What Causes Edema?

Excessive fluid retention in the interstitial space is called edema, which usually refers to fluid retention in the skin and subcutaneous tissue, and increased fluid in the body cavity is called effusion. According to the range of distribution, edema can be local or systemic, and systemic edema often has serous fluid, such as ascites, pleural effusion, and pericardial effusion. Systemic edema mainly includes cardiogenic edema, renal edema, hepatic edema, malnutrition edema, myxedema, idiopathic edema, drug-induced edema, and senile edema. According to the degree of edema, it can be divided into mild, moderate and severe edema. Mild edema is only found in the soft tissues of the eyelid and suborbital, subcutaneous tissues of the anterior tibial and ankle, and slight depression of the tissue can be seen after finger pressure. Moderate: There is visible edema in loose tissues throughout the body, and obvious or deeper tissue depressions can appear after finger pressure, and the recovery is slow. Severe: The whole body tissue is severely edema, the skin in the lower part of the body is tense and shiny, and there may even be fluid exudation, sometimes accompanied by pleural, abdominal, and sheath fluid.

Basic Information

English name: edema
Visiting department: Internal medicine

Common causes: Caused by kidney, liver, cardiogenic, malnutrition
Common symptoms: Mild edema, only slight depression of subcutaneous tissue such as eyelid and anterior tibia

Causes of Edema

Causes of imbalance in body fluid balance: decreased colloid osmotic pressure of plasma; increased hydrostatic pressure in capillaries; increased permeability of capillary wall; obstructed lymphatic reflux

1. Decreased plasma colloid osmotic pressure

Found in protein malabsorption or malnutrition and kidney disease with a lot of proteinuria. When the amount of plasma albumin is reduced to 25 g / L or the total protein is reduced to 50 g / L, edema may occur, which is systemic.

2. Increased hydrostatic pressure in capillaries

Found in various reasons caused by venous occlusion or venous reflux disorders. Obstruction of local venous return causes tissue edema or edema in the corresponding part, such as cirrhosis of the gastrointestinal wall and ascites, and vena cava return disorder during heart failure causes systemic edema.

3. Increased capillary wall permeability

Vasoactive substances (histamine, kinin), bacterial toxins, and hypoxia can increase the permeability of capillary walls and cause edema. Edema of inflammatory lesions is mainly due to increased permeability of the capillary wall, and edema caused by angioedema and allergies is also this mechanism. This kind of edema usually occurs in the damaged part of the blood vessel wall.

4. Obstructed lymphatic reflux

After radical mastectomy for breast cancer, edema of the affected upper limb may occur due to the destruction of local lymphatic circulation after axillary lymph node resection. In filariasis, lower limbs and scrotum are often blocked by parasites due to parasites, and lower limb and scrotal edema often occur. In addition, extensive embolization of lymphatic cancer cells can cause local edema.

5. Renin-angiotensin-aldosterone system assists sodium and sodium retention

The renin-angiotensin-aldosterone system plays an auxiliary role in the formation of edema in heart failure, liver cirrhosis, and nephrotic syndrome. Reduced stroke volume during heart failure, insufficient blood perfusion in the kidney, stimulation of glomerular receptors, increased renin secretion, renin changes angiotensinogen to active angiotensin , and then converts the role of enzymes Angiotensin is changed to angiotensin , which acts on the spheroid cells of the adrenal cortex to secrete aldosterone, thereby promoting sodium reabsorption in the renal tubules, causing sodium retention, causing an increase in blood crystal osmotic pressure. The person stimulates the osmotic baroreceptors of the blood vessel wall to make the posterior pituitary gland secrete antidiuretic hormone, thereby enhancing the water reabsorption of the renal tubules. The retention of water promotes the development of cardiogenic edema. The edema and ascites during liver cirrhosis are also involved in aldosterone. This is due to the inactivation of aldosterone by liver cells. At the same time, after the formation of ascites, the circulating blood volume is reduced and aldosterone secretion is increased. Nephrotic syndrome is caused by a large amount of albumin loss, low plasma protein levels, edema, body fluids escaping from the blood vessels to the outside of the blood vessels, circulating blood volume decreases, and the activity of the renin-angiotensin-aldosterone system is stimulated.

Clinical manifestations of edema

Systemic edema

(1) Heart diseases Congestive heart failure, constrictive pericarditis, etc. caused by various causes such as rheumatism, hypertension, syphilis, and various diseases such as valves and myocardium.

(2) Kidney disease Acute glomerulonephritis, chronic glomerulonephritis, nephrotic syndrome, renal failure of pyelonephritis, renal arteriosclerosis, tubular lesions, etc.

(3) Liver diseases Cirrhosis, liver necrosis, liver cancer, acute hepatitis, etc.

(4) Nutritional factors Insufficient primary food intake, seen in hunger caused by war or other reasons (such as severe famine); Secondary malnutrition edema seen in various pathological conditions, such as secondary inadequate food intake (Anorexia nervosa, lack of appetite in severe illness, gastrointestinal disorders, pregnancy vomiting, oral disorders, etc.); digestive disorders (insufficient digestive fluid, hyperintestinal peristalsis, etc.); excessive excretion or loss (large area burns and exudates) Bleeding, acute or chronic blood loss, etc.), as well as impaired protein synthesis, severe diffuse liver disease, etc.

(5) Pregnancy factors During the second half of pregnancy, hypertension during pregnancy, etc.

(6) Endocrine disease syndrome of abnormal antidiuretic hormone secretion, hyperadrenal function (Cushing's syndrome, increased aldosterone secretion), hypothyroidism (anterior pituitary hypofunction, hypothalamic thyroid hormone-releasing hormone secretion) , Hyperthyroidism and so on.

(7) