Oedema and Vascular disease in horses Flashcards

1
Q

Give a definition of oedema

A

‘Abnormal and excessive accumulation of fluid in the interstitium’
Not a disease, but a sign of disease

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2
Q

Describe the different distributions of oedema

A

Local vs generalised
- Dependant: accumulation in the lowermost parts of the body (species differences).
- Local: occurs where local conditions favour its development e.g. head or single limb
- ‘Anasarca’: Generalised subcutaneous oedema
- Pulmonary oedema: Initially in the interstitium and then in the alveoli. Life threatening.

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3
Q

Describe the pathophysiology of oedema

A
  • Increases in hydrostatic pressure forces fluid out into tissues, this pressure is higher at the arterial end compared to the venous end
  • The colloid oncotic pressure forces fluid back into vessels: more protein in the blood compared to the interstitial fluid
  • At the arterial end the hydrostatic pressure is greater than the colloid oncotic pressure so fluid is forced out of the vessel. This is opposite at the venous end
  • Excess fluid leaves as lymph
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4
Q

Describe the 4 mechanisms of oedema

A
  • increased capillary hydrostatic pressure
  • decreased capillary oncotic pressure
  • lymphatic obstruction
  • increased capillary permeability
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5
Q

Name the main cause of increased hydrostatic pressure

A

Congestive heart failure

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6
Q

List some other causes of increased hydrostatic pressure

A
  • Portal hypertension (liver disease)
  • Intra-thoracic mass
  • Pulmonary oedema from L sided HF
  • Venous thrombosis – e.g. Jugular thrombosis
  • Increased intra-abdominal pressure
  • Elevated Na+
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7
Q

List some causes of decreased colloid osmotic pressure

A
  • Protein losing enteropathy or nephropathy
  • Haemorrhage
  • Proteinaceous effusions
  • Chronic hepatopathy
  • Malnutrition (Protein, Energy Malnutrition)
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8
Q

List some causes of lymphatic obstruction

A
  • Confinement - “stocking-up“
  • Lymphangitis
  • Tumours
  • Post Partum
  • other local swelling
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9
Q

List some causes of increased vascular permeability

A
  • Vasculitis: immune mediated, infectious, toxic, neoplastic, traumatic, UV light
  • Systemic Inflammatory response syndrome (SIRS) / ‘Endotoxaemia’
  • Inflammatory cascade: margination and activation of neutrophils, endothelial dysfunction
  • Local inflammation
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10
Q

List and describe some possible causes of the following case:
- Diarrhoea 2 days
- Dull
- Temp 39.2 C
- HR 68 bpm
- MM: Congested
- VENTRAL PITTING OEDEMA

A
  • Losing protein in the diarrhoea so the colloid oncotic pressure is decreasing
  • Endotoxaemia – leaky vessels
  • Multi organ failure: reduced contractility of the heart, increased venous blood pressure
  • SIRS causes widespread vasodilation which explains the congested MMs – body loses the ability to send blood to the most vital places (heart and brain)
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11
Q

Upon haematology you see low levels of white blood cells, explain the reason for this?
Same case:
- Diarrhoea 2 days
- Dull
- Temp 39.2 C
- HR 68 bpm
- MM: Congested
- VENTRAL PITTING OEDEMA

A

Proteins marginated to the blood vessel walls
This attracts neutrophils which stick to the vessel wall (lower levels in blood)
This damaged the vessel making it more permeable

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12
Q

On the biochemistry results you find increased blood urea nitrogen, increased creatinine and low albumin, explain why?
Same case:
- Diarrhoea 2 days
- Dull
- Temp 39.2 C
- HR 68 bpm
- MM: Congested
- VENTRAL PITTING OEDEMA

A
  • Low circulating volume so kidneys aren’t being perfused with enough blood
  • Low albumin: lost easily as it’s a small molecule and it has a more dramatic effect on colloid osmotic pressure
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13
Q

Describe the main features of systemic inflammatory response syndrome

A
  • Increased capillary permeability
  • Reduced cardiac output
  • Increased capillary hydrostatic pressure
  • Margination of neutrophils causes capillary leak
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14
Q

Describe some features you might seen on PME of generalised oedema

A

Severe colitis – thickened, necrotic
Lung – lobules separated by oedema
Foam coming up the trachea – sign of pulmonary oedema

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15
Q

Name 4 vascular diseases of horses

A

Vasculitis
Arterial Aneurysm & Rupture
Thrombosis & Thrombophlebitis
Lymphangitis

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16
Q

Infectious Equine Viral Arteritis (EVA) causes what type of vasculitis?

A

Panvasculitis - affects all of the vessels

17
Q

Describe the clinical signs of Infectious Equine Viral Arteritis (EVA)

A

Clinical signs very variable
+/- pyrexia, dull, oedema, stiff gait, oedematous mm
Respiratory disease / ABORTION

18
Q

Why is infectious equine viral arteritis an important disease?

A

Notifiable – Must tell a DEFRA is case suspected

19
Q

How is infectious equine viral arteritis transmitted?

A

Respiratory or venereal transmission
Carrier stallions = reservoir – pass to females during service

20
Q

Name 4 other infectious causes of vasculitis

A
  • Equine Herpes Virus: respiratory / Neuro / abortion
  • Equine Infectious Anaemia
  • Hendra virus: pulmonary, neurological
  • African Horse Sickness
21
Q

Name the cause of a severe generalised immune mediated vasculitis

A

Purpura haemorrhagica

22
Q

Immune mediated vasculitis are caused by which types of hypersensitivity?

A

Type 1 - IgE - Histamine
Type 3 - immune complex

23
Q

Purpura haemorrhagica occurs secondary to which disease?

A

Strangles

24
Q

What is purpura haemorrhagica?

A

Bleeding under the skin
- very variable severity

25
Q

List some other causes of vasculitis in horses

A

Septic
Traumatic
Verminous e.g. Strongylus vulgaris
Photosensitisation
Toxic
Neoplastic

26
Q

What is an aneurysm?

A

Out budging of a BV of the artery. Weakness in the wall that gradually gets bigger and bigger
Most commonly from aortic root in stallions
Aneurysm dissects into pericardium or cardiac chamber

27
Q

How does an aneurysm most common present?

A

Sudden onset pericardial effusion

28
Q

Describe the features of an aorto-iliac thrombosis

A

Uncommon
Aetiology unknown (S.vulgaris?)
Lameness / HL pain
Diagnosis by rectal +/- US

29
Q

Which type of catheter is more thrombogenic?

A

Teflon

30
Q

What is another term used to describe lymphangitis?

A

‘Fat/Big Leg’ / ‘Monday morning leg’

31
Q

Define lymphangitis

A

Inflammation or infection of lymph vessels

32
Q

Describe the main features of lymphangitis

A

Common!
Usually localised
Sometimes secondary to penetrating wound / cellulitis

33
Q

Describe how horses with lymphangitis present

A

Normally pain on palpation
Pain over lymphatics
Will normally bear weight on the limb
Swollen, +/- serum ooze / crusting
Examine for primary wound

34
Q

What is the main DDx for lymphangitis?

A

Septic synovitis

35
Q

How is lymphangitis treated?

A
  • Anti-inflammatories (NSAIDs +/- Corticosteroids)
  • Antimicrobials (Staph. often involved)
  • Topical Cleaning
  • Local cold / support
  • Encourage walking
  • Tetanus prophylaxis