Polyuria is defined as the daily production and excretion of more than 3 liters of urine. It is commonly reported as increased urination, particularly at night (nocturia). Polyuria may be aggravated by overhydration, caffeine or alcohol consumption, and ingestion of hyperosmolar substances such as glucose or salt.

Pathophysiology

Polyuria arises from mechanisms affecting renal water handling:

• Central causes: Dysfunction of the hypothalamus or posterior pituitary reduces antidiuretic hormone (ADH) secretion, impairing water reabsorption.

• Renal causes: Normal ADH levels but impaired tubular water reabsorption due to renal disorders or electrolyte imbalances.

• Drug-induced: Diuretics, cardiotonics, vitamin D, demeclocycline, phenytoin, lithium, or propoxyphene increase urine output.

• Psychogenic polydipsia: Compulsive water intake overwhelms renal concentrating capacity, producing dilute polyuria.

Emergency interventions

Although polyuria itself is rarely life-threatening, it can cause hypovolemia or electrolyte imbalance requiring prompt management:

• Assess and correct fluid deficits with oral or intravenous fluids.

• Monitor vital signs and orthostatic changes to detect hypovolemia.

• Track daily intake and output and perform daily weights.

• Evaluate and correct electrolyte abnormalities (sodium, potassium, calcium).

• For suspected diabetes insipidus, a fluid deprivation test may be indicated.

History and Physical Examination

Fluid Status Assessment

• Evaluate for signs of hypovolemia: tachycardia, orthostatic hypotension, dry mucous membranes, decreased skin turgor, fatigue, or recent weight loss >5%.

• If hypovolemia is present, initiate fluid replacement.

Polyuria Pattern and Associated Symptoms

• Determine onset, duration, and precipitating factors.

• Ask about daily fluid intake, nocturia, visual changes, headaches, or head trauma.

• Assess history of urinary tract obstruction, diabetes mellitus, renal disease, chronic hypokalemia, hypercalcemia, or psychiatric disorders.

Neurologic and Genitourinary Examination

• Examine level of consciousness.

• Palpate bladder and inspect urethral meatus.

• Obtain a urine specimen and measure specific gravity.

Medical causes

Other Causes

• Diagnostic tests: Contrast media in radiographic studies may transiently induce polyuria.

• Drugs: Diuretics, cardiotonics, vitamin D, demeclocycline, phenytoin, lithium, propoxyphene.

Special Considerations

• Maintain adequate fluid balance; record intake and output accurately.

• Weigh the patient daily and monitor vital signs.

• Review medications for potential contributors and adjust if possible.

• Prepare for laboratory studies: serum electrolytes, osmolality, blood urea nitrogen, creatinine.

Patient Counseling

• Explain the underlying disorder and the importance of fluid replacement.

• Teach signs of dehydration to monitor at home.

• Emphasize daily weight monitoring and reporting abnormal findings.

Pediatric Pointers

• Major pediatric causes: congenital nephrogenic diabetes insipidus, medullary cystic disease, polycystic kidney disease, distal renal tubular acidosis.

• Children are at higher risk for dehydration; check urine specific gravity with each void.

• Watch for decreased weight, dry mucous membranes, pale/mottled skin, low urine output, or absent tears.

Geriatric Pointers

• Chronic polyuria in elderly patients often indicates underlying disease.

• Evaluate for malignancy or other systemic conditions contributing to polyuria.

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.