Clinical Pathology in small animals

Question 1

A 5 year old female neutered English Springer Spaniel presented because of acute weakness and exercise intolerance
EXAMINATION
The dog was lethargic with pale mucous membranes. Further abnormalities included dyspnoea, tachycardia and a bounding pulse. Radiographs of the thorax revealed a mild thoracic effusion, which was bloody when aspirated.

Interpret these results

Answer 1

Haematology:
* Borderline leycocytosis on a slight neutrophilia - suggests stress (epinephrine or glucocorticoid effect)
* Moderate normocytic-normochromic anaemia present
○ Non-regenerative due to absence of polychromasia, hypochromasia and macrocytosis of erythrocytes
* Haemorrhagic thoracic effusion, hypoproteinaemia and prolonged coagulation time suggests the anaemia is due to subacute haemorrhage prior to the onset of regeneration
Biochemistry:
* Increase of urea, normal creatinine suggests GI haemorrhage (decreased GFR or diet effect should also be considered)
* Moderate hyponatraemia, hypochloraemia, hypocalcaemia and hypokalaemia suggest 3rd space fluid losses due to thoracic effusion
* 3rd space fluid loss due to thoracic effusion => hypovolaemia and subsequent secretion of ADH and a thirst response
* Hypoproteinaemia + hypoalbuminaemia + low globulins likely due to haemorrhage
* Hyperglycaemia suggests stress-induced glucocorticoid effect
* Triglyceride increase not significant
Coagulation Profile:
* Prolonged aPTT and PT suggests a disorder of secondary haemostasis
* PT prolongation is greater than aPTT - this is highly suggestive of acut coumarin (rodenticide) intoxication

DIC = differential diagnosis
* but aPTT more affected that PT in DIC
* Would expect thrombycytopaenia and decreased fibrinogen
Measurement of D-dimers used to rule out DIC

Question 2

HISTORY
A 10-year-old male cross-breed dog is reported to have vomited 4 days ago and then become anorexic. He had been receiving meloxicam for arthritis, was polydipsic but now hardly drank any water.
EXAMINATION
The dog was flat on examination, was dehydrated, a degree of mental obtundation was observed and hepatomegaly was observed on ultrasound.

Interpret these results

Answer 2

• Normocytic-normochromic non-regenerative anaemia
  
  • Slight neutrophilia and monocytosis may be stress related but toxic changes in neutrophils reflects inflammation/infection
  • Hyperglycaemia + glucosuria (if persistent and accompanied by clinical signs) suggest DM
  • Hyponatraemia and hypochloraemia probably secondary to osmotic diuresis
  • Hyponatraemia may also be directly linked to hyperglycaemia - osmotic movement out of cells into plasma
  • Hyperphosphataemia probably secondary to azotaemia
  • Lactic acidosis may also cause hyperphosphataemia
  • Lactic acidosis possible in non-ketotic diabetics due to overproduction as a result of tissue hypoxia and/or deficient removal/hepatic failure with circulatory collapse - lactic acid was not measured
  • Sample haemolysis or delayed removal of serum/plasma from eryhtrocytes can also falsely contribute to hyperphasphataemia
  • Azotaemia consistent with renal disease
  • USG should be interpreted with caution in diabetic patients as osmotic diuresis may contribute to impairment of kidneys concentrating ability => inappropriate USG
  • Evidence of hepatic dysfunction by increased bile acids (bilirubinuria may be due to hepatopathy)
    Hypercholesterolaemia may be associated with DM, acute pancreatitis, cholestasis and decreased lipolysis

Question 3

HISTORY
A 12.5 yr old entire female Old English Sheepdog had anorexia for 5 days. She had been polydipsic but was not longer drinking at time of presentation

Interpret these results

Answer 3

• Mild to moderate anaemia with mild regeneration
  
  • Leukocytosis characterised by neutrophilia with a marked left shift, toxic change and monocytosis - leukogram changes indicate severe, ongoing inflammation
  • Lymphocytes low-normal, indicating stress
  • Mild azotaemia - needs to be interpreted with USG (not available)
  • ALP and GGT increase may be due to cholestasis and/or enzyme induction
  • Hypoalbuminaemia and low A/G ration may be due to albumins role as a negative acute phase protein (urinalysis should be done to explore albumin loss via kidneys)
  • Pyometra most likely in this dog
  • Anaemia due to inflammatory disease
    Leukogram abnormalities due to increased demand for phagocytic cells

Question 4

HISTORY
A 5 year old male neutered cross-bred dog had accidental access to the skin cream used by his owner. He now has PU/PD.

Interpret these results

Answer 4

Urinalysis
* Urea and creatinine increase suggests azotaemia
* Pre-rena azotaemial:
○ Likely secondary to polyuria
○ Slight increase in total protein and albumin which is likely due to haemoconcentration secondary to dehydration
○ Asynchronous increase in urea compared to creatinine, likely due to dehydration as urea is absorbed by the renal tubules => increased levels in peripheral blood
○ No evidence of chronic renal failure as dog is in good body condition, no anaemia, and PU/PD is acute
○ USG not useful here are hypercalcaemia lowers USG
* USG:
○ Low and hyposthenuric (would expect hypersthenuria with pre-renal azotaemia)
○ Due to hypercalcaemia - causes nephrogenic diabetes insipidus (renal tubules are not responding to ADH)
○ Increased ionised Ca inhibitis ADH activity
○ Increased Ca reduces tubular resorption of Na and CL in the ascending loop of Henle which reduces the osmotic gradient needed for water resorption in the distant nephron
Hypercalcaemia:
* Possibly Increased calcium mobilisation from bone or absorption from intestine due to primary hyperparathyroidism (increased PTH), also causes hypophosphataemia and phosphatric action (measure PTH in this case)
* Possibly humoral hypercalcaemia malignancy - production of PTHrP by neoplastic cells
* Possible increased Vit D - promotes intestinal absorption of Ca and phosphate
Possibly decreased urinary excretion due to renal failure (would have decreased free calcium, increased total calcium)