Oedema

2021-02-25 12:00 AM

Oedema is the presence of excess fluid in the intercellular space. It has many causes.

Oedema

Oedema is the presence of excess fluid in the intercellular space. It has many causes.

  • Increased hydrostatic pressure causes oedema in congestive heart failure (generalized oedema), portal hypertension, renal retention of salt and water, and venous thrombosis (local oedema).
  • Hypoalbuminemia and decreased colloid osmotic pressure cause oedema in liver disease, nephrotic syndrome, and protein deficiency (e.g., kwashiorkor).
  • Lymphatic obstruction (lymphedema) causes oedema in the tumour, following surgical removal of lymph node drainage, and in parasitic infestation (filariasis → elephantiasis).
  • Increased endothelial permeability causes oedema in inflammation, type I hypersensitivity reactions, and with some drugs (e.g., bleomycin, heroin, etc.).
  • Increased interstitial sodium causes oedema when there is increased sodium intake, primary hyperaldosteronism, and renal failure.
  • Specialized forms of tissue swelling due to increased extracellular glycosaminoglycans also occur, notably in pretibial myxedema and exophthalmos(Graves disease).
  • Anasarca is severe generalized oedema. Effusion is fluid within the body cavities.

Types of Oedema Fluid

  • Transudate is an oedema fluid with low protein content.
  • Exudate is oedema fluid with high protein content and cells. Types of exudates include purulent (pus), fibrinous, eosinophilic, and hemorrhagic.
  • Lymphedema related to lymphatic obstruction leads to the accumulation of protein-rich fluid which produces non-pitting oedema.
  • Glycosaminoglycan-rich oedema fluid shows increased hyaluronic acid and chondroitin sulfate and causes myxedema.

Active hyperemia versus congestion (passive hyperemia): an excessive amount of blood in a tissue or organ can accumulate secondary to vasodilatation (active, e.g., inflammation) or diminished venous outflow (passive, e.g., hepatic congestion).