Estimation of glomerular filtration rate in a pediatric population using non-contrast kidney phase contrast magnetic resonance imaging

BACKGROUND

Glomerular filtration rate (GFR) is a key measure of kidney function but often inaccurately ascertained by serum creatinine and cystatin C in pediatrics. In this pilot trial, we evaluated the relationship between GFR calculated by using phase-contrast MRI (PC-MRI) biomarkers and GFR by 125I-iothalamate clearance in youth undergoing bone marrow transplantation (BMT).

METHODS

A total of twenty-one pediatric BMT candidates (8-21 years of age) were recruited for a research kidney PC-MRI. After completion of 125I-iothalamate clearance, same-day PC-MRI measurements were completed of the kidney circulation without a gadolinium-based contrast agent. MRI included a non-contrast balanced-SSFP-triggered angiography to position ECG-gated breath-held 2D PC-MRI flow measurements (1.2 × 1.2 × 6 mm3). A multivariate model of MRI biomarkers estimating GFR (GFR-MRI) was selected using the elastic net approach.

RESULTS

The GFR-MRI variables selected by elastic net included average heart rate during imaging (bpm), peak aorta flow below the kidney artery take-offs (ml/s), average kidney artery blood flow, average peak kidney vein blood flow, and average kidney vein blood flow (ml/s). The GFR-MRI model demonstrated strong agreement with GFR by 125I-iothalamate (R2 = 0.65), which was stronger than what was observed with eGFR by the full age spectrum and Chronic Kidney Disease in Children under 25 (CKiD U25) approaches.

CONCLUSION

In this pilot study, noninvasive GFR-MRI showed strong agreement with gold standard GFR in youth scheduled for BMT. Further work is needed to evaluate whether non-contrast GFR-MRI holds promise to become a superior alternative to eGFR and GFR by clearance techniques. A higher resolution version of the Graphical abstract is available as Supplementary information.

Association of Abdominal Arterial Calcification Score with Patients' Survival and Kidney Allograft Function after Kidney Transplant

BACKGROUND

Abdominal arterial calcification (AAC) is common among candidates for kidney transplant. The aim of this study is to correlate AAC score value with post-kidney transplant outcomes.

METHODS

We modified the coronary calcium score by changing the intake data points and used it to quantitate the AAC. We conducted a retrospective clinical study of all adult patients who were transplanted at our center, between 2010 and 2013, and had abdominal computed tomography scan done before transplantation. Outcomes included mortality, pulse pressure (PP) measured by 24 h ambulatory blood pressure monitoring system, and kidney allograft function measured by iothalamate clearance.

RESULTS

For each 1000 increase of AAC score value, there is an associated 1.05 increase in the risk of death (95% CI 1.02, 1.08) (p < 0.001). Overall median AAC value for all patients was 1784; Kaplan-Meier curve showed reduced survival of all-cause mortality for patients with AAC score value above median and reduced survival among patients with cardiac related mortality. The iothalamate clearance was lower among patients with total AAC score value above the median. Patients with abnormal PP (< 40 or > 60 mmHg) had an elevated median AAC score value at 4319.3 (IQR 1210.4, 11097.1) compared to patients with normal PP with AAC score value at 595.9 (IQR 9.9, 2959.9) (p < 0.001).

CONCLUSION

We showed an association of AAC with patients' survival and kidney allograft function after kidney transplant. The AAC score value could be used as a risk stratification when patients are considered for kidney transplant.

Analysis of Estimated and Measured Glomerular Filtration Rates and the CKD-EPI Equation Race Coefficient in the Chronic Renal Insufficiency Cohort Study

This diagnostic/prognostic study examines the estimated glomerular filtration rates (eGFR) and iothalamate clearance glomerular filtration rates (iGFR) and the Chronic Kidney Disease-Epidemiology (CKD-EPI) equation race coefficient in the Chronic Renal Insufficiency Cohort study.

A New Panel-Estimated GFR, Including β2-Microglobulin and β-Trace Protein and Not Including Race, Developed in a Diverse Population

RATIONALE AND OBJECTIVE

Glomerular filtration rate (GFR) estimation based on creatinine and cystatin C (eGFRcr-cys) is more accurate than estimated GFR (eGFR) based on creatinine or cystatin C alone (eGFRcr or eGFRcys, respectively), but the inclusion of creatinine in eGFRcr-cys requires specification of a person's race. β2-Microglobulin (B2M) and β-trace protein (BTP) are alternative filtration markers that appear to be less influenced by race than creatinine is.

STUDY DESIGN

Study of diagnostic test accuracy.

SETTING AND PARTICIPANTS

Development in a pooled population of 7 studies with 5,017 participants with and without chronic kidney disease. External validation in a pooled population of 7 other studies with 2,245 participants.

TESTS COMPARED

Panel eGFR using B2M and BTP in addition to cystatin C (3-marker panel) or creatinine and cystatin C (4-marker panel) with and without age and sex or race.

OUTCOMES

GFR measured as the urinary clearance of iothalamate, plasma clearance of iohexol, or plasma clearance of [51Cr]EDTA.

RESULTS

Mean measured GFRs were 58.1 and 83.2 mL/min/1.73 m2, and the proportions of Black participants were 38.6% and 24.0%, in the development and validation populations, respectively. In development, addition of age and sex improved the performance of all equations compared with equations without age and sex, but addition of race did not further improve the performance. In validation, the 4-marker panels were more accurate than the 3-marker panels (P < 0.001). The 3-marker panel without race was more accurate than eGFRcys (percentage of estimates greater than 30% different from measured GFR [1 - P30] of 15.6% vs 17.4%; P = 0.01), and the 4-marker panel without race was as accurate as eGFRcr-cys (1 - P30 of 8.6% vs 9.4%; P = 0.2). Results were generally consistent across subgroups.

LIMITATIONS

No representation of participants with severe comorbid illness and from geographic areas outside of North America and Europe.

CONCLUSIONS

The 4-marker panel eGFR is as accurate as eGFRcr-cys without requiring specification of race. A more accurate race-free eGFR could be an important advance.

Creatinine-Based and Cystatin C-Based GFR Estimating Equations and Their Non-GFR Determinants in Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

eGFR equations have been evaluated in kidney transplant recipients with variable performance. We assessed the performance of the Modification of Diet in Renal Disease equation and the Chronic Kidney Disease Epidemiology Collaboration equations on the basis of creatinine, cystatin C, and both (eGFR creatinine-cystatin C) compared with measured GFR by iothalamate clearance and evaluated their non-GFR determinants and associations across 15 cardiovascular risk factors.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A cross-sectional cohort of 1139 kidney transplant recipients >1 year after transplant was analyzed. eGFR bias, precision, and accuracy (percentage of estimates within 30% of measured GFR) were assessed. Interaction of each cardiovascular risk factor with eGFR relative to measured GFR was determined.

