Assessment of Electrolyte Free Water Clearance in Renal Transplant Recipients

Background Few studies have been done on free water excretion capacity in renal transplant recipients. Objectives This study was designed to compare electrolyte free water clearance (E-CH2O) in renal transplant recipients with healthy control group. Methods A cross-sectional study was conducted to determine three-hour creatinine clearance (CCl), E-CH₂O, and percent urine output in 3 hours after administering 20 mL/Kg oral water loading following 12-hour fasting, in 22 renal transplant recipients with good graft function (creatinine < 1.5 mg/dL) and 26 healthy controls. Patients with diabetes mellitus, hypertension, ischemic heart disease, or liver disease, hypovolemia and hypoalbuminemia were excluded. Statistical analysis was done using t-test, K-square, and Pearson’s correlation test. Results We recruited 25 recipients (73% patients in living and 27% in cadaveric donor transplantation) and 26 healthy control groups.3 patients refused to collect urine and finally 22 patients finished the protocol. The mean age of subjects was 37.68 ± 13.88 and 31.40 ± 8.20 years old in renal transplant recipients and control groups, respectively. In patient group male to female ratio was 9/13 and in control group was14/12. Although the 3h-CCl was similar (126.49 ± 53.52 vs. 109.99 ± 47.06 mL/min) in two groups (P > 0.05), the E-CH2O (1.83 ± 1.22 vs. 2.94 ± 2.02) and 3-hour urine output percent (55.93 ± 22.86 vs74.11 ± 30.38) in kidney recipients was significantly lower than healthy controls (P < 0.05). There wasn’t any significant correlation between E-CH2O and 3h-CCl in renal transplant recipients. Donor source and gender did not affect 3h-CCl and E-CH2O in renal transplant patients. Conclusions This study demonstrated that E-CH₂O has been decreased in renal transplant patients in comparison with control group when there was not any difference between3h- CCl in two groups. This indicates that E-CH₂O may be decreased earlier than 3h-CCl in transplant patients.