Differential Diagnosis for Inability to Maintain Sodium

The inability to maintain sodium levels can be caused by various conditions. Here's a differential diagnosis organized into categories:

• Single Most Likely Diagnosis

  • Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH): This condition is characterized by the excessive release of antidiuretic hormone (ADH), leading to water retention and subsequent dilutional hyponatremia. It's a common cause of hyponatremia, especially in hospitalized patients.

• Other Likely Diagnoses

  • Heart Failure: Decreased cardiac output can lead to increased ADH secretion and activation of the renin-angiotensin-aldosterone system, causing water and sodium retention.
  • Nephrotic Syndrome: Excessive loss of albumin in the urine can lead to decreased oncotic pressure, causing fluid to shift from the vascular space to the interstitial space, and subsequent activation of ADH and the renin-angiotensin-aldosterone system.
  • Liver Cirrhosis: Portal hypertension and decreased liver function can lead to increased ADH secretion and activation of the renin-angiotensin-aldosterone system, causing water and sodium retention.

• Do Not Miss Diagnoses

  • Adrenal Insufficiency: Primary or secondary adrenal insufficiency can lead to decreased production of aldosterone, causing impaired sodium retention and potassium excretion.
  • Diabetic Ketoacidosis: Although typically associated with hypernatremia, diabetic ketoacidosis can cause hyponatremia due to the osmotic effects of glucose and the subsequent shift of water into cells.
  • Cerebral Salt Wasting: A rare condition characterized by excessive renal sodium loss due to a defect in renal tubular function, often seen in patients with cerebral disorders.

• Rare Diagnoses

  • Pseudohypoaldosteronism: A rare genetic disorder characterized by resistance to aldosterone, leading to impaired sodium retention and potassium excretion.
  • Bartter Syndrome: A rare genetic disorder affecting the kidneys' ability to reabsorb sodium and chloride, leading to excessive urinary loss of these electrolytes.
  • Gitelman Syndrome: A rare genetic disorder affecting the kidneys' ability to reabsorb sodium, chloride, and potassium, leading to excessive urinary loss of these electrolytes.