RESULTS

Median measured GFR was 55.0 ml/min per 1.73 m(2). eGFR creatinine overestimated measured GFR by 3.1% (percentage of estimates within 30% of measured GFR of 80.4%), and eGFR Modification of Diet in Renal Disease underestimated measured GFR by 2.2% (percentage of estimates within 30% of measured GFR of 80.4%). eGFR cystatin C underestimated measured GFR by -13.7% (percentage of estimates within 30% of measured GFR of 77.1%), and eGFR creatinine-cystatin C underestimated measured GFR by -8.1% (percentage of estimates within 30% of measured GFR of 86.5%). Lower measured GFR associated with older age, women, obesity, longer time after transplant, lower HDL, lower hemoglobin, lower albumin, higher triglycerides, higher proteinuria, and an elevated cardiac troponin T level but did not associate with diabetes, smoking, cardiovascular events, pretransplant dialysis, or hemoglobin A1c. These risk factor associations differed for five risk factors with eGFR creatinine, six risk factors for eGFR Modification of Diet in Renal Disease, ten risk factors for eGFR cystatin C, and four risk factors for eGFR creatinine-cystatin C.

CONCLUSIONS

Thus, eGFR creatinine and eGFR creatinine-cystatin C are preferred over eGFR cystatin C in kidney transplant recipients because they are less biased, more accurate, and more consistently reflect the same risk factor associations seen with measured GFR.

Renal function equations before and after living kidney donation: a within-individual comparison of performance at different levels of renal function

BACKGROUND AND OBJECTIVES

The Modification of Diet in Renal Disease (MDRD) study equation and the Cockcroft-Gault (CG) equation perform poorly in the (near-) normal range of GFR. Whether this is due to the level of GFR as such or to differences in individual characteristics between healthy individuals and patient with chronic kidney disease (CKD) is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We evaluated the performance of MDRD, CG per BSA (CG/(BSA)) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations compared with measured GFR (mGFR; I-iothalamate) at 4 months before and 2 months after donation in 253 consecutive living kidney donors.

RESULTS

mGFR declined from 103 ± 15 to 66 ± 11 ml/min per 1.73 m(2) after donation. All equations underestimated mGFR at both time points. Arithmetic performance analysis showed improved performance after donation of all equations, with significant reduction of bias after donation. Expressed as percentage difference, mGFR-estimated GFR (eGFR) bias was reduced after donation only for CG/(BSA). Finally, in 295 unselected individuals who were screened for donation, mGFR was below the cutoff for donation of 80 ml/min per 1.73 m(2) in 19 individual but in 166, 98, and 74 for MDRD, CDK-EPI, and CG/(BSA), respectively.

CONCLUSIONS

A higher level of GFR as such is associated with larger absolute underestimation of true GFR by eGFR. For donor screening purposes, eGFR should be interpreted with great caution; when in doubt, true GFR should be performed to prevent unjustified decline of prospective kidney donors.

Elevated vascular endothelial growth factor levels are associated with aortopulmonary collateral vessels in patients before and after the Fontan procedure

BACKGROUND

Aortopulmonary collaterals (APCs) are frequently observed before and after the Fontan procedure. However, the mechanism of the development of APCs is unknown. We hypothesized that one or several antiangiogenic and/or angiogenic growth factors might play a role in the development of APCs.

METHODS

Eighty-five patients were enrolled and divided into 3 groups (Fontan group: 30 patients after the Fontan procedure, cyanotic group: 29 patients with cyanotic heart disease, and control group: 26 patients with cyanotic heart disease after biventricular repair). We measured basic fibroblast growth factor, vascular endothelial growth factor (VEGF), hepatocyte growth factor, and endostatin at catheterization. Angiographic evaluation for the presence of APCs using a 4-point scale (grade 1: absent APCs, > or = grade 2: significantly present APCs) was performed, and the relation of the serum levels of these factors to the presence of APCs was assessed.

RESULTS

The grade of APCs significantly increased in the Fontan group, but it decreased in the control group. The serum VEGF levels were higher in the Fontan group (280 +/- 174 pg/mL) and the cyanotic group (302 +/- 245 pg/mL) than in the control group (111 +/- 91 pg/mL) (P = .0004), and they were higher in patients with APCs (383 +/- 204 pg/mL) than in those without APCs (115 +/- 65 pg/mL) (P < .0001). There was no significant difference in the serum basic fibroblast growth factor, hepatocyte growth factor, and endostatin levels between the 3 groups.

CONCLUSIONS

Aortopulmonary collaterals increase after the Fontan procedure. Serum VEGF levels are associated with the presence of APCs. Vascular endothelial growth factor may play a role in the development of APCs in patients with cyanotic heart disease and after the Fontan procedure.

Preemptive Living Donor Kidney Transplantation: Do the Benefits Extend to All Recipients?

BACKGROUND

Preemptive kidney transplantation (prior to the institution of dialysis) avoids the morbidity and mortality of dialysis; however, detailed studies of high-risk patients are lacking. The aim of the current study was to compare recent outcomes of preemptive (P) versus nonpreemptive (NP) living donor kidney transplantation with an emphasis on high-risk recipients.

METHODS

We retrospectively analyzed 438 sequential solitary living donor kidney transplants at our institution between January 2000 and December 2002. In all, 44% were preemptive. NP recipients were dialyzed for 21+/-36 months (range 1-312 months).

RESULTS

Overall, three-year patient survival was similar in the NP and P groups. When stratified by diabetes and age >65 years, P and NP recipients again showed similar survival. Death-censored three-year graft survival was better in the P group (97% vs. 90%, P=0.01), but was not significant by multivariate analysis. Delayed graft function was more frequent in NP vs. P (10% vs. 4%; P=0.01), but other early complications were similar including: acute rejection, 16% vs. 11% (P=0.11); primary nonfunction, 3% vs. 2% (P=0.38); and wound complications, 19% vs. 17% (P=0.54). Glomerular filtration rate at three years was similar in the two groups (53+/-23 preemptive vs. 52+/-20 ml/min nonpreemptive; P=0.37).

CONCLUSION

With prompt referral and workup, preemptive kidney transplantation can be performed successfully in a large percentage of renal allograft recipients. Preemptive transplantation avoids unnecessary dialysis and should be emphasized as initial therapy for many patients with end-stage renal disease.

Estimating absolute glomerular filtration rate in children

Normal values of glomerular filtration rate (GFR) in children are often expressed in a value adjusted to adult ideal body surface area. These values work well for many clinical situations, but in infants and children, especially those with atypical body mass, they may not accurately reflect renal function. Most body composition values in children are expressed in developmentally appropriate ranges. Absolute GFR (ml/min) also changes during childhood increasing rapidly in infancy and then gradually with age and body size. Previously, we developed a bedside equation for estimating GFR (ml/min) in children that accounted for changes with age and body size, and which correlated well with steady-state cold iothalamate GFR (ml/min) measurements: GFR (ml/min) = k(*)sqrt[(age(months) + 6)*wt (kg)/serum Cr (mg/dl)], where k=0.95 for females and 1.05 for males. In the present study GFR (ml/min) measured by iothalamate infusion was compared by correlation analysis with estimates calculated from the above equation in 566 children. This equation provides clinicians with a simple bedside method to estimate absolute GFR (ml/min).

