Chronic Kidney Injury

Question 1

what kind of acid-base disorder develops with chronic kidney disease and why?

Answer 1

patients with chronic kidney disease can still acidify urine, but produce less ammonia - therefore cannot excrete the normal quantity of H+ —> metabolic acidosis

as renal function worsens, net daily acid excretion is limited, and anions of retained organic acids cause anion gap metabolic acidosis

Question 2

what is the net effect of PTH vs calcitriol on plasma calcium and phosphate concentrations?

Answer 2

net effect of PTH is only to raise plasma calcium (little effect on PO4)

net effect of calcitriol is to raise both plasma calcium and phosphate

• note calcitriol also has negative feedback on PTH, which may play a major role in secondary hyperparathyroidism associated with chronic renal failure

Question 3

explain why persistent hyperparathyroidism develops in chronic renal failure

Answer 3

renal failure leads to phosphate retention —> decreased calcitriol synthesis (which increases plasma Ca2+ and PO4)

calcitriol normally has negative feedback effect on PTH, so when it decreases there is uninhibited release of PTH —> persistent hyperparathyroidism

Question 4

describe the effects of persistent hyperparathyroidism on bone health in patients with chronic kidney disease

Answer 4

prolonged hyperPTH —> bone resorption —> osteitis fibrosa cystica: skeletal demineralization, bone cysts, spontaneous fractures, tendon ruptures

hyperPTH also predisposes to development of metastatic calcifications in arteries, soft tissues, viscera

can be treated with high levels of calcitriol (neg. feedback on PTH synthesis)

Question 5

almost all patients with chronic renal failure are anemic - what type of anemia typically develops?

Answer 5

normochromic, normocytic, hypoproliferative (low reticulocyte count)

peripheral smear also will show echinocytes (“burr cells”)

anemia is due to decreased erythropoietin (EPO) secretion (due to decreased renal mass)

Question 6

calciphylaxis

Answer 6

aka calcific uremic arteriolopathy: chronic inflammation, hyperphosphatemia, hyperparathyroidism contribute to vascular calcification

can be seen with chronic kidney disease