Oedema and Vascular disease in horses Flashcards
Give a definition of oedema
‘Abnormal and excessive accumulation of fluid in the interstitium’
Not a disease, but a sign of disease
Describe the different distributions of oedema
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.
Describe the pathophysiology of oedema
- 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
Describe the 4 mechanisms of oedema
- increased capillary hydrostatic pressure
- decreased capillary oncotic pressure
- lymphatic obstruction
- increased capillary permeability
Name the main cause of increased hydrostatic pressure
Congestive heart failure
List some other causes of increased hydrostatic pressure
- 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+
List some causes of decreased colloid osmotic pressure
- Protein losing enteropathy or nephropathy
- Haemorrhage
- Proteinaceous effusions
- Chronic hepatopathy
- Malnutrition (Protein, Energy Malnutrition)
List some causes of lymphatic obstruction
- Confinement - “stocking-up“
- Lymphangitis
- Tumours
- Post Partum
- other local swelling
List some causes of increased vascular permeability
- 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
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
- 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)
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
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
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
- 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
Describe the main features of systemic inflammatory response syndrome
- Increased capillary permeability
- Reduced cardiac output
- Increased capillary hydrostatic pressure
- Margination of neutrophils causes capillary leak
Describe some features you might seen on PME of generalised oedema
Severe colitis – thickened, necrotic
Lung – lobules separated by oedema
Foam coming up the trachea – sign of pulmonary oedema
Name 4 vascular diseases of horses
Vasculitis
Arterial Aneurysm & Rupture
Thrombosis & Thrombophlebitis
Lymphangitis