Renal interaction between itraconazole and cimetidine

Renal drug interactions can result from competitive inhibition between drugs that undergo extensive renal tubular secretion by transporters such as P-glycoprotein (P-gp). The purpose of this study was to evaluate the effect of itraconazole, a known P-gp inhibitor, on the renal tubular secretion of cimetidine in healthy volunteers who received intravenous cimetidine alone and following 3 days of oral itraconazole (400 mg/day) administration. Glomerular filtration rate (GFR) was measured continuously during each study visit using iothalamate clearance. Iothalamate, cimetidine, and itraconazole concentrations in plasma and urine were determined using high-performance liquid chromatography/ultraviolet (HPLC/UV) methods. Renal tubular secretion (CL(sec)) of cimetidine was calculated as the difference between renal clearance (CL(r)) and GFR (CL(ioth)) on days 1 and 5. Cimetidine pharmacokinetic estimates were obtained for total clearance (CL(T)), volume of distribution (Vd), elimination rate constant (K(el)), area under the plasma concentration-time curve (AUC(0-240 min)), and average plasma concentration (Cp(ave)) before and after itraconazole administration. Plasma itraconazole concentrations following oral dosing ranged from 0.41 to 0.92 microg/mL. The cimetidine AUC(0-240 min) increased by 25% (p < 0.01) following itraconazole administration. The GFR and Vd remained unchanged, but significant reductions in CL(T) (655 vs. 486 mL/min, p < 0.001) and CL(sec) (410 vs. 311 mL/min, p = 0.001) were observed. The increased systemic exposure of cimetidine during coadministration with itraconazole was likely due to inhibition of P-gp-mediated renal tubular secretion. Further evaluation of renal P-gp-modulating drugs such as itraconazole that may alter the renal excretion of coadministered drugs is warranted.

A comparison of prediction equations for estimating glomerular filtration rate in adults without kidney disease

The ability of the Modification of Renal Disease (MDRD) equation to predict GFR when compared with multiple other prediction equations in healthy subjects without known kidney disease was analyzed. Between May 1995 and December 2001, a total of 117 healthy individuals underwent (125)I-iothalamate or (99m)Tc-diethylenetriamine-pentaacetic acid (DTPA) renal studies as part of a routine kidney donor evaluation at either Brigham and Women's Hospital or Boston Children's Hospital. On chart review, 100 individuals had sufficient data for analysis. The MDRD 1, MDRD 2 (simplified MDRD equation), Cockcroft-Gault (CG), Cockcroft-Gault corrected for GFR (CG-GFR), and other equations were tested. The median absolute difference in ml/min per 1.73 m(2) between calculated and measured GFR was 28.7 for MDRD 1, 18.5 for MDRD 2, 33.1 for CG, and 28.6 for CG-GFR in the (125)I-iothalamate group and was 31.1 for MDRD 1, 38.2 for MDRD 2, 22.0 for CG, and 31.1 for CG-GFR in the (99m)Tc-DTPA group. Bias was -0.5, -3.3, 25.6, and 5.0 for MDRD 1, MDRD 2, CG, and CG-GFR, respectively, in subjects who received (125)I-iothalamate and -33.2, -36.5, 6.0, and -15.0 for MDRD 1, MDRD 2, CG, and CG-GFR, respectively, in those who received (99m)Tc-DTPA studies. Precision testing, as measured by linear regression, yielded R(2) values of 0.04 for CG, 0.05 for CG-GFR, 0.15 for MDRD 1, and 0.14 for MDRD in those who underwent (125)I-iothalamate studies and 0.18 for CG, 0.21 for CG-GFR, 0.40 for MDRD 1, and 0.38 for MDRD 2 for those who underwent (99m)Tc-DTPA studies. The MDRD equations were more accurate within 30 and 50% of the measured GFR compared with the CG and CG-GFR equations. When compared with the CG equation, the MDRD equations are more precise and more accurate for predicting GFR in healthy adults. The MDRD equations, however, consistently underestimate GFR, whereas the CG equations consistently overestimate measured GFR in people with normal renal function. In potential kidney donors, prediction equations may not be sufficient for estimating GFR; radioisotope studies may be needed for a better assessment of GFR. Further studies are needed to derive and assess GFR prediction equations in people with normal or mildly impaired renal function.

Simultaneous voiding cystourethrography and voiding urosonography reveals utility of sonographic diagnosis of vesicoureteral reflux in children

AIM

To evaluate the diagnostic potential of voiding urosonography (VUS) compared with fluoroscopic voiding cystourethrography (VCUG) under identical conditions and to evaluate potential reasons for false-negative VUS results, particularly regarding bladder concentrations of the US contrast agent, Levovist.

METHODS

Fifty-six paediatric patients (M/F 34/22, mean age 2.3 y, age range 1 mo-14 y) underwent simultaneous VUS and VCUG under identical conditions. The bladder was filled by simultaneous administration of Levovist and the X-ray contrast medium, DIP Conray. Levovist concentrations in bladders were calculated using amounts of Levovist injected and total DIP Conray infused when reflux was first observed in either procedure.

RESULTS

Sensitivities of VUS and VCUG for detection of vesicoureteral reflux (VUR) were both 86%, assuming that VUR detected by either method represented a true-positive, and no reflux by either method represented a true-negative. Patients under 24-mo of age displayed a better VUS sensitivity, of 94%. Levovist concentrations in bladders ranged from 1.8% to 23%, with older children tending to demonstrate increased bladder capacity and lower concentration. All VUS false-negative units displayed Levovist bladder concentrations of less than 5%.

CONCLUSION

The present simultaneous study suggests that: 1) the two techniques demonstrate similar sensitivity for detection of reflux; 2) sustained Levovist bladder concentrations of below 5% may not allow detection of reflux on VUS; and 3) VUS represents a suitable technique, particularly for small children whose bladder capacity is not so large.

Contrast-enhanced US of Microcirculation of Superficially Implanted Tumors in Rats

PURPOSE

To determine the ability of contrast material-enhanced ultrasonography (US) to assess replenishment time in a rat kidney and adenocarcinoma tumor model.

MATERIALS AND METHODS

Mammary adenocarcinoma cells were implanted into the subcutaneous tissues of the flank of 11 rats. Resultant tumors were imaged serially with contrast-enhanced US and compared with images of the rat kidney, a highly perfused normal organ. The US acquisition and processing methods yield images of perfused tumor regions and the times required to achieve 80% replenishment. Findings at contrast-enhanced computed tomography (CT) and light microscopy of hematoxylin-eosin-stained tumor tissue were compared. Paired Student t test was performed to compare the accuracy of US with that of histologic examination and CT in the detection of viable tumor regions.

RESULTS

Replenishment of the kidney cortex microvasculature requires 1-5 seconds compared with a replenishment time of 6-14 seconds in tumors. Over the time course of tumor growth, the mean perfusion time becomes progressively longer, and a wider range of perfusion times is detected. Comparison of findings at US, CT, and histologic examination suggested that all three methods yield correlated estimates of the percentage of viable perfused tumor cells. Results of the t test suggested that the viable tumor percentages observed at US are not significantly different from those observed at CT and histologic examination (US vs CT, P =.92; US vs histologic examination, P =.94).

CONCLUSION

Repeated measurements of microvascular flow rate can be accomplished in a rat animal model with a minimally invasive technique.

