Pathophysiology of congestion + oedema

Question 1

What is congestion?

Answer 1

• relative excess of blood in vessels of tissue/organ

- this is a passive process and can be acute or chronic

Question 2

Examples of congestion

Answer 2

Local acute congestion
-deep vein thrombosis

Local chronic congestion
-hepatic cirrhosis

Generalised acute congestion
-congestive cardiac failure

Question 3

How does deep vein thrombosis lead to congestion?

Answer 3

• In DVT, there is cclusion of the vein which causes localised acute congestion.
• Blood will back up from veins, venules + capillaries
• This will decrease outflow of blood and decrease the pressure gradient.
• It will also decrease venous return. In extreme cases, No O2 > ischaemia +infarction

Question 4

What is hepatic cirrhosis?

Answer 4

• When the liver does not function properly due to liver damage (HBV, alcohol)
• regenerating liver forms nodules of hepatocytes with intervening fibrosis
• there is a loss of normal structure due to altered hepatic BF
• Portal BF can be blocked and congestion in the portal vein and its branches will occur. This eill increase portal venous pressure. An alternative circulation ( collateral circulation) is used which anastomoses with systemic circulation.
• If local chronic congestion, haemorrhage risk

Question 5

What is congestive cardiac failure?

Answer 5

• When the heart is unable to clear blood in right and left ventricles ( ineffective pump,)
• CO will decrease which decrease GFR, renin-angiotensin-aldesterone system will be activated and increases Na+ & H2O retention > increasing PV

Question 6

Examples that may cause an ineffective heart pump

Answer 6

• Ischaemic disease

- valve disease

Question 7

Treatment of overload of fluid in system

Answer 7

diuretics

Question 8

State the effects of congestive cardiac failure

Answer 8

• heart cannot clear blood from ventricles
• back flow of blood into veins

Pulmonary oedema

• left heart failure; blood dams back into lungs
• crepitations in lungs, tachycardia

Liver - central venous congestion

• right heart failure
• blood dams back to systemiccirculation
• raised JVP, hepatomegaly, peripheral oedema

Question 9

The effect of hepatic central venous congestion on liver

Answer 9

Pericentral hepatocytes  (red)
-stasis of poorly ocygenated blood

Periportal hepatocytes (pale)
- better due to oxygenated blood in close proximity of hepatic arterioles

Question 10

What is an oedema?

Answer 10

-accumulation of fluid in the extravascular space ( body cavities, intracellular tissue compartment)

Question 11

What is a peripheral oedema?

Answer 11

-increased ISF in tissues

Question 12

What is a effusion?

Answer 12

• fluid collection in body cavities

- pleural, pericardial, joint effusions, ascites ( abdnominal cavity)

Question 13

What is a transudate oedema?

Answer 13

• A filtrate of blood and can be caused due to increased pressure in veins/capillarie(changes in the haemodynamic forces)
• can be due to cardiac failure, or fluid overload

Question 14

What is found in a transudate oedema?

Answer 14

• no protein(albumin) and has fewer cells
• Rich in water and electrolytes
• Low specific gravity

Question 15

What is an exudate oedema?

Answer 15

-fluid rich in protein/cells
part of inflammatory process due to increase vascular permeability
-caused by tumour, inflammation and allergy
-higher protein/albumin content ( cells)
-Water an electrolytes
-high specific gravity

Question 16

Describe the pathophysiology of a pulmonary oedema

Answer 16

-Hydrostatic pressure causes a transudate
Left ventricular failure
- pressure in left atrium to increase which causes backflow of bloos to pulmonary veins, capillaries and arteries.
-this caused raised pulmonary vascular pressure and increases pulmonary BV
-Increased capillary hydrostatic pressure increases filtration > Pul.oedema

In lungs

• perivascular and intersitial transudate
• progresssive oedematous widening of alveolar septa + accumulation of oedema fluid in alveolar spaces

Question 17

Describe the pathophysioogy of a peripheral oedema

Answer 17

Right heart failure

• heart cannot enoty RV during systole so blood retained in systmic veins will increase pressure in capillaries + increase filtration.
• This leads to a peripheral oedema and secondary portal venous congestion via liver.

Congestive cardiac failure causes:

• R+L ventricles failure
• pul oedema/peripheral at same time

Question 18

State the pathophysiology of lymphatic blockage

Answer 18

Lymphatic pobstruction will cause hydrostatic pressure upset

• if this is blocked, lymphoedema
• e.g. breast cancer may require radiotherapy to axilla > fibrosis which leads to a decrease in outflow > oedema of upper limb

Question 19

Describe the pathophysiology of oedema in abnormal renal function

Answer 19

• results in salt and H2O retention
• secondary in heart failure > reduced renal BF
• primary > acute tubular damage ( eg hypotension)
• both decreases renal function

-This increases salt and H20, Intravascular fluid volume, secondary capillary hydrostatic pressure > oedema

Question 20

Describe the pathophysiology of low protein oedema

Answer 20

Oncotic pressure - transudate

• capillary oncotic pressure requires normal protein levels
• Hypoalbuminaemia will lead to decreased capillary oncotic pressure increased fitratin

Question 21

Examples of hypoalbunaemiea

Answer 21

Nephrotic syndrome
-leaky renal glomerular basement membrane > lose protein > oedema

Hepatic cirrhosis
-diffuse nodules and fibrosis in liver > liver unable to synthesise sufficient protein

Malnutrition
- insufficient intake of protein

Question 22

Describe the pathophysiology of permeability oedema

Answer 22

Endothelial permeability

• damage to endothelial lining leads to an increase in ‘pores’ of membrane.
• This leads to osmotic reflection coefficient of endothelium to decrease towards 0
• proteins and larger molecules can now leak out
• caused by acute inflammation ( pneumonia, burns etc)