Edema and Its Types

  • Swelling in the tissues caused by excessive accumulation of fluid.
  • Can be generalized and local.
  • In generalized edema, entire body is involved.
  • Local edema occurs in some specific body areas.
  • Areas like abdomen, lungs, feet, ankles, legs are involved.
  • There is accumulation of fluid which may be outside and inside the cell.

Edema Types

  • Depending on accumulation of excess fluid, it is of two types.
  • Accumulation occurs in the body compartment.
  • They are: a) intracellular and b) extracellular.

A) Intracellular Edema

  • It is the condition of fluid accumulation inside the cell.
  • It occurs due to

i) Malnutrition,

ii) Poor metabolism and

iii) Inflammation of the tissues.

Edema due to malnutrition

  • Occurs due to poor intake of food and poor circulatory system.
  • Nutritive supply of the substances cannot occur.
  • This leads to poor exchange of ions.
  • This poor exchange occurs due to depressed ionic pumps in cell membrane.
  • Sodium ions mostly cannot be pumped out that leak into the cells.
  • Sodium gets excess inside the cells due to poor pumping action.
  • This causes endosmosis resulting in edema i.e., intracellular.

Edema due to poor metabolism

  • Blood supply won’t be proper.
  • This causes poor metabolism.
  • This also leads to lack of oxygen.
  • In this condition, cell membrane can’t function properly.
  • Thus, edema occurs.

Edema due to inflammation of tissues

  • Permeability of cell membrane increases as inflammation occurs.
  • Many ions including sodium moves inside the cells.
  • This results to endosmosis and finally intracellular edema results.

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B) Extracellular Edema

  • Outside the cell if fluid accumulates, called extracellular edema.
  • Caused when fluid from capillaries leaks into interstitial space.
  • This leaking of fluid is abnormal.
  • Also, lymphatic vessels obstruction hampers fluid return.
  • The return of fluid generally occurs from interstitium to blood.

Following conditions lead to extracellular edema

  • Lymphatic obstruction
  • Increased endothelial permeability.
  • Decreased plasma proteins level.
  • Renal disease.
  • Failure of heart.

Edema due to lymphatic obstruction

  • Also called lymphedema.
  • Common in cases of filariasis caused by some parasitic worms.
  • Parasitic worms block or obstructs the drainage of lymph.
  • They are found living in the lymphatic.
  • This results in lymph accumulation along with cellular reaction.
  • The condition finally leads to swelling mostly in legs and scrotum.
  • Fibrosis results as lymphatic drainage is obstructed repeatedly in this part.
  • Hence, development of elephantiasis occurs.
  • In elephantiasis, skin thickens and affected area enlarges extremely.
  • Mostly affects limbs (legs), genitals, certain areas of trunk and parts of head.


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Edema due to increased endothelial permeability

  • In burns, inflammation, trauma, allergic reactions, immunologic reactions endothelial permeability increases.
  • This leads to oozing out of the fluid.
  • Fluid released in this way thus accumulates developing edema.

Edema due to decreased plasma proteins level

  • Decreased plasma proteins decreases colloidal osmotic pressure.
  • This increases capillary permeability which increases capillary filtration.
  • Thus, more amount of water leaks out of the capillary.
  • Leaked water accumulates in the spaces of tissues.
  • This finally results to extracellular edema.
  • Conditions like malnutrition, liver diseases, renal diseases, burns and inflammation cause decrease in plasma proteins.

Edema due to renal diseases

  • Retention of water and electrolytes cannot occur in some renal diseases.
  • It occurs as the kidney fails to excrete water and the electrolytes (mostly sodium).
  • Thus, from blood fluid leaks into interstitial space causing extracellular edema.
  • Initiation of edema development occurs in legs.
  • Then, it slowly progresses to the entire body.

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Edema due to heart failure

  • Various reasons are responsible for causing edema in heart failure.
  • They are as follows:

a) Failure of heart to pump blood

  • Increase in venous pressure and capillary pressure as heart cannot pump blood from veins to arteries.
  • Capillary permeability increases which cause leakage of fluid from blood into interstitial fluid.
  • This results to extracellular edema.

b) Fall in blood pressure during heart failure

  • Glomerular filtration rate decreases which results in sodium and water retention.
  • This increases the volume of blood and body fluid.
  • This in turn increases the hydrostatic pressure of capillary.
  • These both factors togetherly increase the accumulation of fluid.
  • Thus, extracellular edema occurs.

c) Low supply of blood to kidneys during heart failure

  • Renin secretion increases in this condition.
  • Thus, aldosterone secretion becomes more.
  • Reabsorption of sodium and water from renal tubules into ECF increases.
  • This results in the development of extracellular edema.

Pulmonary edema

  • If fluid accumulates in pulmonary interstitium, it is called pulmonary edema.
  • In left heart failure, right ventricle pumps blood to pulmonary circulation.
  • This blood cannot return from lungs to the left side of the heart.
  • This is because of weakness of this side of the heart.
  • Thus, pulmonary vascular pressure increases.
  • This causes leaking of fluid from capillaries to pulmonary interstitium.
  • Thus, pulmonary edema occurs which may be life threatening.


i) https://www.medicalnewstoday.com/articles/159111#:~:text=Types%20include%3A,the%20lungs%2C%20making%20breathing%20difficult.

ii) https://lasvegasveincenter.com/edema-types-causes-symptoms-and-treatment/

iii) https://www.stylecraze.com/articles/effective-home-remedies-for-edema/

Edema and Its Types