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 antidiuretic hormone
(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.
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 parathyroid (PTH) level (hyperparathyroidism)
-
Serum ADH level (diabetes insipidus)
-
24-hour urine calcium (hyperparathyroidism)
-
Serum growth hormone, luteinizing hormone (LH), and
follicle-stimulating hormone (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)
Pictures
Book Source Details
- Book Title: Differential Diagnosis in Primary Care
- Author(s): R. Douglas Collins MD, FACP
- 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
» Next page: Diabetes Insipidus (The 5-Minute Pediatric Consult)
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