Physiological discordance between clinical examination, bioimpedance spectroscopy, and lung ultrasound in maintenance hemodialysis patients without heart failure

Background and objectives Accurate volume assessment in maintenance hemodialysis remains challenging because no single bedside method fully characterizes extracellular fluid overload. We evaluated discordance among clinical examination, bioimpedance spectroscopy, and abbreviated six-zone lung ultrasound, the prevalence of subclinical pulmonary congestion, and factors associated with pulmonary congestion. Methods In this single-center cross-sectional study, 116 adults receiving maintenance hemodialysis without clinically recognized heart failure underwent standardized clinical examination, whole-body bioimpedance spectroscopy, and predialysis six-zone lung ultrasound. Subclinical pulmonary congestion was defined as a prespecified total B-line count of ≥3 in clinically euvolemic patients. Agreement was assessed using Cohen’s kappa, and independent associations were evaluated using multivariable Poisson regression. Results Among 49 clinically euvolemic patients, 27 (55.1%) had subclinical pulmonary congestion, representing 23.3% of the cohort. Clinical examination showed fair agreement with lung ultrasound for ≥3 B-lines (κ = 0.28; 95% CI, 0.11–0.45), whereas agreement between lung ultrasound and bioimpedance-defined overhydration was slight (κ = 0.16; 95% CI, −0.03 to 0.35). Bioimpedance-derived overhydration, but not interdialytic weight gain, was independently associated with subclinical pulmonary congestion. Conclusion Discordance among clinical examination, bioimpedance spectroscopy, and lung ultrasound was common and is consistent with the hypothesis that these modalities capture partially distinct aspects of volume status and pulmonary congestion. Abbreviated lung ultrasound frequently identified clinically occult pulmonary congestion despite apparent clinical euvolemia, supporting a multidimensional approach to bedside volume assessment in maintenance hemodialysis.