Types of Edema: Causes, Symptoms, and Treatments

Edema is defined as an accumulation of fluid in the space between cells. Learn more about the different types of edema.

Written and verified by el biólogo Samuel Antonio Sánchez Amador.

Last update: 15 May, 2023

Edemas are defined as the accumulation of fluid in the extracellular or interstitial space. It should be noted that it’s not a disease in itself, but a clinical sign, that is, a reliable and observable medical manifestation that something is wrong inside the patient. The world of edema is extensive and complex, as the different types of edema can be classified according to the temperature they present, the extent, or their location, among other parameters.

On this opportunity, we’ll present the causes, symptoms, and treatment options for the different types of edema.

What is edema?

According to the Medicina Interna de México journal, edema is defined as the accumulation of fluid in the interstitium —the space between cells— that manifests as a dimple when pressing on the skin of the affected area. The excess trapped in the tissues gives the damaged area a soft and bulging appearance.

In patients with average weight and height, for edema to be apparent, it must have about 5 to 10 pounds of fluid or the interstitial fluid must represent more than 10% of body weight. The accumulation of fluids is more evident in the regions of the body in which there’s an abundance of loose tissue, such as the ankles or the sacral area.

As indicated by the Clínica de la Universidad de Navarra (CUN), the most common symptoms of edema are localized swelling, striated or shiny skin in the affected area, and the characteristic sensation of heaviness. In any case, it’ll manifest itself in very different ways depending on what part of the body it affects.

The characteristics and causes of edema

When investigating one of these clinical signs, the following parameters should be taken into account:

• Onset: Acute or chronic.
• Location: Face, hands, ankles, legs, genitals, abdomen, or cavities such as the pleura.
• Time: Edema can occur in the morning, night, or evening, or have no relation to the time of day.
• Consistency and color: It can be soft or hard, white, red, or pigmented.
• Sensitivity: It can be painless or cause a feeling of heaviness.
• Temperature: It can be hot or cold.

Most edemas are caused by greater than normal capillary filtration, although there may be other underlying reasons. According to the Mayo Clinic and other professional portals already mentioned, the causes of edema can be included in the following basic pillars:

1. An increase in blood vessel pressure. For example, a thrombosis -the formation of a clot in arteries, veins, and capillaries-, varicose veins, or heart failure.
2. A decrease in the amount of osmotic proteins or particles that tend to hold water within the blood vessels. Oncotic pressure allows fluids to be distributed correctly between the interstitium and the circulatory system. If this is modified, edema may appear.
3. The alteration of the wall of the blood vessels by different events. If the membrane of one of these ducts is injured for any reason, it may favor the outflow of fluid into the interstitium.
4. The obstruction of the lymphatic vessels.
5. A combination of several factors: Medications, cirrhosis, kidney damage, and many more disease.

The types of edema

We’ve already taken a long walk through the definition of edema and its possible causes, so we’re ready to dig into the different types of edema that exist. It should be noted that these clinical signs can be classified according to the parameters listed above, although we’re only going to focus on their location.

First of all, we have to note that there are two main types of edema: Generalized and localized. According to the MSDmanuals portal, generalized or systemic edemas are those that cause diffuse swelling in all tissues of the body. They’re caused by heart failure, liver failure, and certain kidney diseases.

1. Cardiogenic pulmonary edema

The Mayo Clinic informs us about the particularities of cardiogenic pulmonary edema. This happens when there’s an abnormal increase in the pressures in the heart. In general, it usually occurs when the overloaded left ventricle is unable to pump an adequate amount of blood to the lungs.

As a consequence of this, there’s an increase in pressure in the right atrium, which translates into an increase in the pressure of the vessels and capillaries in the pulmonary alveoli. In short: there’s an accumulation of fluid in the lungs due to a malfunction of the heart.

Coronary artery disease, cardiomyopathy, and other heart conditions can promote the development of cardiogenic pulmonary edema. Mild edema usually goes away on its own, but in more severe cases diuretics may be prescribed so that the patient eliminates fluids through urine.

