What diseases can cause edema? How is edema caused?

Edema is a common phenomenon. Edema is actually an excess of body fluid in the skin and subcutaneous tissue. Some of it is related to physical constitution, while others are related to body functions. For example, drinking a lot of water before going to bed or consuming too much salt is edema. Some diseases can also cause edema.

What diseases can cause edema?

1. Cardiogenic edema

After right heart failure caused by various heart diseases, systemic edema will occur. It is mainly caused by the increase of systemic venous pressure and capillary filtration pressure caused by right heart failure. The characteristics of this edema are that it first occurs in the lower limbs and gradually develops to the whole body. The development speed is relatively slow, and there is an obvious history of heart disease.

2. Nephrogenic edema

Edema caused by kidney disease is called nephrogenic edema, which is mainly caused by glomerulonephritis, which leads to reduced glomerular filtration rate, water and sodium retention, and fluid entering the interstitial space to form edema. Nephritic edema usually occurs first on the face, such as the eyelids, and is obvious in the morning, gradually developing to the lower limbs and the whole body, and is easy to be sunken when pressed.

3. Hepatic edema

Patients with decompensated cirrhosis are likely to experience systemic edema and pleural effusion, which first occurs in the lower limbs, ankles, and gradually spreads to the whole body. Edema of the face and upper limbs is rare. Laboratory tests show obvious liver function impairment.

4. Malnutrition edema

Hypoalbuminemia, mainly caused by malnutrition, causes a decrease in plasma osmotic pressure, fluid retention in the tissue spaces, and edema starts from the lower limbs and feet and spreads to the whole body.

5. Endocrine edema

The characteristic is non-pitting edema, which is more obvious on the face than on the lower limbs. Hypothyroidism, hypopituitarism, and hypercortisolism are all seen in this type of edema.

What causes edema?

1. Increased venous hydrostatic pressure.

If there is an obstruction in venous blood return, it may cause blood stasis in the venous system, increase the hydrostatic pressure, increase the pressure in the capillaries, increase the pressure difference with the surrounding tissues, and lead to increased exudate of water.

Common causes of venous blood return disorders include heart failure (left heart failure causes pulmonary congestion and edema, right heart failure causes systemic edema, especially in the lower limbs), venous thrombosis (common deep vein thrombosis in the lower limbs leads to lower limb edema), compression by the pregnant uterus (compression of the common iliac vein causes lower limb edema), tumor compression, etc.

2. Plasma colloid osmotic pressure decreases.

Plasma colloidal osmotic pressure is mainly maintained by albumin. When albumin synthesis decreases or is lost in large quantities, plasma colloidal osmotic pressure decreases, the average actual filtration pressure increases, and tissue fluid production increases.

Common causes of decreased plasma albumin include: cirrhosis (decreased synthesis), severe malnutrition (decreased synthesis), malignant tumors (increased consumption), tuberculosis (increased consumption), nephrotic syndrome (loss in urine), etc.

3. Lymphatic drainage disorder.

When lymphatic vessels are blocked, lymphatic return is obstructed, and protein-containing edema fluid accumulates in the interstitial space, which can form lymphedema. For example, when treating breast cancer, breast and axillary lymph node removal or radiotherapy may cause edema of the affected upper limb. In filariasis, fibrosis of the inguinal lymphatic vessels and lymph nodes can cause edema of the affected limb and scrotum, which is called "elephantiasis" in severe cases.

4. Inflammatory response.

Local inflammation will increase the permeability of the capillary wall and cause plasma proteins to leak into the tissue spaces. In addition, local tissue cells will necrotize and disintegrate, and large molecular proteins will break down into small molecules, increasing the colloidal osmotic pressure in the tissue spaces, all of which will lead to local tissue edema.

How to check edema

First, blood should be drawn to test liver and kidney function and whether plasma albumin is normal. Urinalysis should be checked to see if there is any urine protein. It is necessary to assess whether the heart function is normal and whether there is any possibility of heart failure. Color Doppler ultrasound should be used to check whether the veins are unobstructed and whether there is any venous thrombosis. These are some of the most common causes of edema in clinical practice.