Pitting Edema · What Is It, Causes, Grading, Diagnosis, Treatment, and More

In general, edema refers to any swelling that arises from excess fluid build-up in the body. It occurs when there is an imbalance in the mechanisms that regulate fluid movement between blood vessels and surrounding tissues, causing an accumulation of interstitial fluid under the skin.  

Pitting edema is a specific type of edema that’s associated with pitting, or indentation, in the affected areas and is often caused by systemic conditions such as heart failure, kidney disease, or low protein levels, where fluid retention is the main issue. The excess fluid that builds up in pitting edema is mainly composed of water. Conversely, non-pitting edema is typically associated with local conditions like lymphatic obstruction, inflammation, or thyroid problems, where fluid is trapped in the tissues due to poor lymphatic drainage or tissue fibrosis. As a result, fluid build-up can be composed of a variety of substances, including proteins, salts, and water.  

Additionally, most cases of pitting edema are dependent or peripheral. Dependent edema occurs as a result of gravity pulling blood down, which can ultimately result in tissue swelling, most often affecting the legs and feet. This type of edema is called dependent because it develops in body parts that are in a dependent, or lower, position relative to the heart. Peripheral edema, on the other hand, is a general term that refers to the swelling of tissues in the outer parts of the body, such as the hands, legs, and feet. Peripheral edema is not strictly related to gravity, although it often overlaps with dependent edema. 

Pitting edema can have several different causes. It may be the result of localized problems with blood vessels, a side effect of certain medications, or a sign of other underlying conditions.  

Poor Circulation and/or Fluid Retention  

Pitting edema is commonly caused by poor circulation or the retention of excess fluids. Some common risk factors that may lead to these problems include sitting or standing in one position for too long, low protein levels in the blood, obesity, and pregnancy.  

Medications  

Certain medications may increase the risk of pitting edema, such as high blood pressure medication, non-steroidal anti-inflammatory drugs (NSAIDs), steroids, estrogens, and certain medications for diabetes.  

Venous Insufficiency 

Venous insufficiency is a condition in which the veins in the legs are weakened or not working properly. As a result, the veins are not able to return blood to the heart efficiently, thus fluid ends up being forced out of the veins and into the surrounding tissue. This can lead to pooling of blood and fluid build up in the legs, resulting in peripheral edema. Varicose veins, or enlarged and twisted veins, are a common sign of venous insufficiency. 

Deep Vein Thrombosis 

Deep vein thrombosis occurs when a blood clot forms in a vein deep inside the body, usually the legs. The blood clot can damage the valves that help pump up blood back to the heart, leading to peripheral edema in the legs. Even after the blood clot resolves, the affected vein may become narrowed or obstructed, which can disrupt venous blood flow and create a higher pressure in the veins, leading to venous insufficiency.  

Congestive Heart Failure  

Congestive heart failure is when the heart cannot pump blood to the rest of the body as well as it should. As a result, blood may accumulate in the lower limbs and cause peripheral edema. In some cases, congestive heart failure may lead to fluid build-up in the lungs as well, causing pulmonary edema, which may lead to shortness of breath. Congestive heart failure may also cause abdominal edema, also known as ascites.  

Cirrhosis 

Cirrhosis is a liver disease characterized by permanent scarring and fibrosis of the liver, which receives blood from the spleen and gastrointestinal organs via the portal vein. When fibrosis becomes extensive, the liver can start to fail, and blood coming from the portal vein may start to back up, leading to portal hypertension, which refers to increased blood pressure in the portal vein. As a result, fluid may start to leak out of the portal vein and into the abdomen, leading to ascites. This fluid can also accumulate in the legs, resulting in peripheral edema. Over time, the high blood pressure in the portal vein can also cause varices, or enlarged veins, in the esophagus or abdomen.  

Kidney Disease 

Kidney disease can lead to the build-up of excess fluid and sodium in the body, which may cause fluid retention and lead to peripheral edema in the legs. Damage to the nephrons, which are the small filtering units in the kidneys, can lead to nephrotic syndrome, a condition that causes the kidneys to excrete too much protein in urine, resulting in declining protein levels in the blood and excess fluid retention. This can also give rise to peripheral edema.  

Although pitting edema alone may not be serious, the underlying conditions causing it might be of more concern, so it's important to properly diagnose and treat them.  

Over time, if pitting edema is left untreated, the swelling may cause long-term tissue damage that results in stiff and cracking skin, as well as increased risk of ulceration and infection in the affected tissues. In severe cases, excess fluid may leak into the skin, leading to the formation of large edematous blisters. These blisters tend to have a soft roof and are filled with serous fluid that may ooze out of the blister when there is enough pressure. 

A grading system is often used to determine the severity of the edema on a scale from +1 to +4. It’s determined by applying pressure on the affected area and then measuring the depth of the pit, or depression, and how long it lasts, also known as a rebound time.

Grade +1: up to 2mm of depression, rebounding immediately  

Grade +2: 3–4mm of depression, rebounding in 15 seconds or less 

Grade +3: 5–6mm of depression, rebounding in 60 seconds 

Grade +4: 8mm of depression, rebounding in 2–3 minutes