Crozer Chester Medical Center, USA
Reena Bansal has completed her MBBS from Mysore Medical College and Research Institute in the year 2008 and Masters from Rajiv Gandhi University of Health Sciences in the year 2011. She is currently associated as Resident Physician with Crozer Chester Medical Center since 2014.
Introduction: Hyponatremia is a common condition seen in clinical practice. SIADH is a common cause of this hyponatremia, especially in small cell lung cancer. It usually accompanies but can also precede the diagnosis of the tumor with an incidence of about 3.7% to 5%. We report this interesting case of hyponatremia, which led to the diagnosis of lung cancer. Case Report: A 78 year old Caucasian female was admitted with complaints of intermittent nausea and vomiting for 3 months. She was found to have sodium levels of 119. She denies being on any water pills, excessive fluid intake or recent medication changes. She had a 50 pack year smoking history. Management: Severe hyponatremia in the setting of nausea in a patient who has been a chronic smoker with no hx of diabetes, heart failure, cirrhosis or kidney disease and with normal thyroid functions and lipids and the increased urine osmolality, led us to the diagnosis of SIADH. However, work up for the cause of SIADH, in the setting of 50 pack year history of smoking made us to a CAT scan of the lung, which revealed a dominant 2.0×1.6 cm medial right lower lobe pulmonary nodule with multiple smaller bilateral pulmonary nodules with mediastinal and hilar lymphadenopathy. She has given a few doses of tolvaptan with appropriate response in sodium. Discussion: Hyponatremia secondary to SIADH is a known paraneoplastic manifestation of lung cancer. The incidence of hyponatremia in lung cancer is reported to be only 1% in NSCLC and 15% in SCLC. It is important to treat hyponatremia but it is equally important to evaluate the cause of hyponatremia. In our patient, the single complaint of nausea led us to the diagnosis of lung cancer eventually.