Flashcards in Oedema & Lymphoedema Deck (16):
What is the difference between oedema and lymphoedema?
- Oedema = accumulation of an excessive amount of watery fluid in cells, tissues or serous cavities.
- Lymphoedema = swelling (esp. in subcutaneous tissue) as a result of obstruction of lymphatic vessels or lymph nodes and the accumulation of large amounts of lymph in the affected region.
How can one differentiate between oedema and lymphoedema?
- Swelling does not pit in lymphoedema.
The lymphatic obstruction prevents drainage of water and proteins from the IS - increased protein content in IS stimulates inflammatory response - proliferation of fibroblasts and change in organisation of fluid space.
- Swelling pits in oedema.
Pressing temporarily increases hydrostatic pressure, pushing fluid out of the IS.
What determines the movement of fluid in/out of capillaries?
1. Hydrostatic pressure gradient
2. Oncotic pressure gradient
3. Vascular permeability
What is vascular permeability?
Histological architecture of capillaries determines permeability of capillaries to water.
What is the hydrostatic pressure gradient?
Physical force of fluids against their enclosing barriers.
- positive for plasma within capillaries (remnant of blood pressure generated by heart) though declines towards the venal side due to resistance to blood flow generated by capillary
- negative for interstitial fluid within IS due to action of lymphatic pumping
What is the oncotic pressure gradient?
Osmotic pressure generated by the presence of proteinaceous solutes.
Higher in plasma than in IS as plasma proteins cannot cross the capillary barrier.
What is the arteriolar and venular capillary hydrostatic pressures and the blood colloid oncotic pressure?
- 35 mmHg
- 15 mmHg
- 25 mmHg
What is the consequence of pathological processes disturbing the Starling Forces?
Excessive water filtration out of capillaries leading to localised or generalised oedema.
What are the causes and consequences of derangement of hydrostatic pressure gradient?
- venous thrombosis
- right heart failure
Consequences: ineffective venous drainage of blood - backup of blood - increased hydrostatic pressure on venous side (congestion) - oedema.
What are the causes and consequences of derangement of oncotic pressure.
- Nephrotic syndrome
Consequences: poor synthesis or excessive loss of plasma proteins (esp. albumin) - reduced plasma oncotic pressure - oedema.
What are the causes of derangement of vascular permeability?
Damage of tight architecture of capillaries can occur due to immune-mediated processes in acute inflammation or due to thermal damage in burns.
Where does oedema usually first appear?
- At the ankles because gravity in the upright human body can cause a vertical gradient of venous pressures.
- Sacral oedema in someone lying/sitting.
What is the likely cause of oedema when ankle swelling is absent at the beginning of the day but appears later on?
- Venous pressure problems
What is the likely cause of oedema if ankle swelling is unilateral?
- Venous insufficiency
- Lack of muscle use (e.g. OA in 1 knee so decreased pressure)
- Cellulitis (inflammatory cells in interstitium - increased protein content - fluid build-up)
Where is oedema likely to appear in patients with hypoproteinaemia (nephrotic syndrome)?
- Periorbital oedema often appears first thing in the morning.
- Negative pressure in head when lying so increased venous pressure, and lax skin around eyelids provides swelling space.