Polydipsia

Polydipsia is fluid drinking in excess of 2 L/m²/day. In normal older children, water intake must surpass 10 L/m²/day to cause hyponatremia. In contrast, neonates and small infants cannot dilute urine to the same extent. These infants are prone to develop hyponatremia at water intake in excess of 4 L/m²/day.

Differential Diagnosis

• Diabetes mellitus (type I and type II)
  –Hyperglycemia drives an osmotic diuresis that causes polyuria, which then leads to dehydration, increased thirst, and polydipsia
• Diabetes insipidus
  –Abnormal water balance due to vasopressin (ADH) deficiency or resistance, causing excretion of large amounts of dilute urine
• Central or neurogenic diabetes insipidus (vasopressin deficiency)
  –Congenital
  –Familial (autosomal dominant)
  –Acquired: Neurosurgery, tumor (e.g., craniopharyngioma), head trauma, infiltrative/inflammatory, infectious
  • Nephrogenic diabetes insipidus (decreased responsiveness of the kidneys to vasopressin)
    –Familial (X-linked dominant and recessive forms)
    –Acquired: Renal disease, obstructive uropathy, hypercalcemia/hypercalciuria
    –Hypokalemia, drug-induced (e.g., lithium, diuretics, ethanol, cisplatin)
    –Gestational DI: Increased clearance of ADH by placental vasopressinase, lower osmolar threshold for thirst and ADH release
  • Primary polydipsia
    –Compulsive water drinking
    –Dipsogenic DI
  • Primary hyperaldosteronism
  • Diabetes insipidus, diabetes mellitus, optic atrophy, and deafness (DIDMOAD) syndrome
  • Bartter syndrome
  • Hypertension (e.g., pheochomocytoma)
  • Neuroblastoma
  • Cystinosis
  • Congestive heart failure

  Workup and Diagnosis

  • History: Quantification of fluid intake and urine output, drinking overnight, polyphagia, polyuria, nocturia, enuresis, psychosocial factors, interference with normal activities, growth progression, weight loss, weakness, fatigue, leg cramps/muscle aches, neurologic symptoms (headaches, visual changes)
  • Physical exam: Vital signs (HR, BP), weight, height, hydration assessment (mucous membranes, capillary refill, extremities’ temperature, skin turgor), neurologic exam (optic discs, EOM), energy level, muscle pain
  • Initial labs
    –Serum electrolytes, BUN, creatinine, glucose, calcium
    –Urinalysis with specific gravity, glucose and ketones
    –Simultaneous serum and urine osmolality (mOsm/kg)
    –Serum osm >300 and urine osm <300 =DI
    –If serum osm <270 and urine osm >600 DI unlikely
  • Further diagnostic workup
    –Water deprivation test in case of ambiguous history and labs (patient deprived of water, then ability to concentrate urine is assessed)
    –Differentiates between DI and water intoxication, and between central DI and nephrogenic DI (by response to a dose of vasopressin administered at the end of the study)
  • MRI of brain with special attention to the pituitary
  • Imaging of adrenal glands if hyperaldoterone suspected

  Treatment

  • Insulin and/or oral medications for DM
  • Central DI
    –Desmopressin treatment for older children
    –Not in immediate post-op period
    –Free water replacement
    –Desmopressin may lead to hyponatremia in infants and in postoperative cases that may also involve SIADH
  • Nephrogenic DI
    –Thiazide diuretics
    –Mild salt depletion
    –Prostaglandin synthesis inhibitors
  • Behavioral modification for compulsive water drinking
  • Surgical intervention for tumor
  • Strict measurement of input and output
  • Must assess presence or absence of intact thirst mechanism for central DI
  >>

Book Source Details

• Book Title: In A Page: Pediatric Signs and Symptoms
• Author(s): Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan
• Year of Publication: 2007
• Copyright Details: In A Page: Pediatric Signs and Symptoms, Copyright © 2007 Lippincott Williams & Wilkins.

Other Book Chapters Related to Diabetes insipidus

Read excerpts from these other book chapters related to Diabetes insipidus:

Copyright Details: In A Page: Pediatric Signs and Symptoms, Copyright © 2008 Williams & Wilkins.

More About Causes of Diabetes insipidus

• Back to symptom: Diabetes insipidus: Introduction (review 30 causes)
• Next Book Extract About Diabetes insipidus: POLYDIPSIA (Differential Diagnosis in Primary Care)
• All Book Extracts: All Online Book Extracts for Diabetes insipidus

More About This Book: Title: In A Page: Pediatric Signs and Symptoms Authors: Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 1-4051-0427-9

 » Next page: POLYDIPSIA (Differential Diagnosis in Primary Care)

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