Edema is the collection of fluid in the interstitial spaces or serous cavities. It becomes evident only when 5-6 liters of fluid has accumulated in the water depots.
Pitting on pressure occurs when the circumference of the limb is increased by 10%.
Mechanism of Edema
One or more of the following factors may be responsible.
- Increased capillary permeability when it is damaged e.g. acute inflammation.
- Increased capillary pressure e.g. cardiac failure.
- Decreased osmotic pressure of the blood e.g. hypoproteinemia.
- Damaged lymphatic drainage e.g. filariasis.
Venous edema commonly occurs in the lower limbs which are most dependent. However, if the patient is recumbent (i.e. lies on his back), it may be present only over the sacral region which is, then, most dependent. Lymphatic edema may occur in either limbs or over scrotum depending upon the site of involvement.
Apart from this it may occur in lungs [pulmonary ] and brain [cerebral ]
- Cardiac: CCF, LVF, pericarditis
- Renal: Acute nephritis, nephrosis
- Hepatic: Cirrhosis of liver, portal hypertension
- Venous: Inferior vena cava obstruction
- Endocrine: Myxedema
- Allergic: Angionurotic edema
- Nutritional: Anemia, hypoproteinemia, beriberi.
- Toxic: Epidemic dropsy
- Pressure by new growth, metastasis
- Traumatic: Bruises, sprains, fractures
- Infections: Cellulitis, boils, carbuncle
- Metabolic: Gout
- Venous: Venous thrombosis, varicose veins
- Hereditary: Milroy’s disease
Common Conditions with Edema
Congestive Cardiac Failure
- The swelling is found on the most dependent parts of the body as gravity plays an important part.
- In an ambulatory patient swelling is in the feet, ankles and legs
- In the recumbent patient it is mainly over the sacrum, lumbar region and genitalia.
- Swelling is most marked in the evening.
Left Ventricular Failure
Here accumulation of fluid in the lung comes much earlier than swelling of the feet, resulting in
- Basal rales.
Here since there is obstruction to the flow of blood into the right atrium, edema of feet may occur, but no edema of lungs occurs because the heart is able to pump the little blood it receives into the lungs and general circulation. It is associated with raised JVP, hepatomegaly and ascites.
- Edema is generalized and not restricted to the dependent parts of the body.
- It is more noticeable in the early morning.
- The fluid accumulates initially in the loose connective tissues, hence it is most marked around the eyelids and face.
- The cause of edema is damage to the endothelial lining of the capillaries, disturbance of fluid and sodium excretion and later also due to hypoproteinemia.
The swelling is generalized and massive due to hypoproteinemia following massive albuminuria.
Hepatic (Portal hypertension):
Here ascites occurs before edema of feet. This occurs due to hypoproteinemia and compression of the hepatic branches of the portal vein. Ascites leads to pressure on the venous circulation in the lower limbs leading to edema of the legs.
Inferior vena cava obstruction
This is characterized by bilateral nondependent painless pitting edema. Collateral dilated veins are usually present in the flanks with flow of blood from below upwards.
Here edema is non-pitting, associated with puffy face, weight gain, weakness, alopecia, hoarse voice, rough dry skin, constipation, anemia and menstrual disturbances.
Allergic (Angioneurotic edema):
This often resembles myxedema with swelling over the face and limbs. There is usually intense itching and bronchospasm.
This is characterized by dependent edema with puffiness of face, pallor and cachexia.
In filariasis, edema occurs due to destruction of the lymphatic filter action of the lymph glands with consequent blocking and dilation of the lymph vessels. Subsequently there is transudation of lymph, rich in proteins, into the tissues. Later connective tissues proliferate leading to elephantiasis. This is characterized by unilateral non-pitting edema with rough skin. There may be history of fever with rigors especially at night and initially pitting edema. Blood smear may show microfilaria.
This commonly affects the big toe with marked pain, edema and deformity of the part involved. Tophi may be present. There may be history of renal colic or renal stones.
This is characterized by unilateral painful pitting edema.