contrast medium clearance should replace endogenous creatinine clearance, especially in patients referred for urography.

Simultaneous Urography and Determination of Glomerular Filtration Rate

The total plasma clearance of iohexol at urography and 51Cr-EDTA was compared in 31 patients with di- or tetraparesis. A reference 51Cr-EDTA clearance was also performed 24 hours prior to the urography. The GFR was calculated from one, 2 or 4 plasma samples collected 180, 210, 240 and 270 min after the injection. An X-ray fluorescence analyzer was used for the analysis of iohexol in plasma as well as the contrast medium clearance calculations. It was shown that single or multiple sample clearance of iohexol and 51Cr-EDTA were equivalent methods for measurement of the GFR. The GFR was not affected by iohexol in a dose routinely used for urography. It was concluded that the patient comfort is improved if 51Cr-EDTA clearance is replaced by contrast medium clearance in association with urography.

Simultaneous Urography and Determination of Glomerular Filtration Rate

The total plasma clearance of iohexol at urography and 51Cr-EDTA was compared in 31 patients with di- or tetraparesis. A reference 51Cr-EDTA clearance was also performed 24 hours prior to the urography. The GFR was calculated from one, 2 or 4 plasma samples collected 180, 210, 240 and 270 min after the injection. An X-ray fluorescence analyzer was used for the analysis of iohexol in plasma as well as the contrast medium clearance calculations. It was shown that single or multiple sample clearance of iohexol and 51Cr-EDTA were equivalent methods for measurement of the GFR. The GFR was not affected by iohexol in a dose routinely used for urography. It was concluded that the patient comfort is improved if 51Cr-EDTA clearance is replaced by contrast medium clearance in association with urography.

Comparative trial of Omnipaque 350 (iohexol) and Telebrix 350 (sodium-meglumine-ioxithalamate) in left ventriculography and coronary arteriography

In a double-blind randomized trial, the hemodynamic and electrophysiologic effects of the low-osmolar nonionic contrast medium iohexol (Omnipaque) and the standard high-osmolar ionic monomer sodium-meglumine-ioxithalamate (Telebrix) at left ventricular angiography and selective coronary arteriography were evaluated. Sixty patients were divided into two groups of 30 patients; one group received Omnipaque in a dosage of 350 mgI/ml and the other group received Telebrix in a dosage of 350 mgI/ml. The Omnipaque showed significantly less effects on heart rate and myocardial contractility, and induced less electrophysiological changes than did Telebrix. However, there was a significant increase of 10% in the diameter of the left coronary artery following selective coronary injection with Telebrix, while Omnipaque induced practically no change in vessel diameter. All hemodynamic and electrophysiologic effects proved to be short-lasting. We conclude that ionic and nonionic agents are similarly efficacious in providing adequate images with minimal risk to the patient. However, the nonionic agents exert slightly more alterations in cardiac hemodynamics and in electrocardiographic intervals. The vasodilatory effect on coronary artery diameter by Telebrix may entail a more rapid clearance of contrast medium from the coronary circulation, which might be of some advantage over nonionic contrast media.

Quality of Urography and Renal Clearance of Ionic and Nonionic Contrast Media

The authors evaluated whether urographic quality correlated with patient hydration and the level of their renal function, depending on whether they received ionic or nonionic contrast media. One hundred patients with normal serum creatinine levels were randomly assigned to receive intravenous urography with either an ionic high-osmolar or a nonionic low-osmolar contrast medium. Patient hydration was evaluated by measuring urine osmolality in a sample voided just before the examination. The plasma concentration of iodine was determined in a single blood sample drawn approximately 3 hours later. From these determinations the plasma clearance of contrast medium was calculated. The urograms were assessed blindly with regard to nephrographic and pyelographic opacification, as well as overall diagnostic quality. The clearance varied between 42 and 115 mL x minutes-1 x 1.73 m-2. No systematic correlation of practical significance was found between the clearances and the urogram quality. A high urinary osmolality before the examination tended to improve quality with both media. It is not possible to assess glomerular filtration rate from nephrographic and pyelographic opacification, or from overall quality of routine urograms in patients with normal serum creatinine levels.

