Abstract: FR-PO0577
Combining Ultrasonography and Body Composition Monitoring to Enhance Diagnosis of Syndrome of Inappropriate Antidiuresis
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Clinical - 2
November 07, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical
Authors
- Suphavejkornkij, Natthasit, King Chulalongkorn Memorial Hospital Division of Nephrology, Bangkok, Thailand
- Udomkarnjananun, Suwasin, King Chulalongkorn Memorial Hospital Division of Nephrology, Bangkok, Thailand
- Praditpornsilpa, Kearkiat, King Chulalongkorn Memorial Hospital Division of Nephrology, Bangkok, Thailand
- Avihingsanon, Yingyos, King Chulalongkorn Memorial Hospital Division of Nephrology, Bangkok, Thailand
- Noppakun, Kajohnsak, Chiang Mai University Faculty of Medicine, Chiang Mai, Thailand
- Townamchai, Natavudh, King Chulalongkorn Memorial Hospital Division of Nephrology, Bangkok, Thailand
Background
Euvolemic hyponatremia due to syndrome of inappropriate antidiuresis (SIAD) remains a diagnostic challenge. Physical examination and single time-point laboratory markers such as urine sodium (UNa), urine osmolality (Uosm) often yield limited diagnostic accuracy due to physiologic variability. This is one of the first studies to assess extracellular water overload (%ECWOH),defined as the percentage of extracellular volume in excess of predicted normal, as measured by Body Composition Monitoring(BCM), to aid the diagnosis of SIAD
Methods
We conducted a prospective cross-sectional study of 32 hospitalized patients with hypotonic hyponatremia. Final diagnoses was independently adjudicated by two nephrologists based on clinical and laboratory data throughout admission. Nephrologists were blinded to IVC and BCM results. Each patient underwent a single-session assessment including serum/urine biochemistry, IVC ultrasound, and body composition monitoring (BCM). Both IVC ultrasound and BCM were performed at the same time-point to reflect volume status. We analyzed %ECWOH as both a continuous and categorical variable (cutoffs at -20% to 10%)
Results
Among the 32 hyponatremia patients(mean serum sodium was 125.6 +- 4.1 mmol/L), 19 were diagnosed with SIAD and 13 with non-SIAD hyponatremia. %ECWOH between -20% and 10% yielded sensitivity of 85% and specificity of 66.7% for diagnosing SIAD. As a continuous variable, %ECWOH demonstrated the highest diagnostic performance (AUC = 0.78). UNa >30 mmol/L had moderate sensitivity (73.7%) but poor specificity (16.7%). IVC CI < 50% had limited value (specificity of 7.7%). Combining %ECWOH with IVC CI improved specificity to 75%
Conclusion
BCM-derived %ECWOH outperformed traditional laboratory and ultrasound markers in diagnosing SIAD. This noninvasive physiologic assessment may enhance diagnostic precision when used alongside conventional clinical and laboratory assessment. Using of BCM may reduce diagnostic delay and improve individualized treatment for hyponatremic patients