Uric acid homeostasis in the evaluation of diuretic-induced hyponatremia.
BACKGROUND
Diuretics are one of the most common causes of severe hyponatremia. The responsible pathogenetic mechanisms remain unclear. Serum uric acid concentration has been proposed as an index of differentiating between two pathophysiologic constructs of diuretic-induced hyponatremia-extracellular volume depletion and syndrome of inappropriate antidiuretic hormone secretion (SIADH)-like state-but its discriminating value has not been verified in large series of patients. Here we attempt to illuminate the pathophysiology of diuretic-induced hyponatremia by focusing on uric acid homeostasis. Additionally, we analyze the epidemiology and clinical characteristics of the disorder.


METHODS
We studied prospectively 158 adult patients with hyponatremia on admission to our internal medicine clinic. Here we report on those with diuretic-induced hyponatremia.


RESULTS
Forty patients (13 male and 27 female) had diuretic-induced hyponatremia, rendering it the most common cause of the disorder (25.3%). These patients had lower mean ([Na+]) (121.2 +/- 7.2 vs 126.4 +/- 4.1 mEq/L, p = .0001) than the remaining hyponatremic patients. Patients with serum uric acid levels < 4 mg/dL (n = 14) exhibited a biochemical profile consistent with a SIADH-like state, whereas patients with serum uric acid levels > or = 4 mg/d (n = 26) were consistent with extracellular volume depletion.


CONCLUSIONS
Diuretics are the most common cause of community-developed hyponatremia. The serum uric acid level effectively discriminates between two biochemical profiles of diuretic-induced hyponatremia, one consistent with extracellular volume depletion and another that simulates SIADH.
Liamis
George
G
Department of Internal Medicine, Medical School, University of Ioannina, Ioannina, Greece.
Christidis
Dimitrios
D
Alexandridis
George
G
Bairaktari
Eleni
E
Madias
Nicolaos E
NE
Elisaf
Moses
M
D000368:Aged; D003404:Creatinine / Q000097:blood; D003937:Diagnosis, Differential; D004232:Diuretics / Q000009:adverse effects*; D004487:Edema / Q000097:blood / Q000150:complications / Q000175:diagnosis; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000097:blood* / Q000139:chemically induced*; D020896:Hypovolemia / Q000097:blood / Q000150:complications / Q000175:diagnosis; D007177:Inappropriate ADH Syndrome / Q000097:blood / Q000150:complications / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D011446:Prospective Studies; D012964:Sodium / Q000097:blood; D014508:Urea / Q000097:blood; D014527:Uric Acid / Q000097:blood*
D004232:Diuretics; D014527:Uric Acid; D014508:Urea; D012964:Sodium; D003404:Creatinine