renal tubular acidosis Flashcards
what type of acid base disorder is caused due to renal tubular acidosis ?
non AG MA
what does RTA often present with in terms of anion disturbances ?
low bicarb
abnormal potassium
what are the three physiologic causes of TA ?
1- inability of the PCT to allow for the reabsorption of the bicarb
2- inability of the collecting duct to take in hydrogen
3- the nephrons inability to respond to aldosterone
what are the features of type 2 RTA ?
defect in the bicarb reabsorption in the PCT , allowing for an increased excretion of bicarb in the urine
it is often asymptomatic
why is there hypokalemia in Type 2 renal tubular acidosis ?
loss of bicarb causes diuresis
hence the hypokalemia ( volume contraction)
what is the urine pH in RTA ?
type 1 RTA : alkaline because we cant secrete hydrogen ions
type 2: initially alkaline then eventually becomes acidic
type 4: acidic due to the decreased excretion of ammonia
what is the treatment for RTA type 2 ?
sodium bicarbonate
what ar the associations with RTA type 2?
fanconi’s syndrome
multiple myeloma
how does acetazolamide cause RTA type 2 ?
carbonic anhydrase inhibitor , increased elimination of bicarb
causes a non anion gap MA
what is the pathology associated with Type 1 RTA ?
inability of the alpha intercalated cells of the collecting duct to secrete hydrogen with a decreased production of bicarb - hence the metabolic acidosis
what are the potassium levels associated with each type of RTA ?
type 1 RTA : hypokalemia
Type 2 RTA: hypokalemia
Type 4 RTA : hyperkalemia
what are the urine pH levels associated with each type of RTA ?
type 1 : alkali
type 2 : initially alkali then acidic
type 4: acidic
how is a diagnosis of type 1 RTA ?
metabolic acidosisi
with an alkali pH
associated with chronic kidney stones
can cause growth failure and rickets in children
what are the different causes associated with RTA type 1 ?
autoimmune diseases
amphotericin B toxicity
congenital anomalies of the urinary tract
analgesics nephropathy
what drugs are associated with distal RTA ?
amphotericin B
what is the urine anion gap ?
it is a measurement of the renal acid secretion
which is calculated with
Na + k -CL
what is the value of the urinary anion gap in a patient with just metabolic acidosis ?
UAG should be normal
what is the urinary anion gap a measure of ?
the cause on non AG metabolic acidosis
ammonia is always excreted with chlorine
so if there is chlorine in the urine then ammonia is being excreted normally
if there is little chlorine in the urine that means that that the UAG will be positive
if the UAG is positive what is this an indication of ?
it means that the kidneys are not excreting the ammonia 3edel , usually due to RTA ( not in type 2 , H here is intact) , only positive in type 4 or type 1
what is an ammonium chloride challenge ?
given a dose of ammonium chloride
expected result : should lower the ph
if not - we have RTA
what is the classic case associated with distal RTA ?
a patient with an autoimmune disease
recurrent bilateral kidney stones
very low bicarb on blood work
hypokalemia
urine is high
UAG is positive
what is the treatment for distal RTA ?
sodium bicarbonate
what is the pathology associated with type 4 RTA ?
hypoaldosteronism
the distal tube , in the collecting duct where it is not responding to aldosterone or due to a deficiency
decreases sodium resorption will lead to hyperkalemia
what is the major pathologic defect in type 4 RTA ?
decreased NH4 excretion
with a low urinary pH
