polydipsia
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Introduction
Increased thirst & fluid intake.
Etiology
- psychogenic polydipsia (mental illness)
- xerostomia (dry mouth)
Clinical manifestations
Laboratory
- 24 hour urine volume (confirm polyuria)
- urine glucose negative
- urine osmolality: low* although may be higher than expected
- serum sodium: hyponatremia
- plasma osmolality: low
- plasma ADH (vasopression in plasma) is low
- plasma copeptin# distinguishes diabetes insipidus from primary polydipsia[2]
- activity low in diabetes insipidus
- not widely available[2]
* distinguish from SIADH where urine osmolality is increased
# fragment of the arginine vasopressin prohormone
Differential diagnosis
- diabetes insipidus (hypernatremia)
- SIADH:
- serum sodium is low (primary laboratory finding)
- low 24 hour urine volume
- urine osmolality inappropriately high
- osmotic diuresis due to uncontrolled diabetes mellitus
- hemoglobin A1c high, urine glucose positive, urine osmolality high
More general terms
References
- ↑ Medical Knowledge Self Assessment Program (MKSAP) 17, American College of Physicians, Philadelphia 2015
- ↑ 2.0 2.1 2.2 Fenske W, Refardt J, Chifu I et al. A copeptin-based approach in the diagnosis of diabetes insipidus. N Engl J Med 2018 Aug 2; 379:428. PMID: https://www.ncbi.nlm.nih.gov/pubmed/30067922 https://www.nejm.org/doi/10.1056/NEJMoa1803760
Rosen CJ, Ingelfinger JR. A reliable diagnostic test for hypotonic polyuria. N Engl J Med 2018 Aug 2; 379:483. PMID: https://www.ncbi.nlm.nih.gov/pubmed/30067935 https://www.nejm.org/doi/10.1056/NEJMe1808195 - ↑ Nigro N, Grossmann M, Chiang C, Inder WJ. Polyuria-polydipsia syndrome: a diagnostic challenge. Intern Med J. 2018 Mar;48(3):244-253. PMID: https://www.ncbi.nlm.nih.gov/pubmed/28967192 Review.