low serum bicarbonate concentration (may be 7.5) and fractional excretion of bicarbonate (>15–20%).The blood potassium level is usually low.This parameter can distinguish patients with distal RTA from those who have normal anion gap metabolic acidosis and hypokalemia due to other causes. Urine ammonium excretion is reduced and can be estimated indirectly by measurement of the urine anion gap or osmolal gap.Urine sodium concentration is typical>25 mEq/L.Urinary pH below 5.3 generally excludes distal (but not proximal) RTA.High urine pH (>5.3 usually in the 6.5–7 range) regardless of serum bicarbonate concentration.Hereditary distal RTA is the most common cause of RTA in children. Other diseases (pyelonephritis, Hodgkin disease, amyloidosis, sarcoidosis, medullary sponge kidney, sickle cell disease, Wilson’s disease).Drugs (e.g.lithium,toluene, ifosfamide, amphotericin B) or.Hypercalciuria ie in hyperparathyroidism.Autoimmune disease such as( Sjögren syndrome, SLE, rheumatoid arthritis, chronic active hepatitis).Major causes of distal RTA in adults are It is suspected in any patient with metabolic acidosis with a normal anion gap(non-anion gap metabolic acidosis) and high urine pH greater than 5.0.Ī negative gap indicates ammonium is present, and a positive gap indicates ammonium is not present. Renal tubular acidosis type 1 is characterized by impaired secretion of H+ by A-type intercalated cells of the collecting ducts and therefore ammonium.

Renal tubular acidosis is classified into four forms whereby all these are characterized by a normal anion gap and hyperchloremic metabolic acidosis. Renal tubular acidosis refers to a group of disorders in which metabolic acidosis develops as a result of defects in the kidney's ability to acidify the urine.

Type 1 rta