oedema Flashcards
what is oedema
A regional condition characterized by an excess of watery fluid collecting in the cavities or tissues of the body
Capillary wall is selective in what passes through, regulated by:
gaps between adjacent endothelial cells
glycocalyceal layer overlying the endothelium
it is normal permeable to water electrolytes and small dissolved molecules and impermeable to proteins and cells
on the top of endothelial cells there is something called Glycocalyx this acts as a barrier to fluid loss and WBC migration
exchange at the capillary bed is a result of what pressures
oncotic and blood pressur e
what is hydrostatic pressure
The force of hydrostatic pressure means that as blood moves along the capillary, fluid moves out through its pores and into the interstitial space.
in the capillaries water goes from low to high osmotic pressure
true water is drawn across to try to equalise the osmotic pressures on each Side of the membrane - this pulls fluid back in to the capillaries - oncotc pressure
Net fluid movement results from the balance between the outward (hydrostatic) and inward (oncotic) pressure gradients
DP = (PC – PIF) – s (pC – pIF)
net outward pressure = hydrostatic gradient( out) - 1 ( oncotic gradient)
overall does slightly more fluid leave or come in
leave as some fluid return via lymph
net filtration pressure is
hydrostatic pressure - oncotic pressure
where do we find the 2 special capillary beds
glomerular ( fenestrations and higher hydrostatic ) and pulmonary ( lower hydrostatic - no fluid loss despite negative alveolar pressure and surface tension)
When formed because of a disturbance of the trans-capillary forces/flows, and the capillary wall is intact, it is described as
transudative
The fluid has the same composition as that normally present in the interstitium, containing little or no protein
Capillary endothelial damage (e.g. toxicity or inflammation) increases its permeability so that protein can pass
The resulting fluid loss into the interstitium is
exudative
The fluid composition differs from normal interstitial fluid in being high in protein
difference between exudative and transudative
“Transudate” is fluid buildup caused by systemic conditions that alter the pressure in blood vessels, causing fluid to leave the vascular system. “Exudate” is fluid buildup caused by tissue leakage due to inflammation or local cellular damage
Transudative effusions are caused by some combination of increased hydrostatic pressure and decreased plasma oncotic pressure. Exudative effusions result from increased capillary permeability, leading to leakage of protein, cells, and other serum constituen
Transudates are of low protein content
Exudates are of high protein content
causes of oedema
increased fluid loss - raised hydrostatic from HF or venous obstruction - increased capillary premaeabiltiy leading to exudate
decreased fluid reabsorption - reu
causes of oedema
increased fluid loss - raised hydrostatic from HF or venous obstruction - increased capillary premaeabiltiy leading to exudate
decreased fluid reabsorption - reduced ocotic pressure in intravasucalr space usually resulting from low albumin conc - lose protein - transudate
impaired lymphatic return - due to obstruction returning flow usually metastatic tumour - transudate
A 37 year old woman had a cancer in her left breast treated 2 years ago by wide local excision and axillary node sampling (the nodes were clear of tumour on histology).
The cancer was oestrogen receptor positive and she has been treated with tamoxifen since the operation.
She developed swelling in her left arm that got progressively worse soon after surgery. Now 2 years later, she has learned to manage the disease thanks to the support of a specialised clinic.
What is the likely mechanism of the oedema formation, and how is it managed?
the oedema is caused by lymp obstruction in axilla probs from the surgery
transudate
mx compression bandages limb elevation exercise weight management massage every effort should be made to prevent infection in the arm
An 11 year old girl has developed steadily worsening puffiness of her face. She had an upper respiratory infection 3 weeks earlier. On examination she has generalised oedema throughout most of her body.
Testing her urine reveals 4+ of protein.
How has the widespread oedema been brought about, what is the name of the condition and how is it likely to progress?
large quantities of protein in the urine indicate nephrotic syndrome - glomerular basement membrane is damaged to cause protein loss in ruine.
result in hypoproteinaaemia dimsihing the osmotic pressure gradient pulling fluid back into the capillary from the interstitium leading to oedema.
minimal change disease caused this - which responds well to corticosteroids and she will probably fully recover
A 51 year old man was successfully treated for prostate cancer with pelvic radiotherapy, chemotherapy and surgery 2 years ago. 18 months after going into remission he developed oedema in one leg.
Although he knows that this is a common side-effect after pelvic radiotherapy, he recently read that this might also be a complication associated with chemotherapy.
What is the likely mechanism of the oedema formation after pelvic radiotherapy?
What are the potential mechanisms and the link between chemotherapy and lower limb oedema?
radiotherapy cause long term damage to structure including bladder, pelvis, nerves and lymph - oedema
recent tumour in the pelvic LN could also be a cause of his oedema
many chemo agents are toxic to the endothelium and result in fluid loss to the itnerstitium because of breakdown of the normal integrity of the circulation
also possible for chemo to lead to cardiac damage which may produce oedema secondary to HF
