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polydipsia

Increased thirst & fluid intake. Etiology: - psychogenic polydipsia (mental illness) - xerostomia (dry mouth) - anticholinergics (amitriptyline) Clinical manifestations: - polyuria 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

General

sign/symptom

References

  1. Medical Knowledge Self Assessment Program (MKSAP) 17, American College of Physicians, Philadelphia 2015
  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: 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: 30067935 https://www.nejm.org/doi/10.1056/NEJMe1808195
  3. Nigro N, Grossmann M, Chiang C, Inder WJ. Polyuria-polydipsia syndrome: a diagnostic challenge. Intern Med J. 2018 Mar;48(3):244-253. PMID: 28967192 Review.