Association of fluid overload with kidney disease progression in advanced CKD: a prospective cohort study

Background: Fluid overload is a common phenomenon in patients in a late stage of chronic kidney disease (CKD). However, little is known about whether fluid overload is related to kidney disease progression in patients with CKD. Accordingly, the aim of the study was to assess the association of the severity of fluid status and kidney disease progression in an advanced CKD cohort.

Study design: Prospective observational cohort study.

Setting & participants: This cohort study enrolled 472 non-dialysis-dependent patients with CKD stages 4-5 who were in an integrated CKD care program from January 2011 to December 2011 and followed up until December 2012 or initiation of renal replacement therapy (RRT).

Predictors: Tertile of fluid overload, with cutoff values at 0.6 and 1.6 L.

Outcomes: RRT, rapid estimated glomerular filtration rate (eGFR) decline (faster than 3 mL/min/1.73 m(2) per year), and change in eGFR.

Measurements: The severity of fluid overload was measured by a bioimpedance spectroscopy method. eGFR was computed using the 4-variable MDRD (Modification of Diet in Renal Disease) Study equation.

Results: During a median 17.3-month follow-up, 71 (15.0%) patients initiated RRT and 187 (39.6%) experienced rapid eGFR decline. The severity of fluid overload was associated with increased risk of RRT (tertile 3 vs tertile 1: adjusted HR, 3.16 [95% CI, 1.33-7.50]). Fluid overload value was associated with increased risk of rapid eGFR decline (tertile 3 vs tertile 1: adjusted OR, 4.68 [95% CI, 2.30-9.52]). Furthermore, the linear mixed-effects model showed that the reduction in eGFR over time was faster in tertile 3 than in tertile 1 (P=0.02).

Limitations: The effect of fluid volume variation over time must be considered.

Conclusions: Fluid overload is an independent risk factor associated with initiation of RRT and rapid eGFR decline in patients with advanced CKD.