Oedema + Vascular disease in horses

Question 1

What is oedema?

Answer 1

• Abnormal and excessive accumulation of fluid in the interstitium

Anasarca = generalised subcutaneous oedema

Question 2

What oedema is life threatening?

Answer 2

• Pulmonary oedema - frothy noses
• Cerebral oedema

Question 3

What is the 4 mechanisms of oedema?

Answer 3

1. Increased capillary hydrostatic pressure
2. Decreased capillary oncotic pressure
3. Lymphatic obstruction
4. Increased capillary permeability

Question 4

What would cause increased hydrostatic pressure?

Answer 4

• Congestive heart failure
• 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+

Question 5

What would cause decreased colloid osmotic pressure?

Answer 5

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

Question 6

What would cause lymphatic obstruction?

Answer 6

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

Question 7

What would cause increased vascular permeability?

Answer 7

• 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

Question 8

What are vascular disorders in horses?

Answer 8

1. Vasculitis
2. Arterial Aneurysm & Rupture
3. Thrombosis & Thrombophlebitis
4. Lymphangitis

Question 9

What is EVA - equine viral arteritis?

Answer 9

• Arterivirus - causes Panvasculitis
• Respiratory or venereal transmission
• Clinical signs very variable
  – +/- pyrexia, dull, oedema, stiff gait, oedematous mm
  – Respiratory disease / ABORTION
• Notifiable
• Carrier stallions = resevoir

Question 10

What are other infectious causes of vasculitis?

Answer 10

• Equine Herpes Virus-1 – Respiratory / Neuro / abortion
• Equine Infectious Anaemia
• Hendra virus – Pulmonary, Neurological
• African Horse Sickness
  – Pulmonary Form (most severe)
  – Cardiac Form

Question 11

What is immune mediated vasculitis?

Answer 11

– Allergic oedema/hypersensitivity reactions
– Local - urticaria, wheals
– General – swollen limbs/head
– Severe generalised = purpura haemorrhagica
– liberation of vaso-active substances

• Type 1 (IgE mediated) + Type 3 (Immune complex) hypersensitivity

Question 12

What are other forms of vasculitis?

Answer 12

• Septic
• Traumatic
• Verminous
• Photosensitisation
• Toxic
• Neoplastic

Question 13

Where are arterial aneurysms + rupture most common?

Answer 13

• From aortic root in stallions - dissect into pericardium / cardiac chamber

Question 14

What are different thrombosis / thrombophlebitis?

Answer 14

• Aorto-iliac thrombosis - lameness / HL pain (rectal dx)
• Jugular catheters causing thrombosis (bad hygiene/ hypercoagulable state (SIRS))

Question 15

What is lymphangitis?

Answer 15

• Inflammation / infection of lymph vessels
  *painful but will weight bear on limb
• Swollen / serum ooze / crusting
• Ddx = septic synovitis

Question 16

How would you treat lymphangitis (fat/big leg / ‘monday morning leg’)?

Answer 16

• Anti-inflammatories = NSAIDS +/- corticosteroids
• Antimicrobials - staph often involved
• Topical cleaning
• Local cold / support
• Encourage walking
• Tetanus prophylaxis