Glomerular filtration rate in children with solid tumors: normative values and a new method for estimation

Many chemotherapy regimens used in children are nephrotoxic. Accurate dosing of these medications requires that some estimation of glomerular filtration rate (GFR) be performed prior to initiating chemotherapy. However, few studies evaluating normal GFR in children exist. The authors report normal values for GFR for children with nonhematogenous malignancies using a highly accurate method of directly measuring GFR and an equation for estimating absolute GFR in these children. Children with nonhematogenous malignancies with no evidence of renal involvement or prior use of nephrotoxic agents had their GFR measured using an iothalamate infusion methodology. A total of 111 children (males and females) with a mean age = 7.95 years (range 2.8 months-19.5 years) were included in the study. GFR adjusted for body surface area (mL/min/1.73 m(2)) increases in the first 2 years of life and then plateaus at a level comparable to adult values. GFR adjusted for body surface area for males >2 years = 131.3 +/- 22.5, females = 126.8 +/- 24.4 mL/min/1.73 m(2) (p value not significant). Absolute GFR in mL/min can be easily estimated by a simple formula (r(2) =.97) based on the child's weight and serum creatinine: GFR (mL/min) = k sqrt[ ( (agemos+ 6)* wt) / Cr serum ] where agemos is age in months, wt is weight in kg, and k = 1.05 for males and 0.95 for females. The accurate measurement of GFR remains vitally important in the safe and effective treatment of pediatric solid tumors. This study provides a set of normal GFR values for these children and an equation for easy estimate of absolute GFR.

[The value and adaptability of glomerular filtration rate and reserve test (review of the literature)]

In normal conditions only 75% of kidney function capability are in use. Resting part of kidney function is called renal functional reserve. It is a very important indicator for prediction of renal insufficiency in chronic renal diseases, morphological changes or reduced mass of kidney parenchyma. More common test to estimate renal functional reserve is a method of measurement of glomerular filtration rate (clearance) before and after provocation of renal filtration by acute peroral protein load. The value and the possibilities to put in practice this test as well the factors influencing the results of glomerular filtration rate were estimated in this review.

Functional effects of renal artery stent placement on treated and contralateral kidneys

BACKGROUND

This study examined the effects of stent placement for renal artery stenosis on the function of treated and contralateral kidneys.

METHODS

Eighteen patients who underwent stent placement for unilateral renal artery stenosis presenting with hypertension and/or renal failure were studied before angiography and stent placement and at their one-year follow-up. Renal vein blood samples were taken at both sides, at each side simultaneously with a sample from the aorta, to measure the plasma renin concentration and the concentrations of 131I-hippuran and 125I-thalamate during constant systemic infusion of these radiochemicals. This allowed an assessment of the single-kidney contributions to the total renin secretion, effective renal plasma flow (131I-hippuran clearance) and glomerular filtration rate (125I-thalamate clearance).

RESULTS

At the one-year follow-up, the vein-to-artery renin ratio at the treated side had decreased to normal, from 1.65 +/- 0.131 to 1.23 +/- 0.076 (mean +/- SEM; P = 0.011), indicating an improved renal blood flow. Contralaterally it rose from 1.09 +/- 0.042 to 1.17 +/- 0.029 (P = 0.055) at follow-up. The extraction ratio of 131I-hippuran improved at the treated side (0.48 +/- 0.049 to 0.62 +/- 0.034; P = 0.003) and contralaterally (0.67 +/- 0.033 to 0.73 +/- 0.026; P = 0.043). The extraction ratio of 125I-thalamate, which equals filtration fraction, improved at both sides (0.12 +/- 0.014 to 0.17 +/- 0.012 at the treated side, P = 0.001; 0.18 +/- 0.013 to 0.22 +/- 0.011 contralaterally, P = 0.002). Two-kidney effective renal blood flow and glomerular filtration rate remained unchanged.

CONCLUSION

Renal artery stenting was capable of causing improvement of glomerular filtration rate of the treated kidney, although the overall glomerular filtration rate did not change.

Evaluation of renal function in transplant patients on tacrolimus therapy

Glomerular filtration rate (GFR), as measured by 24-hour creatinine clearance and clearance of iothalamate, and effective renal plasma flow (ERPF), as measured by the clearance of para-aminohippuric acid (PAH), were evaluated at 2 weeks, 1 month, and 3 months after transplantation in 8 renal transplant patients and at 1 month and 1 year after transplantation in 9 liver transplant patients receiving tacrolimus (Prograf) therapy. In renal transplant patients, there was a significant increase in GFR after transplantation. There was no change in GFR at 1 and 3 months as compared to 2 weeks after transplantation, while ERPF (ml/min/1.73 m2) was lower (p < 0.05) at 3 months (212+/-42) compared to 1 month (306+/-118) after transplantation. In liver transplant patients, GFR and ERPF were below normal despite normal serum creatinine concentrations, but there was no difference in GFR or ERPF at 1 month and 1 year after transplantation. Although below normal, renal function was well preserved in transplant patients while receiving chronic tacrolimus therapy over the study period. Dosage alterations ofrenally eliminated drugs may be required for drugs with a narrow therapeutic index.

Creatinine-based estimation of rate of long term renal function loss in lung transplant recipients. Which method is preferable?

BACKGROUND

Progressive renal function loss during long-term follow up is common after lung transplantation and close monitoring is warranted. Since changes in creatinine generation and excretion may occur after lung transplantation, the reliability of creatinine-based methods of renal function assessment to serial measurements of glomerular filtration rate (GFR) were compared in this population.

METHODS

Renal function with serial measurements of GFR by iothalamate clearance every 6 months after transplantation was studied in a cohort of 40 lung transplant recipients with at least 24 months of follow up, transplanted between November 1990 and October 1995 in this center. The correlation between the rate of renal function loss calculated from the slope of GFR and the following creatinine-based indices: 1/S-creatinine, Cockcroft clearance and Levey estimation were analyzed. The absolute difference between GFR and Cockcroft clearance and Levey estimation pre- post-transplantation at several points was also studied.

RESULTS

The slopes of 1/S-creatinine (r = 0.85), Cockcroft clearance (r = 0.86), and the Levey estimation (r = 0.84) correlated significantly with the slope of GFR as measured by iothalamate clearance. However, all creatinine-based slopes underestimate the rate of GFR loss. Cockcroft clearance and the reciprocal value of serum creatinine do not detect small GFR losses. During long-term follow up a time-dependent discrepancy between Cockcroft clearance, Levey estimation and GFR was observed which may partially explain the observations for this population.

CONCLUSION

Creatinine-based slopes correlate with GFR slopes after lung transplantation, but consistently underestimate the rate of GFR decline. The Levey estimation is the most sensitive method used to detect small GFR losses and may be preferable when no GFR measurement is available. In special conditions when an accurate renal function assessment is needed true GFR may be necessary.

[Segmental anatomy of the liver in computed tomography: do we localize the lesion accurately?]

PURPOSE

To evaluate if Couinaud's model using the planes of the major veins is an adequate tool for the presurgical localization of focal liver lesions.

