POLYDIPSIA
Excessive thirst is best analyzed by the application of physiology. Increased desire for water may be due to a decreased intake, as in prolonged abstinence, vomiting of pyloric stenosis and intestinal obstruction, and diarrhea of any cause. Poor transport of fluid in hemorrhagic or vasomotor shock and CHF may be the cause. Anything that decreases the effective circulatory volume, such as hypoalbuminemia, may cause retention of salt and consequent thirst through the renin–angiotensin–aldosterone mechanism. Increased output of water may be responsible for polydipsia. The increased output may result from a solute diuresis in diabetes mellitus and hypercalcemic states (e.g., hyperparathyroidism); an increased glomerular filtration rate in hyperthyroidism; inability of the kidney to respond to ADH in chronic glomerulonephritis, aldosteronism, and renal diabetes insipidus; or a lack of ADH in diabetes insipidus. Increased output of salt and water in excessive sweating of work or fever will lead to thirst. This mechanism is an additional factor in hyperthyroidism and diabetes mellitus where diaphoresis is common.
POLYDIPSIA
A neurosis may be responsible for polydipsia in neurogenic diabetes insipidus. Drugs such as lithium and demeclocycline hydrochloride (Declomycin) can damage the distal tubule and cause renal diabetes insipidus. Drugs such as belladonna alkaloids, amitriptyline hydrochloride, parasympatholytic drugs, and gallic acid may cause a dry mouth and an excessive thirst. Alcohol may cause excessive thirst by inhibiting ADH.
Approach to the Diagnosis
The approach to the diagnosis of polydipsia involves establishing the presence or absence of other symptoms such a polyuria, polyphagia, weakness, and weight loss. Polydipsia with polyuria and excessive appetite (polyphagia) should suggest diabetes mellitus or hyperthyroidism, whereas polydipsia with polyuria alone should suggest a form of diabetes insipidus (pituitary, renal, or psychogenic). The laboratory workup involves checking intake and output, blood sugars, electrolytes, and a thyroid profile.
Other Useful Tests
- Urinalysis (renal or pituitary diabetes insipidus)
- Serum and urine osmolality (diabetes insipidus)
- Serum PTH level (hyperparathyroidism)
- Serum ADH level (diabetes insipidus)
- 24-hour urine calcium (hyperparathyroidism)
- Serum growth hormone, LH, and FSH levels (pituitary tumor)
- Hickey–Hare test (diabetes insipidus)
- Pitressin test (renal diabetes insipidus)
- CT scan or MRI of the brain (pituitary tumor)
- Microscopic examination of the urinary sediment (chronic renal disease)
Book Source Details
- Book Title: Differential Diagnosis in Primary Care
- Author(s): R. Douglas Collins
- Year of Publication: 2007
- Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2007 Lippincott Williams & Wilkins.
Other Book Chapters Related to Diabetes insipidus
Read excerpts from these other book chapters related to Diabetes insipidus:
Medical Books Excerpts
- POLYDIPSIA
- "Algorithmic Diagnosis of Symptoms and Signs" (2003)
- [ read ]
- Polydipsia
- "Handbook of Signs & Symptoms (Third Edition)" (2006)
- [ read ]
- Polydipsia
- "Professional Guide to Signs & Symptoms (Fifth Edition)" (2006)
- [ read ]
- Polydipsia
- "The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter" (2000)
- [ read ]
- Polydipsia
- "Signs & Symptoms: A 2-in-1 Reference for Nurses" (2007)
- [ read ]
Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2008 Williams & Wilkins.
More About Causes of Diabetes insipidus
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