What is renal tubular acidosis?
Renal tubular acidosis (RTA) occurs when the kidneys do not remove acids from the blood into the urine as they should. The acid level in the blood then becomes too high, a condition called acidosis. Some acid in the blood is normal, but too much acid can disturb many bodily functions.
Why is urine anion gap negative in proximal RTA?
Normal anion gap in the presence of acidosis (hyperchloremic metabolic acidosis) suggests increased urinary (proximal RTA) or gastrointestinal loss (diarrhea) of bicarbonate or impaired excretion of H+ ions (distal RTA). production, resulting in a negative urine anion gap.
Why is anion gap normal in renal tubular acidosis?
Metabolic Acidosis Normal anion gap acidosis (low serum HCO3 but normal anion gap) is caused by excess bicarbonate loss from either the gut (diarrhea) or kidney (renal tubular acidosis). An elevated or so-called positive anion gap suggests the presence of another unmeasured anion.
When should urine anion gap be checked?
A negative urine anion gap can be used as evidence of increased NH4+ excretion. In a metabolic acidosis without a serum anion gap: A positive urine anion gap suggests a low urinary NH4+ (e.g. renal tubular acidosis). A negative urine anion gap suggests a high urinary NH4+ (e.g. diarrhea).
Which RTA has positive urine anion gap?
In patients with distal renal tubular acidosis (RTA) of several etiologies, the UAG is positive, despite the prevailing metabolic acidosis, and this is a useful bedside diagnostic index of impaired ammonium excretion (2) (Figure 1).
What is urine anion gap in RTA?
The urine anion gap is an ‘artificial’ and calculated measure that is representative of the unmeasured ions in urine. Usually the most important unmeasured ion in urine is NH4+ since it is the most important form of acid excretion by the kidney.
What causes anion gap acidosis?
Causes. The most common causes of high anion gap metabolic acidosis are: ketoacidosis, lactic acidosis, kidney failure (also known as renal failure), and toxic ingestions.
What causes high anion gap?
High anion gap acidoses are most often due to ketoacidosis, lactic acidosis, chronic kidney disease, or certain toxic ingestions. Normal anion gap acidoses are most often due to gastrointestinal or renal HCO 3 − loss.