Endocrine Abstracts

Despite the high prevalence of hyponatraemia and it’s clinical significance as a marker of underlying pathology, guidelines for imaging in patients with hyponatraemia are lacking. This retrospective review aims to evaluate the yield of radiological imaging specifically performed in the workup of hyponatraemia, and identify risk factors for underlying pathology. 134 patients out of a total 9194 patients undergoing CT in TUH between October 2021 and October 2023 were included in this study. 54% (n = 72) were female, mean age 71.9 years and nadir serum sodium concentration (pNa) 122 mmol/l. CT brain-thorax-abdomen-pelvis was performed in 44%, thorax only in 18% and CT thorax-abdomen-pelvis in 15%. 81% of CT imaging studies revealed abnormalities, with 60% having hyponatraemia-related findings. Non-malignant respiratory pathology was most common,61%, followed by malignancy,23%. 25% of patients with thoracic abnormalities on CT had a normal CXR. There were significantly higher rates of smoking (50% vs 8%,P = 0.01), alcohol excess (26% vs 4%,P = 0.02), lower BMI (23.7 vs. 27.5,P = 0.01), and lower serum albumin (39 vs. 43,P = 0.003) in patients with abnormal CTs compared with those with normal imaging, while pNa and age were not significantly different between the two groups. Rates of malignancy were similar in those with SIAD and those with hypo- and hypervolemic hyponatraemia, 10% vs 21%,P = 0.24; 35% of those with malignancy had a UNa <20 mmol/l. This study underscores the need for a low threshold for CT imaging in patients with hyponatraemia, especially but perhaps not limited to those with SIAD. These findings advocate for prospective studies to refine imaging protocols.