Urine Sodium and Urine Osmolality as Predictors for Non-Response to Treatment in Syndrome of Inappropriate Antidiuretic Hormone Secretion

Introduction Hyponatremia is a common electrolyte imbalance, often caused by the Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH). SIADH results from excessive water retention due to inappropriate ADH secretion. While fluid restriction is a standard treatment, responses vary, and there is a need to identify predictors of non-response. Methods This prospective observational study involved 171 patients with SIADH. Inclusion criteria included serum sodium <125 mmol/L and urine osmolality >100 mOsm/kg along with others. Patients received fluid restriction (1 litre/day) with or without hypertonic saline. Data collection included clinical features, laboratory parameters, and response to treatment at 12 and 24 hours. The association between urine sodium, urine osmolality, and treatment response was analysed. Results The median age was 69 years, with a male predominance (59.1%). Pneumonia (28.7%) and malignancies (14%) were common aetiologies. Significant predictors of non-response to fluid restriction included high urine sodium and urine osmolality at the specified time limit. The group that failed to achieve the 24-hour serum sodium target had higher urine osmolality and sodium levels than responders. These findings align with previous studies highlighting the predictive value of urine osmolality and urine sodium. Conclusion Elevated urine sodium and urine osmolality significantly predict non-response to fluid restriction in SIADH. Identifying these markers can guide personalized treatment strategies, improving outcomes and avoiding unnecessary interventions