Renal Tubular Acidosis

Question 1

What is renal tubular acidosis?

Answer 1

Metabolic acidosis due to pathology of tubules of kidney as this leads to disruption of the tubules regulation/balancing of hydrogen and bicarbonate ions between blood and urine

Question 2

What are the 4 types of renal tubular acidosis and why are they associated with acidosis?

Which are the most important clinically?

Answer 2

Type 1:

• pathology of the distal tubule
• unable to excrete H+

Type 2

• proximal tubule pathology-> Fanconi syndrome= main cause
• unable to reabsorb bicarbonate

Type 3:
-combo of type 1 + 2= VERY RARE

Type 4: (most common cause)
-reduced aldosterone

Question 3

What are examples of causes of type 1 renal tubular acidosis?
How might someone present?
What is the result biochemically?
How are they treated?

Answer 3

Genetic
SLE
Sjogrens syndrome 
Pirmary biliary cirrhosis 
Hyperthyroidism 
Sickle cell anaemia 
Marfans syndrome 

Px:

• FTT in children
• Hyperventilation i.e. respiratory compensation
• CKD
• osteomalacia

Hypokalaemia (due to H+ and K+ linked )
Metabolic acidosis
High urinary pH i.e. >6

Tx:
-oral bicarb

Question 4

What are the causes of type 4 renal tubular acidosis?
What are the biochemical results?
How is it managed?

Answer 4

Reduced aldosterone due to:

• adrenal insufficiency
• ACEi
• spironalactone
• SLE
• Diabetes
• HIV

Results:

• hyperkalaemia
• high chloride
• metabolic acidosis
• low urinary pH

Tx:

• fludrocortisone
• sodium bicarbonate
• Tx for hyperkalaemia= calcium gluconate

Question 5

What does lack of aldosterone lead to acidosis?

Answer 5

Due to secondary action of aldosterone is to stimulate renal excretion of H+ and retain HCO3-
I.e. decreased aldosterone leads tp decreased H+ excretion and HCO3- reabsorption-> acidosis

Question 6

Why does lack of aldosterone lead to hyperkalaemia?

Answer 6

Normal action of adolsterone is to increase excretion of K+

Therefore decreased aldosterone leads to decreased excretion