METHODS

Biphasic helical CT scans were performed on patients evaluated for liver resection using an increased IV bolus of contrast medium (180 ml lopamidol) and 2 mm image reconstruction increments. During the first evaluation, all liver lesions were localized in the conventional way using the planes of the 3 major hepatic veins and the portal trunks as segmental boundaries. In a second review, all lesions were attributed to the nearest peripheral portal branches. The path and the segmental attribution of the portal branches were analysed. Evaluations were performed using an interactive cine mode as well as three-dimensional reconstructions.

RESULTS

20 of 126 (16%) liver lesions had a different segmental location if the individual anatomy of the peripheral portal branch was used instead of the conventional technique. These different locations were due to the path of the portal trunks or the path of the peripheral portal branches crossing the planes of the major hepatic veins.

CONCLUSION

The segmental anatomy of the liver using the planes of hepatic veins and portal trunks according to Couinaud is not an accurate tool for the presurgical localization of liver lesions in many cases.

Renal dysfunction associated with the perioperative use of diclofenac

Postoperative renal dysfunction in rats is induced by ketorolac dosed concurrently with gentamicin. Herein, we report the renal effects of diclofenac in four groups of rats: control (C = anesthesia, surgery); diclofenac (D = anesthesia, surgery, diclofenac 18 mg x kg(-1) x d(-1)); gentamicin (G = anesthesia, surgery, gentamicin 20 mg x kg(-1) x d(-1)); and diclofenac and gentamicin (DG = anesthesia, surgery, diclofenac, gentamicin). Renal function, after three treatment days, was assessed using histology, p-aminohippurate (PAH), and iothalamate (IOT) clearances, serum and urine electrolytes, osmolality, urea, and creatinine. Urine output was increased (from 5.2 to 12.5 mL/24 h), and urine osmolality was decreased (from 2121 to 883 mOsm/kg) in the DG group. PAH and IOT clearances were decreased in the G and DG groups (PAH by 18%, IOT by 22%; PAH by 38%, IOT by 43%, respectively); there were no changes in the C and D groups. Urea and creatinine clearances were decreased by 61% and 43%, respectively, in the DG group. Kidney sections showed the most severe pathologic changes in the DG group. Our data indicate that the perioperative combination of diclofenac and gentamicin was deleterious to renal function.

IMPLICATIONS

Diclofenac alone does not result in significant perioperative renal dysfunction, but the combination of gentamicin and diclofenac is deleterious to renal function. Considering this and previous findings, the evidence suggests that treatment with aminoglycosides may be a significant risk factor for inducing perioperative renal failure during treatment with nonsteroidal antiinflammatory drugs.

Moderate renal failure in association with prolonged acquired hypothyroidism in children

We evaluated five children with prolonged primary hypothyroidism and noted a significant reduction in renal function (40%), which was reversible with hormonal replacement. This decline was higher than reported in adults and was of sufficient magnitude to warrant altering drug-dosing schedules. Furthermore, patients with moderately reduced renal function should be carefully evaluated for signs and symptoms of hypothyroidism.

Benefits of direct glomerular filtration rate (GFR) determination versus creatinine-based tests for evaluating renal function

To diagnose renal disease earlier and thereby reduce the number of patients with endstage renal disease, accurate, specific diagnostic tests are necessary. The author explains the benefits of using tests that rely on the glomerular filtration rate measurement rather than on traditional creatinine-based diagnostic tests.

Creatinine clearance as a measure of GFR in screenees for the African-American Study of Kidney Disease and Hypertension pilot study

Serum creatinine and endogenous creatinine clearance (CrCl) are widely used measures of renal function. This study compares the precision, bias, and sources of error in using different CrCl measures to estimate the glomerular filtration rate (GFR) in 118 men and women screened for the African-American Study of Kidney Disease and Hypertension (AASK) pilot study. We measured serum creatinine, 24-hour CrCl, and CrCl during timed clearance periods conducted simultaneously with an 125I-iothalamate GFR study. Serum creatinine was measured using two different kinetic rate Jaffe methods (CX3 and Hitachi). After standardization for body surface area, the different measures of renal function available for each individual were compared with the 125I-iothalamate GFR simultaneous to the CrCl. In a subset of 50 participants, the CrCl measures were compared with a follow-up GFR (fGFR). The mean 125I-iothalamate GFR was 65.2 (SD, 26.4), with a range of 11 to 122 mL/min/1.73 m2. The mean +/- SD percentage differences from the GFR were -9%+/-22% for the Cockcroft-Gault estimated CrCl, 1%+/-29% for the 24-hour CrCl, and 8%+/-16% for the CX3 simultaneous CrCl. The Hitachi method overestimated serum creatinine and underestimated GFR. Compared with an fGFR, the mean +/- SD differences were 2%+/-19% for the first GFR, -6%+/-20% for the Cockcroft-Gault estimated CrCl, 10%+/-28% for the 24-hour CrCl, and 14%+/-29% for the CX3 simultaneous CrCl. Thus, the increased precision with which the timed CrCl predicted its simultaneous GFR did not extend to improved ability to predict a future GFR. The fractional excretion of creatinine, measured as the ratio of the CX3 simultaneous CrCl to 125I-iothalamate clearance, increased with decreasing GFR but was lower than expected (mean +/- SD of 1.21+/-0.16 for GFRs between 20 and 40 mL/min/1.73 m2). The lower fractional excretion explains why the 24-hour and Cockcroft-Gault CrCls did not overestimate GFR, but the reasons for this lower excretion are uncertain. Creatinine assay specificity and calibration are important sources of variability that must be examined in any CrCl measure of GFR. We conclude that despite requiring substantially more time and effort, neither the outpatient 24-hour urine nor the timed CrCl offered increased precision over a calculation based on serum creatinine, sex, age, and weight in predicting GFR.

Estimation of the glomerular filtration rate in NIDDM patients from plasma creatinine concentration after cimetidine administration

OBJECTIVE

Glomerular filtration rate (GFR) can be estimated in patients with renal disease from plasma creatinine concentration, age, sex, and body weight according to the formula of Cockcroft and Gault. The hypothesis that this method can be improved when tubular secretion of creatinine is inhibited by cimetidine was studied in NIDDM patients.

RESEARCH DESIGN AND METHODS

In 30 outpatients with NIDDM and normo- (n = 10), micro- (n = 9), or macroalbuminuria (n = 11), GFR was measured as the urinary clearance during continuous infusion of 125I-labeled iothalamate. Plasma creatinine concentration was analyzed with an enzymatic assay before and after 800 mg t.i.d. oral cimetidine was given during a 24-h period.

RESULTS

Plasma creatinine rose in all patients after cimetidine administration and, as a consequence, the clearance calculated with the Cockcroft-Gault formula fell. The ratio of this formula and GFR decreased from 1.16 +/- 0.20 to 0.97 +/- 0.16 (means +/- SD). This ratio tended to be smaller in the normo- (0.93) than in the micro- (0.98) and macroalbuminuric (1.00) groups. Also, 20 patients with a BMI < 30 kg/m2 had a smaller ratio than those with a BMI > 30 kg/m2 (0.92 vs. 1.07; P < 0.05). Bland and Altman analysis showed a difference of the Cockcroft-Gault formula and GFR of 12.0 +/- 17.4 ml.min-1 (1.73 m2)-1, which decreased to -3.8 +/- 14.8 ml.min-1.(1.73 m2)-1. The same analysis of 24-h creatinine clearance with urine collection and GFR showed larger standard deviations.

