Nutritional Status over Time in Hemodialysis and Peritoneal Dialysis

Abstract. Malnutrition is a risk factor for mortality in the dialysis population. So far, prospective studies comparing the time course of nutritional status in new hemodialysis (HD) and peritoneal dialysis (PD) patients have not been published. The aims of this study were to compare the time course of nutritional status in patients who were starting HD or PD and to identify the baseline determinants of that time course. In this prospective multicenter cohort study, data were collected from 3 (baseline) to 24 mo after the start of dialysis. Repeated measures ANOVA was used to establish the time course of nutritional status. Differences were adjusted for baseline characteristics. A total of 250 consecutive new patients were included: 132 started on HD, and 118 started on PD. A univariate analysis demonstrated a decrease in serum albumin (SA) in patients who started on HD and an increase in patients who started on PD. Body fat increased in PD; LBM did not change. The protein equivalent of nitrogen appearance normalized to ideal weight decreased in PD after 1 yr. In a multivariate analysis, SA at 2 yr was 2.0 g/L (95% confidence interval [CI], 0.3 to 3.8) higher in patients who started on PD compared with patients who started on HD. The increase in body fat was 3.2 kg (95% CI, 1.6 to 4.9) higher in women who started on PD than in others. Patients who had diabetes gained 2.3 kg (95% CI, 0.6 to 4.1) more fat than patients who did not have diabetes. Kt/Vureadid not affect the time course of nutritional status, but a higher Ktureawas associated with a higher SA at 24 mo. Nutritional status at the start of dialysis, gender, and diabetic status might be considered in making the choice for dialysis modality. Furthermore, providing a higher Ktureamay improve protein metabolism.

Anthropometry-based equations overestimate the urea distribution volume in hemodialysis patients

BACKGROUND

Protein intake in hemodialysis patients can be estimated indirectly from the protein equivalent of total nitrogen appearance (PNA) during the interdialytic period. A reliable estimate of the patient's urea distribution volume (UDV) is required to assess protein intake from PNA values. UDV values are derived frequently from simple anthropometric equations.

METHODS

UDV values based on anthropometric methods were compared with UDV values determined by direct dialysate quantitation (DDQ) in 54 stable chronic hemodialysis patients. The anthropometric methods included the following: the Watson equations (WAT), a fixed proportion of postdialysis body weight, 58% for males and 55% for females (% body wt), and skinfold thickness measurements (SFT). Postdialysis blood samples were drawn at 15-minutes postdialysis.

RESULTS

UDV(WAT) and UDV(SFT) overestimated UDV(DDQ) by about 8 L [limits of agreement (LOA): 2.6 to 14.2 L] in males and about 6 L (LOA: -0.8 to 12.4 L) in females. The overestimation by UDV(%BW) was even larger: 10.5 L (LOA: 2.0 to 19.0 L) in males and 11.1 L (LOA: 2.1 to 20.1 L) in females. The difference between UDV(%BW) and UDV(DDQ) correlated with the percentage of body fat (r = 0.57) and body mass index (r = 0.48). In a subgroup of seven patients, UDV was also determined by dilution (DIL) of the stable isotope [(13)C]urea. UDV(WAT) and UDV(%BW) overestimated UDV(DIL) significantly. In contrast, UDV(DDQ) was significantly smaller than UDV(DIL), even after correction for incomplete postdialysis equilibration. PNA values calculated using the various UDV estimates were compared with dietary protein intake (DPI) assessed from food records. PNA(DDQ) (61 +/- 10 g/day) did not differ significantly from DPI (63 +/- 13 g/day), but the agreement in individual patients varied considerably (LOA, -24 to 20 g/day). Anthropometric-based PNA values overestimated DPI by 8 to 16 g/day.

CONCLUSIONS

Anthropometry-based equations overestimate UDV values in hemodialysis patients, leading to an overestimation of PNA values. Although PNA measurements by DDQ appear to be more reliable for assessing protein intake, PNA(DDQ) values should be interpreted with caution in individual hemodialysis patients.

Relating protein intake to nutritional status in haemodialysis patients: how to normalize the protein equivalent of total nitrogen appearance (PNA)?

BACKGROUND

The protein equivalent of total nitrogen appearance (PNA) is assumed to be a reliable estimate of dietary protein intake in haemodialysis patients. Protein requirements are related to body size. In order to standardize PNA to individual differences in body size, PNA is normalized to various terms related to the patient's body weight. It is not clear which is the most appropriate method to normalize PNA.

