Disorders of Calcium and Phosphorus SA

Question 1

what forms of calcium are in circulation?

Answer 1

iCa or free ionized calcium (55%): biologically active

protein bound calcium (35%): albumin and globulins

complexed calcium (10%): bound to phosphate, bicarb, citrate, lactate, oxalate

Question 2

what are the main factors that influence calciums distribution?

Answer 2

• iCa is tightly regulated by interacting feedback loops involving iCa, PTH, calcitriol and calcitonin
• PTH related protein binds to PTH receptors in bone and kidneys
• phosphorus absorption and excretion are regulated with calcium

Question 3

if phosphorus x tCa > 60-70 =

Answer 3

tissue mineralization

Question 4

main differential dx of hypocalemia in dogs

Answer 4

hypoalbuminemia
chronic renal failure
acute pancreatitis
eclampsia or puerperal tetany

Question 5

main differential dx of hypercalcemia in dogs

Answer 5

• primary hyperparathyroidism
  hypercalcemia of malignancy
• hypercalcemia of malignancy: hurmoral or local
• chronic renal failure
• hypervitaminosis D
• granulomatous Dz
• idiopathic hypercalcemia (cats)
• hypoadrenocorticism
• non-malignant osteolyic lesions
• acute renal injury

Question 6

hypoalbuminemia

Answer 6

Low tCa, normal iCa; clinically insignificant

can mask hypercalcemia

Question 7

acute pancreatitis

Answer 7

precipitation of calcium in peripancreatic fat +/- hypomagnesemia and calcitonin release

Question 8

chronic renal failure

Answer 8

decreased renal phosphate clearance resulting in hyperPhos and Ca-Phos precipitation in tissues

decreased renal synthesis of 1-alpha-hydroxylase leading to decreased calcitriol

Question 9

eclampsia or puerperal tetany

Answer 9

increased Ca mobilization for fetal skeletons and milk production +/- poor diet intake or parathyroid atrophy from Ca supplementation

Question 10

if Ca is low and Phos is high

Answer 10

chronic kidney disease, acute kidney injury, urinary tract obstruction, hypoparathyroidism, phosphate-containing enema, or other causes of hyperphos

Question 11

clinical signs of hypocalcemia

Answer 11

muscle tremors/fasiculations
facial rubbing
seizures
tachycardia/arrhythmias

Question 12

treatment of hypocalcemia

Answer 12

acute/emergent: calcium gluconate 10%

subacute/chronic: calcium supplements and vitamin D metabolites

Question 13

primary hyperparathyroidism

Answer 13

excesssive PTH from parathyroid gland tumor

Question 14

hypercalcemia of humoral malignancy

Answer 14

tumor distant from bone, secretion of PTHrP, calcitriol, and/or cytokines

Lymphoma is common and AGASACA is less common

Question 15

hypercalcemia of local malignancy

Answer 15

tumor in the bone, secretion of PTHrP and/or cytokines, osteolysis

lymphoma is common and multiple myelomas are less common

Question 16

chronic renal failure

Answer 16

renal secondary hyperparathyroidism from decreased calcitriol production and hypocalcemia from Ca-Phos tissue precipitation

Question 17

hypervitaminosis D

Answer 17

typically from toxin ingestion ex. rodenticide, anti psoriasis cream, lilles

Question 18

granulomatous disease

Answer 18

-activate macrophages synthesize calcitriol
-fungal, parasitic, sterile nodular pancreatitis

Question 19

If high Ca and low-normal Phos

Answer 19

primary hyperparathyroidism, HyperCa of malignancy (humoral)

Question 20

If both Ca and Phos are high

Answer 20

hypervitaminosis D, chronic renal failure, hypadrenocorticism, hyperCa of malignancy (local, osteolytic)

Question 21

if concurrent azotemia with hypercalcemia

Answer 21

CKD, AKI, hypervitaminosis D, hyperadrenocorticism, hyperCa of malignancy, granulomatous disease

Question 22

what clinical signs are associated with hypercalcemia?

Answer 22

• renal: pu/pd (ADH inhibition), tubular damage (mineralization)
• neuromuscular (depressed cell membrane excitability); weakness, twitching, seizures
• gastrointestinal (direct effects on chemoreceptor trigger zone)
• cardiac; bradyarrhythmias, cardiac arrest

Question 23

treatment of acute/emergent hypercalcemia

Answer 23

hypercalcemia - induced renal failure, high risk of tissue mineralization

• IV Fluids (NaCl 0.9% ideal)
• Furosemide
• glucocorticoids
• sodium bicarb (save for lifethreatening)

Question 24

treatment of subacute/chronic hypercalcemia

Answer 24

furosemide, glucocorticoids, biphosphonates (decrease osteoclastic activity)

Question 25

common causes and clinical signs of hypophosphatemia

Answer 25

common causes:

• primary hyperparathryroidism
• malignancy- associated hypercalcemia
• diabetic ketoacidosis

clinical signs:

• if severe, hemolysis, rhabdomyolysis, respiratory disease, and neurologic abnormalities

Question 26

hypophosphatemia treatment

Answer 26

• prevent with proactive monitoring and supplementation
• emergent treatment is indicated for severe symptomatic hypophos and asymptomatic animals at risk for developing symptoms
• potassium phosphate IV CRI

Question 27

hyperphosphatemia common causes and clinical signs

Answer 27

common causes:

• chronic or acute kidney injury
• hypervitaminosis D
• hypoparathyroidism
• young growing animals

clinical signs: rare

Question 28

hyperphosphatemia treatment

Answer 28

emergent (rare):
- IV fluids and parenteral glucose +/- insulin

chronic tx:
- dietary restriction (low protein diet)
- oral phosphate binders