CONCLUSIONS

GFR can be estimated in an acceptable way from plasma creatinine concentration after cimetidine administration in outpatients with NIDDM. Despite a nonsignificant underestimation in normoalbuminuric and overestimation in overweighted patients, this method is superior to 24-h creatinine clearance with outpatient urine collection.

Long-term renal function in heart transplant recipients receiving cyclosporine therapy

BACKGROUND

Immunosuppression with cyclosporine has improved allograft function and reduced both morbidity and mortality in organ transplantation. However, cyclosporine-induced nephrotoxicity still is a concern. The purpose of our study was to evaluate the effects of cyclosporine on renal function in orthotopic heart transplant recipients.

METHODS

Thirty-nine patients who received transplants from 1985 to 1991 and had at least three yearly glomerular filtration rate measurements posttransplantation by 125I-iothalamate clearance method were included in the study. In addition, serum creatinine (before and after transplantation) and cyclosporine doses were analyzed.

RESULTS

Maintenance immunosuppression at 1 year consisted of prednisone (0.1 mg/kg/day), azathioprine (2 mg/kg/day), and cyclosporine (12-hour trough level 100 to 150 ng/ml by fluorescence polarization immunoassay). The mean serum creatinine at 1 year was significantly higher than the mean pretransplantation serum creatinine (1.51 +/- 0.32 versus 1.28 +/- 0.38, p < 0.05) and stabilized after the first year. The mean glomerular filtration rate by 125I-iothalamate clearance method was 70.6 +/- 20.3 ml/min/1.73 m2 (range 32 to 105) at 1 year and remained relatively stable during the follow-up period of up to 7 years. Creatinine clearance calculated by the Cockcroft and Gault formula overestimated the true glomerular filtration rate after the third year. The mean cyclosporine dosage was significantly lower after the first-year dose of 3.9 +/- 1.8 mg/kg/day (p < 0.05). Three patients in 39 started hemodialysis at 5, 7, and 10 years after transplantation.

CONCLUSION

Our data indicate that the adequacy of renal function is preserved with long-term cyclosporine therapy in heart transplant recipients.

A method for accurate measurement of GFR in conscious, spontaneously voiding rats

Renal function measurement by clearance methods relies on accurately timed urine collection. In small experimental animals, renal function measurement is usually performed under anesthesia and/or with the application of bladder catheters to ensure accurate urine collection. To avoid both anesthesia and the need for bladder catheters we developed a method to measure glomerular filtration rate (GFR) in spontaneously voiding conscious rats. GFR was measured as the urinary clearance of constantly infused 125I-iothalamate. To correct for incomplete bladder emptying urinary clearance of 125I-iothalamate was multiplied by the ratio of plasma and urinary clearance of simultaneously infused 131I-hippuran, a correction method that has been previously validated in humans. Reproducibility of the technique was evaluated by analysis of the results of four consecutive clearance periods during the day (intra-assay variation) in a group of 17 rats and of two consecutive clearance periods on two or three separate days in a group of 20 rats (inter-assay variation), all with normal renal function. Application of the correction method reduced the intra-assay coefficient of variation (mean +/- SD) from 37.4 +/- 14.3 to 5.4 +/- 2.3% (P < 0.05). The mean inter-assay coefficient of variation fell slightly from 23.4 +/- 10.3 to 11.0 +/- 7.2% (P < 0.10). In rats with moderately impaired renal function (N = 8) the intra-assay variation fell from 27.9 +/- 20.7 to 2.7 +/- 1.6% (P < 0.05). Our data show that this correction method is a useful technique to assess renal function in conscious, spontaneously voiding rats.

Determination of glomerular filtration rate with Visipaque in patients with severely reduced renal function

Iodixanol (Visipaque, Nycomed Imaging AS, Oslo, Norway), and isotonic, dimeric and non-ionic contrast medium (CM), and iohexol (Omnipaque, Nycomed Imaging AS, Oslo, Norway), a low-osmolar, monomeric and non-ionic contrast medium, were used as glomerular filtration rate (GFR) markers in patients with severely impaired renal function. Different methods for determining GFR were compared. A total of 16 patients with s-creatinine > 400 mumol/l were enrolled in the study; 8 in each CM group. Serum-iodine was measured, and plasma CM clearance was determined using the Bröchner-Mortensen method, the single-sample method and conventional method. The ratios between the results obtained from the conventional method and each of the two other methods were calculated. These data were plotted against the mean of the pairs compared, and the upper and lower limits of agreement were calculated as the mean ratio +/- 2SD. The comparison showed a high degree of agreement between methods, and the two simpler methods seem to be good alternatives to the conventional method, which gave good estimates of GFR (vs that determined by means of renal 125I-iothalamate clearance) when 24-h blood samples were included. However, slight overestimations of GFR, due to extrarenal excretion of the CM, were observed. In summary, serum clearance of iodixanol, as determined by the Bröchner-Mortensen method or single-sample method seems to be a simple and accurate marker for GFR in patients with severely reduced renal function. The findings obtained with iodixanol were similar to those obtained with iohexol.

Accurate measurement of impaired glomerular filtration using single-dose oral cimetidine

To improve the validity of a timed creatinine clearance as a measure of glomerular filtration rate (GFR), we investigated whether a single 800-mg dose of oral cimetidine was sufficient to inhibit tubular secretion of creatinine (TScr). Forty-five 3-hour timed creatinine clearances (Clcr) with single 800-mg dose oral cimetidine (TCC) in 17 renal transplant recipients with marked renal function impairment (creatinine 2.0 to 7.1 mg/dL) were compared with simultaneous [125I]-iothalamate GFR (Cliothal). For comparison, 13 timed Clcr without cimetidine (TC), and 36 24-hour Clcr were performed. The TCC was the most accurate: the ratio (mean +/- SD) of TCC:Cliothal was 1.12 +/- 0.02, compared with 1.33 +/- 0.08 for Clcr:Cliothal and 1.53 +/- 1.02 for TC:Cliothal. The difference between Cliothal and TCC was small over the range of GFRs tested (mean +/- 2 SD), 0.9 +/- 2.5 mL/min/1.73 m2. The intraclass correlation (R) for within-subject reproducibility of the TCC in five subjects was 0.8 (95 percent CI; 0.5, 0.9), and in 11 subjects who had at least three GFR determinations over 24 weeks, the TCC was as responsive to change in GFR as Cliothal. There was an inverse relationship between fractional excretion of cimetidine and GFR (r2 = -0.70), suggesting increased tubular secretion of cimetidine with decreasing GFR. In conclusion, a single 800-mg oral dose of cimetidine was effective in inhibiting TScr such that the TCC was an accurate, reproducible, and responsive test of GFR.

