Yield of workup for patients with idiopathic presentation of the syndrome of inappropriate antidiuretic hormone secretion

• Most patients with SIADH of unknown etiology do not have an underlying disorder.
• Consequently, yield of diagnostic modalities is low for these patients.
• The yield of diagnostic workup is higher in young patients with recent onset of SIADH.
• Our data suggest that extensive workup is not required for most of these patients.

PurposeTo determine the proportion of patients for whom the syndrome of inappropriate antidiuretic hormone secretion (SIADH) is the presenting symptom of an underlying disorder, to describe the yield of different diagnostic modalities for patients with SIADH and an unknown etiology, and to define patients for whom such a workup is indicated.MethodsA single center retrospective study including all patients diagnosed with SIADH without an apparent etiology in a large community hospital and tertiary center between 1.1.07 and 1.1.13. Two physicians reviewed every patient's medical file for predetermined relevant clinical data.ResultsEleven of the 99 patients without an apparent etiology for SIADH at presentation were found to have an underlying cause on workup. Yield of performed workup was low, with a pathology demonstrated on 0%–30.8% of tests according to the different modalities used. Patients with presumed idiopathic SIADH at presentation who were later found to have a specific etiology were younger than patients with true idiopathic SIADH, had a significantly shorter duration of hyponatremia prior to SIADH diagnosis, had higher urine osmolality and a clinical presentation suggestive of an undiagnosed disorder.ConclusionsOur findings support a clinically-based approach to patients with idiopathic SIADH, rather than an extensive routine workup for all patients.