29 October 2020
Background: The evolution and prognostic impact of loop diuretic efficiency according to chronic kidney disease (CKD) severity is unclear. Methods: This retrospective cohort study includes 783 CKD patients on oral loop diuretic therapy with a 24-h urine collection available. Acute kidney injury and history of renal replacement therapy were exclusion criteria. Patients were stratified according to Kidney Disease Improving Global Outcomes (KDIGO) glomerular filtration rate class. Loop diuretic efficiency was calculated as urine output, natriuresis, and chloruresis, each adjusted for loop diuretic dose, and compared among strata. Risk for onset of dialysis and all-cause mortality was evaluated. Results: Loop diuretic efficiency metrics decreased from KDIGO class IIIB to IV in furosemide users and from KDIGO class IV to V with all loop diuretics ( p value <0.05 for all comparisons). The correlation between loop diuretic efficiency and creatinine clearance was moderate at best (Spearman’s ρ 0.298–0.436; p value <0.001 for all correlations). During median follow-up of 45 months, 457 patients died (58%) and 63 received kidney transplantation (8%), while dialysis was started before in 328 (42%). All loop diuretic efficiency metrics were significantly and independently associated with both the risk for dialysis and all-cause mortality. In KDIGO class IV/V patients, low loop diuretic efficiency (i.e., urine output adjusted for loop diuretic dose ≤1,000 mL) shortened median time to dialysis with 24 months and median time to all-cause mortality with 23 months. Conclusion: Low loop diuretic efficiency is independently associated with a shorter time to dialysis initiation and a higher risk for all-cause mortality in CKD.