pathology 6 - vascular and fluid balance - OEDEMA

Question 0

what is the interstitial space?

Answer 0

part of the ECF and is 15% of BW. it will expand.

transcellular may also expand eg. incavities during oedema.

Question 1

explain what oedema is? sign of ? where does it accumulate?

Answer 1

increased accumulation of fluid. sign of a diseased state.
fluid balance has gone wrong and accumulates in the interstitial space. may also be seen as free fluid in the body cavities.

Question 2

what do you call oedema in the
pleura?
pericardium?
peritoneum?

Answer 2

hydrothorax
hydropericardium - septicaemia
hydroperitoneum - ascites eg. swollen abdomen/heart failure/johnes.

Question 3

what is anascara?

Answer 3

generalised oedema. severe and subcutaneous - often see it in aborted foetuses.

Question 4

what is the difference between trasudate and exudate?

Answer 4

exudate - alot of cells!!!!!

Question 5

2 types of oedema appearances?

Answer 5

dependant - tends to sink with gravity and so see as ventral abdomen, limbs, brisket, jaws

pitting oedema - push finger into it…subcutaneous - leaves an indentation

Question 6

microvascular oedema.relates to starlings law. explain the process?

Answer 6

2 main pressures. hydrostatic and osmotic pressure.
at the arterial end hydrostatic pressure is bigger inside the artery and so forces fluid out into the interstitial space and then into the capillary bed and into the cells. (hyrdostatic higher than osmotic)
at the venous end hydrostatic is much lower and osmotic is still high (proteins shouldnt move out) so fluid moves IN from the interstitial space.

slight surplus removed by lymphatics. interstitium only has a small osmotic pressure.

Question 7

for microvascular fluid balance to all work you need?

Answer 7

intact vascular system
fucntioning lymphatics
correct serum albumin levels (protein colloid)

Question 8

oedema can occur by 4 main mechanisms;

Answer 8

1. high hydrostatic pressure of blood
2. high vascular permeability
3. low plasma colloid pressure (osmotic)
4. lymphatic obstruction

Question 9

1. explain how a high blood hydrostatic pressure could cause oedema?

Answer 9

increased blood volume. lymphatics cant deal with the extra volume. could be generalised/localised.
general - cardiac failure (depends on which side)
localised - thrombus, tumour, torsion.

Question 10

2. explain how an increased vascular permeability could cause oedema?

Answer 10

acute inflammation - endothelial cells retract and gaps are enlarged - fluid escapes + blood flow is increased to site of inflammation to deliver neutrophils.

hypersensitivity - type 1 - anaphylaxis - igE - mediators released and vasoconstrict and fluid leakage.

Question 11

3. explain how colloidal osmotic pressure could cause oedema?

Answer 11

ability of protein to attract fluids (albumin)
hypoalbuminaemia - lowered osmotic pressure and so fluid may not be reabsorbed. eg. starvation, liver disease.

increased loss due to kidney or GI tract
liver disease - albumin produced here. fascioliasis, cirrhotic liver.

renal loss - glomerula amyloidossis , loss of protein if no intact BM.

Question 12

4. explain how lymphatic obstruction may cause oedema?

Answer 12

cant remove the excess, eg. tumour spread (emolisation) or due to parasitic migration (larvae through lymohatics)

subcutaneous oedema - lymphangitis in equine limb/ascites.

Question 13

what may happen in pulmonary oedema?

Answer 13

alveoli normally kept dry due to normal fluid dynamics. efficient lymphatic drainage and integrity of the BM.

left sided heart failure causes a back up to the lungs - pneumonia. or due to leaky capillaries in the lungs. fluid accumulates in the interlobular septa
alveolar walls fill with fluid and alveolar spaces fill. lungs become heavy and wet. drown from within

Question 14

difference between transudate and exudate?

Answer 14

transudate - <0.5% protein not inflammatory, low cell count, no coagulation

exudate - 2-4% protein, fibrinogen, coagulates, high cell count - inflammatory!!!