METHODS

We calculated five commonly used variants of normalized PNA and related them to indices of nutritional status in 57 stable chronic haemodialysis patients, 57 +/- 15 (mean +/- SD) years of age. PNA, determined by direct dialysate quantification, was normalized to actual post-dialysis dry body weight (DBW), normal body weight (DBWnormal), lean body mass (LBM), normal lean body mass (LBMnormal), and 'normalized' body weight (N). Nutritional status was assessed using an index of nutrition composed of anthropometry derived parameters and plasma albumin concentration.

RESULTS

PNA(DBW) (0.85 +/- 0.14 g/kg/d) tended to be higher than PNA(DBWnormal) (0.81 +/- 0.14 g/kg/d). PNA(LBM) (1.17 +/- 0.19 g/kg/d) did not differ from PNA(LBMnormal) (1.19 +/- 0.21 g/kg/d). PNA(N) (1.06 +/- 0.14 g/kg/d) was significantly higher than PNA(DBW) and PNA(DBWnormal), but lower than PNA(LBM) and PNA(LBMnormal). Actual PNA (61 +/- 13 g/d) correlated significantly with DBW (r=0.52) and LBM (r=0.63) indicating that large patients eat more protein. Interestingly, actual PNA correlated with plasma albumin (r=0.33) and with the overall index of nutrition (r=0.27) as well. PNA(DBW) correlated negatively with relative DBW (r=-0.32), expressed as a percentage of normal values, indicating that PNA(DBW) is relatively high in underweight patients. In contrast, PNA(DBWnormal) correlated positively with all nutritional parameters as well as with the overall index of nutrition (r=0.33). PNAN and PNA(LBM) did not correlate with the nutritional status, but PNA(LBMnormal) correlated positively with relative DBW (r=0.50) and with overall nutritional status (r=0.34). PNA(DBWnormal) and PNA(LBMnormal) in well-nourished patients showed overlap with the values in patients with evident malnutrition, despite the positive correlation of the normalized PNA values with nutritional status.

CONCLUSIONS

Normalizing PNA by DBWnormal and LBMnormal appeared to be the most appropriate method to standardize protein intake in haemodialysis patients. Since actual PNA is the purest estimate of protein intake that correlated with nutritional status, we recommend to evaluate actual PNA as well in studies that relate protein intake to patient outcome.

Assessing dialysis adequacy and dietary intake in the individual hemodialysis patient

BACKGROUND

Urea kinetic modeling (UKM) and food records are widely used to assess the dialysis adequacy. Clinicians use these methods in individual patients to decide whether the dialysis prescription should be adjusted. We determined the variation in UKM parameters and dietary intake within individual patients in order to determine the required number of UKM measurements, and the number of food recording days to assess dialysis adequacy and dietary intake reliably.

METHODS

Session-to-session variation in urea reduction ratio (URR), Kt/V, urea distribution volume (UDVDDQ), and protein catabolic rate (PCR) was determined during three mid-week dialysis sessions in 50 stable hemodialysis patients on three-times per week hemodialysis with a Kt/V of 0.98 +/- 0.13 (mean +/- SD). The dialysis prescription was kept constant. The day-to-day variation in dietary protein intake (DPI) and dietary energy intake (DEI) was determined from seven-day food records. The 90th percentile value of the coefficient of variation (CV) was used to determine the number of measurements.

RESULTS

The variation in URR [CV, 2.4% (0.3 to 9.5) median (range)] and in Kt/V [CV, 4.0% (0.6 to 11.6)] was small in the majority of the patients. The variation in UDVDDQ [CV, 4.9% (0.3 to 25.7)] and PCR [CV, 9.3% (0.8 to 28.5)] was considerably larger. The variation in DPI [CV, 17.3% (8.4 to 64.0)] was larger than that in DEI [CV, 12.9% (5.0 to 33.0)]. To assess the URR within +/- 10% of its true value, the average of two measurements was required. Reliable assessment of Kt/V required three measurements. URR and Kt/V could be assessed reliably from a single measurement in 86 and 66% of the patients, but we were not able to distinguish these patients beforehand. Reliable estimation of UDVDDQ required six measurements. The required number of measurements for PCR, DPI, and DEI was determined using a precision of +/- 20%. To assess PCR reliably, three measurements were needed. Estimation of DPI and DEI required seven and five food recording days, respectively.

