Evaluation of Bedside Physical Examination Findings and Point-of-Care Ultrasound Markers for Early Detection of Fluid Overload in Patients with Acute Kidney Injury

Background: Acute kidney injury (AKI) frequently precipitates positive fluid balance and iatrogenic fluid overload, which independently correlate with prolonged mechanical ventilation, renal replacement therapy dependence, and elevated mortality. Traditional bedside physical examination markers—such as peripheral edema, pulmonary auscultation, and daily body weight—exhibit notoriously low sensitivity and specificity for detecting early interstitial and intravascular congestion. Point-of-care ultrasound (POCUS) has emerged as a transformative diagnostic modality allowing real-time, non-invasive hemodynamic and tissue perfusion assessment. This study evaluates the diagnostic efficacy of combining structured physical examination findings with comprehensive multi-organ POCUS markers, including inferior vena cava (IVC) collapsibility, lung ultrasound (LUS) B-lines, and venous excess ultrasound (VExUS) grading, for the early detection of fluid overload in critically and acutely ill patients with AKI. Methods: A prospective observational cohort study was conducted over a twelve-month period involving 140 adult patients admitted with confirmed AKI across medical and surgical intensive care units. Baseline clinical evaluation recorded traditional physical signs of congestion (peripheral pitting edema, jugular venous distension [JVD], basal crackles, hepatomegaly). Serial POCUS examinations evaluated IVC maximum and minimum diameters, respiratory collapsibility index, pulmonary B-line scores across an 8-zone scanning protocol, and hepatic-portal-renal venous Doppler flow patterns (VExUS grading). Fluid overload was quantified as cumulative percentage weight gain from baseline admission weight (threshold ≥10%). Results: Among the 140 analyzed cohorts, 58 patients (41.4%) developed clinically significant fluid overload (≥10% weight gain). Traditional physical examination demonstrated high specificity but poor sensitivity (JVD sensitivity 42.1%, specificity 88.3%; peripheral edema sensitivity 51.7%, specificity 74.4%). Conversely, multi-organ POCUS parameters exhibited superior diagnostic performance. A high LUS B-line score (>15 bilateral B-lines) demonstrated a sensitivity of 84.5% and specificity of 81.7% for detecting clinically relevant extravascular lung water. An engorged, non-reactive IVC (>2.1 cm with <50% collapsibility) combined with severe VExUS grade 2 or 3 venous congestion patterns predicted worsening AKI and diuretic resistance with an area under the receiver operating characteristic curve (AUROC) of 0.89 (95% CI, 0.84–0.94), significantly outperforming traditional clinical assessment alone (AUROC 0.64, p < 0.001). Conclusion: Conventional physical examination parameters grossly underestimate occult fluid accumulation in patients with acute kidney injury. Integrating serial multi-organ POCUS— specifically lung ultrasound, inferior vena cava dynamics, and VExUS grading—provides a rapid, highly accurate diagnostic framework for early recognition of fluid overload, guiding targeted decongestive therapies, and potentially mitigating adverse renal outcomes.