From Brew to Bronchoscopy: A Case of Hyponatremia That Was Anything but Basic.

We present the case of a 53-year-old female with a history of chronic alcohol use, hypertension, chronic obstructive pulmonary disease (COPD), and significant smoking history, who presented with severe hyponatremia. Initial laboratory studies revealed a sodium level of 115 mEq/L. The patient reported chronic vomiting, poor oral intake, and heavy alcohol consumption. Her hyponatremia was initially attributed to multiple factors, including alcohol-related dehydration, beer potomania, and potential medication-induced syndrome of inappropriate antidiuretic hormone (SIADH) secretion. However, further evaluation with chest computed tomography (CT) revealed extensive mediastinal lymphadenopathy. Bronchoscopy with fine-needle aspiration confirmed a diagnosis of small cell lung cancer (SCLC). This case highlights the importance of a comprehensive evaluation for hyponatremia, particularly in patients with malignancy risk factors, to avoid overlooking severe underlying conditions such as cancer.