1. Renal Pathology K - Cox

• RTA Type 1 - Distal RTA; impaired renal hydrogen ion excretion
• RTA Type 2 - Proximal RTA; impaired bicarbonate resorption
• RTA Type 4 - Abnormal aldosterone production or response
• Type 1 Defect - collecting duct alpha-intercalated cells impaired acid (H+) excretion

  • H+ dependent ATPase
• Distal RTA - Type 1

  • decrease NH4 and titratable acid excretion
  • HCO3 wasting
• Clinical - Distal RTA type 1

  • hyperchloremic metabolic acidosis
  • hypokalemia
  • low urinary NH4+ --> urine pH >5.5
• Proximal RTA type 2 - caused by defective PCT HCO3 reabsorption/regeneration due to defects:

  • H+ secretion by HNE3 or H+ATPase
  • impaired luminal or cytosolic carbonic anhydrase II
  • HCO3- reabsorption Na+/3HCO3- cotransporter NBCE
• Proximal RTA (Type 2)

  • serum HCO3 and blood pH depressed
  • distal HCO3 reabsorption intact
• Proximal RTA - Type 2

  • key lab finding - hyperchloremic metabolic acidosis with hypokalemia
  • variable pH --> if given Bolus of NH4Cl - urine pH decreases (compared to type 1)
  • hypokalemia
• RTA (hyperkalemia) - type 4

  • hypoaldosteronism and hypoadrenalism causing metabolic acidosis
• RTA Type 4

  • Na+ renal loss due to aldosterone sensitive ENaC channel
  • K+ retention - ROMK channel due to decrease Na+ reabsorption