Effects of diet and antihypertensive therapy on creatinine clearance and serum creatinine concentration in the Modification of Diet in Renal Disease Study

Factors other than the glomerular filtration rate (GFR) can affect creatinine clearance (Ccr) and serum creatinine concentration (Pcr). The effect of dietary protein and antihypertensive therapy on Ccr the reciprocal of the Pcr (1/Pcr). and their determinants (GFR, creatinine clearance from tubular secretion (CTScr), and creatinine excretion (UcrV) values) was assessed in patients participating in the Modification of Diet in Renal Disease (MDRD) Study. This study compared the effects of assignment to a low versus usual-protein diet and to a low versus usual-blood pressure goal on the decline in these measurements over 3 yr in 585 patients with baseline GFR of 25 to 55 mL/min per 1.73 m2 (Study A). This study also assessed correlations and associations of these measurements with each other and with protein intake, blood pressure, class of antihypertensive agents, and renal diagnosis in 840 patients with baseline GFR of 13 to 55 mL/min per 1.73 m2 (Studies A and B). In Study A, the estimated mean decline in GFR at 3 yr did not differ significantly between the low and usual-protein diet groups (-10.9 versus -12.1 mL/min). In contrast, CTScr declined more in the low-protein diet group (-7.8 versus -3.6 mL/min, P < .05). Consequently, the low-protein diet group had a greater decline in Ccr (-17.6 versus -14.4 mL/min, P < .05). The low-protein diet group also had a greater decline in UcrV (-306 versus -92 mg/day, P < .05). The decline in UcrV was proportionately greater than the decline in CTScr hence the decline in 1/Pcr was less in the low-protein diet group (-0.091 versus -0.122 dl/mg, P < .05). Similarly, in Study A, there was no significant difference in the decline in GFR at 3 yr between the low and usual-blood pressure groups (-10.7 versus -12.3 mL/ min). However, there was a lesser decline in CTScr in the low blood pressure group (-4.7 versus -6.7 mL/ min, P < .05). Consequently, the decline in Ccr was less in the low blood pressure group (-14.2 versus -17.8 mL/min, P < .05). There was no significant difference in UcrV between the blood pressure groups (-192 versus -205 mg/day). Hence, the decline in 1/Pcr paralleled the decline in Ccr; it was less in the low blood pressure group (-0.091 versus -0.122 dL/mg, P < .05). In Studies A and B, correlations of rates of decline in Ccr and GFR were 0.64 and 0.79, respectively (P < 0.001). Correlations of rates of decline in 1/Pcr and GFR were 0.79 and 0.85, respectively (P < 0.001). In Studies A and B combined, baseline GFR, CTScr and UcrV correlated significantly with protein intake (r = 0.45, 0.47, and 0.36, respectively; P < 0.001), but not with blood pressure. Baseline CTScr was significantly lower in patients with polycystic kidney disease and tubulointerstitial diseases or urinary tract diseases, compared with glomerular and other diseases (P < 0.05). It was also lower in patients who were taking calcium channel blockers, compared with patients not taking these agents, and in patients not taking diuretics, compared with patients taking diuretics (P < 0.05). These results show that creatinine secretion and excretion are affected by protein intake. Creatinine secretion is also affected by antihypertensive therapy and renal diagnosis. In the MDRD Study, the low-protein diet reduced creatinine secretion and excretion, and the low blood pressure goal slowed the decline in creatinine secretion. These effects caused differences between the diet groups and between the blood pressure groups in Ccr and 1/Pcr that were not the result of differences in GFR. Studies assessing the effects of these interventions on the progression of renal disease should measure GFR in addition to Ccr and Pcr.

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.

Case report: mobile fatty globules in benign cystic teratoma of the mediastinum

Benign cystic teratoma is a well recognized cause of an anterior mediastinal mass. The presence of fat, found in approximately half the cases, suggests the diagnosis. We report a new feature, which consists of components of the tumour drifting upwards (anteriorly) during the course of a computed tomography examination. The appearance is compared with a popular light fitting.

Measurement of glomerular filtration rate using nonradioactive Iohexol: comparison of two one-compartment models

Radioisotopic methods for the determination of the glomerular filtration rate (GFR) are highly accurate but require the collection of multiple blood and urine samples and are costly to perform due to personnel, material, and analysis costs. Nonradioactive methods of GFR determination have the potential of minimizing procedure costs while preserving accuracy. We determined the GFR simultaneously by 125I-iothalamate and nonradioactive iohexol clearance methods in 41 adults. The study group consisted of 54% males, with a mean age of 50.7 (range 28-79) years and a mean GFR by 125I-iothalamate clearance of 66.5 +/- 28.3 (range 10-118) ml/min. The iohexol concentrations were measured by a simplified high-performance liquid chromatography method that did not require sample preparation. The iohexol plasma clearance was calculated by both a new one-compartment model as well as by Jacobsson's one-compartment model. Using Jacobsson's single-sample model and data from the 240-min point, there was an excellent correlation between 125 I-iothalamate and nonradioactive iohexol clearance values: r2 = 0.95, standard error of the estimate = 11.4 ml/min, and intrapatient coefficient of variation = 16.9%. However, this formula tended to overestimate GFRs < 30 ml/min and to underestimate GFRs > 80 ml/min. The new one-compartment model is a modification of Bubeck's model, originally used for the determination of renal plasma blood flow. Using this modified model, there was an excellent correlation between 125I-iothalamate and nonradioactive iohexol clearance values at all levels of GFR tested: r2 = 0.95, standard error of the estimate = 9.2 ml/min, and intrapatient coefficient of variation = 13.7%. In conclusion, the determination of the plasma clearance of iohexol by a nonradioactive technique and a monoexponential model is a simple and accurate method of determining the GFR in patients with varying degrees of renal impairment.

Extended measurement of glomerular filtration rate and effective renal plasma flow in ambulatory patients

We describe a standardized clearance method over 5 h (one hour equilibration followed by eight consecutive 30 min clearance periods [period 2-9]) for the estimation of GFR (iothalamate I125) and ERPF (hippuran I131) during water diuresis in ambulatory and exercising patients. Four groups were examined. In group I (normal controls, n = 15) there were no significant changes in GFR, ERPF and FF (P > 0.10) during repeated clearance periods (mean of period 2-5 versus period 6-9). The reproducibility of the method was studied at a mean interval of 3.7 weeks in a group of patients with stable reduction of GFR (group II, n = 7). The values for GFR, ERPF, FF and RVR did not change significantly in this group, and correlated significantly between repeated studies (r = 0.81 to r = 0.99). In group III (untreated hypertensive patients with reduced GFR, n = 13) there was a time dependent 7.2% decrease in GFR (P < 0.05), significantly different from group I (P < 0.02), a 10.0% decrease in ERPF (P < 0.01) and no significant change in FF (P = 0.08) when the mean of period 2-5 was compared with the mean of period 6-9. In healthy controls (group IV, n = 8) light sustained bicycle exercise (25 W) induced a 7.1% decline in GFR (P < 0.01), 17.4% decline in ERPF (P < 0.001) and a 13.6% increase in FF (P < 0.001). We conclude that ambulatory measurements of GFR and RPF can be carried out over a period of 5 h with satisfactory precision and repeatability. Ambulatory hypertensive patients with moderately reduced GFR showed the same degree of time dependent downward drift of GFR and ERPF without exercise as was seen in healthy individuals during light exercise. Accordingly, in these groups single clearance periods imply a risk for under or overestimation of renal function, and time controls are necessary during clearance studies.

