Top 20 Canine Conditions Part 2

For my own personal use only:
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  • Dive into the next 5 of the top 20 canine diagnoses.
  1. Heart failure
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    Echocardiogram of dog with dilated cardiomyopathy showing marked left atrial and left ventricular dilation
    • Classic case:
      • Cough, exercise intolerance
      • Abdominal distension
      • +/- Heart murmur or arrhythmia
      • Harsh lung sounds/crackles
    • Dx:
      • Thoracic radiography shows:
        • Heart enlargement
        • Dilated pulmonary veins
        • Interstitial to alveolar lung changes in caudodorsal lung fields
      • Echocardiography shows:
        • Left atrial +/- left ventricular enlargement (causing pulmonary edema)
        • +/- Poor contractility
        • Valvular insufficiency
        • Right atrial and ventricular dilation (causing ascites)
    • Tx:
      • Acute:
        • Diuretics: furosemide
        • Oxygen therapy (cage or nasal cannula)
        • Positive inotrope and vasodilator: pimobendan
        • Decrease stress, mild sedation if needed
      • Chronic:
        • Diuretics: furosemide
        • Positive inotrope and vasodilator: pimobendan
        • ACE-inhibitor
        • Restrict exercise and dietary salt
    • Pearls:
      • Prognosis is guarded

  2. Heartworm
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    Heartworm (Dirofilaria immitus) microfilaria at 400X
    image
    D. immitus on a stained blood smear (AW image)
    • Classic case:
      • Cough and exercise intolerance
      • Abdominal distension
      • Weight loss/poor body condition
    • Dx:
      • Annual screening with antigen SNAP test
        • Detects protein secreted by adult female worm 5 mos post-infection
        • False negatives if:
          • Antigen/antibody complex formation
          • No adult female worms (e.g., immature females or males only)
          • Light parasite load
      • Microfilaria test: recommended annually
        • Types of tests:
          • Modified Knotts
          • Filter test
          • Direct smear of anti-coagulated blood
      • Thoracic radiography shows:
        • Enlarged, tortuous, +/- blunted pulmonary arteries
        • Pulmonary parenchymal disease
        • Right heart enlargement
      • Echocardiography shows:
        • Pulmonary artery dilation
        • Right heart dilation
        • Visible heartworms in pulmonary artery
        • Caval syndrome: heartworms visible in right ventricle +/- right atrium
    • Tx:
      • Doxycycline
        • Daily, 30 d prior to adulticide
      • Heartworm prevention: macrocyclic lactones
        • Prevent new infections
        • Eliminate susceptible larvae and microfilaria (pretreat with diphenhydramine and corticosteroids if microfilaria positive)
        • Treat monthly, starting 2 mos prior to adulticide
      • Adulticide: melarsomine dihydrochloride
        • 3-dose protocol: IM once, wait 1 mo, then 2 doses given 24 h apart
        • Kills 98% of heart worms
        • STRICT exercise restriction during adulticide therapy and continuing for 6-8 wks after final dose
      • Corticosteroids
        • Tapering anti-inflammatory dose to control clinical signs of pulmonary thromboembolism
        • Start 1-2 mos prior to adulticide if symptomatic or microfilaria positive
      • Surgical extraction of adult worms
        • Indicated for dogs with caval syndrome
    • Pearls:
      • Prognosis:
        • Good to guarded depending on severity
        • Poor to grave for caval syndrome
      • Doxycycline therapy to reduce Wolbachia (intracellular bacteria essential for worm survival) makes worms more susceptible to adulticide therapy
      • 7% of infected dogs are negative on SNAP and positive for microfilaria

