The Pathophysiology of Congestion and Oedema Flashcards
What is Darcy’s law?
Blood flow = Total pressure/ Resistance
What is congestion?
Relative excess of blood in vessels of tissue or organ
What type of process is congestion?
Passive process, secondary phenomenon
Give an example of local acute congestion
Deep vein thrombosis
Give an example of local chronic congestion
Hepatic cirrhosis
Give an example of generalised acute congestion
Congestive cardiac failure
What does congestion cause?
Ischaemia and infarction
What is hepatic cirrhosis a result of?
Serious liver damage
What is the long term effect of hepatic cirrhosis on the liver?
Regenerated liver forms nodes of hepatocytes with intervening fibrosis so changes hepatic blood flow and can cause blockage of portal blood flow. This causes local chronic congestion with a haemorrhage risk
What is the final consequence of hepatic cirrhosis?
Portal-systemic shunts
What is a portal-systemic shunt?
A bypass of the liver by the body’s circulatory system
What is congestive cardiac failure?
When the heart is unable to clear blood from the right and left ventricles, it reduces CO, which reduces renal glomerular filtration rate which increases the amount of fluid in the body so there is fluid overload in the veins
What is the treatment of congestive cardiac failure?
Diuretics
What is the effect of congestive cardiac failure on the lungs?
Pulmonary oedema
How does pulmonary oedema happen?
There is left heart failure so blood dams back into the lungs
What is the effect of congestive cardiac failure on the liver?
Central venous congestion
How does central venous congestion happen?
There is right heart failure so blood dams back to the systemic circulation. This increases the JVP which causes hepatomegaly and peripheral oedema
What does the liver look like in central venous congestion?
“Nutmeg” liver has red/brown and pale spots
What is the name of the red spots in the liver?
Pericentral hepatocytes
What is the name of the pale spots in the liver?
Periportal hepatocytes
Which hepatocyte is better oxygenated?
Periportal hepatocytes due to the proximity of hepatic arterioles
Why does filtration occur at the arterial side of a capillary?
Because capillary hydrostatic pressure is greater than capillary oncotic pressure
Why does reabsorption happen at the venous side of the capillary?
Because capillary oncotic pressure is greater than capillary hydrostatic pressure
What are the three factors that affect net flux and filtration?
Hydrostatic pressure
Oncotic pressure
Permeability and area off endothelium
What is oedema?
Accumulation of abnormal amounts of fluid in the interstitium
What is effusion?
Accumulation of abnormal fluid in body cavities
What is oedema a result of?
Alterations in the haemodynamic forces acting across the capillary wall
What is effusion a result of?
Inflammatory processes
What is transudate?
Extravascular fluid that is low in proteins, specific gravity and nucleated cell types
What is exudate?
A fluid rich in proteins, albumin, H2O, electrolytes and cellular elements that has seeped out of blood vessels, usually in inflammation.
Has a high specific gravity.
What causes oedema formed of transudate?
Cardiac failure
Fluid overload
What causes oedema formed of exudate?
Tumour
Inflammation
Allergy
Part of inflammatory process due to increased vascular permeability
What is the pathophysiology of pulmonary oedema formed of transudate?
Left ventricular failure causes:
Increased LA pressure
Increased pulmonary vascular pressure
Increased pulmonary blood volume
Increased capillary hydrostatic pressure
Increased filtration
Pulmonary oedema
Perivascular and interstitial transudate in the lungs
Progressive oedematous widening of alveolar septa
Accumulation of fluid in the alveolar spaces
What is the pathophysiology of peripheral oedema caused by right heart failure?
RV cannot be emptied in systole Blood retained in the systemic veins Increased pressure in capillaries Increased filtration Peripheral oedema Secondary portal venous congestion
What is the pathophysiology of lymphatic blockage?
Lymphatic obstruction
Hydrostatic pressure upset
Lymphedema
What does abnormal renal function result in?
Increased salt and water retention
Increased intravascular fluid volume
Increased capillary hydrostatic pressure
Oedema
What is abnormal renal function secondary to?
Heart failure reduces renal blood flow
When is there primary abnormal renal function?
With acute tubular damage such as in hypertension
Why do low protein levels cause oedema?
Because capillary oncotic pressure requires normal protein levels to be normal
What type of oedema is caused by low protein levels?
Transudate oedema
Give examples of what can cause low protein oedema
Nephrotic syndrome
Hepatic cirrhosis
Malnutrition
How does nephrotic syndrome cause oedema?
Causes leaky renal glomerular basement membrane
Lose proteins
Generalised oedema
Oedema caused by endothelial permeability is which type of oedema?
Exudate oedema
What is the pathophysiology of permeability oedema?
Damage to endothelial lining
Increased number of pores in the membrane
Proteins and larger molecules can leak out
What can cause permeability oedema?
Acute inflammation such as pneumonia
Burns
