(Posted:27-Jun-2015)

Oedema is a tissue swelling due to an increase in interstitial fluid. The distribution of water between the vascular and interstitial space is determined by the balance between hydrostatic pressure,which forces water out of the capillary and colloid osmotic pressure,which sucks fluid into the vascular space. Types of oedema: *On extent of involvement: Localized and generalized oedema. *On pathophysiologically: Inflammatory and non inflammatory oedema. *On nature of fluid: Exudate and transudate. *On clinical base:pitting oedema &non; pitting oedema. 1)Localized oedema: Inflammatory cause: Any cause of tissue inflammation,including infection,injury or ischaemia liberates mediators,e.g:histamin,bradykinine,cytokines,which causes vesodilatation and increase capillary permeability.Thus causes oedema. Venous cause:Any increase venous pressure will increase hydrostatic pressure with capillaries,producing oedema in the area drained by the vein. Lymphatic causes: Any cause of impaired lymphatic flow may produce localized oedema.Lymphoedema is common in some tropical countries because of lymphatic obstruction by filarial worms. 2)Generalized oedema: There are two principal causes of generalized oedema: •Fluid overload •Hypoproteinaemia. *Fluid overload may be due to heart failure and renal disease or stem from iotrogenic causes.Heart failure causes oedema in the following ways: Renal underperfusion activates the renin angiotensin aldosteron system and release vesopressin leading to salt and water retention.Renal blood flow is reduced,causing increase reabsorption of salt and water.When the patient lies flat,blood is redistributed from the legs into the torso,increasing venous return to the heart.In the failing heart this results increased end diastolic pressure within the left ventricle,leading to pulmonary oedema. Renal disease:e.g:Acute glomerulonephritis,may reduce urine volume,with increasing circulating and extracellular fluid volume and increased tubular reabsorption of sodium. Iotrogenic causes result from the action of the medical profession.These include excessive fluid replacement,especially intravenously,whice produce fluid overload. *Hypoproteinaemia: Hypoproteinaemia,particularly hypoalbuminaemia,reduces oncotic pressure and encourage fluid to move to the interstitial space,thus causing oedema.Nephrotic syndrome causes heavy proteinuria and most patient with a hepatic cause will have features of chronic liver disease.