Renal Tubular Acidosis: Types, Causes and Treatment

Renal tubular acidosis is a disease in which occurs when kidneys are unable to remove the acids from the body and leads to accumulation of acids in the body. It can be due to defect in the kidneys or maybe inability of kidneys to remove excess acid from the body. The metabolic acidosis that occurs might be due to inability of the kidneys to remove/secrete the excess H+ ions into the urine or it might be due to improper absorption of the Bicarbonate ions into the body from the infiltrate. The blood ph will fall and patient will consequences like dehydration, mental status changes etc. There will be Normal anion gap metabolic acidosis( NAGMA) , Urine anion gap will be positive .

Renal Tubular Acidosis Types

1. RTA1 ( Site involved is Distal Convoluted Tubule)
2. RTA 2 ( Site involved is Proximal Convoluted tubule )
3. RTA 4 ( Site involved is Distal Convoluted Tubule)

RTA1

• In type 1 RTA , The alpha intercalated cells of the DCT are involved. There function is to excrete H+ ions .
• In this type, there is a damage to these cells and that leads to inability to excrete the H+ ions that causes metabolic acidosis.
• The manifestations are:
  • There will be impaired chloride excretion also as kidney will try to maintain the electroneutrality. Hence Hyperchloremic metabolic acidosis will occur.
  • H+ excretion will not occur leading to improper absorption of K+ ions hence hypokalemia will occur causing muscle cramps , weakness and tachyarrythmias.
  • The increased H+ ions can affect bones and can cause Rickets in children and Osteomalacia in adults.
  • There will be formation of calcium oxalate stones.
  • There will be decreased urinary citrate concentration in the urine. Citrate acts as an inhibitor of calcium oxalate stones therefore there will be more chances of  formation of calcium oxalate stones formation.

Causes

• Multiple myeloma 
• Scleroderma
• Sjogren’s syndrome
• Toxins like Toluene inhalation
• Drugs like Lithium and amphotericin.

Treatment

• Oral sodium bicarbonate or potassium bicarbonate should be administered
• It will neutralize the metabolic acidosis and will also reduce damage to the bone caused by hypercalciuria.

Also Read: Pancreas Hormones: Location and Function

RTA2

• Renal tubular acidosis type 2 occurs when there is a damage to the proximal convoluted tubule whose function is bicarbonate reabsorption and to maintain the pH of the blood.
• There is a reduction in the level of bicarbonate ions in the blood.

Causes

• Multiple myeloma 
• Heavy metal poisoning 
• Sjogren syndrome 
• Wilson disease 
• Drugs like tenofovir topiramate 
• Expired antibiotics
• The manifestations of RTA type 2 are:
  • Hypokalemia 
  • Bicarbonaturia
  • Glucosuria 
  • Amino aciduria
  • Phosphaturia

Treatment

• Patient should be administered with oral sodium bicarbonate or potassium bicarbonate which will neutralize the metabolic acidosis.
•  Thiazide diuretics can be given that can cause diuresis which will lead to metabolic alkalosis and hence it will counterbalance the metabolic acidosis.

Also Read: Hemostasis: Stages, Steps and Clinical Applications

RTA Type 4

• The other name of RTA type 4 is hyporeninemic hypoaldosteronism RTA.
• It is the most commonly seen renal tubular acidosis type in clinical practice.
• There is a damage to the distal convoluted tubular cells which leads to the resistance of epithelial sodium channels (Enac). These channels show resistance to aldosterone and hence impaired H+ ion excretion will occur and there will be inability of kidney to acidify the urine and also impaired potassium ion excretion will occur which will lead to hyperkalemia.

Causes

• Diabetic nephropathy
• HIV associated nephropathy
• Chronic tubule interstitial diseases

                                            Acid secretion at the level of DCT

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Treatment

• There should be dietaries potassium restriction
• Hormonal replacement with fludrocortisone should be started 
• Furosemide should be prescribed it will lead to reduction in hyperkalemia.

Also Read: Synapse: Components, Types and Function

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