Swelling

Edema is an excessive accumulation of fluid in the intercellular (interstitial) spaces of tissues or in serous cavities of the body. Clinically, it is manifested as swelling, increased volume of an organ or body part.

At its core, edema is a symptom indicating an imbalance between the inflow of fluid into tissues from capillaries and its outflow back into the vascular bed and lymphatic system.

Etiology and pathophysiology

The development of edema is based on one of four basic mechanisms that disrupt the normal fluid exchange between blood and tissues:

• Increase in hydrostatic pressure in capillaries. Excess pressure “squeezes” fluid out of the blood vessels. The classic cause is heart failure, which causes blood to stagnate in the veins.
• Decrease in oncotic pressure of plasma. Lack of proteins in the blood (primarily albumin) reduces its ability to “retain” water in the vascular bed. It is characteristic of kidney disease (nephrotic syndrome) and liver disease (cirrhosis).
• Increased capillary permeability. The walls of blood vessels become permeable and allow fluid and proteins into the tissues. A typical example is an inflammation or allergic reaction.
• Disorder of lymphatic outflow (lymphedema). The lymphatic system fails to drain interstitial fluid.

Clinical significance

Edema is one of the most important clinical signs requiring diagnosis to identify its underlying cause. Peripheral edema of the lower extremities is the most common, characterized by a dimple that remains after finger pressure.

Depending on the localization, edema can be life-threatening. Pulmonary edema and cerebral edema are urgent conditions requiring emergency medical attention.

Diagnostic search is aimed at identifying the underlying disease. It includes anamnesis, physical examination, laboratory tests and instrumental studies (ECG, echocardiogram, ultrasound). Treatment of edema always consists in treating the cause of edema.