RENAL PHYSIOLOGY-URINARY ANION GAP
SUMMARY
1. The Urine Anion Gap (UAG) is used to evaluate the etiology of normal AG metabolic acidosis to differentiate between GIT loss of HCO3- and RTA.
2. UAG is an estimate of unmeasured ions, particularly NH4+, expressed in mEq/L: 
3. Normal value of UAG is close to 0.
4. A positive UAG value suggests low urinary NH4+ which decreases Cl- in the urine (e.g., RTA Type 4).
5. A negative UAG value suggests high urinary NH4+ which increases Cl- in the urine (e.g., diarrhea). Remember neGUTive UAG in cases of diarrhea.
Reference(s)
Wilkinson, I., Furmedge, D. and Sinharay, R. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press. Get it on Amazon.
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