Congestion and Oedema: Pathophysiology Flashcards
What is the fundamental truth about the flow of water?
It flows downhill, down the pressure gradient
What is Darcy’s law?
Q=(delta)P/R
What is congestion?
Relative excess of blood in vessels od tissue or organ
What kind of process is congestion?
- Passive process
- Secondary phenomenon
Is congestion acute or chronic?
Can be either
What types of congestion are there?
- Local acute congestion
- Local chronic congestion
- Generalised acute congestion
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
How does DVT relate to congestion?
Vein is blocked causing localised acute congestion
How can DVT cause ischaemia and infarction?
- Blood backs up in the veins, venules and capillaries
- Decreased outflow of blood
- Local, acute congestion
- Decreased pressure gradient
- Decreased flow across system
- No O2 delivery
What is hepatic cirrhosis?
Regenerative nodules of hepatocytes with intervening fibrosis
What causes hepatic cirrhosis?
Liver damage e.g. HBV, alcohol
What does hepatic cirrhosis result in?
Loss of normal architecture leading to altered hepatic flow
What does blocked portal blood flow lead to?
- Congestion in portal vein and branches
- Increased portal venous pressure
- Collateral circulation- several sites anastomose with systemic circulation
What type of risk does local chronic congestion pose?
Haemorrhage risk
What clinical appearances can portal-systemic shunts result in?
- Oesophageal varices
- Caput medusae
What is congestive cardiac failure?
- Heart unable to clear blood, right and left ventricles
- Ineffective pump
What is the pathophysiology of congestive cardiac failure?
- Decreased CO
- Decreased renal GFR
- Increased amount of fluid in body
What does an increased amount of fluid in the body lead to?
Increased fluid overload in the veins
What is the treatment for fluid overload in the veins?
Diuretics
What are the effects of congestive heart failure?
- Heart cannot clear blood from ventricles
- Back pressure, blood dammed back in veins
- Liver experiences central venous congestion
- Acute and chronic changes in lungs leading to pulmonary oedema
What is central venous congestion associated with?
- Right heart failure
- Increased JVP
- Hepatomegaly
- Peripheral oedema
What is pulmonary oedema associated with?
-Left heart failure
-Crepitations in the lungs
Tachycardia
What appearance does the liver take with hepatic central venous congestion?
- Nutmeg liver
- Red/brown + pale spotty appearance macroscopically
What is the red part of the nutmeg liver in hepatic central venous congestion?
- Pericentral hepatocytes
- Stasis of poorly oxygenated blood
What is the pale part of the nutmeg liver in hepatic central venous congestion?
- Periportal hepatocytes
- Relatively better oxygenated due to proximity of hepatic arterioles
What is normal microcirculation?
Constant movement of fluid through capillary beds: process of dynamic equilibrium
What is normal microcirculation driven by?
Hydrostatic pressure from the heart
What is normal microcirculation balanced by?
Osmotic pressures and endothelial permeability
Where does filtratiuon occur in the normal microcirculation?
From capillary beds to interstitium
Why does filtration occur at the arterial side?
Capillary hydrostatic pressure > capillary oncotic pressure
Why does reabsorption occur at the venous side?
Capillary oncotic pressure > capillary hydrostatic pressure
What 3 components affect net flux and filtration?
- Hydrostatic pressure
- Oncotic pressure
- Permeability characteristics and area of endothelium
What do disturbances of normal components lead to?
Oedema
What is oedema?
Accumulation of abnormal amounts of fluid in the extravascular space
Give examples of extravascular space.
- Intracellular tissue space (extracellular space)
- Body cavities
What is peripheral oedema?
Increased interstitial fluid in tissues
What is an effusion?
Fluid collections in body cavities
Give 3 examples of effusions.
- Pleural effusion
- Pericardial effusion
- Joint effusions
What is an effusion in the abdominal cavity known as?
Ascites
What are the characteristics of a transudate oedema?
- Alterations in the haemodynamic forces which act across the capillary wall
- Cardiac failure, fluid overload
- Not much protein/albumin
- Lots of H2O and electrolytes
- Low specific gravity
What are the characteristics of an exudate oedema?
- Part of the inflammatory process due to increased vascular permeability
- Tumour, inflammation, allergy
- Higher protein/albumin content
- H2O and electrolytes
- High specific gravity
What is the pathophysiology of pulmonary oedema with left ventricular failure?
- Increased left atrial pressure causing passive retrograde flow to pulmonary veins, capillaries and arteries
- Increased pulmonary vascular pressure
- Increased pulmonary blood flow
- Increased capillary hydrostatic pressure causing increased filtration and pulmonary oedema
What is the pathophysiology of pulmonary oedema in the lungs?
- Perivascular and interstitial transudate
- Progressive oedematous widening of alveolar space
- Accumulation of oedema fluids in alveolar spaces
What is the pathophysiology of peripheral oedema?
- Right heart failure
- Blood retained in systemic veins
- Congestive cardiac failure
Why does right heart failure lead to peripheral oedema?
Cannot empty right ventricle in systole
Why does blood retained in systemic veins lead to peripheral oedema?
Increased pressure in capillaries leads to increased filtration and peripheral oedema
Why does congestive cardiac failure lead to peripheral oedema?
- Right and left ventricles fail
- Pulmonary oedema and peripheral oedema at the same time
- All about hydrostatic pressure
What does lymphatic obstruction cause?
Hydrostatic pressure upset
What happens if the lymphatic system is blocked?
Lymphoedema
Why might someone with breast cancer develop lymphoedema?
- May require radiotherapy to axilla
- Causes fibrosis
- Decreased outflow
- Oedema of upper limb
What is the pathophysiology of oedema in abnormal renal function?
- Abnormal renal function results in salt and H2O retention
- Secondary in heart failure due to reduced renal blood flow
- Primary in acute tubular damage
What is decreased renal function a result of?
- Increased salt and H2O
- Increased fluid volume
- Secondary increased hydrostatic capillary pressure
- Oedema
What does capillary oncotic pressure require?
Normal protein levels
What can lead to hypoalbuminaemia?
- Nephrotic syndrome
- Hepatic cirrhosis
- Malnutritions
Why does nephrotic syndrome lead to hypoalbuminaemia?
- Leaky renal glomerular basement membrane
- Lose proteins
- Generalised oedema
Why does hepatic cirrhosis lead to hypoalbuminaemia?
- Diffuse nodules and fibrosis in liver
- Liver unable to synthesis enough protein
Why does malnutrition lead to hypoalbuminaemia?
Insufficient intake of protein
What is the pathophysiology of low protein oedema?
- Oncotic pressure
- Transudate
What is the pathophysiology of permeability oedema?
- Endothelial permeability
- Exudate
Why does damage to the endothelial lining lead to oedema?
- Increased pored in membrane
- Leads to osmotic reflection coefficient of endothelium decreases towards 0
- Proteins and larger molecules can leak out
Give examples of when oedema due to permeability of endothelium may occur?
- Acute inflammation such as pneumonia
- Burns