CONCLUSIONS

The session-to-session variation in URR and Kt/V is small in stable hemodialysis patients. Nevertheless, the averaged value of two to three measurements is required to assess the dose of dialysis reliably. Assessment of dietary intake requires at least three PCR measurements or food records for at least one week. Basing clinical decisions on a single dialysis adequacy assessment is an unjustified practice that should be abandoned.

Erythrocyte Na+/Li+ countertransport and Na+/K+-2Cl- co-transport measurement in essential hypertension: useful diagnostic tools or failure? A meta-analysis of 17 years of literature

1.A meta-analysis of 17 years of literature on erythrocyte Na+/Li+ countertransport (NLCT) and Na+/K+ co-transport (COT) measurements in relation to essential hypertension is presented. The analysis aimed to answer two questions: (i) Which clinical or laboratory variables influence NLCT and COT flux values? (ii) How useful are NLCT and COT measurements as a diagnostic aid in essential hypertension?2. Regression analysis was performed on the mean flux values and relevant clinical and laboratory values. Studies in both normotensive and hypertensive subjects were stratified for variables which showed a significant association with the measured flux. For hypertensive subjects the studies were also stratified for medication. Means of strata were calculated after weighing the mean of a study by the inverse of its own variance and were compared in normotensive as well as hypertensive subjects using a t-test.3.The analysis did not demonstrate systematic effects of laboratory variables for either NLCT or COT. It was found that essential hypertension, family history of hypertension, gender and antihypertensive medication are main determinants for the flux values of both transport systems. After stratification for these determinants, significant differences in weighed mean flux values between normotensive and hypertensive subjects were demonstrated. However, these differences are much smaller than the variance in the weighed mean flux values, suggesting the existence of other unknown variables that strongly affect the flux rates.4.In conclusion, NLCT and COT measurements cannot be of diagnostic use in essential hypertension.

Determination of urea kinetics by isotope dilution with [13C]urea and gas chromatography-isotope ratio mass spectrometry (GC-IRMS) analysis

1. Stable urea isotopes can be used to study urea kinetics in humans. The use of stable urea isotopes for studying urea kinetic parameters in humans on a large scale is hampered by the high costs of the labelled material. We devised a urea dilution for measurement of the distribution volume, production rate and clearance of urea in healthy subjects and renal failure patients using the inexpensive single labelled [13C]urea isotope with subsequent analysis by headspace chromatography-isotope ratio MS (GC-IRMS) of the [13C]urea enrichment. 2. The method involves measurement of the molar percentage excess of [13C]urea in plasma samples taken over a 4 h period after an intravenous bolus injection of [13C]urea. During the sample processing procedure, the plasma samples together with calibration samples containing a known molar percentage excess of [13C]urea are acidified with phosphoric acid to remove endogenous CO2, and are subsequently incubated with urease to convert the urea present in the plasma samples into CO2. The 13C enrichment of the generated CO2 is analysed by means of GC-IRMS. This method allows measurement of the molar percentage excess of [13C]urea to an accuracy of 0.02%. 3. Reproducibility studies showed that the sample processing procedure [within-run coefficient of variation (CV) < 2.8% and between-run CV < 8.8%] and the GC-IRMS analysis (within-day CV < 1.3% and between-day CV < 1.3%) could be repeated with good reproducibility. 4. In clinical urea kinetic studies in a healthy subject and in a renal failure patient without residual renal function, reproducible values of the distribution volume, production rate and clearance of urea were determined using minimal amounts of [13C]urea (25-50 mg). 5. Because only low [13C]urea enrichments are needed in this urea dilution method using GC-IRMS analysis, the costs of urea kinetic studies are reduced considerably, especially in patients with renal failure.

[Dialysis an the elderly]

In the Netherlands, only one third of the patients of 65 years or older with terminal renal failure are currently admitted to dialysis treatment. Dialysis in older patients frequently leads to adequate survival and good subjective quality of life. In other words, age as such is not a contraindication to dialysis. Haemodialysis and peritoneal dialysis have about the same clinical results in older patients, as is the case in younger age groups; the choice depends on patient-linked factors and on the patient's preference. It is to be expected that in a number of years the majority of dialysis patients will be aged 65 years or older.

