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Polyuria is urine output of > 3 L/day; it must be distinguished from frequency, which is the need to urinate many times during the day or night but in normal or less than normal volumes. Either problem can include nocturia.
Etiology
Polyuria implies water or solute diuresis. Causes of water diuresis include central or nephrogenic diabetes insipidus, psychogenic polydipsia, and hypotonic IV infusions. Causes of solute diuresis include diabetes mellitus, IV saline infusions, high-protein tube feedings, relief of urinary tract obstruction, and Na-wasting nephropathy.
The most common causes of frequency include UTIs, urinary incontinence, benign prostatic hyperplasia (BPH), and urinary tract calculi.
Evaluation
History and physical
examination:
History can sometimes distinguish polyuria from frequency and suggest a cause. Polyuria caused by diabetes insipidus is suggested by a history of malignancy or chronic granulomatous disease (via hypercalcemia), use of certain drugs ( lithium , cidofovir , foscarnet ), and less common conditions (eg, sickle cell disease, renal amyloidosis, sarcoidosis, Sjögren's syndrome) whose manifestations are often more prominent than and precede the polyuria.
Abrupt onset of polyuria at a precise time suggests central diabetes insipidus (see Pituitary Disorders: Central Diabetes Insipidus), as does preference for extremely cold or iced water. Polyuria caused by diuresis is suggested by a history of diuretic use or diabetes mellitus, and that caused by polydipsia is suggested by a history of psychiatric illness (bipolar disorder, schizophrenia). Dysuria suggests frequency from UTI or calculi; prior pelvic surgery suggests incontinence, and weak urinary stream suggests frequency caused by BPH.
Physical examination generally plays a limited role in the evaluation of polyuria and frequency.
Testing:
Measures of urinary volume in 24 h distinguish polyuria ( > 3 L/day) from frequency if the difference is not obvious by history alone; output > 5 L/day suggests central diabetes insipidus, lithium toxicity, or polydipsia. Urinalysis should be performed to detect UTI or glycosuria. Serum Na measurements can distinguish polydipsia (Na < 137 mEq/L) from diabetes insipidus (Na >142 mEq/L). Diagnosis of diabetes insipidus is made by completely restricting free water intake, then measuring urine volume and osmolarity, and serum Na and osmolarity (see Pituitary Disorders: Diagnosis; see Abnormal Renal Transport Syndromes: Nephrogenic Diabetes Insipidus).
Treatment
Treatment varies by cause.
Last full review/revision November 2005
Content last modified November 2005
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