Nephrology

Transtubular Sodium Gradient (TUNaG) calculator

Enter the published formula inputs below to calculate and interpret this score.

Clinical inputs

Tunag Urine Sodium Mmol L (mmol/L)

Tunag Serum Sodium Mmol L (mmol/L)

Tunag Urine Osmolality Mosm Kg (mOsm/kg)

Tunag Serum Osmolality Mosm Kg (mOsm/kg)

Result

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Formula inputs

Tunag Urine Sodium Mmol L (mmol/L)Accepted range: 0 to 200
Tunag Serum Sodium Mmol L (mmol/L)Accepted range: 120 to 160
Tunag Urine Osmolality Mosm Kg (mOsm/kg)Accepted range: 50 to 1200
Tunag Serum Osmolality Mosm Kg (mOsm/kg)Accepted range: 260 to 340

Primary source

Fenske W et al. Diagnostic work-up of hyponatremia: the role of the TUNaG. J Clin Endocrinol Metab. DOI: 10.1210/jc.2011-2981. PMID: 22278497. Scope: TUNaG (%) = [(UNa/PNa)/(Uosm/Posm) − 1] × 100 for assessing renal sodium handling in hyponatremia. (2012)

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