Renal tubular acidosis topic is clearly explained for the benefit of both UG and PG students of medicine and biochemistry students.

1. Dr.S.Sethupathy,M.D.,Ph.D.,
Professor of Biochemistry,
Rajah Muthiah Medical College,
Annamali University

2.  Renal tubular acidosis (RTA) is due
either inherited or acquired kidney’s
inability to reabsorb bicarbonate or
secrete H+ secretion.
 It is characterized by normal anion gap
metabolic acidosis (Hyperchloremic)
 GFR will be normal or near normal.

4.  Classical form
 Inability to acidy urine maximum
 Distal defect – decreased H+ secretion
 Metabolic acidosis
 K+ secreted in stead of H+ - hypokalemia
 Urine pH > 5.5
 Hypercalciuria
 Renal stones

12.  Urinary loss of sodium causes volume contraction
 Increased aldosterone section
 Increased tubular secretion and decreased
reabsorption of potassium in proximal tubules
 Resulting in hypokalemia
 Chronic acidosis leads to decreased reabsorption
of Ca2+ -Hypercalciuria
 Acidosis and hypokalemia cause increased
reabsorption of citrate – hypocitraturia
 Hypercalciuria , hypocitraturia, alkaline urine –
leads to Calcium phosphate stone formation -
nephrocalcinosis

13.  Failure to thrive, growth
retardation
 Polyuria, polydipsia
 Nephrolithiasis
 Weakness, transient paralysis-
hypokalemia

16.  Bicarbonate administration – initially 2-3 meq/
Kg/day
 Then increased till serum bicarbonate level
becomes normal
 Usually maintenance dose will be 5-10
meq/kg/day
 Continued Life long

32.  Hypochloremic metabolic acidosis
 Decreased serum PO4
 Hypokalemia
 Proteinuria
 Urine anion gap = Na+ + K+ − Cl. where the
concentrations are expressed in units of
milliequivalents/liter (mEq/L).
 low urinary AG = GI loss of base
 no change in urinary AG = renal loss of base
 negative urinary AG = severe diarrhea
 positive urinary AG = altered urinary acidification

33.  The underlying defect is the impaired
cation exchange in the distal tubules with
reduced excretion of H+ and K+
 Hyperkalemic acidosis present
 Hypoaldosteronism or decreased
response to aldosterone
 Type 3 RTA no longer used.

34.  Hypoaldosteronism (low renin) -
Hyporeninemic hypoaldosteronism
(diabetes mellitus/mild renal impairment,
chronic interstitial nephritis, non-steroidal anti-
inflammatory drugs, beta-blockers)
 Hypoaldosteronism (high renin) –
Primary adrenal defect (congenital
hypoaldosteronism; Addison disease,
adrenalectomy, AIDS)
inhibition of aldosterone secretion (heparin,
ACE inhibitors, AT1 receptor blockers)

35.  Aldosterone resistance (drugs) -
Diuretics (amiloride, triamterene,
spironolactone),
calcineurin inhibitors (cyclosporine,
tacrolimus),
antibiotics (trimethoprim, pentamidine)
 Aldosterone resistance (genetic) -
Pseudohypoaldosteronism (PHA) types I
and II

42. Thank you