Systematic renal function evaluation using iohexol or inuline clearance before lung transplantation in adult CF patients

Introduction Cystic fibrosis (CF) patients are at risk for kidney injury even before undergoing lung transplantation because of prolonged exposure to aminoglycoside and complications of diabetes mellitus. The usual equations estimating the glomerular filtration rate (GFR) such as Cockroft or MDRD Formula are not adapted in CF population due to patients’ low body weight [1] . The aim of our study was to measure precisely the GFR of CF adult patients before lung transplantation. Materiels et methodes Iohexol or Inuline clearance was realized in 21 adult CF patients, when they entered the lung transplant waiting list ( n  = 17) or when the patient was considered by the clinician at high risk for renal disease ( n  = 4). No patient was treated with aminoglycoside at the time of GFR measurement. BMI, history of diabetes mellitus and high blood pressure were recorded. Exposure to intravenous aminoglycoside within the 5 years before GFR measurement was calculated. Urines samples were collected to check for proteinuria and albuminuria. Resultats Our population was predominantly male (57%). Mean age at GFR measurement was 31 years old. Mean BMI was 19 kg/m 2 . Only one patient had a history of high blood pressure, and 43% of patients were diabetic. Fourteen percent of patients had albuminuria of more than 30 mg/L and none of them had proteinuria. Mean days of exposure to IV aminoglycoside therapy within the 5 years before GFR evaluation was 169 days (Ranging from 60 to 280 days). Tobramycin was the most used aminoglycoside at the mean posology of 7.6 mg/kg/day. GFR was measured using iohexol for 15 patients and inuline was used for the remaining 6 patients. Mean measured GFR was 107 mL/min/1.73m 2 . Only 2 patients had a measured GFR  2 for which GFR estimation using CKD EPI was unable to detect the moderate decline in kidney function (estimated GFR >90 mL/min/1.73m 2 ). Discussion Our sample was representative of the CF population. Despite prolonged exposition to high dose of aminoglycoside associated with a high prevalence of diabetes mellitus, no major decline in GFR is observed in our cohort. Conclusion There is no significant decrease in renal function in CF patients before lung transplantation.