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. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press.
Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
Therapeutic Guidelines. Melbourne: Therapeutic Guidelines Limited. https://www.tg.org.au [Accessed 2021].