Renal 131I-hippurate clearance overestimates true renal blood flow in the instrumented conscious dog

We evaluated renal 131I-hippurate clearance (ERPFhip) as a measure of renal blood flow (RBF) in chronically instrumented conscious dogs. When adjusted for renal hippurate extraction (Ehip, 0.77 +/- 0.01) and hematocrit (Hct, 39.7 +/- 1%), calculated RBFhip (656 +/- 37 ml/min) markedly exceeded renal blood flow measured with renal artery blood flow probes (RBFprobe, 433 +/- 27 ml/min). The discrepancy could not be explained by flow probe calibration, because in vivo comparison of flow probe values with renal venous outflow showed only a slight underestimation of renal blood flow (slope 0.93, 95% confidence interval 0.89-0.97). Redistribution of hippurate from erythrocytes into renal venous plasma during or shortly after blood sampling led to an underestimation of Ehip by 4 +/- 1% and thus could only explain a small part of the difference. Extrarenal hippurate clearance was excluded, because the amount of 131I-hippurate cleared from plasma equaled that appearing in the urine (303 +/- 17 and 307 +/- 17 ml/min). Applying these corrections, we found that RBFhip still exceeded RBFprobe by 37 +/- 3%. These data indicate that renal blood flow measured by the hippurate clearance technique markedly overestimates true renal blood flow. Because other errors were excluded, a combination of sampling of nonrenal blood and intrarenal hippurate extraction from erythrocytes might play a role.

Angiotensin-converting enzyme inhibition-induced changes in hippurate renography and renal function in renovascular hypertension

We studied the mechanism of angiotensin-converting enzyme (ACE) inhibition-induced changes in hippurate renography of the poststenotic kidney.

METHODS

Ten male mongrel dogs, six with unilateral and four with bilateral renal artery stenosis, were equipped with renal artery blood flow probes and catheters in the aorta, atrium and both renal veins.

RESULTS

Enalaprilat (10 mg intravenously) in conscious dogs with renal artery stenoses produced changes in all stenotic (n = 11) but not in nonstenotic kidney 123I-hippurate renograms (n = 6). Renographic changes correlated significantly with initiation of intrarenal 131I-hippurate retention, a decrease in mean arterial pressure (MAP), renal extraction of 131I-hippurate and 125I-iothalamate (r = 0.68, r = 0.62, r = 0.84, r = 0.83, respectively) but not with renal blood flow changes (r = 0.34). Furthermore, renal uptake of 131I-hippurate and 125I-iothalamate decreased in stenotic kidneys with a grade II renogram (-52 +/- 11% and -79 +/- 6%, respectively). Iodine-125-hippurate autoradiograms of stenotic kidneys during ACE inhibition showed tracer retention mainly in the proximal tubular cells. Results during osmotic diuresis supported our findings.

CONCLUSION

Angiotensin-converting enzyme inhibition-induced hippurate retention curves of poststenotic kidneys appear to result from a sequence of events. A decrease in MAP combined with efferent vasodilation leads to a decrease in intraglomerular capillary pressure. This decrease in pressure causes a decrease in glomerular filtration rate and proximal tubular urine flow. This decrease in turn hampers tubular hippurate transit and transport across the luminal membrane, leading to intrarenal hippurate retention and, in more severe cases, decreased renal hippurate uptake.

Drug-induced changes in renal hippurate clearance as a measure of renal blood flow

We studied the accuracy of the plasma 131I-hippurate clearance technique to monitor drug-induced changes in renal blood flow (RBF) by comparing it to a flow probe technique in six conscious, chronically instrumented dogs. Placebo caused no change in RBF, either established by hippurate clearance (ERPFhip) or by renal blood flow probe (RBFprobe). Enalaprilate induced a rise in ERPFhip and RBFprobe (+26 +/- 5 and 44 +/- 12%), as did dopamine (+16 +/- 4 and +33 +/- 5%). Intravenous infusion of norepinephrine induced a rise in ERPFhip (+2 +/- 6%, NS) and in RBFprobe (+18 +/- 3%), as did nitroprusside (+14 +/- 4% and +13 +/- 6%, NS). Indomethacin induced a fall in ERPFhip (-8 +/- 2%) and in RBFprobe (-7 +/- 3%, NS), as did angiotensin II (-19 +/- 1 and -26 +/- 3%). Renal hippurate extraction (Ehip) was affected by enalaprilate, dopamine, and angiotensin II (-5 +/- 2, -7 +/- 1, and +5 +/- 2%, respectively). Hematocrit (Hct) was affected by dopamine, norepinephrine, and nitroprusside (+2 +/- 1, +6 +/- 1, and -6 +/- 2%, respectively). Drug-induced changes in ERPFhip correlated well with changes in RBFprobe (r = 0.902, P < 0.01). Changes in Ehip did not independently affect this relation, whereas changes in Hct did: delta RBF(% of baseline) = 1.529 x delta ERPFhip(% of baseline) + 1.296 x delta Hct(% of baseline). These data indicate that drug-induced changes in plasma hippurate clearance can, even when changes in renal hippurate extraction are unknown, be used as a reliable indicator of changes in renal blood flow if changes in hematocrit are taken into account.

