Renal Tubular Acidosis Flashcards
What is the primary defect in type 1 (distal) RTA?
Inability to excrete acid into the urine from the distal tubule
Failure to acidify the urine
What are some causes of distal RTA?
Familial Sjogrens Autoimmune hepatitis Primary biliary cirrhosis SLE RA Drugs (ifosfamide, amphoterican B, lithium, glue sniffing) Hypercalciurua (hyperparathyroidism, sarcoidosis, vit d intoxication) Wilson's Medullary sponge kidney Obstructive uropathy Renal transplant rejection
What are the typical findings in distal RTA?
Urine ph 5.5 or greater
Plasma bicarbonate is variable but usually low sometimes lower then 10
Potassium low (corrects with alkali therapy)
Urinary sodium should be above 25meq/l as lower levels can impair distal acidification without RTA
What are the general findings of a RTA?
Hyperchloraemic normal anion gap metabolic acidosis
What is proximal (type 2) RTA?
Failure to re-absorb bicarbonate in the proximal tubule
85% of bicarbonate is re-absorbed in the proximal tubule, the rest in the distal tubule
What are the findings in proximal RTA?
Bicarbonate low, usually 12-20
Urinary ph is variable, can be less then 5.3 given some distal re-absorption of bicarbonate but if given bicarbonate load, distal re absorption is overwhelmed and urinary pH rapidly increases
Hypokalaemia which is made worse by giving alkali therapy
What are some causes of proximal RTA?
Familial Drugs (ifosfamide, tenofovir, carbonic anhydrase inhibitors ie.acetazolamide and topirimate, amino glycosides) Amyloidosis Multiple myeloma Vitamin D deficiency Renal transplant Heavy metals (lead, mercury, copper) Paroxysmal nocturnal hemoglobinuria
What is type 4 RTA
Also known as hyperkakaemic RTA
2 types make up this class
- hypoaldosteronism
- voltage dependent renal tubular acidosis (reduced sodium re-absorption in the distal tubule)
What are the findings in type 4 RTA
Variable bicarbonate levels (in hypoaldosteronism will be greater then 17)
Variable urinary pH (greater then 5.3 with voltage defects, less then 5.3 with hypoaldosteronism)
Increased plasma potassium
What is Fanconi’s syndrome?
Generalized proximal tubule dysfunction resulting in failure of resorption of bicarbonate (proximal RTA) + hypophosphatemia, renal glucosuria, hypouricaemia + aminoaciduria
What are some causes of increased anion gap acidosis?
Lactic acidosis
Ketoacidosis (diabetes, starvation, alcohol)
Ingestions (methanol, ethylene glycol, aspirin, toluene - glu)
Uremia
What are some causes of normal anion gap acidosis?
Diarrhea/vomitting, GI losses RTA Carbonic anhydrase inhibitors Urethral diversion Chronic kidney disease
What is the normal value for an anion gap
8-16
What are some complications of distal RTA
Renal stones
