Endocrine Abstracts

Background: Syndrome of Inappropriate Anti-diuretic Hormone (SIADH) secretion is the most common cause of hyponatremia in cancer patients. About 14% of hyponatremia in medical inpatients is due to underlying tumor-related conditions. We performed an audit to evaluate prevalence of lung malignancy in patients newly diagnosed with SIADH and to assess proportion of patients having radiological evidence of lung cancer through chest x ray and/or CT chest imaging six months after established biochemical diagnosis of SIADH.

Methods: A comprehensive retrospective review of case notes and the laboratory database was conducted for 47 patients (23 Males/24 Females, mean age 77.65 ± 13.49 years) diagnosed with SIADH in our Centre in 2019. Mean sodium level at diagnosis was 123.24 ± 5.12 mmol/l . A minimum of 6 months follow-up data were reviewed and radiological findings of lung malignancy through chest x ray and/or CT chest at baseline and 6 months after established diagnosis of SIADH were analysed.

Results: At SIADH diagnosis, 73% of patients had either CXR, CT Chest, or CT chest abdomen and pelvis at baseline. Radiological data suggested that eight patients (23%) had lung malignancy (new/old) and three patients (9%) had metastatic disease at baseline. At 6 months, one out of 12 patient (0.08%) who had the chest imaging developed new lung cancer.

Conclusion: A significant percentage of SIADH patients were positive lung malignancy in our cohort. Therefore, we suggest that screening these patients at SIADH diagnosis for lung cancer through radiological imaging seems to be a reasonable approach. Although further imaging studies at 6 months does not appear to add significantly. Our observations need to be confirmed and extended in larger cohorts.