Relationship between blood pressure during haemodialysis and ambulatory blood pressure in between dialyses

BACKGROUND

Ambulatory blood pressure measurements in haemodialysis patients are relevant in view of the high cardiovascular morbidity and mortality in chronic haemodialysis patients.

METHODS

Twelve normotensive patients were studied from the beginning of one dialysis until the end of the next (mean 64 h, SD 19 h) using a Spacelabs oscillometric blood-pressure recorder.

RESULTS

A circadian blood pressure rhythm was present in six of the 12 patients. In seven patients the lowest pressure recorded (including the dialysis sessions) occurred 5-6 h after dialysis (late post-dialysis dip). Blood pressure did not increase sharply in the hours before dialysis although it increased slightly in the interdialytic interval as a whole, at a mean rate of 5.6 mmHg per 24 h (SD 4.1, P < 0.001). We could not find a blood pressure measurement during dialysis (or combination of measurements) which reliably reflects interdialytic blood pressure: the 95% confidence intervals were 25 mmHg or higher.

CONCLUSION

Ambulatory blood pressure measurements are needed for adequate monitoring of the control of blood pressure in haemodialysis patients.

Determination of protein catabolic rate in patients on chronic intermittent hemodialysis: urea output measurements compared with dietary protein intake and with calculation of urea generation rate

We assessed the agreement between different methods of determining protein catabolic rate (PCR) in hemodialysis patients and the possible influence of postdialysis urea rebound and the length of the interdialytic interval on the PCR determination. Protein catabolic rate derived from measured total urea output was compared with recorded daily protein intake (DPI) and calculated urea generation rate (G), calculated by the interdialytic increase in serum urea and an estimated urea distribution volume using either the Watson equation or 58% of postdialysis body weight, and by single-pool urea kinetic modelling. In 16 patients PCR derived from calculated G by fixed urea distribution volume showed a significant decrease with blood samples obtained 10 minutes after dialysis onward as compared with immediately after dialysis, leading to an approximately 6% decrease at 60 minutes. Protein catabolic rate values derived from blood samples taken 15 to 60 minutes after dialysis were not significantly different. Urea kinetic modelling led to a significant increase in calculated PCR with samples from 5 minutes after dialysis onward and a total increase by 11.5% at 60 minutes. Different methods for determining PCR were compared in 13 clinically stable outpatients treated with conventional hemodialysis on cellulose acetate membrane dialyzers during 1 week. The mean PCR calculated from measured total urea output was 61.3 g/24 hr (range, 43.7 to 83.2 g/24 hr). Assessment of DPI as compared with PCR calculated from measured total urea output was lower by 7.5% (95% confidence intervale [CI], 1.4 to 17.5).(ABSTRACT TRUNCATED AT 250 WORDS)

GC-MS determination of ratios of stable-isotope labelled to natural urea using [13C15N2]urea for studying urea kinetics in serum and as a means to validate routine methods for the quantitative assay of urea in dialysate

A GC-MS determination of urea in serum or spent dialysate is described, using 13C15N2-labelled urea and assaying the area ratio of labelled to natural urea by mass fragmentographic monitoring of fragments m/e 153 and 156, after its eventual conversion into the trimethylsilylether-derivative of 2-hydroxypyrimidine. The procedure can be successfully applied in the follow-up of the disappearance of labelled urea in serum after intravenous injection in man, enabling kinetic parameters of urea to be established, e.g. for purposes of studying the effectiveness of dialysis procedures. Furthermore the method can be used for validation of routine methods for measuring urea in other fluids, in particular dialysate. Examples are given of both applications of the GC-MS method described.

