The Role of Fractional Excretion of Uric Acid in the Differential Diagnosis of Hypotonic Hyponatraemia in Patients with Diuretic Therapy

The Combined Use of Fractional Urate and Potassium Excretion in the Diagnosis of Diuretic-Induced Hyponatremia

“…SIAD is generally associated with sUA level <4 mg/dL and the relative increase in FEUA value >12% [ 5 ] dependent on a decrease in urate tubular reabsorption [ 22 ] whereas secretion seems to be appropriate for the level of uricemia [ 23 ]. Fenske et al showed that FEUA was a reliable marker to discriminate SIAD vs. diuretic-induced hyponatremia patients at admission, but a bias of this study was that only 13% of enrolled patients were treated with thiazide therapy [ 5 ] and a recent study has suggested that FEUA value does not identify correctly SIAD vs. TIH patients [ 8 ]. Our data confirmed that FEUA is a poor marker in the differential diagnosis of SIAD vs. TIH patients, probably in consideration that the bulk of TIH patients shows a phenotype of euvolemia resembling SIAD pattern (in our study 22/30 patients, 73%).…”

“…Retrospectively, 143 patients, older than 18 years, presenting hyponatremia <130 mEq/L, urine osmolality >100 mEq/kg, and serum osmolality <280 mEq/kg were consecutively identified. A total of 98 patients were enrolled with the diagnosis of SIAD or diuretic-induced hyponatremia, as previously indicated [ 8 ]. Further eligibility criteria were a normal kidney, thyroid and adrenal function, sufficient dietary daily intake (at least 10 mEq/kg as solutes), no polydipsia story, and if treated, at least three months of oral diuretic therapy (hydrochlorothiazide, metolazone, indapamide, furosemide, and potassium canrenoate).…”

“…Fenske et al demonstrated that the fractional excretion of uric acid value (FEUA) could discriminate between SIAD and diuretic-induced hyponatremia in these confounding patients [ 5 ]. But instead, further investigations suggested that SIAD and thiazide-induced hyponatremia (TIH) showed similar FEUA values resulting in the diuretic withdrawal still mandatory to a correct diagnosis [ 8 ].…”

Korean Society of Nephrology 2022 Recommendations on controversial issues in diagnosis and management of hyponatremia

“…In an observational study of 298 patients admitted with profound hypoosmolar hyponatremia (Na of <125 mmol/L), FEUA was higher in patients with SIAD compared with other hyponatremia etiologies (p < 0.001) [9]. We identified direct evidence from five observational studies (387 patients) that interpreted FEUA and FENa in hyponatremia patients due to SIAD and on diuretics [8][9][10][11][12]. Of these, one study was conducted with only patients taking thiazide diuretics, and in the other four studies, the group of patients taking thiazide or loop diuretics was not separated in our meta-analysis.…”

Korean Society of Nephrology 2022 Recommendations on controversial issues in diagnosis and management of hyponatremia

“…In an observational study of 298 patients admitted with profound hypoosmolar hyponatremia (Na of <125 mmol/ L), FEUA was higher in patients with SIAD compared with other hyponatremia etiologies (p < 0.001) [20]. We identified direct evidence from five observational studies (387 patients) that interpreted FEUA and FENa in hyponatremia patients due to SIAD and on diuretics [19][20][21][22][23]. Of these, one study was conducted with only patients taking thiazide diuretics, and in the other four studies, the group of patients taking thiazide or loop diuretics was not separated in our meta-analysis.…”