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SMALL ANIMAL > 1.1.4: Pulmonary parenchymal disease - interstitial disease > Flashcards

1.1.4: Pulmonary parenchymal disease - interstitial disease Flashcards

1
Q

French heartworm =

A

Angiostrongylus vasorum
This is a vascular worm; the adults live in the pulmonary arteries.

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2
Q

Describe the life cycle of Angiostrongylus vasorum

A

Indirect life cycle
Definitive host = dog/wild canids
Intermediate host = slugs/snails
Secondary intermediate/ paratenic host = frogs

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3
Q

Clinical signs of Angiostrongylus vasorum

A
  • Most common: breathlessness / cough
  • Bleeding
  • Neuro signs
  • Often complex signs not limited to respiratory tract
  • Often asymptomatic in early stages
  • Chronic cough: productive, with occasional haemoptysis
  • Dyspnoea
  • Tachypnoea
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4
Q

What causes the clinical signs of Angiostrongylus vasorum infection?

A

Larval migration through lung airway

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5
Q

In heavy burdens, Angiostrongylus vasorum causes hypertension where and what effect does this have on the heart?

A

Pulmonary hypertension
Pressure within right ventricle increases because it is trying to eject blood into a vascular bed that is full or worms

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6
Q

Dogs with Angiostrongylus vasorum can show prolonged bleeding/ anaemia/ subcutaneous or internal haemorrhage. What tests could you do for this and what would they find?

A
  • Angiostrongylus vasorum can cause immune-mediated thrombocytopaenia ± thrombopathia
  • There is prolonged Activate Partial Thrombin Time (APTT)
  • There is prolonged Prothrombin Time (PT)
  • There are elevated D-dimers/ FDPs which can lead to chronic DIC
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7
Q

Describe the neurological signs you might see with Angiostrongylus vasorum infection

A
  • Paresis
  • Seizures
  • Depression
  • Spinal pain
  • Behavioural changes
  • Ataxia
  • Loss of vision

These signs are associated with aberrant nematode migration or subdural haemorrhage secondary to coagulopathies

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8
Q

Egg deposition/ the presence of L1 A. vasorum leads to:
a) Type III hypersensitivity
b) complement activation
c) granuloma formation

A

c) granuloma formation
* And also pulmonary inflammation and pulmonary arteriolar vasoconstriction which contributes to pulmonary hypertension.
* There is end arteritis and fibrosis of vessels.

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9
Q

Adult antigens of A. vasorum cause:
a) pulmonary inflammation and granuloma formation
b) Type III hypersensitivity and complement activation

A

b) Type III hypersensitivity and complement activation
This leads to immune infiltrate into the lungs and other tissues

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10
Q

Why might it be hard to diagnose A. vasorum ?

A
  • Larvae are intermittently shed in faeces
  • Take a pooled sample to try and minimise the chances of this
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11
Q

How can you diagnose A. Vasorum ?

A
  • Pooled faecal sample -> L1 in faeces and flotation techniques
  • L1 in faeces can be detected by smear methods
  • L1 in BAL fluid
  • SNAP tests
  • PCR on BAL / pharynx swabs
  • Supportive evidence: radiograph may show alveolar infiltrates
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12
Q

Describe the radiographic changes you might see with A. vasorum

A

Mixed alveolar and interstitial pattern
There is haemorrhage into the alveoli, and larval migration through the interstitium

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13
Q

What are the licensed treatments for A. vasorum in dogs?

A
  • Imidacloprid + moxidectin
  • Milbemycin oxime + praziquantel

Unlicensed but effective: fenbendazle orally for 7-21 days; levamisole, ivermectin

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14
Q

What are the risks associated with treatment of A. vasorum ? What supportive treatment can you give to mitigate this?

A
  • There is danger associated with treatment - killing lots of parasites at once, releasing lots of antigens at once and thereby provoking host response
  • Clotting problems may persist after treatment

Supportive treatment
* Bronchodilators to mitigate airway hyper-responsiveness
* Corticosteroids may reduce tendency for acute deterioration after beginning anthelmintic therapy
* Phosphodiester inhibitors for ongoing pulmonary hypertension
* Cage rest ± oxygen therapy if dyspnoea present

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15
Q

Prevention for A. vasorum

A
  • Moxidectin + Imidacloprid
  • Treatment in the PPP prevents establishment of the adult parasites
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16
Q

Signalment for Interstitial Pulmonary Fibrosis (IPF)

A

IPF a.k.a. Westie lung
* WHWT and other terriers e.g. staffies
* Middle-aged to older dogs
* Seen in cats uncommonly

17
Q

History suggestive of IPF

A
  • Insidious onset
  • Chronic breathlessness which is slowly progressive
  • May have coughing - this indicates that there is some degree of airway disease as well
  • Exercise intolerance
  • Cyanosis
  • Syncope
18
Q

Where can respiratory problems occur and how can we localise them?

