Abstract
BackgroundExcess extracellular volume is a major clinical problem in patients with chronic kidney disease (CKD). However, whether the extracellular volume status is associated with disease progression is unclear. We investigated the association between the extracellular volume status and renal outcomes.MethodsWe performed a retrospective cohort study of 149 patients with CKD who underwent bioelectrical impedance analysis (BIA) from 2005 to 2009. Patients were categorized according to tertiles of extracellular volume status. The extracellular volume status was assessed by examining the ratio of extracellular water measured by BIA (ECWBIA) to the total body water calculated using the Watson formula (TBWWatson). The main outcomes were adverse renal outcomes as defined by a decline of ≥50% from the baseline glomerular filtration rate or initiation of renal replacement therapy.ResultsA higher %ECWBIA/TBWWatson ratio tended to be associated with older age, male sex, diabetes mellitus, resistant hypertension, lower renal function, lower serum albumin levels, higher proteinuria levels, and a higher frequency of furosemide use. In the multivariate analysis, proteinuria remained independently associated with the %ECWBIA/TBWWatson ratio. Both the intracellular and extracellular water volumes decreased with age (correlation between ICW and age, r = -0.30, P < 0.001; correlation between ECW and age, r = -0.17, P = 0.03). Consequently, the %ECWBIA in the body fluid composition increased with age. During a median follow-up of 4.9 years, patients in the highest tertile of the %ECWBIA/TBWWatson ratio were at greater risk of adverse renal outcomes (16.6 per 100.0 patient years) than were those in the lowest tertile (8.1 per 100.0 patient years) or second tertile (5.6 per 100.0 patient years) (log-rank P = 0.005). After adjustment for covariates, the %ECWBIA/TBWWatson ratio was significantly associated with adverse renal outcomes (hazard ratio, 1.21; 95 % confidence interval, 1.10–1.34; P < 0.001).ConclusionsThe ECWBIA/TBWWatson ratio was independently associated with adverse renal outcomes. Proteinuria was independently associated with the extracellular volume status. The balance between ICW and ECW changes with age in that the percentage of ECW content in the body fluid composition increases. Elderly patients with CKD may thus be susceptible to volume overload.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2369-15-189) contains supplementary material, which is available to authorized users.
Highlights
Excess extracellular volume is a major clinical problem in patients with chronic kidney disease (CKD)
The extracellular water measured by BIA (ECWBIA)/ECWPeters ratio was positively correlated with a higher prevalence of resistant hypertension and furosemide use, lower serum albumin level, and higher Urinary protein-to-creatinine ratio (UPCR) level; it was highly dependent upon height, explaining why height was included in the equation described by Peters et al [10]
The %ECWBIA/ TBWWatson ratio exhibited a significant correlation with most demographic factors among these three parameters
Summary
Excess extracellular volume is a major clinical problem in patients with chronic kidney disease (CKD). Excess extracellular volume is a major clinical problem in patients with chronic kidney disease (CKD) and causes lower extremity edema, hypertension, pulmonary vascular congestion or edema, and heart failure [1]. In bioimpedance analysis (BIA), the ratio of extracellular water (ECW) to total body water (TBW) has been used as an indicator of the fluid volume status [2,3,4,5,6]. Using the Body Composition Monitor, which assesses the extracellular volume status by comparing the measured ECW to the expected ECW, Tsai et al recently reported an association between fluid overload and adverse kidney outcomes in the short term in patients with advanced stage 4 to 5 CKD [8]
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