Physiology Clinical Principals Flashcards
Why in the face of reduced net ammonium excretion does the kidney adapt itself by increasing acid excretion as titratable acid?
The kidney is limited in the amount of titratable acid by the rate of excretion of the available buffers. Phosphate excretion is regulated by the state of phosphate balance, and there is only a mild increase in metabolic acidosis. So, enhanced titratable acidity can only help so much in the contribution to acid excretion if ammonium formation is reduced.
What is type 1 renal tubular acidosis?
Called “distal” tubular acidosis, Type 1 is associated with a defect in the collecting tubule’s ability to excrete protons. Untreated patients have a urine pH > 5.5 and this is associated with hypokalemia. Increased risk for calcium phosphate kidney stones is seen in these patients. Associate this disease when you see metabolic acidosis in patients with a normal anion gap.
What is type 2 renal tubular acidosis?
Called “proximal” tubular acidosis, Type 2 is associated with a defect with bicarbonate reabsorption. May be similar in presentation to Fanconi’s syndrome. Patients typically have a urine pH <5.5. Associated with hypokalemia
What is type 4 renal tubular acidosis?
Associated with hypoaldosteronism. This syndrome is due to lack of collecting tubule response to aldosterone. Resulting hyperkalemia impairs ammonia genesis int eh proximal tubule to cause decreased buffering capacity and decreased urine pH
Why does GFR only decrease by about 20-30% rather than 50% after removal of a kidney (i.e. after malignancy or donation)?
One response to nephron loss is compensatory hypertrophy and hyper filtration of the remaining kidney mass. Thus, although you are losing only 50% of your kidney mass, the nephrons in the other kidney have increased their filtration rates by 50% to correspond with this loss and only decrease the overall GFR by 20-30%.
Why does acidosis increase calcium levels in the blood?
You commonly see an increase in calcium in acidosis because hydrogen ions compete with calcium ions for binding to anionic sites on proteins or smaller molecules. Thus, if you have acidosis, there’s more protons readily available for binding to these molecules and calcium will be displaced.