Differences in erythrocyte sodium transport between human plasma and artificial medium: the role and character of sodium efflux and influx stimulating plasma factors

The main objective of this study was to further characterize the plasma factor(s) which stimulate sodium efflux from erythrocytes, which we reported previously. Dialysis of plasma against an artificial medium using membranes with varying molecular mass cut-off points revealed relative molecular mass(es) of the factor(s) of 100-1000 Da. The factor(s) could be absorbed on Dowex at pH 1.5 and Amberlite at pH 11.0, indicating 'Zwitterionic' character. They are hydrophilic and resistant to acid hydrolysis. These characteristics and direct measurements of contents made amino acids likely candidates for the efflux stimulating properties of the factor(s). Indeed, plasma amino acids added to artificial medium could abolish the sodium efflux difference between plasma and the artificial medium. The efflux stimulating effect of amino acids appeared not to be the result of sodium influx stimulation. A coincident finding was that plasma also contains dialyzable sodium influx stimulating factor(s) which are not amino acids.

Changes in renal function induced by ACE-inhibition in the conscious two-kidney, one-clip Goldblatt hypertensive dog

In order to study why the diagnostic sensitivity of 123I-hippurate renography for a renal artery stenosis is improved by angiotensin converting enzyme (ACE-) inhibition we used the model of the conscious chronically instrumented two-kidney, one-clip Goldblatt hypertensive dog. Urine flow (UV), renal blood flow (RBF), glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured (with constant infusion of 125I-iothalamate and 131I-hippurate, respectively) for both kidneys separately before and after a bolus injection of a mild unilateral renal artery stenosis (approximately 30% reduction of RBF). During ACE-inhibition, there were remarkable falls in poststenotic GFR (from 37 +/- 5 to 4 +/- 2 ml/min, p less than 0.05), ERPF (from 111 +/- 13 to 21 +/- 10 ml/min, p less than 0.05) and UV (from 0.86 +/- 0.15 to 0.075 +/- 0.045 ml/min, p less than 0.05), whereas RBF of the poststenotic kidney slightly increased (from 193 +/- 18 to 237 +/- 27 ml/min, p less than 0.05). The concentration of hippurate and thalamate in the blood remained remarkably constant while the excretion of the tracers by the poststenotic kidney diminished and renal retention of 123I-hippurate was seen on the renogram. In 2 dogs, the experiments were repeated during mannitol infusion. In that situation, there was a much smaller decrease of poststenotic UV and GFR whereas ERPF even showed a small increase comparable to the RBF changes.(ABSTRACT TRUNCATED AT 250 WORDS)

The mechanism and diagnostic value of angiotensin I converting enzyme inhibition renography

The effect of angiotensin converting enzyme (ACE) inhibition on the sensitivity of radionuclide renography in the diagnosis of a unilateral renal artery stenosis was tested both in a conscious dog model and in the human situation. ACE inhibition (10 mg enalaprilic acid, intravenously) markedly improved the sensitivity of [123I]hippuran renography in 10 renovascular hypertensive dogs with a mild to moderate unilateral renal artery stenosis from 50 to 100%. This improved sensitivity was due to an ACE-inhibition-induced delayed tracer handling at the stenotic side without an appreciable change in the renographic curve at the contralateral side. A similar phenomenon was observed in 15 hypertensive patients with an angiographically proved unilateral renal artery stenosis. Both [123I]hippuran and 99mTc-diethylenetriaminepentaacetic acid (DTPA) handling was delayed on the stenotic side after oral enalapril treatment. However, only a moderate increase in sensitivity was observed comparing control renograms to ACE-inhibition renograms: from 87 to 93% for hippuran, and from 60 to 86% for DTPA. Eight of these 15 patients underwent either surgery or angioplasty resulting in a successful correction of the stenosis. Hypertension was more or less cured in five patients. Each of these patients had shown an ACE-inhibition-induced change in the renogram at the stenotic side, suggesting that such a response may predict the curability of the hypertension. However, of the three patients that showed no blood pressure change upon successful revascularization, two showed a positive ACE-inhibition renogram. In conclusion, in an ideal setting as obtained in animal experiments, ACE inhibition improves the sensitivity of renographic studies to 100%. However, its value in the clinical setting needs more standardization.