Polyuria
A relatively common sign, polyuria is the daily production and excretion of more than 3 L of urine. It’s usually reported by the patient as increased urination, especially when it occurs at night. Polyuria is aggravated by overhydration, consumption of caffeine or alcohol, and excessive ingestion of salt, glucose, or other hyperosmolar substances.
Polyuria usually results from the use of certain drugs, such as a diuretic, or from a psychological, neurologic, or renal disorder. It can reflect central nervous system dysfunction that diminishes or suppresses secretion of antidiuretic hormone (ADH), which regulates fluid balance. Alternatively, when ADH levels are normal, it can reflect renal impairment. In both of these pathophysiologic mechanisms, the renal tubules fail to reabsorb sufficient water, causing polyuria.
History
Explore the frequency and pattern of the polyuria. When did it begin? How long has it lasted? Was it precipitated by a certain event? Ask the patient to describe the pattern and amount of his daily fluid intake. Is the patient unusually tired or thirsty? Has he recently lost more than 5% of his body weight? Check for a history of visual deficits, headaches, or head trauma, which may precede diabetes insipidus. Also check for a history of urinary tract obstruction, diabetes mellitus, renal disorder, chronic hypokalemia or hypercalcemia, or psychiatric disorder (both past and present). Find out the schedule and dosage of any drugs the patient is taking.
Physical assessment
Take vital signs, noting increased body temperature, tachycardia, and orthostatic hypotension (a 10 mm Hg or greater decrease in systolic blood pressure upon standing and a 10 beats per minute or greater increase in heart rate upon standing). Inspect for dry skin and mucous membranes, decreased skin turgor and elasticity, and reduced perspiration.
Perform a neurologic assessment, noting especially any change in the patient’s level of consciousness. Then palpate the bladder and inspect the urethral meatus. Obtain a urine specimen and check its specific gravity.
Medical causes
Acute tubular necrosis
During the diuretic phase of acute tubular necrosis, polyuria of less than 8 L/day gradually subsides after 8 to 10 days. Urine specific gravity (1.010 or less) increases as polyuria subsides. Related findings include weight loss, decreasing edema, and nocturia.
Diabetes insipidus
With diabetes insipidus, polyuria of about 5 L/day with a specific gravity of 1.005 or less is common, although extreme polyuria — up to 30 L/day — occasionally occurs. Polyuria is commonly accompanied by polydipsia, nocturia, fatigue, and signs of dehydration, such as poor skin turgor and dry mucous membranes.
Diabetes mellitus
With diabetes mellitus, polyuria seldom exceeds 5 L/day, and urine specific gravity typically exceeds 1.020. The patient usually reports polydipsia, polyphagia, weight loss, weakness, frequent urinary tract infections and yeast vaginitis, fatigue, and nocturia. The patient may also display signs of dehydration and anorexia.
Glomerulonephritis (chronic)
Polyuria gradually progresses to oliguria with chronic glomerulonephritis. Urine output is usually less than 4 L/day; specific gravity is about 1.010. Related GI findings include anorexia, nausea, and vomiting. The patient may experience drowsiness,fatigue, edema, headache, elevated blood pressure, and dyspnea. Nocturia, hematuria, frothy or malodorous urine, and mild to severe proteinuria may also occur.
Hypercalcemia
Elevated plasma calcium levels may lead to nephropathy, usually producing polyuria of less than 5 L/day with a specific gravity of about 1.010. Accompanying signs and symptoms include polydipsia, nocturia, constipation, paresthesia and, occasionally, hematuria, and pyuria. With severe hypercalcemia, the patient’s condition worsens rapidly and he experiences anorexia, vomiting, stupor progressing to coma, and renal failure.
Hypokalemia
Prolonged potassium depletion may lead to nephropathy, which results in polyuria — usually less than 5 L/day with a specific gravity of about 1.010. Associated findings include polydipsia, circumoral and foot paresthesia, hypoactive deep tendon reflexes, fatigue, hypoactive bowel sounds, nocturia, arrhythmias, and muscle cramping, weakness, or paralysis.
Postobstructive uropathy
After resolution of a urinary tract obstruction, polyuria — usually more than 5 L/day with a specific gravity of less than 1.010 — occurs for up to several days before gradually subsiding. Bladder distention and edema may occur with nocturia and weight loss. Occasionally, signs of dehydration appear.
Pyelonephritis
Acute pyelonephritis usually results in polyuria of less than 5 L/day with a low but variable specific gravity. Other findings include persistent high fever, flank pain (usually unilateral), hematuria, costovertebral angle tenderness, chills, weakness, dysuria, urinary frequency and urgency, tenesmus, and nocturia. Occasionally, nausea, anorexia, vomiting, and hypoactive bowel sounds occur.
Chronic pyelonephritis produces polyuria of less than 5 L/day that declines as renal function worsens. Urine specific gravity is usually about 1.010 but may be higher if proteinuria is present. Other effects include irritability, paresthesia, fatigue, nausea, vomiting, diarrhea, drowsiness, anorexia, pyuria and, in late stages, elevated blood pressure.
Sickle cell anemia
Sickle cell anemia may cause nephropathy, typically producing polyuria of less than 5 L/day with a specific gravity of about 1.020. Additional findings include polydipsia, fatigue, abdominal cramps, arthralgia, priapism and, occasionally, leg ulcers and bony deformities.
Other causes
Diagnostic tests
Transient polyuria can result from radiographic tests that use contrast media.
Drugs
Diuretics characteristically produce polyuria. Cardiotonics, vitamin D, demeclocycline, phenytoin, lithium, methoxyflurane, and propoxyphene can also produce polyuria.
Special considerations
Maintain adequate fluid balance when the patient has polyuria. Record intake and output accurately, and weigh the patient daily. Closely monitor the patient’s vital signs to detect fluid imbalance, and encourage him to drink adequate fluids. Review his medications, and recommend modification where possible to help control symptoms.
Prepare the patient for serum electrolyte, osmolality, blood urea nitrogen, and creatinine studies to monitor fluid and electrolyte status, and for a fluid deprivation test to determine the cause of polyuria.
Pediatric pointers
The major causes of polyuria in children are congenital nephrogenic diabetes insipidus, medullary cystic disease, polycystic renal disease, and distal renal tubular acidosis.
Because a child’s fluid balance is more delicate than an adult’s, check his urine specific gravity at each voiding, and be alert for signs of dehydration. These include a decrease in body weight, decreased skin turgor, dry mucous membranes, decreased urine output, absence of tears when crying, and pale, mottled, or gray skin.
Geriatric pointers
In elderly patients, chronic pyelonephritis is commonly associated with an underlying disorder. The possibility of associated malignant disease must be investigated.
Patient counseling
Teach your patient about his underlying disorder and the need to replace fluids. Have him weigh himself daily and report any weight loss to his health care provider. Explain the signs and symptoms of dehydration and the importance of increasing fluid intake, especially in hot weather.
Pictures
Book Source Details
- Book Title: Signs & Symptoms: A 2-in-1 Reference for Nurses
- Author(s): Springhouse
- Year of Publication: 2007
- Copyright Details: Signs & Symptoms: A 2-in-1 Reference for Nurses, Copyright © 2007 Lippincott Williams & Wilkins.
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Copyright Details: Signs & Symptoms: A 2-in-1 Reference for Nurses, Copyright © 2008 Williams & Wilkins.
More About Causes of Urinary urgency
» Next page: Urinary frequency (Signs & Symptoms: A 2-in-1 Reference for Nurses)
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