  3. Pyometra
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    Lateral radiograph demonstrating distended uterus with pyometra
    • Classic case:
      • Intact middle-aged female 3-4 wks past estrus
      • +/- Mucoid, purulent, or hemorrhagic vulvar discharge
      • Polyuria/polydipsia
      • Vomiting, anorexia, abdominal pain
      • Enlarged, palpable uterus
    • Dx:
      • Abdominal radiography: distended, tubular, enlarged, fluid-filled uterus
      • Vaginal cytology: degenerative neutrophils +/- phagocytized bacteria
      • Abdominal ultrasonography: enlarged fluid-filled uterus; differentiates from pregnancy
    • Tx:
      • Stabilization:
        • IV fluids
        • Broad-spectrum antibiotics
        • Analgesics
      • Surgical:
        • Ovariohysterectomy is Tx of choice for all animals not intended for breeding
      • Medical:
        • Option for young breeding animals
        • Referral recommended
    • Pearls:
      • Prognosis: guarded to good if uterus is intact
      • Rule out pyometra in any systemically ill intact female

  4. Flea allergy dermatitis (FAD)
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    Flea allergy dermatitis
    • Classic case:
      • Acute onset of moderate to severe pruritus
      • More common in warmer seasons but can be year round
      • Excessive self-grooming and hair loss, especially rear half of body
      • +/- Visible live fleas
    • Dx:
      • History and physical exam
      • Flea comb to find fleas/flea dirt
      • Positive response to flea eradication
    • Tx:
      • Acute:
        • Tapering dose of corticosteroids for pruritus
        • Topical/oral flea adulticide
      • Chronic:
        • Ongoing use of oral/topical flea adulticide
        • Oral monthly flea development inhibitors (lufenuron)
        • Environmental control: frequent vacuuming, removal of outdoor organic debris
    • Pearls:
      • Prognosis is good with long-term management
      • 15% of dogs do not have evidence of fleas

  5. Lameness overview: hip dysplasia, panosteitis, osteochondrosis dissecans (OCD), hypertrophic osteodystrophy (HOD), Legge-Perthes disease
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    Hip dysplasia: VD radiograph with right luxation of hip and thickening of both femoral necks
    • Classic case:
      • Hip dysplasia: "bunny hopping" gait, lameness, difficulty rising, positive Ortolani sign (hip laxity)
      • Panosteitis, HOD, OCD: young, medium to giant breeds, more common in males, acute lameness, fever
        • Panosteitis: long bone pain
        • HOD: swollen and warm distal limb, metaphyseal pain
        • OCD: joint effusion, decreased range of motion
      • Legge-Perthes disease (avascular necrosis of femoral head): 3- to 12-mo-old small or toy breeds, pelvic limb lameness
    • Dx: Radiography
      • Hip dysplasia:
        • Shallow acetabulum
        • Flattening of femoral head
        • Over 50% of femoral head covered by acetabular rim
        • Thickened femoral neck
      • Panosteitis: multiple long bones have increased medullary opacity, periosteal new bone
      • HOD: double physeal line
      • OCD: (can use CT)
        • Flattening of subchondral bone, joint mouse, joint effusion
        • Always image both limbs
      • Legge-Perthes disease: loss of bone opacity at femoral epiphysis, moth-eaten appearance of femoral neck and head
    • Tx:
      • Hip dysplasia:
        • Surgical: triple pelvic osteotomy, femoral head ostectomy, total hip replacement
        • Medical: NSAIDs, weight loss, joint supplements
      • Panosteitis, HOD: analgesics
      • OCD: surgical debridement or medical Tx with joint supplements and analgesics
      • Legge-Perthes disease: surgical femoral head ostectomy or total hip replacement, analgesics
    • Pearls:
      • Hip dysplasia: PennHIP method is more accurate for Dx at an earlier age than OFA method
      • Panosteitis, HOD: prognosis is excellent but flare-ups may occur, repeat radiography may be necessary to diagnose
      • OCD: prevent by avoiding excessive food and calcium and vitamin D supplements
      • Legge-Perthes disease: prognosis with surgery is good to excellent

Images courtesy Dr. Laura Cousins (heartworm microfilaria, pyometra radiograph, hip dysplasia radiograph), Kalumet (echocardiogram), and Caroldermoid (FAD).

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