To compare plasma clearance based glomerular filtration rate measurement with serum creatinine-based estimate glomerular filtration rate measurement methods (schwartz formula) in patients with posterior urethral valves

Comparison of plasma clearance based GFR measurement with serum creatinine-based eGFR methods (Schwartz formula) in patients with posterior urethral valves. A retrospective analysis of the patients with Posterior urethral valve (PUV) referred for glomerular filtration rate measurement (GFR) was done. Cystoscopic diagnosis of PUV was made and the patient underwent valve fulguration. After adequate oral hydration, 1mCi of Tc99m-diethyl-triamine-penta-acetic acid (DTPA) was administered intravenously and glomerular filtration rate (mGFR) was measured from calculating plasma clearance of Tc99m-DTPA by obtaining two venous blood samples at 60 min and 180 min after injection using the modified Russell's. mGFR was normalized to patients' body surface area (BSA), which was calculated by Dubois and Dubois Formula. Creatinine clearance based Schwartz formula was used to estimate the GFR (eGFR). Further patients were categorized into 6 stages of chronic kidney disease in accordance with the National Kidney Foundation (NKF) classification. Total 62 patients with a diagnosis of PUV were enrolled. The mean age was 8.5 ± 6.5 years and 56 of them were male. Patients had mean serum creatinine of 1.15± 0.9 mg/dl, blood urea nitrogen 19± 15 mg/dl, and albumin 4.4± 1.61 gm/dl. Mean mGFR was 61.6±31.8 ml/min/1.73 m2 body surface area (BSA) and mean eGFR (Schwartz formula) was 56.28± 24.4 ml/min/1.73 m2 BSA. As per NFK classification, 14, 21, 13, 8 and 6 patients were categorized into CKD stage I to V respectively. More than three fourth of the PUV patients have low mGFR (CKD II-V). eGFR overestimate the GFR in all the subgroups. There was no significant correlation between the eGFR and mGFR in all stages of CKD except for stage III. In view of loss of muscle mass in the CKD patients, the eGFR is not sensitive for the measuring the true GFR in PUV patients and mGFR is recommended.51-52 (author)