Edema is a medical term for swelling caused by the build-up of fluid in body tissue. It can occur anywhere in the body, especially in the hands, arms, legs, ankles, and feet.
Edema is usually caused by health conditions such as pregnancy or medication side effects, or it may be a symptom of heart conditions or liver or kidney disease.
To treat edema, the doctor may prescribe medications to remove excess fluid from the body and encourage you to reduce your salt intake. If edema occurs as a sign of disease, the underlying cause must be addressed as well.
The formation of edema is usually controlled by creating a balance between a number of forces, two of the most important being oncotic pressure and hydrostatic pressure. Oncotic pressure is generated by the proteins present in blood plasma. It is also known as osmotic pressure. Hydrostatic pressure is generated by fluids.
Types of Edema
There are various types of edema, some of which are specific to certain parts of the body, while others are more general.
- General edema: In general edema, an individual starts noticing swelling or water retention in various parts of the body, such as the face, arms, legs, abdomen, or feet. This accompanies other symptoms, such as puffiness, bloating, pitted skin or skin that holds an imprint, and tightening of the skin. Pitted skin indicates a severe case of edema, wherein the skin retains an indentation after pressing it for ten to thirty seconds. General edema is usually caused by some form of trauma, pregnancy, past or current illnesses, or any imbalance of the chemicals present in the body.
- Corneal edema: Corneal edema refers to water retention in the cornea. This then leads to swelling of the cornea and other eye problems. The main causes of corneal edema are ocular surgery, an increase in ocular pressure, dehydration, endothelial disorder, viral infections affecting the body, or a traumatic injury.
- Skin edema: Skin edema is known to be harmless and mostly occurs in skin cells and tissues. It is also called cutaneous edema. Although it is harmless, there are instances where it can be painful. One suffering from skin edema, may encounter issues such as parts of the skin being tight, water retention, and puffiness. The cause of skin edema is usually some kind of surface allergic reaction caused by mosquito bites, chemical reactions, or other skin irritants.
Cerebral edema: In cerebral edema, fluid accumulates in the extracellular and intracellular space located in the brain. The causes for the condition can be metabolic abnormalities due to an underlying medical condition or a bodily response to oxygen deprivation at high altitudes. Cerebral edema, which is also known as brain edema, is a very severe form, since it can lead to loss of consciousness and permanent brain damage. This edema is mostly caused by a blockage in fluid drainage, head trauma, brain tumors, high altitudes, and low blood sodium. The symptoms seen in brain edema include feelings of confusion, unconsciousness, severe headaches, and in serious cases, coma. Cerebral edema is further sub-categorized into four parts: vasogenic, osmotic, cytotoxic, and interstitial cerebral edemas.
- Vasogenic cerebral edema occurs when there is a breakdown in the blood brain barrier. Due to this breakage, plasma leaks into the brain, which first reaches the white matter before entering the gray matter. The causes of vasogenic cerebral edema are any kind of cardiovascular event, brain trauma, or a brain tumor. If cancer is involved, vasogenic is caused by the release of destructive compounds from those tumors, which compromise the integrity of the blood brain barrier.
- Osmotic cerebral edema is known to occur when there is an increase in the brain osmolality compared to the plasma osmolality. The pressure generated drives the fluids into the brain, which leads to edema.
- Cytotoxic cerebral edema is due to the sodium and potassium pump malfunctioning. This then leads to the accumulation of water and sodium, which swells the white and gray matter. Cytotoxic edema does not affect the blood brain barrier.
- Interstitial cerebral edema occurs when the barrier between the brain and the cerebrospinal fluid ruptures. This causes the cerebrospinal fluid to flow into the brain and accumulate in the white matter and extracellular spaces.
- Myxedema: This kind of edema is quite rare. Myxedema is known to occur when the connective tissues are filled with water-loving, carbohydrate-like compounds known as hyaluronan. These water-loving compounds are known to attract water into the tissue matrix, due to which it quickly swells. Myxedema may worsen if the transfer of fluids in the tissues to the lymphatic system is hampered. This kind of edema is seen mostly among the elderly, as they are more prone to this edema because they sit for longer durations.
- Pulmonary edema: This type of edema happens because of an accumulation of fluids in the lungs due to a blockage in the pulmonary veins. As blood pressure rises in the blood vessels located in the lungs, a rush of fluids fills the lungs. The cause of pulmonary edema is improper functioning of the left ventricle of the heart. It is also triggered by inhaling harmful air-borne chemicals or toxins, or through exposure to high altitudes.
- Peripheral edema: Peripheral edema is known to mostly occur in the ankles, feet, and legs. This is one of the most common types of edema. Peripheral edema leads to swelling in the lower extremities. The causes of peripheral edema are hypertension, pregnancy, age, kidney disease, heart failure, and other medical conditions. If one has been sitting or standing for longer durations, they may also experience peripheral edema. There are certain kinds of medicines which can cause peripheral edema, including NSAIDs, corticosteroids, calcium channel blockers, and pioglitazone.
- Lymphedema: This type of edema is usually due to failure of the lymphatic system to remove fluids from the interstitial spaces. There are various causes for lymphedema, but it is usually a result of the reticence of the lymphatic system’s pumping actions due to certain medicines.