urine anion gap


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urine anion gap

Abbreviation: UAG
The sum of the concentrations of sodium and potassium in a specimen of urine, minus the urine chloride concentration. The UAG is used to assess the source of a metabolic acidosis. A positive value indicates the kidney is responsible for the acidosis. A large negative value indicates the kidneys are compensating for a metabolic acidosis caused by other organs.
See also: gap
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The syndromic picture of marked hypokalaemia ([K.sup.+] = 2 mmol/l), hypophosphataemia (P[O.sub.4] =0.43 mmol/l), normal anion gap metabolic acidosis with respiratory compensation in the presence of alkaline urine, high urinary potassium levels ([K.sup.+] = 31 mmol/l), positive urine anion gap, normal aldosterone levels and normal thyroid function tests indicated a diagnosis of distal renal tubular acidosis.
The diagnosis of distal RTA in our case was made on the basis of the patient's clinical presentation of profound muscle weakness, normal anion gap metabolic acidosis associated with hypokalemia, nephrocalcinosis, elevated urine pH, and positive urine anion gap. The history of Sjogren's Syndrome and SLE in our patient is also compelling, as distal tubular acidosis has been well documented to be associated with a variety of autoimmune disorders [1, 8].