Hypercalcemia and hypocalcemic disorders in dogs and cats Flashcards
function of calcium in the body
Intracellular second messenger involved in signalling systems
Nerve conduction and neuromuscular transmission
Coagulation
Muscle contraction
Membrane stability
3 main hormone systems in control of Ca
parathyroid hormone (PTH)
vitamin D + its metabolites
calcitonin
PTH - when is it secreted
secreted by the chief cells of the parathyroid gland in response to decr serum levels of ionised calcium
PTH - effects
kidneys - decr Ca excretion and incr calcitriol production
bone - incr Ca resorption
GIT - incr Ca absorption by effects on calcitriol production
incr phosphate excretion through enhanced phosphaturia - hyperparathyroidism tends to develop nephrocalcinosis.
PTHrP (parathyroid hormone related peptide)
PTH like factor excreted by some neoplastic cells + causes hypercalcemia with malignancy.
Vitamin D and its metabolites
steroid hormone
The biologically active metabolite is calcitriol
Vitamin D synthesised in skin or ingested in the diet
converted in the liver and kidneys to the active for.
calcitrol effects
incr serum Ca by incr GI absorption of Ca
facilitates renal reabsoprtion of Ca + mobilises Ca + phosphorus from bone
Calcitonin
secreted in response to hypercalcemia by the C cells of the thyroid gland
physiological effects are minor
Measurement of calcium
Clinically total serum calcium is most commonly measured parameter
ionised calcium is the physiologically significant value controlled by homeostatic mechanisms
measuring Ca with serum albumin conc
common cause of a total hypercalcemia is an incr albumin conce seen with dehydration.
total calcium is incr this is d/t incr in bound fraction + is of no physiological significance
patient with low serum albumin may have a normal total Ca but has incr in ionised calcium that is potentially life-threatening
hypercalcaemia - clinical signs
often vague - can be mistaken for natural aging
PU/PD, anorexia, dehydration, weakness/lethargy and vomiting
severe less common signs - facial pruritis, oral discomfort, cardiac arrhythmias, seizures/twitching, acute renal failure and death.
hypercalcaemia - effects on kidney
interferes with kidney’s ability to conc urine - patients may be dehydrated with a pre-renal azotaemia but still have urine with a relatively low specific gravity
exacerbated d/t high Ca also causes vasoconstriction of the afferent glomerular arteriole, decr in GFR + azotemia.
hypercalcaemia - causes - non pathologic
Young animals
Lab error
Spurious (lipaemia)
hypercalcaemia - causes - transient incosequential
Hypoadrenococrticism
Haemoconcentration
Hyperproteinaemia
hypercalcaemia - causes - pathologic
Malignancy (esp lymphoma, anal sac adenocarcinoma) Primary hyperparathyroidism Renal failure Hypervitaminosis D Granulomatous disease (fungal infection, lungworm) Toxic Skeletal lesions Idiopathic (cats)
hypercalcaemia - most common causes
neoplasia
primary hyperparathyroidism, chronic renal failure, granulomatous inflammatory disorders and hypoadrenocorticism
Primary hyperparathryroidism - cause
parathyroid adenoma of the parathyroid glands
nodule is non-palpable but readily ultrasonographically demonstrable
Evaluation of patient with hypercalcemia
PE including rectal examination
Haematology, biochemistry, UA
Aspiration of masses/enlarged lymph nodes
Imaging of thorax and abdomen to assess for neoplasia
Bone marrow aspirate
Ultrasound of neck
ACTH stimulation test
Test for other granulomatous (infectious) disease –dependent on geographical location
PTH/PTHrP levels
Calcitriol measurement
hypercalcaemia - treatment of underlying disease
Chemotherapy for some neoplastic diseases
surgery for neoplastic disease and primary hyperparathyroidism
Anti-fungals/antiparastitics in granulomaotus disease
hypercalcaemia - treatment without definitive diagnosis
Diuresis with 0.9%NaCl Bisphosphonates therapy e.g. palmidronate Calcitonin Furosemide Peritoneal dialysis
why not to use glucocorticoids`
lower serum Ca but mask underlying disease - diagnosis more difficult
long term effect of hyercalcaemia
renal failure secondary to soft tissue mineralisation
more likely if the phosphorus level is also elevated
hypocalcaemia - clinical signs
muscle tremors/cramps, stiff gait, behavioural change, panting, hyperthermia tachycardia, hypotension, death
hypocalcaemia - causes
Chronic renal failure Eclampsia (pregnancy disorder) Acute pancreatitis Iatrogenic (post thyroidectomy/parathyroidectomy, post blood transfusion) Ethylene glycol toxicity Intestinal malabsorption Primary hypoparathyroidism
hypocalcaemia - treatment - acute
IV 10% calcium gluconate
hypocalcaemia - treatment - chronic
Oral calcium supplementation
vitamin D metabolite
Ergocalciferol (cheap but long half-life)
Dihydrotachysterol (intermediate price, intermediate half-life
Calctriol (most expensive but shortest half life)