What are the indications for referring a patient with SIADH to secondary care for further evaluation?

For patients with syndrome of inappropriate antidiuretic hormone secretion (SIADH) or suspected SIADH, referral to secondary care is indicated in several situations:

• Immediate Hospital Admission:
  • If the patient has acute onset hyponatraemia (duration less than 48 hours) or severe hyponatraemia (serum sodium concentration less than 125 mmol/L) ¹.
  • If the patient is symptomatic ¹.
  • If there are signs of hypovolaemia ¹.
  • If a rapidly decreasing serum sodium concentration is observed ¹.
• Urgent 2-Week Wait Referral:
  • If malignant disease is suspected as an underlying cause of SIADH ¹.
• Referral to an Endocrinologist (urgency based on clinical judgement):
  • If SIADH or another endocrine cause of hyponatraemia is suspected ¹.
  • If the cause of hyponatraemia is not clear, particularly if it is persistent and no cause can be identified in primary care ¹.
  • If the patient has asymptomatic, moderate hyponatraemia (serum sodium concentration of 125–129 mmol/L) ¹.
  • If the serum sodium concentration remains low after stopping a medication that may have been contributing to the hyponatraemia ¹.
• Specialist Supervision for Treatment:
  • Treatment with Tolvaptan for hyponatraemia secondary to SIADH should be initiated in hospital or under specialist supervision ¹.