PATHOLOGY - Hypoadrenocorticism (Addison's) Flashcards
What is the pathophysiology of hypoadrenocorticism?
Hypoadrenocorticism results in decreased cortisol and aldosterone production. Decreased cortisol production will lead to a lack of appropriate immune response resulting in poor wound healing, increased susceptibility to secondary infection and cause the individual to lack a stress leukogram. Decreased aldosterone production will increase renal potassium retention and renal sodium excretion causing hyperkalaemia and hyponatraemia resulting in polyuria and polydipsia
What are the potential causes of hypoadrenocorticism?
Autoimmune destruction of the adrenal glands (most common)
Trilostane/mitotane treatment
Adrenalectomy
Adrenal haemorrhage
Adrenal neoplasia
Adrenal infarction
Adrenal infection
(T/F) Autoimmune destruction of the adrenal glands is heritable
TRUE. You should make breeders aware of this if they plan to breed a dog with hypoadrenocorticism
What is the typical signalement for hypoadrenocorticism?
Female, young to middle aged dogs
Younger animals as this is an immune mediated disease
Which dog breeds are predisposed to hypoadrenocorticism?
Poodles
Bearded Collies
Rottweilers
West Highland White Terriers
What are the clinical signs of hypoadrenocorticism?
The clinical signs of hypoadrenocorticism are very variable between patients but generally present as a failure to thrive
What are the clinical signs of an acute addisonian crisis?
Collapse
Severe dehydration
Hypovolaemia
Anorexia
Vomiting
Bradycardia
Haemorrhagic gastroenteritis
What causes bradycardia in an acute addisonian crisis?
Hypoadrenocorticism results in decreased aldosterone production which would usually retain sodium and excrete potassium renally. Decreased aldosterone results in increased potassium retention and hyperkalaemia which can result in bradycardia
Usually hypovolaemia etc would prevent with tachycardia so this bradycardia can be a key sign of addison’s
What are the potential complications of an acute addisonian crisis?
Acute renal failure
Pancreatitis
Gastrointestinal haemorrhage
Disseminated intravascular coagulation (DIC)
Pulmonary thromboembolism
How can hypoadrenocorticism present on haematology?
Anaemia
No stress leukogram or reverse stress leukogram
Normal haematology
What are the characteristics of a reverse stress leukogram?
Neutropenia
Lymphocytosis
Eosinopenia
How can hypoadrenocorticism present on biochemistry?
Hyponatraemia
Hyperkalaemia
Azotaemia
Hypercalcaemia
Hypoglycaemia
Hypoalbuminaemia
Hypocholesterolaemia
How can hypoadrenocorticism present on urinalysis?
Low urine specific gravity (USG)
Which differential diagnoses is often confused with hypoadrenocorticism?
Renal failure is often confused with hypoadrenocorticism as both diseases have a similar clinical presentation, cause azotaemia, and a low USG. Furthermore, acute kidney injury can present with hyperkalaemia, however chronic renal failure typically presents with hypokalaemia
Which diagnostic test can you do to get a definitive diagnoses of hypoadrenocorticism?
ACTH stimulation test
How do you treat an acute addisionian crisis?
Intravenous fluid therapy
Manage hyperkalaemia
Hydrocortisone sodium succinate
Which fluids should you use for patients in acute addisonian crisis?
NaCl fluids as these patients are hyponatraemic
What are the aims of intravenous fluid therapy when treating an acute addisonian crisis?
Correct fluid deficits
Manage maintenance requirements
Manage ongoing losses
Treat shock if indicated
Manage hyperkalaemia
What can be used to manage hyperkalaemia in patients in an acute addisonian crisis?
IV fluid therapy and calcium gluconate can be used as it is a cardioprotectant but it is only indicated in severe bradycardia due to hyperkalaemia
Why should you not use insulin and glucose to correct hyperkalaemia in patients in an acute addisonian crisis?
You should not use insulin and glucose in patients in an acute addisonian crisis as they already have low glucose and you risk causing hypoglycaemic collapse
What is hydrocortisone sodium succinate?
Hydrocortisone sodium succinate is a combination of a mineralocorticoid and a glucocorticoid
Give these after you do ACTH stim test
What can you administer to patients in acute addisionian crisis if there is not hydrocortisone sodium succinate available?
Dexamethasone
Prednisolone
Give these after you do ACTH stim test
What should you monitor in patients being treated for an acute addisonian crisis?
TPR
Mucous membranes
CRT
Urine output
Respiration
Electrolytes
Blood glucose
Blood calcium
PCV/TP
How do you treat hypoadrenocorticism long term?
Desoxycortone pivalate (DOCP) and prednisolone
Fludrocortisone
What is desoxycortone pivalate (DOCP)?
Desoxycortone pivalate (DOCP) is a pure mineralocorticoid, which for the treatment of hypoadrenocortisone has to be combined with prednisolone
DOCP should only be used when electrolyte imbalances have been corrected
What is fludrocortisone?
Fludrocortisone is a combination of a mineralocorticoid and a glucocorticoid
Why is desoxycortone pivalate (DOCP) and prednisolone the preferred long term treatment for hypoadrenocorticism?
Desoxycortone pivalate (DOCP) and prednsolone are both in injectable forms (requiring monthly injections) which allows for more specific dose adjustments compared to fludrocortisone which is only available as an oral tablet
