Iohexol plasma and urinary concentrations in cirrhotic patients: A pilot study.

BACKGROUND: Renal failure is an independent prognostic factor for survival in patients with cirrhosis. Equations to calculate serum creatinine significantly overestimate the glomerular filtration rate (GFR). Plasma clearance of direct biomarkers has been used to improve the accuracy of evaluations of GFR in this population, but no study has simultaneously measured plasma and urinary clearance, which is the gold standard. AIM: To study calculated plasma and urinary concentrations of iohexol, based on the kinetics of samples collected over 24 h from cirrhotic patients with three different grades of ascites. METHODS: One dose of iohexol (5 mL) was injected intravenously and plasma concentrations were measured 11 times over 24 h in nine cirrhotic patients. The urinary concentration of iohexol was also measured, in urine collected at 4, 8, 12 and 24 h. RESULTS: The plasma and urinary curves of iohexol were similar; however, incomplete urinary excretion was detected at 24 h. Within the estimated GFR limits of our population (> 30 and < 120 mL/min/1.73 m²), the median measured GFR (mGFR) was 63.7 mL/min/1.73 m² (range: 41.3-111.3 mL/min/1.73 m²), which was an accurate reflection of the actual GFR. Creatinine-based formulas for estimating GFR showed significant bias and imprecision, while the Brochner-Mortensen (BM) equation accurately estimated the mGFR (r = 0.93). CONCLUSION: Plasma clearance of iohexol seems useful for determining GFR regardless of the ascites grade. We will secondly devise a pharmacokinetics model requiring fewer samples andvalidate the BM equation.

Age-specific normal reference ranges for 99mTc-DTPA glomerular filtration rate to use with two-sample slope-intercept method and Jodal Brochner-Mortensen correction.

Glomerular filtration rate (GFR) varies with age, the calculation method, and the correction factor for slope-intercept overestimation. Hence, any normal reference range accompanying the results should be suitably adapted to the method used. For Nuclear Medicine Departments using a two-sample slope-intercept method, the lack of appropriate age-specific normal reference range has been a hindrance to adopting the recently updated Jodal Brochner-Mortensen (JBM) correction over other older and more widely used methods. A retrospective analysis of the routine GFR calculation and clinical reports generated locally from 2006 to 2020 was carried out. GFR was calculated with 99mTc-DTPA plasma clearance using a two-sample slope-intercept method with JBM correction. Age-specific normal range equations were developed from normal healthy subjects. Published normal reference ranges were modified with appropriate correction reversal and compared with the locally developed reference ranges. Age-specific normal GFR reference ranges for 99mTc-DTPA with slope-intercept method and JBM correction were developed and validated with current literature. Normal reference range (Mean ± 2SD) for Normalised GFR (ml min-1 (1.73m2)-1) within 95% confidence limits suitable for use with JBM correction is 100.6 ± 35.2 for children above 2 years and 102.9 - 0.00629 × (Age)2 ± 19.4 for adults. Availability of age-specific normal GFR reference ranges applicable to the target population and appropriately tailored to the calculation method and correction factor enables Nuclear Medicine Departments to update their calculation methods in line with the current literature and also facilitates accurate reporting and evaluation of the calculated GFR results.

Estimation of GFR Using Iohexol Plasma Clearance in Korean without Renal Disease / 대한신장학회잡지

BACKGROUND: Plasma clearance of iohexol (Omnipaque(r)) which used widely in radiologic procedure is considered as useful method for estimation of GFR because iohexol is neither reabsorbed nor secreted from tubule after filtered as inulin and its extrarenal clearance is negligible. Plasma clearance of iohexol can be calculated from two compartment model or one compartment model with Brochner-Mortensen (B-M) modification which convenient and reliable. But there were controversies about sufficient sampling numbers and times for B-M modification of iohexol clearance. METHODS: Nineteen healthy Korean without renal disease underwent measurement of iohexol clearance. Iohexol was given as a single iv dose, and 14 blood sample were drawn up to 300 min. A reference GFR was iohexol clearance calculated from two-compartment model using 14 samples (CL-T). From 8, 3 and 2 samples clearances were calculated by B-M modification (CL-M8, 3 and 2 respectively). The accuracy of estimates was evaluated as percent of estimates falling within 10% above or below the reference GFR. Accuracy of CCr and equations for GFR estimation were also compared. RESULTS: CL-T, CL-M8, CL-M3 and CL-M2 were not different (101.9+/-24.0, 101.9+/-18.7, 101.7+/-18.6, 101.9+/-19.5 mL/min/1.73 m2 respectively). Accuracy of CL-M8, 3 and 2 were not different (74%, 84% and 79% respectively, p>0.05). MDRD equation had higher accuracy (47%) compared with other equations. CONCIUSION: These results indicate that sampling number for measuring iohexol plasma clearance using simplified method might be reduced to only two without accuracy loss in Korean without renal disease.