Some Causes of Polyuria
Cause | Suggestive Findings | Diagnostic Approach* |
|---|---|---|
Water diuresis† | ||
| Abrupt or chronic onset of thirst and polyuria Sometimes follows trauma, pituitary surgery, or hypoxic or ischemic cerebrovascular insult or occurs during the first few weeks of life | Laboratory tests Water deprivation test with ADH challenge ADH measurement when diagnosis remains unclear |
| Gradual onset of thirst and polyuria in a patient with:
| Laboratory tests Water deprivation test with ADH challenge |
Polydipsia
| Anxious, middle-aged woman History of psychiatric illnesses Infiltrating lesions of the hypothalamus (usually sarcoidosis) | Laboratory tests Water deprivation test with ADH challenge |
Excessive hypotonic IV fluid administration | Hospitalized patient receiving IV fluids Possibly edema | Resolution after fluids stopped or rate of administration decreased |
Diuretic use | Recent initiation of diuretic for volume overload (eg, due to heart failure or peripheral edema) Patients who are likely to surreptitiously use diuretics for weight loss (eg, those with eating disorders or concerns about weight, athletes, adolescents) | Clinical evaluation |
Adipsic diabetes insipidus (ADI) (a hypothalamic disorder characterized by absent thirst from loss of osmoreceptor function and polyuria from AVP deficiency accompanied byhypernatremia) | Polyuria without excessive thirst Sometimes lesions in the hypothalamic region, such as a germinoma or craniopharyngioma, or recent anterior communicating artery repair | Sometimes hyperosmolality (eg, 300 to 340 mOsm/kg [or mmol/kg]) and hypernatremia without excessive thirst |
Gestational diabetes insipidus (resulting from increased ADH metabolism) | Polydipsia (with excessive thirst) and polyuria that develop for the first time during the third trimester | Inappropriately normal plasma sodium (normally decreases by about 5 mEq/L [or mmol/L] in late pregnancy) with urine osmolality lower than plasma osmolality Resolution 2–3 weeks postpartum |
Solute diuresis† | ||
Uncontrolled diabetes mellitus | Thirst and polyuria in a young child or in an obese adult with family history of type 2 diabetes | Finger-stick glucose measurement |
Isotonic or hypertonic saline infusions | Hospitalized patient receiving IV fluids | Laboratory tests (eg, 24-hour urine collection showing total osmole excretion [osmolality × urine volume]) Stopping or slowing rate of administration (to confirm that polyuria resolves) |
High-protein tube feedings | Any patient receiving tube feedings | Switching to tube feedings with lower protein content (to confirm that polyuria resolves) |
Relief of urinary tract obstruction | Polyuria after bladder catheterization in a patient with bladder outlet obstruction | Clinical evaluation |
* Most patients should have measurement of urine and plasma osmolarity and serum sodium. | ||
† Urine osmolality is typically < 300 mOsm/kg (300 mmol/kg) in water diuresis and > 300 mOsm/kg (300 mmol/kg) in solute diuresis. | ||
ADH = antidiuretic hormone. | ||