Rapid DNA fragmentation from hypoxia along the thick ascending limb of rat kidneys

Extensive DNA fragmentation, a marker for programmed cell death, was selectively and rapidly induced by hypoxia in the thick ascending limbs of rat kidneys. In isolated perfused kidneys, DNA breaks were present in medullary tubules as early as after 10 minutes of local hypoxia and were prevented by reduction of metabolic work. In a model of radiocontrast-induced acute renal failure, DNA breaks were detected selectively along thick ascending limbs as early as 15 minutes following insult, preceding overt morphological damage. Hypoxia induces rapid DNA fragmentation along thick ascending limbs, where programmed cell death could play an important role in nephron injury and kidney failure.

Effects of recombinant human erythropoietin on renal function in chronic renal failure predialysis patients

A study was undertaken to ascertain the effects of recombinant human erythropoietin (r-HuEPO) on renal function in chronic renal failure predialysis patients. The effect of improvement of anemia by r-HuEPO on the rate of decline in renal function in predialysis patients has not been previously studied prospectively in a large number of patients using reliable measures of glomerular filtration rate (GFR). To investigate the efficacy, safety, and impact of r-HuEPO therapy in chronic renal insufficiency patients, a 48-week, randomized, open-label, multicenter study was initiated in 83 anemic, predialysis (serum creatinine 3 to 8 mg/dL) patients. Serial GFRs were measured using 125I-iothalamate clearance. Forty patients were randomized to the untreated arm and 43 patients to the treatment arm (50 U/kg r-HuEPO subcutaneously three times weekly). Baseline characteristics were comparable for the r-HuEPO-treated and untreated groups. During this 48-week study, GFR, mean arterial blood pressure, and daily protein intake were not significantly different between the two groups. There was a statistically significant increase in hematocrit for the r-HuEPO-treated group that was not associated with acceleration of deterioration in residual renal function. This was demonstrated by the lack of a significant (P = 0.376) between-group difference in mean change in GFR from baseline to last available value for the r-HuEPO-treated (-2.1 +/- 3.2 mL/min) and untreated (-2.8 +/- 3.5 mL/min) groups. This study concludes that r-HuEPO therapy improves anemia in predialysis patients and does not accelerate the rate of progression to end-stage renal disease.

Effects of DDAVP on renal hemodynamics and renin secretion in subjects with essential hypertension

Intravenous (i.v.) infusion of the selective vasopressin (V2) agonist 1-desamino-8-D-arginine vasopressin (DDAVP, Desmopressin) in humans causes a fall in blood pressure, an increase in heart rate, and a rise in plasma renin and noradrenaline. The present study was designed to demonstrate the vasodilatory properties of DDAVP in the renal circulation and to describe the effect of DDAVP on renin secretion. Seven male subjects (31-63 years) with hypertension, who showed no signs of renal parenchymal disease, received an i.v. infusion of DDAVP (400 ng/kg in 10 minutes). They were studied at the time they were undergoing renal vein renin sampling and renal angiography as part of the diagnostic work-up of their hypertension. 131I-Hippurate clearance was used to measure effective renal plasma flow (ERPF). True renal plasma flow was calculated as ERPF divided by the renal extraction ratio of 131I-hippurate. 125I-Thalamate clearance was used to measure glomerular filtration rate (GFR). Measurements were made before and 15-20 minutes after administration of DDAVP. Angiography was performed in the same session after the last blood samples had been collected. In all patients the renal arteries were normal and the extraction ratios of 131I-hippurate and 125I-thalamate (Ehip, Ethal) were not different for the left and right kidney, and in all seven patients a diagnosis of essential hypertension was made. After DDAVP systolic blood pressure decreased by 14.4 mmHg (2.0-26.8) (mean, 95% confidence interval, p < 0.05). Diastolic blood pressure decreased by 12.1 mmHg (2.9-21.7, p < 0.01). Heart rate increased by 17.5 bpm (11.7-23.2, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

The clinical and radiological evaluation of primary brain neoplasms in children, Part II: Radiological evaluation

Data collected over the past 8 years on the radiological appearance of common pediatric primary brain neoplasms are presented. An emphasis is placed on the newer radiological imaging modality of magnetic resonance imaging (MRI). Part I of this article emphasized the clinical evaluation of these brain neoplasms. Three hundred eighty-five children with known brain neoplasms ranging in age from newborn to 18 years were evaluated with one or all of the following radiological modalities: MRI, computed tomography (CT), water-soluble myelography (WSM), WSM with CT, and angiography. Contrast-enhanced MRI and CT scans both were accurate in delineating these brain neoplasms although MRI provided better resolution and delineation than CT. Angiography provided information on the vascularity of the neoplasms and their relationship to prominent arterial and venous structures. Water-soluble myelography with CT and gadolinium-enhanced MRI of the spine were equally accurate in demonstrating metastatic spread to the spinal canal and spinal cord. Magnetic resonance imaging with gadolinium was more accurate than CT with contrast in demonstrating recurrent or residual neoplasm at the operative site and metastatic spread to the brain. Magnetic resonance imaging with gadolinium is the best radiological modality to fully evaluate pediatric brain neoplasms.

Glomerular filtration rates in persons evaluated as living-related donors--are our standards too high?

We have retrospectively analyzed the glomerular filtration rate by 125-I iothalamate clearance and creatinine clearance in a group of 661 persons evaluated as potential kidney donors. The average GFR in this population is lower than that reported in previous studies and ranges from 102 +/- 15 and 114 +/- 17 ml/min for males and females age 21-30 to 84 +/- 13 and 79 +/- 15 ml/min for males and females age 51-60. Furthermore, there has been a gradual decrease in GFR in this population from 1970 to 1990 in both the entire population and in those under the age of 40. The cause of this drop is not apparent. These data can be utilized to determine the appropriateness of a potential donor for donation, and may indicate that our current standards are too high.

Case report: an unexpected intravenous pyelogram appearance in an azotemic patient

The authors discuss the unusual intravenous pyelogram (IVP) findings in a patient with blunt abdominal trauma. Although the patient had apparent renal dysfunction, both nephrogram and pyelogram were seen clearly after a moderate dose of iothalamate. This may be explained by the fact that the underlying complete obstruction was relieved by his traumatic bladder rupture, prior to the contrast study. Alternatively, evidence of azotemia may be an artifact, resulting from resorption of urea and creatinine after rupture. Thus, the nephro-pyelogram may accurately reflect his renal function.

HPLC determination of rubber septum contaminants in the iodinated intravenous contrast agent (sodium iothalamate)

A simple and rapid method is described for the determination of 2-mercaptobenzothiazole and mercaptobenzothiazole disulfide leached from rubber closures into the iodinated contrast medium (sodium iothalamate). The contaminants were extracted with methylene chloride and analyzed by high-performance liquid chromatography using ultraviolet detection at wavelengths of 272 and 328 nm. The structures of the impurities were confirmed unequivocally by mass spectrometry. The minimum detectable level was 1 microgram/100 mL (0.01 ppm). The quantitation of contaminants leached from rubber stoppers provides a means for evaluating possible health risks of the extractables.