Edema is the collection of fluid in the interstitial spaces or serous cavities. This could occur due to inflammation of the part or changes in hydrostatic pressure across vessels becomes evident only when 5-6 liters of fluid has accumulated in the water depots.
There could be many causes, localized, for example, in the ankle, to being generalized.
It could be the presenting symptom. It is also an important clinical sign. For example, bilateral pedal swelling may indicate cardiac failure or puffiness around the eye may show kidney involvement.
Venous swelling 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 the most dependent. Lymphatic swelling may occur in either limb or over scrotum depending upon the site of involvement.
Apart from this, it may occur in lungs [pulmonary ] and brain [cerebral ], etc.
One or more of the following factors may be responsible for the swelling
- Increased capillary permeability when it is damaged e.g. acute inflammation.
- Increased capillary pressure e.g. cardiac failure.
- The decreased osmotic pressure of the blood e.g. hypoproteinemia.
- Damaged lymphatic drainage e.g. filariasis.
Fluid exchange is kept by equilibrium in by following forces
- Hydrostatic pressure
- The force exerted by the blood confined within capillaries
- Drives fluid out of capillaries
- Osmotic pressure
- Determined by concentration gradients
- The fluid moves from higher osmotic to lower
- Opposes hydrostatic pressure
- Oncotic pressure or colloid osmotic pressure)
- The osmotic force exerted by plasma proteins (albumin)
- Drives fluid from the interstitium into the capillaries
Pitting and Non-Pitting Edema
Pitting edema is the one where pronged pointed pressure, for example, a fingertip, results in the formation of depression or pit that takes substantial time to get normal.
Pitting edema is caused by
- Fluid retention [compare with non-pitting]
- drugs such as calcium channel blockers, protein deficiency like hypoalbuminemia [Nephrotic syndrome, liver cirrhosis, malnutrition, protein-losing enteropathy]
- Increased Hydrostatic Pressure like chronic venous insufficiency, pregnancy, deep vein thrombosis, post-thrombotic syndrome
- Increased capillary permeability: as in inflammation, burns, allergic reactions, etc.
Nonpitting edema is caused by lymphedema, myxedema, and lipedema. It is called so because it does not pit on pressure.
- Lymphedema occurs due to lymphatic obstruction
- Myxedema occurs in hypothyroidism
- Lipedema occurs due to the proliferation of fat cells which lead to water retention
Bilateral versus Unilateral
The manifestation of edema is most pronounced in lower limbs. Depending on the causation [genearalized or localized] the swelling could be in both limbs or a single limb.
Bilateral Swelling Causes
- Cardiac causes
- Chronic heart failure
- Renal causes
- Acute nephritis
- Hepatic Causes
- Inferior vena cava obstruction
- Angioneurotic edema
- Pressure by new growth, metastasis
- Venous thrombosis
- Varicose veins
- Milroy’s disease [congenital abnormalities in the lymphatic system]
Different Types of Edema
- Affects the legs, feet, and ankles
- Can occur in arms too
- Occurs when fluid gathers in your feet and lower legs
- Common in pregnancy and old age
- Swelling in legs and arms
- Often occurs due to blockage of lymph circulation
- Can occur after malignancies and radiotherapy
- Fluid collects in the air sacs in
- Difficulty in breathing
- Fluid builds up in the brain
- Serious condition
- Macular edema
- Fluid collection in the macula of the eye [center of the retina]
Edema Occurring in Different Conditions
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 an obstruction to the flow of blood into the right atrium, swelling of feet may occur, but not lungs 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.
- Swelling 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 swelling 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 swelling in both legs.
Inferior vena cava obstruction
This is characterized by bilateral nondependent painless pitting swelling. Collateral dilated veins are usually present in the flanks with the flow of blood from below upwards.
Here swelling is non-pitting, associated with a 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 swelling with puffiness of face, pallor, and cachexia.
In filariasis, edema occurs due to the 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 a history of fever with rigors especially at night and initially pitting edema. A peripheral blood smear may show microfilaria.
This commonly affects the big toe with marked pain, swelling, and deformity of the part involved. Tophi may be present. There may be a history of renal colic or renal stones.
This is characterized by unilateral painful pitting swelling.
Small bumps like after mosquito bites do not cause any symptoms.
But those with history of allergy may have a life-threatening issue especially when they cause angioedema.
Swollen legs could become heavy leading to walking difficulty. Persistent severe swollen legs can develop skin ulcers.
Swollen lungs can cause shortness of breath and sometimes low oxygen levels in the blood. A cough may be present
Treatment of Edema
Mild swellings need to be watched. Swollen feet in pregnancy and old age are relieved by lifting the foot on a stool or raised surface to avoid gravity-related accumulation.
For other types, the treatment of the underlying cause is the most important.