Polyuria – Definition, Causes, Symptoms, Diagnosis and Treatment
POLYURIA
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Last Updated : 10/1/2014
Jagdish Kathwate
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What is polyuria
Polyuria is the passage of large volumes of urine with an increase in urinary frequency. A normal daily urine output in children is about one liter. Polyuria is defined as a daily urine output of more than 3 liters.

What are Causes of polyuria in children
• Endocrine:
• Diabetes mellitus.
• Cranial diabetes insipidus.
• Cushing's syndrome.
• Renal:
• Chronic kidney disease.
• Relief of chronic urinary obstruction.
• Early chronic pyelonephritis.
• Nephrogenic diabetes insipidus.
• Iatrogenic:
• Diuretic therapy.
• Other drugs - e.g., lithium, tetracyclines.
• Metabolic:
• Hypercalcaemia (e.g., osteoporosis treatment, multiple bony metastases, hyperparathyroidism).
• Potassium depletion (e.g., chronic diarrhoea, diuretics, primaryhyperaldosteronism).

How polyuria presents
Thirst, increased fluid intake: thirst will usually accompany polyuria. In psychogenic polydipsia (most often seen in adolescents), thirst with compulsive water drinking is the predominant symptom.
Nocturia will usually be a feature of true polyuria, and secondary enuresis in children can occur.
Associated general symptom - e.g., weight loss, malaise, headache and shortness of breath - increase the likelihood of significant pathology.
Weight loss: rapid onset of weight loss is a feature of type 1 diabetes. Weight loss is also a feature of chronic renal failure and may also be due to dehydration in diabetes insipidus.
Symptoms suggestive of diabetes insipidus: daily urine output may be greater than 10 liters. A pituitary tumor may cause headaches, visual disturbance and symptoms of pituitary hormone excess or deficiency. Other brain tumors in the region of the pituitary may be also be responsible - e.g., craniopharyngiomas.
Past medical history: chronic renal failure may be a consequence of diabetes mellitus, connective tissue disease such as systemic lupus erythematosus (SLE), renal vascular disease, pyelonephritis or obstructive uropathy. Cranial diabetes insipidus may be due to pituitary surgery or irradiation, infection (meningitis, cerebral abscess), sarcoidosis or head.
Family history: family history of diabetes mellitus or renal problems - e.g., polycystic kidneys or nephrogenic diabetes insipidus.

What investigations your doctor will do
• Urine tests:
• Urinalysis for diabetes (glucose, ketones) and signs of renal disease (proteinuria). Specific gravity is very low in diabetes insipidus and psychogenic polydipsia.
• Urine osmolality: early morning urine sample in conjunction with a plasma osmolality.
• Quantification of proteinuria: 24-hour urine collection; albumin-creatinine ratio (ACR) for microalbuminuria.
• Blood tests:
• Renal function, electrolytes: calcium, potassium, abnormalities suggesting chronic kidney disease.
• Fasting (preferable) or random glucose.
Complete blood counts, ESR: anemia found in chronic renal failure and collagen vascular diseases. Bone marrow infiltration may be evident in myeloma. ESR raised in collagen vascular diseases, myeloma and malignancy.
• Pituitary function tests.
• Autoantibody screen: if collagen vascular disease is a possible cause of renal failure.
• Serum lithium concentration if relevant.
• Further investigations:
• These investigations (and some of the urine and blood tests) are more likely to be part of secondary care investigations.
• Imaging of the renal tract: ultrasound, X-ray, CT scan of the abdomen.
• Renal biopsy.
• Lateral skull X-ray: may show an enlarged pituitary fossa with pituitary tumors. Calcification is common with craniopharyngiomas.
• MRI or CT scan of brain: for pituitary or other brain tumor.
• Water deprivation and desmopressin test: may be performed under supervision in secondary care and is useful in distinguishing cranial and nephrogenic diabetes insipidus.

What is treatment of polyuria
• Your child may require admission to hospital if significantly dehydrated, whatever the likely cause.
• Fluid balance and electrolyte disturbance will need to be corrected.
• Further management will depend on the results of initial investigations and any confirmed cause of polyuria.



Contributor Information and Disclosures

Jagdish Kathwate
MD Pediatrics. Assistant Professor, Government Medical College, Aurangabad, India.


First Created : 1/9/2002
Last Updated : 10/1/2014

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