Approach to Metabolic Collapse & Hypoadrenocorticism Flashcards
what is the etiology of hypoadrenocorticism
Deficiency of mineralocorticoids (aldosterone), glucocorticoids (cortisol) or both
what is the most common cause of hypoadrenocorticism
Primary adrenocortical insufficiency (Addison’s) with a deficiency of mineralocorticoid and glucocorticoid secretion is the most common
Usually idiopathic —> the cause is not known
Immune-mediated destruction of adrenal cortices is believed to occur in most dogs with idiopathic adrenal insufficiency
what does aldosterone controlled
Loss of aldosterone secretion results in impaired renal conservation of sodium and chloride and excretion of potassium, leading to development of hyponatremia, hypochloremia and hyperkalemia
Inability to retain sodium and chloride reduces extracellular volume, leading to progressive development of hypovolemia, hypotension, reduced cardiac output and decreased perfusion of the kidneys and other tissues
what is the hallmark sign of hypoadrenocorticism
Hallmark sign of hypocortisolism are impaired tolerance to stress and clinical signs often become more pronounced when the animal is placed in stressful situations
what are the breeds that are predisposed to immune mediated hypoadrenocorticism
Young to middle aged dogs, often female
Standard poodles, bearded collies, Rottweilers, west highland white terriers
how does mitotate/trilostane cause hypoadrenocorticism
Adrenal necrosis/suppression
what are other causes of hypoadrenocorticism
Hemorrhage, infarction, infection, tumour
what is the signalment of hypoadrenocorticism
Young to middle aged female dogs with a median age of onset for all breeds of 4 years
Dogs with glucocorticoid deficient hypoadrenocorticism tend to be older at the time of diagnosis than dogs with mineralocorticoid hypoadrenocorticism
Inherited as an autosomal recessive trait in Portuguese water spaniels, nova scotia duck tolling retrievers, standard poodles and bearded collies
what are the clinical signs of hypoadrenocorticism in dogs
Lethargy
Anorexia
Vomiting
Weakness
Diarrhea
Weight loss
Shivering/shaking
Polyuria, polydipsia
Abdominal pain
Most have a long history of unwell, not quite right, poor doer
Wax and wane of symptoms
May look like other diseases (ex IBD, kidney failure, etc)
what are the clinical signs of hypoadrenocorticism in cats
Lethargy
Anorexia
Weight loss
Vomiting
Polyuria, polydipsia
what is the history of hypoadrenocorticism patients
- chronic, vague: often respond to non-specific therapy
- neurological: depression, weakness
- GI signs: inappetance, vomiting, diarrhea
- metabolic: failure to thrive, PUPD
what are the clinical findings of acute hAC (6)
- severe dehydration
- anorexia
- vomiting
- collapsed
- bradycardia
- hemorrhagic gastroenteritis
what are complications of acute hAC (5)
- acute renal failure
- GI hemorrhage
- pancreatitis
- pulmonary thromboembolism
- disseminated intravascular coagulation
what are examples of ddx of hypoadrenocorticism (8)
- Hemorrhagic gastroenteritis (HGE): parvovirus
- Bradycardia: atrioventricular block
- Episodic collapse: myasthenia gravis
- Lethargy: congestive heart failure
- Vomiting/diarrhea: inflammatory bowel disease
- Polyuria/polydipsia: renal failure
- Weight loss: neoplasia
- Abdominal pain: pancreatitis
what is seen on hematology with hAC (2)
- anemia: GI losses, bone marrow suppression, IMHA
dehydration masks severity: 70% of cases are anemic
- white blood cells: ‘reverse stress leukogram’ (low WBC, neutropenia, lymphocytosis, eosinophilia)
what is seen on biochem with hAC (8)
- serum electrolytes: sodium, potassium
- renal parameters: urea/creatinine increased 80%, minimally concentrated urine
- calcium increased 30%
- decreased glucose
- hypoalbuminemia
- hypocholestermia
- liver function decreased
- decreased pH
what do these abnormalities indicate
hypoadrenocorticism
what are the causes of hypokalemia (3)
red blood cell lysis
failure of excretion
others –> rhabdomyolysis
what are the causes of hyponatremia (3)
- excessive loss
- overhydration
- others – lab error, lipemia
what would the sodium:potassium ratio be in hAC
Normal: 27:1 and 40:1
Values are often less than 27 and may be less than 20 in animals with primary adrenal insufficiency
what are the similarities of hAC and renal failure (4)
1. History:
Acute episode after period of illness
2. Clinical examination:
Thin, dehydrated, may be or have collapsed
3. Renal azotemia:
Increased urea and creatinine
Effect of GI hemorrhage
Urine specific gravity 1.007 to 1.030
4. Electrolyte abnormalities:
High potassium:
Acute renal failure and urinary obstruction
Low sodium:
Polyuric phase of acute renal failure
how would you diagnose hypoadrenocorticism
ACTH stimulation test
but cannot distinguish primary hAC from iatrogenic HAC or recent steroid adminstration
how do you interpret ACTH stimulation test
The post ACTH serum cortisol concentration is less than 55 nmol/L (2 ug/dL)
A normal dog will produce cortisol greater than this
If there is a dramatic increase it may be due to stress or it may be due to hyperadrenocorticism (but this would have completely different clinical signs)