2. Ascites

This type of edema responds to the presence of serous fluid between the visceral and parietal peritoneum. As the United States National Library of Medicine indicates, ascites can have multiple causes, including the following:

1. Chronic hepatitis B or C infection
2. Excessive alcohol consumption for many years
3. Fatty liver
4. Clots in the veins of the liver
5. Congestive heart failure
6. Pancreatitis
7. Thickening and scarring of the covering of the heart (pericarditis)

This clinical sign is usually addressed with lifestyle changes and diuretics, depending on the causative agent. You can also resort to a method called paracentesis, by which excess abdominal fluid is removed with a puncture and subsequent extraction.

3. Hydrothorax or pleural effusion

According to the Clinic of the University of Navarra, hydrothorax or pleural effusion is defined as excessive fluid accumulation in the pleural cavity. We’re not going to dwell on this clinical sign, as it’s relatively similar to the one already described. Even so, it should be noted that certain cancers can trigger this event.

4. Hydrocephalus

As its name suggests, hydrocephalus is characterized by the abnormal presence of cerebrospinal fluid (CSF) within the skull. CSF circulates through the brain and spinal cord and is absorbed through the bloodstream.

Unfortunately, when the flow is blocked, it can’t enter the blood. It can also happen that the brain produces quite a lot. Too much cerebrospinal fluid puts pressure on the brain, pushing it up against the skull and damaging its tissues.

Hydrocephalus can be caused by infections, tumors, birth defects, and many other factors. The treatment will depend entirely on the causative agent, but a surgical process can be contemplated to eliminate the excess accumulated during the disease.

5. Lymphedema

As indicated by the Spanish Association Against Cancer (AECC), lymphedema is the abnormal accumulation of fluid in soft tissue due to obstruction of the lymphatic system. Among the most common symptoms of this clinical sign, we find the following:

• A sensation of stiffness or heaviness in the affected limb
• Aches and pains
• Hardening and thickening of the skin in the affected area
• Difficulty with mobilization
• Frequent infections

Lymphedema can be very annoying for those who suffer from it, but 95% of patients show marked improvement with the right treatment. Surgery and changes in the lifestyle of the patient are usually the paths to follow.

Obesity causes lymphedema because the extra weight puts too much pressure on the lymph nodes in the groin, affecting the system. Obese people, therefore, are at greater risk of presenting it.

6. Macular edema

The Barcelona Ophthalmology Center (ICR) tells us that macular edema responds to inflammation or thickening of the macula of the eye, the part of the retina responsible for central vision that allows detail to be captured. Diabetic retinopathy, age-related macular degeneration, uveitis, and cataract surgery are its most common causes.

Macular edema is characterized by three main symptoms: Loss of central vision, blurred vision, and distortion of straight lines. Treatment usually includes anti-inflammatory eye drops, focal laser surgery, or intravitreal injections.

7. Other types of edema

We’ve shown you the types of edema that we consider most important, but you should keep in mind that there are many more. Any soft tissue can swell from a maldistribution of body fluids.

Therefore, we’re going to dedicate these last lines to describing those types of edema that deserve to be cited, although they don’t report as clear a clinical importance as those already mentioned. Among them, we find the following:

1. Cutaneous: Some of them can appear due to simple inflammatory processes, such as a mosquito, wasp, or tick bite.
2. Periorbital: Accumulation of fluid around the eyes. It’s also known as eyelid edema and is usually caused by allergies.
3. Hydropericardium or pericardial effusion: The accumulation of fluid in the pericardial cavity.
4. Pulmonary edema (non-cardiogenic): The accumulation of fluid in the pulmonary alveoli due to an unrequited failure of cardiac disease.

Edema and health

As you may have observed, there are almost as many types of edema as there are parts of the body. Although many of them are caused by unavoidable processes, we’ve seen that others are caused by poor lifestyles, such as chronic alcoholism or morbid obesity. Therefore, taking care of yourself is always the first step to avoiding the appearance of edema.

Treatment will depend on the causative agent. From antibiotics to diuretics, going through many more types of drugs, the healing of edema must always be monitored by a medical professional.