A
  1. URT obstruction
  2. Loss of thoracic capacity (pleural space disease)
  3. Pulmonary parenchymal disease (alveolar or interstitial)
  4. Non-CRS conditions

Localise using clinical exam and thoracic ultrasound

19
Q

What clinical exam findings might you get with a terrier with IPF?

A
  • Marked crackles throughout the lung fields - very crackly, more so than alveolar disease
  • Prolonged expiratory phase with expiratory effort
20
Q

What effect might IPF have on the heart and what changes would you see radiographically?

A
  • May see right-sided cardiomegaly (could enter R-sided heart failure)
  • This is because the right ventricle has difficulty pushing blood through the fibrous interstitium -> leads to high RV pressure and thus cardiomegaly
  • May see “reverse D” on dorsoventral view
21
Q

What interstitial disease might you see these radiographic changes with?

A

Interstitial pulmonary fibrosis (IPF)

22
Q

Diagnosis of IPF

A
  • Suggestive clinical signs: diffuse crackles on auscultation, dyspnoea, coughing
  • Thoracic radiographs: generalised interstitial lung pattern (± chronic coexisting lung disease), ± R-sided cardiomegaly, ± pulmonary hypertension (seen as severe alveolar/interstitial pattern)
  • CT : “ground glass” appearance with diffuse increased opacity without loss of blood vessels
  • BAL : samples are normal or show low cellularity; this helps us rule out other inflammatory conditions e.g. CCB
  • Lung biopsy: only definitive method of diagnosis
23
Q

What clinical/radiographic signs might you see with pulmonary hypertension?

A
  • Generalised / R-sided cardiomegaly/ R HF
  • Severe alveolar/ interstitial pattern
  • Abdominal distension
  • Hepatomegaly
24
Q

True/false: in an older dog with a heart murmur and breathlessness, you can safely assume the two are likely to be connected and can therefore be treated as the same problem.

A

False
in older, small breed dogs, heart murmurs and breathlessness should be considered 2 separate problems until you have established a connection between them!

25
Q

What is the treatment and prognosis for IPF?

A
  • Dog otherwise well but treatment options not great
  • Guarded prognosis; survival ~15 months
  • Treatment extrapolated from humans depends on form - in dogs likely to be usual interstitial pneumonitis

Symptomatic treatment
* Avoid collars -> harnesses only
* Avoid smoke inhalation
* Inhaled therapy: bronchodilator (unlikely to work), corticosteroids
* Oral therapy: bronchodilators (esp in concurrent airway disease), corticosteroids
* Additional immunosuppressive medication e.g. cyclosporin, azathioprine - NO EVIDENCE of clinical efficacy
* Management of pulmonary hypertension -> phosphodiesterase inhibitors e.g. sildenafil, tadalafil, pimobendan

26
Q

What drugs could you use to treat pulmonary hypertension?

A

Phosphodiesterase inhibitors e.g.
* Sildenafil
* Tadalafil
* Pimobendan

27
Q

Imaging modality? Disease?

A

CT of a dog with IPF

28
Q

Lung pattern? Disease?

A

Interstitial pattern: there is a generalised increase in radiodensity but no border obliteration.
This is from a dog with IPF.

29
Q
A

Interstitial pneumonia
Disease affects the interstitium; alveoli and airways are relatively spared.

30
Q

How might metastatic lung disease present?

A
  • May be an incidental finding
  • May present with respiratory difficulty/ tachypnoea
  • Usually presents with dyspnoea rather than cough because tumour arrives by haematogenous spread so is in the interstitium not the airways
31
Q

True/false: all tumours can metastasise to the chest.

A

False
Not all do. The commonest:
* Osteosarcoma
* Haemangiosarcoma
* Thyroid carcinoma
* Melanoma of mucocutaneous junction

32
Q

An owner has opted for solitary metastasis removal of a tumour in their dog’s lungs. What diagnostic imaging modality will help you identify how many areas there are and what surgical approach you need to take?

A

CT

33
Q
A

Nodular interstitial pattern

34
Q
A

Diffuse interstitial pattern/ disease

SMALL ANIMAL (90 decks)

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