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Renal

Urine Anion Gap

Urine anion gap to assess renal NH4+ excretion in normal-anion-gap metabolic acidosis.

Written for clinicians. If you're a parent or patient, don't act on these numbers — talk to your child's doctor.

Inputs

FieldUnitNotes
Sodium mEq/L urine Na
Potassium mEq/L urine K
Chloride mEq/L urine Cl

FAQ

What is the Urine Anion Gap?

Urine anion gap to assess renal NH4+ excretion in normal-anion-gap metabolic acidosis.

What inputs does the Urine Anion Gap need?

Sodium (mEq/L), Potassium (mEq/L), Chloride (mEq/L).

Related guides

Urine Anion Gap: Separating GI Bicarbonate Loss from Renal Tubular Acidosis

The urine anion gap (UNa + UK − UCl) as a bedside surrogate for renal NH4+ excretion in normal-anion-gap metabolic acidosis — negative means GI bicarb loss, positive points to RTA.

Related Renal calculators

Estimated GFR (Bedside Schwartz)

Paediatric estimated GFR using the bedside Schwartz (2009) equation.

Fractional Excretion of Sodium (FENa)

Fraction of filtered sodium excreted in urine — helps distinguish prerenal from intrinsic (ATN) acute kidney injury.

Fractional Excretion of Urea (FEUrea)

Fraction of filtered urea excreted in urine — distinguishes prerenal from intrinsic AKI and stays valid in patients on diuretics.

Transtubular Potassium Gradient (TTKG)

Estimates the driving force for potassium secretion in the cortical collecting duct — used to work up hyper- and hypokalaemia.

Calculated Serum Osmolality

Estimates serum osmolality from sodium, glucose and urea — compare with a measured value to derive the osmolar gap.

Fractional Excretion of Magnesium (FEMg)

Fraction of filtered magnesium excreted in urine — distinguishes renal magnesium wasting from extrarenal loss in hypomagnesaemia.

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