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.

                                                                                         Image source: slideplayer

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.

  Image source: slideshare

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.

Image source: fysiomasters

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.

References: 

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