The clinical challenge of SIADH—three cases

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) remains a challenging disorder to diagnose and treat. Three cases are presented to illustrate these challenges. The first two cases had drug-induced SIADH secondary to a selective serotonin reuptake inhibitor (for depression) or carbamazepine (for trigeminal neuralgia). The third case had SIADH possibly secondary to bronchiectasis. The lowest serum sodium concentrations ranged between 118 and 124 mmol/L in the three cases. Hyponatraemia was not acute and severe symptoms were absent. However, several mild neurological symptoms were present. In the first case, hyponatraemia likely contributed to a fall, which resulted in a fracture of the odontoid process of the axis. The other two cases also had gait disturbances, in addition to nausea, headache, impaired memory, difficulty concentrating and confusion. In at least two of the cases, the underlying cause of SIADH was impossible to reverse. Traditional treatment for SIADH with fluid restriction and demeclocycline failed, caused side effects or increased duration of hospital stay. These examples suggest a need for better treatment options. The introduction of the vasopressin-receptor antagonists for SIADH may be a welcome new therapy to overcome some of these challenges.