Renal Clearance of an Ionic High-Osmolar and a Nonionic Low-Osmolar Contrast Medium

One hundred patients with normal serum creatinine concentration underwent intravenous urography with either an ionic high-osmolar (diatrizoate) or a nonionic low-osmolar (iopamidol) contrast medium after randomization. Before injection of the contrast medium, a blood sample was drawn for determinating serum creatinine concentration, and a urine sample for measurement of urine osmolality. Using x-ray fluorescence, the plasma concentration of iodine (contrast medium) was determined on blood samples drawn approximately 3 and 4 hours after injection of the contrast medium. The glomerular filtration rate was calculated by two different formulas: one requiring only a single sample and one requiring at least two samples (standard). There were poor correlations between the standard contrast medium clearance and the serum creatinine concentration, the estimated creatinine clearance (calculated from a nomogram), as well as the urine osmolality. The 3-hour and the 4-hour single-sample values correlated well with the two-sample values for both contrast media. In patients with normal serum creatinine, the glomerular filtration rate determined by measuring the contrast medium concentration in a single plasma sample obtained at 3 hours, is almost identical to the value determined from two samples. Consequently, two samples are unnecessary.

529. (仮題) 慢性腎不全患者における非イオン性造影剤のクリアランス(第 47 回総会学術大会一般研究発表予稿)

529. (仮題) 慢性腎不全患者における非イオン性造影剤のクリアランス(第 47 回総会学術大会一般研究発表予稿)

Microvascular morphology of bone in arthrosis: Scanning electron microscopy in rabbits

The morphology of the bone microvasculature in rabbit arthrosis was studied by scanning electron microscopy (SEM) and related to changes in intraosseous pressure (IOP) and phlebographic appearance. Unilateral gonarthrosis was induced in 34 rabbits by immobilization of one knee in extension with a plastic splint for 5 weeks. Bilateral IOP recording in a subgroup of 12 rabbits demonstrated hypertension in arthrosis of 22 +/- 2.9 mmHg compared with 11 +/- 4.7 mmHg in control knees. Intraosseous phlebography in 13 rabbits showed a dilated vascular bed with prolonged clearance of contrast media. The morphology of normal microvasculature by SEM of intravascular methyl methacrylate casts in 9 rabbits was characterized by well-defined and well-demarcated sinusoids with only a few arteriovenous shunts, whereas in arthrosis substantial changes included fusion of sinusoids, leakage of cast material through the sinusoid walls, and development of numerous shunts. The study demonstrated profound microvascular morphologic changes that may reflect a vascular genesis for some of the bone changes in arthrosis.

The value of angiography in the follow-up of coronary involvement in mucocutaneous lymph node syndrome (Kawasaki disease)

From September 1976 to August 1988, 205 patients with mucocutaneous lymph node syndrome (Kawasaki disease) were evaluated; 29 were suspected of having coronary artery abnormalities because of either abnormalities on echocardiography (n = 21), congestive heart failure (n = 3), prolonged fever (n = 3) or cardiac arrest (n = 2). All 29 underwent cardiac catheterization and 22 were found to have coronary artery abnormalities. An additional 4 patients were diagnosed solely by autopsy; therefore, 26 patients (12%) in this series had coronary artery abnormalities.The clearance of contrast medium from the coronary arteries after aortography was significantly prolonged in patients with coronary artery aneurysms as compared with that in a control group (p < 0.001). All patients exhibited delayed clearance of contrast medium on the initial aortogram as compared with that on follow-up studies (p < 0.01). Of the 22 patients with angiographically documented coronary artery abnormalities, 19 had right and 20 had left coronary artery involvement; the majority had diffuse involvement of both vessels.In 15 patients who underwent follow-up catheterization 6 months to 7 years after initial study, complete resolution was observed in only 37% of affected coronary artery segments. In four patients, three of whom were asymptomatic, severely stenotic or occluded coronary artery segments were found on late catheterization. Coronary artery bypass surgery was performed in two of these patients. Echocardiography did not detect any of these stenoses. Although echocardiography is important for initial diagnosis and serial evaluation, angiography is essential to fully define the nature and extent of coronary artery lesions, particularly if stenosis is present.

Glomerular Filtration Rate Estimated after Multiple Injections of Contrast Medium during Angiography

In twenty-six patients referred for angiography, clearance of contrast medium was determined with x-ray fluorescence analysis after multiple injections of contrast medium. A formula for correction of the injected amount, which takes into consideration the different times of contrast medium injections, approximating the total injected amount into one injection, was used. A single injection clearance of 51Cr-EDTA was determined at the same time. The results showed a good correlation between the clearance of contrast medium after multiple injections and the 51Cr-EDTA clearance after a single injection (r=0.945). The correlation between contrast medium clearance calculated without correction for the different injection times, and “Cr-EDTA clearance was the same (r=0.946), due to short angiography time and rather low clearance values in our patients. It is concluded that total plasma clearance of contrast medium can easily be estimated after multiple injections. In this way patients with a risk of developing post-angiographic renal failure can be found.