Edema & how its formation

 

Edema & how its formation 

Introduction

Edema is the medical term for swelling caused by an accumulation of fluid in the body's tissues. It can occur in any part of the body, but is most commonly seen in the feet, legs, and ankles. Edema can be caused by a variety of factors, including injury, certain medical conditions, and medications. It is often treated by addressing the underlying cause, as well as by using measures such as elevating the affected limb and using compression stockings.

Physiologically Basis 

Extracellular fluid accumulation can be occurring in two ways.

1.      Abnormal leakage of fluid from plasma to the interstitial space across the capillaries

2.      Failure of lymphatics to return fluid from the interstitium back into the blood.     

Factors contribute to formation of interstitial fluid.

• Starling forces – Filtration (Depend on hydrostatic pressure gradient)

                          Osmosis (Depend on colloid osmotic pressure gradient)

•  Capillary permeability

•  Available surface area

The most common clinical cause of interstitial fluid accumulation is excessive capillary fluid filtration. Mathematically capillary filtration rate expressed as,

             Filtration = K_f ( P_C – P_if – π_c + π_if )

Here, K_f = capillary filtration coefficient

           P_C = capillary hydrostatic pressure

           P_if = interstitial fluid hydrostatic pressure

          π_c = capillary plasma fluid osmotic pressure

         π_if = interstitial fluid osmotic pressure

From this equation you can see that any one of the following factor changes can increase the capillary filtration rate.

•  Increased capillary filtration coefficient.
• Increased capillary hydrostatic pressure.
•  Decreased plasma osmotic pressure.

Causes of extracellular edema

As above mentioned, you have now clear idea about how edema can formation. 

  1) Increased capillary pressure 

     A. Excessive kidney retention of salts and water 

• acute or chronic kidney failure 
• Mineralocorticoid excess 

     B. High venous pressure and venous constriction 

•  Heart failure
• venous obstruction 
• failure of venous pump 

     C. Decreased arteriolar resistance.      

• Excessive body heat
• Insufficiency of sympathetic nervous system 
• Vasodilator drugs 

 2)  Decreased plasma proteins 

     A. Loss of proteins in urine 

     B. Loss of proteins from denuded skin areas 

• Burns 
• Wounds

 C. Failure to produce proteins. 

·    Liver diseases

·    Serious proteins or caloric malnutrition

 

3) Increased capillary permeability

• Immune reactions that cause release of histamine and other immune products 
• Toxins 
• Bacterial infections 
• Vitamin deficiency
• Prolonged ischemia 
• Burns 

4) Blockage of lymph return 

•   Cancer
•  Infections (E.g., filaria) 
•   Surgery  

Treatment for edema 

• Elevating the affected limb to promote drainage of excess fluid.
• Compression stockings or bandages to help reduce swelling.
• Diuretic medications to increase urine output and decrease fluid retention.
• Limiting salt intake to reduce fluid retention.
• Exercise to help improve circulation and reduce swelling.
• Surgery to remove excess fluid or repair underlying issues causing the edema.

It's important to consult with a healthcare provider to determine the most appropriate treatment plan for you as the cause of edema can vary greatly.