Pathophysiology of Congestion & Oedema Flashcards
What does water flow down?
Concentration/pressure gradient
What is Darcy’s law?
Q is blood flow
P is pressure
R is resistance
What is congestion?
Relative excess of blood in vessels of tissue or organ
What are clinical pathological examples of congestion?
Local acute congestion (deep vein thrombosis)
Local chronic congestion (hepatic cirrhosis)
Generalised acute congestion (congestive cardiac failure)
What is deep vein thrombosis?
Thrombus forms in one or more of the deep veins in your body, usually in your legs
What is it called when a thrombus forms in one or more of the deep veins in your body, usually in your legs?
Deep vein thrombosis
What is the pathophysiological process of deep vein thrombosis?
1) Blood backs up in veins, venules and capillaries
2) Decreased outflow of blod
3) Local, acute congestion
4) Decreased pressure gradient
5) Decreased flow across system
6) No oxygen leading to ischaemia and infarction
What is hepatic cirrhosis?
Liver does not unfction properly due to long term damage
What is it called when the liver does not function properly due to long term damage?
Hepatic cirrhosis
What could hepatic cirrhosis be due to?
HBV or alcohol
What does hepatic cirrhosis lead to?
Loss of normal architecture leading to altered hepatic blood flow
Portal blood flow blocked
Haemorrhage risk
What is congestive cardiac failure?
Heart muscle does not pump blood as well as it should
What is it called when the heart muscle does not pump blood as well as it should?
Congestive cardial failure (or heart failure)
What is congestive cardiac failure also known as?
Heart failure
What could congestive cardiac failure be due to?
Ischaemia
Valvular disease
What is the pathophysiology of congestive cardiac failure?
Decreased cardiac output
Decreased renal glomerular filtration rate
Increased amount of fluid in the body
Fluid overload in the veins
What does decreased renal glomerular filtration rate during congestive cardiac failure lead to?
Activation of renin-angiotensin-aldosteron system
Increased sodium and water retention
What are some of the effects of congestive cardiac failure?
Heart cannot clear blood from ventricles
Back pressure, blood dammed back in veins
Pulmonary oedema in lefts (leading to left heart failure where blood dams back into lungs)
Central venous congestion in liver (leading to right heart failure where blood backs into systemic circulation)
What does central venous congestion in liver during congestive cardiac failure cause?
Right heart failure
Increased jugular venous pressure
Hepatomegaly
Peripheral oedema
What is hepatic central venous congestion?
Liver dysfunction due to venous congestion usually due to congestive heart failure
What is liver dysfunction due to venous congestion usually due to congestive heart failure called?
Hepatic central venous congestion
How are pericentral and periportal hepatocytes different in hepatic central venous congestion?
Pericentral hepatocytes are red due to poorly oxygenated blood
Periportal hepatocytes are pale due to better oxygenated blood because of proximity of hepatic arterioles
What is the normal microcirculation?
Constant movement of fluid through capillary beds
What is normal microcirculation driven by?
Hydrostatic pressure from the heart
What is the hydrostatic pressure from the heart balanced by?
Osmotic pressures and endothelial permeability
How does the hydrostatic and oncotic pressure compare in arterial side and venous side?
In arterial side hydrostatic is greater than oncotic so fluid moves out of vessel into interstitial space
In venous side oncotic is greater than hydrostatic so fluid moves into vessel from interstitial space
What are 3 components that affect net flux and filtration?
Hydrostatic pressure
Oncotic pressure
Permeability characteristics and area of endothelium
What does disturbances to the normal components that affect net flux and filtration cause?
Oedema
What is oedema?
A condition characterised by an excess of watery fluid collecting in the cavities or tissues of the body
What is a condition characterised by an excess of watery fluid collecting in the cavities or tissues of the body?
Oedema
What is effusion?
Accumulation of fluid in body cavities
What is accumulation of fluid in body cavities called?
Effusion
What are examples of different kinds of effusions?
Pleural
Pericardial
Joint effusions
Abdominal cavity (ascites)
What are the 2 kinds of oedema?
Transduate
Exudate
What are transduate oedema due to?
Alterations in the haemodynamic forces which act across the capillary wall
(cardiac failure)
(fluid overload)
What is present and not present in transduate?
Not much protein/albumin
Lots of water and electrolytes
What is the specific gravity of transudate?
Low specific gravity
What is exudate due to?
Inflammatory process due to increased vascular permeability
(tumour)
(inflammation)
(allergy)
What is present and not present in exudate?
Higher protein/albumin content
Lots of water and electrolytes
What is the specific gravity of exudate?
High specific gravity
How is transudate different from exudate?
Transudate has low protein/albumin content and low specific gravity
Exudate has high protein/albumin content and high specific gravity
What are some examples of different kinds of oedema?
Peripheral oedema
Pulmonary oedema
Lymphatic blockage
Oedema in abnormal renal function
Low protein oedema
Permeability oedema
What is the pathophysiology of peripheral oedema?
1) Right heart failure means cannot empty right ventricle in systole
2) Blood retained in systemic veins, leading to increased pressure in capillaries
3) Causes increased filtration and peripheral oedema (also cause of secondary portal venous congestion in the liver)
Is pulmonary oedema transudate or exudate?
Transudate (due to hydrostatic pressure)
What is the pathophysiology of pulmonary oedema?
1) Left ventricular failure increases left ventricular pressure leading to passive flow to pulmonary veins, capillaries and arteries
2) Increased pulmonary vascular pressure
3) Increased pulmonary blood volume causing increased capillary hydrostatic pressure which leads to filtration and pulmonary oedema
What happens in the lungs during pulmonary oedema?
Progressive oedematous widening of alveolar septa
Accumulation of oedema fluid in alveolar spaces
What does lymphatic blockage lead to?
Upsetting the hydrostatic pressure
What is lymphatic drainage required for?
Normal flow so it if is blocked it leads to lymphoedema
What does lymphatic blockage lead to?
Lymphoedema
What does abnormal renal function due to oedema result in?
Salt (NaCl) and water retention
What is abnormal renal function secondary in?
Heart failure due to reduced renal blood flow
What is abnormal renal function primary in?
Acute tubular damage such as in hypotension
What is the pathophysiology of decreased renal function?
1) Increased salt and water retention
2) Increases intravascular fluid volume
3) Leads to increased capillary hydrostatic pressure causing oedema
Is low protein oedema transudate or exudate?
Transudate
What does capillary oncotic pressure require?
Normal protein levels
What is a consequence of capillary oncotic pressure requireing normal protein levels?
Hypoalbumincaemia leads to decreased capillary oncotic pressure which increases filtration, leading to oedema
What are examples of low protein oedema?
Nephrotic syndrome where leaky renal glomerular basement membrane causes a loss of protein and generalised oedema
Heaptic cirrhosis where diffuse nodules and fibrosis in the liver means it is unable to synthesise enough protein
Malnutrition due to insufficient protein intake
Is permeability oedema transudate or exudate?
Endothelial permeability so exudate
What is the pathophysiology of permeability oedema?
1) Damage to endothelial lining leads to increase in ‘pores’ in the membrane
2) Osmotic reflection coefficient of endothelium moves down towards 0
3) Proteins and larger molcules can leak out as well as water
What are examples of permeability oedema?
Acute inflammation such as pneumonia
Burns
Generally, what leads to oedema?
Upsetting starling forces that control filtration
