Polydipsia is defined as excessive thirst, which may manifest as increased fluid intake. It is commonly associated with endocrine disorders, renal dysfunction, electrolyte imbalances, and certain medications. Polydipsia can reflect decreased fluid intake, excessive urine output, or abnormal loss of water and salt.

Pathophysiology

The mechanisms underlying polydipsia vary by etiology:

• Diabetes insipidus: Reduced or absent antidiuretic hormone (ADH) activity leads to inability to concentrate urine, causing polyuria and compensatory polydipsia.

• Diabetes mellitus: Hyperglycemia creates a hyperosmolar state, inducing osmotic diuresis and increased thirst.

• Electrolyte imbalances: Hypercalcemia and hypokalemia alter renal tubular function, leading to polyuria and secondary polydipsia.

• Psychogenic polydipsia: Compulsive water intake occurs independent of physiological needs, often associated with psychiatric disorders.

• Renal disorders: Chronic kidney damage impairs urine concentration, resulting in polyuria and polydipsia.

Emergency interventions

While polydipsia itself is rarely immediately life-threatening, associated dehydration or fluid-electrolyte disturbances require prompt management:

• Correct hypovolemia with intravenous fluids as indicated.

• Monitor vital signs in supine and standing positions for orthostatic changes.

• Track intake and output meticulously.

• Manage underlying electrolyte disturbances (e.g., hypercalcemia, hypokalemia) promptly.

• In psychogenic polydipsia, monitor for water intoxication and hyponatremia.

History and Physical Examination

Onset and Pattern

• Determine how much fluid the patient drinks daily and frequency of urination.

• Ask if nocturia occurs and whether urination disturbs sleep.

• Note any recent lifestyle changes, stressors, or psychiatric symptoms.

Medical History

• Family history of diabetes, kidney disease, or psychiatric illness.

• Past medical conditions including endocrine or renal disorders.

• Medication history: diuretics, demeclocycline, phenothiazines, anticholinergics.

Physical Examination

• Vital signs: supine and standing blood pressure and pulse (orthostatic changes may indicate hypovolemia).

• Signs of dehydration: dry mucous membranes, poor skin turgor.

• Weight trends: unexplained weight loss may indicate hyperglycemia or renal disease.

Medical causes

Other Causes

• Drugs: Diuretics, demeclocycline, phenothiazines, anticholinergics.

• Pediatric considerations: Diabetes mellitus or insipidus, Prader-Willi syndrome, neuroblastoma, pheochromocytoma, or habitual polydipsia.

Special Considerations

• Monitor fluid balance (intake/output, daily weights).

• Assess orthostatic vital signs for hypovolemia.

• Ensure adequate hydration as thirst is compensatory.

Patient Counseling

• Educate on underlying cause, treatment, and potential complications.

• Discuss diet, exercise, and home glucose monitoring if relevant.

• Emphasize importance of reporting rapid weight changes, polyuria, or worsening symptoms.

Pediatric Pointers

• In children, polydipsia usually arises from diabetes mellitus or insipidus.

• Rare causes: pheochromocytoma, neuroblastoma, Prader-Willi syndrome.

• Habitual polydipsia may occur without disease; careful assessment needed.

References

1. Berkowitz, C. D. Berkowitz’s Pediatrics: A Primary Care Approach (4th ed.). USA: American Academy of Pediatrics; 2012.

2. Buttaro, T. M., Tybulski, J., Bailey, P. P., Sandberg-Cook, J. Primary Care: A Collaborative Practice (pp. 444–447). St. Louis, MO: Mosby Elsevier; 2008.

3. Colyar, M. R. Well-Child Assessment for Primary Care Providers. Philadelphia, PA: F.A. Davis; 2003.

4. Lehne, R. A. Pharmacology for Nursing Care (7th ed.). St. Louis, MO: Saunders Elsevier; 2010.

5. McCance, K. L., Huether, S. E., Brashers, V. L., Rote, N. S. Pathophysiology: The Biologic Basis for Disease in Adults and Children. Maryland Heights, MO: Mosby Elsevier; 2010.

6. Sommers, M. S., Brunner, L. S. Pocket Diseases. Philadelphia, PA: F.A. Davis; 2012.