The word acidosis refers to the tendency for RTA to lower the blood’s pH. When the blood pH is below normal (7.35), this is called acidemia. The metabolic acidosis caused by RTA is a normal anion gap acidosis.
There are 4 types,only 3 are clinically important.Type 3 is Combined proximal and distal type,RTA type 3 is uncommon and seen only in children.
Type 1 (Distal RTA)-Distal RTA (dRTA) is the classical form of RTA, being the first described.
Underlying Defect-Selective deficiency in H+ secetion in Distal nephron by the alpha intercalated cells.
Electrolyte imbalance-Hypokalemic Hyperchloremic Metabolic acidosis
Despite acidosis urinary PH can not be acidified and is always above 5.5,
Etiology-Renal stone,amphotericin.cirrhosis and collagen vascular disease
Complication-Nephrolithiasis (related to alkaline urine, hypercalciuria, and low urinary citrate)
Type 2 (Proximal rRTA) MOST COMMON TYPE OF RTA IN CHILDREN
Underlying Defect-Defect in proximal tubules’s ability to adequately reabsorb filtered HCO3 ions.
Electrolyte imbalance-Hypokalemic,Hyperchloremic Metabolic acidosis
The distal intercalated cells function normally, so the acidemia is less severe than dRTA and the urine can acidify to a pH of less than 5.3
Etiology-Carbonic Anhydrease inhibitors (acetazolamide,Diamox) ,Fanconi’s syndrome
Di-hard Fan of Type 2
In some patients, their RTA shares features of both Distal RTA and Proximal RTA.
A transient phenomenon in infants and children with dRTA (possibly in relation with some exogenous factor such as high salt intake) and is no longer observed.
This form of RTA has also been referred to as juvenile RTA.
Underlying Defect-inherited carbonic anhydrase II deficiency
Type 4-MC type RTA IN ADULTS
Underlying Defect-Hyporeninemic hypoaldosteronsim leads to defect in Na absorption,H+ and K+ excretion,Dcrease ammoniagenesis and Increase K+
Electrolyte Imbalance-Hyperkalemic,Hyperchloremic Metabolic acidosis
Etiology-MC found in Diabetic nephropathy,tubulointerstitial reanal disease and hypertensive nephrosclerosis.
Aldosterone deficiency (hypoaldosteronism)- Primary vs. hyporeninemic
Drugs: NSAIDs, ACE inhibitors and ARBs, Eplerenone, Spironolactone, Trimethoprim, Pentamidine