Hyponatraemia (low blood sodium levels) affects up to one in three people admitted to hospital. The syndrome of inappropriate antidiuresis (SIAD) is the most common cause of hyponatraemia. The causes of SIAD are varied, and include respiratory and neurological illnesses, medications and malignancy. In some cases, no cause is identified (idiopathic).
At present, there is no consensus on how best to investigate for an underlying cause of hyponatraemia. Our usual practice is to perform a CT scan of the chest, and in some cases, brain, abdomen and pelvis in patients without a clear cause of SIAD, but there is no robust evidence base to support this. This approach is resource-intensive, can prolong a patient’s hospital stay, and may lead to incidental findings that can increase patient distress. We do not routinely repeat CT scans at an interval unless there is a specific reason.
This study will determine the incidence of underlying pathology on imaging in patients with hyponatraemia. The first component will be a retrospective study, looking at the yield of CT in those patients who have already had CT imaging to investigate their hyponatraemia. The second component will prospectively assess patients with SIAD to determine the yield of CT in detecting underlying pathology. We will try to ascertain if there are certain patient features that should prompt a CT, or if all patients with SIAD have CT imaging. This will help inform our clinical practice and guidelines at a national and international level.
How the study benefits patients in TUH and beyond
Our current approach to imaging in patients with hyponatraemia is ad-hoc, and as such has a potential both of over-investigation and missed diagnoses. This study will help identify risk factors for underlying pathology in patients with hyponatraemia so that the patient receives the correct imaging.
Hyponatraemia is more common in older age. Our population in Tallaght University Hospital is ageing, so it is crucial that we address how we investigate these patients in a safe way. We believe that this study will inform national and international guidelines on the role of imaging in the work-up of hyponatraemia, in particular SIAD, and fill a major research gap.
Research papers
Dr Aoife Garrahy, Consultant Endocrinologist, Tallaght University Hospital
Dr. Aoife Garrahy was appointed as a Consultant Endocrinologist in Tallaght University Hospital in 2023, after completing post-CSCST fellowships in Beaumont Hospital, Dublin and in Oxford University Hospital, UK.
Her sub-speciality interests include adrenal and pituitary endocrinology, and disorders of sodium and water balance, in particular hyponatraemia. Her research to date has been clinically focused, with direct implications for patient care, and has been published in the Journal of Clinical Endocrinology and Metabolism, European Journal of Endocrinology, Clinical Endocrinology, Age and Ageing, and European Journal of Clinical Pharmacology.