RTA 11.02.10

RENAL TUBULAR ACIDOSIS : 

RENAL TUBULAR ACIDOSIS Seminar by Dr.Hariharan 11.02.2010

RTA : 

RTA The term Renal Tubular Acidosis (RTA) defines many disorders characterized by metabolic acidosis, secondary to defects in renal tubular reabsorption of bicarbonate (HCO3−) and/or in urinary excretion of hydrogen (H+) Types Distal-Type I RTA Proximal- Type II RTA Type IV

Reabsorption of HCO3 : 

Reabsorption of HCO3 H2CO3 3Na+ 2K+ H2O H2CO3 BLOOD LUMEN HCO3- H+ Na+ NHE-3 NBC-1 Na+ 3HCO3- H2O K+ CA-II CA-IV CO2 CO2 PROXIMAL TUBULE CELL

Type 2-Proximal RTA- Causes : 

Type 2-Proximal RTA- Causes Renal Fanconi’s syndrome- glycosuria, low molecular weight proteinuria, urinary phosphate wasting, hypophosphataemia and hypouricaemia in multiple myeloma, Sjogren’s cystinosis Galactosemia Glycogen storage disease-type I Heriditary Fructose Intolerance Lowe Syndrome Tyrosinemia Wilson’s disease

Slide 5: 

Acquired disorders Amyloidosis Paroxysmal Nocturnal Hemoglobinuria Toxins, such as HAART, Ifosfamide, Lead, Cadmium The autosomal recessive disorder is associated with ocular abnormalities- NBC-1 The autosomal dominant proximal RTA-mutations in the gene CA-II X-linked NHE, NBC, CA IV

Features : 

Features Hyperchloremic metabolic acidosis Bicarbonaturia Hypophosphatemia- rickets, osteomalacia Hypokalemia Normal urine acidification Fall in plasma HCO3 Excretion of urine HCO3 Normal plasma HCO3 Low load of HCO3 to PCT more HCO3 absorbed

Slide 7: 

Hypercalciuria- but no stones In children, the hypocalcemia as well as the HCMA will lead to growth retardation, rickets, osteomalacia and an abnormal vitamin D metabolism. In adults osteopenia is generally seen. Urine pH<5.5

Lab diagnosis of RTA-II : 

Lab diagnosis of RTA-II RTA should be suspected when metabolic acidosis is accompanied by hyperchloremia and a normal plasma anion gap (Na+ - [Cl- + HCO3-] = 8 to 16 mmol/L) in a patient without evidence of gastrointestinal HCO3- losses

Treatment : 

Treatment 5 to 15mmol/ kg body wt of alkali Pottasium supplements

Excretion of acid- cortical collecting tubule : 

Excretion of acid- cortical collecting tubule NH3 3Na+ 2K+ H2O H2CO3 BLOOD LUMEN H+ H+ –ATPase AE-1 Cl- HCO3- H2PO4 K+ CA-II CO2 Alpha intercalated cell ATP ATP ATP NH4 HPO4 H+ K+ H+ –K+ATPase

Distal Type I RTA-causes : 

Distal Type I RTA-causes Autosomal dominant-AE1 gene X-linked, autosomal recessive-deafness-H+ ATPase Galactosemia, ehlers-Danlos, Wilson’s disease, Secondary to Sjogren’s, Hypergammaglobulinemia, chronic active hepatitis, lupus, Amphoterecin B- back leak AE1, H+ATPase, H+K+ ATPase

Features : 

Features In children, distal RTA is almost always observed as a primary entity. Prominent clinical features include impairment of growth, polyuria, hypercalciuria, nephrocalcinosis, lithiasis, K+ depletion Progression of nephrocalcinosis may lead to development of chronic renal failure. If detected early-

Diagnosis : 

Diagnosis Normal anion gap metabolic acidosis pH>5.5 Oral ammonium chloride loading test- blood pH dec but urine pH does not UTI Treatment: Alkali supplements- 0.5 to 2mmol/kg body wt NaHCO3, shohl’s solution( sodium citrate + citric acid) Pottasium salts if hypokalemia

Type IV RTA - Hyperkalemic Distal RTA : 

Type IV RTA - Hyperkalemic Distal RTA Acquired disorder-hyporenenimic hypoaldosteronism, NSAIDS, ACE inhibitors, trimethoprim reduces aldosterone production Reduced aldosterone-DCT secretion of H+ and K+ re abnormal Hyperchloremic acidosis and hyperkalemia Hyperkalemia dec PCT ammonia productionless ammonia to couple with H+  aciduria

Treatment : 

Treatment Treat hyperkalemia- low pottasium diet, fludrocortisone, exchange resins

References : 

References Harrisons- internal medicine Pubmed.com

Thank you : 

Thank you