Pathophysiology of Congestion and Oedema Flashcards
What is the definition of ‘congestion’?
Relative excess of blood in vessels of tissue or organ
Passive process and secondary phenomenon
What are some causes of oedema and congestion?
Heart failure - right and/or left DVT Lymphatic blockade Hepatic cirrhosis Abnormal renal function Low protein oedema Permeability oedema (burns, acute inflammation)
How does a DVT cause congestion?
Blood backs up in veins, venules, capillaries.
Decreased outflow of blood
Decreased pressure gradient
Decrease flow across system
What is hepatic cirrhosis and how does it cause congestion?
Results from liver damage
Regenerating tissue forms nodules of hepatocytes with intervening fibrosis.
- altered hepatic blood flow
Portal flow blocked?
- congestion in portal vein and branches
- increased portal venous pressure
- collateral circulation - several sites anastomose with systemic circulation
Causes local chronic congestion and haemorrhage risk
Consequence of portal-systemic shunts
What is congestive heart failure?
Heart unable to clear blood from right and left ventricles
What is hepatic central venous congestion?
‘Nutmeg’ liver - red/brown and pale spotty appearance
What three components affect net flux and filtration?
Hydrostatic pressure
Oncotic pressure
Permeability characteristics and area of endothelium
What is oedema and why does it happen?
Accumulation of abnormal amounts of fluid in the extravascular space
- ECF and body cavities
Peripheral oedema - increased ISF
Effusions - fluid in cavities
What causes a transudate vs exudate?
Transudate from alterations in haemodyanmic forces which act across the capillary wall
Exudate - part of inflammatory process due to increased vascular permeability
- higher protein/albumin content
What is the pathophysiology of pulmonary oedema?
Increased hydrostatic pressure - transudate
In LVF
- increased LA pressure > retrograde to pulmonary circulation
- increased volume and hydrostatic pressure > filtration and therefore oedema
What is the pathophysiology of peripheral oedema?
Often from RHF
- cannot empty RV in systole
- retrograde pressure build up > increased filtration and therefore oedema
Also secondary portal venous congestion via liver
How can abnormal renal function lead to oedema?
Abnormal renal function results in salt and H2O retention
Secondary in heart failure
Primary from acute tubular damage e.g. hypotension
Increased salt/H2O > increased intravascular fluid volume > increased hydrostatic pressure > fluid into tissue = oedema
How does low protein cause oedema?
Capillary oncotic pressure requires normal protein levels
- hypoalbuminaemia > decreased oncotic pressure > increased filtration into the tissue
Results in transudate (as fluid is retained without change in protein levels)
E.g. nephrotic syndrome,
hepatic cirrhosis, malnutrition
What happens in permeability oedema?
Endothelial permeability physically altered
- results in exudate as proteins can move into tissue
- burns and inflammation (e.g. pneumonia)
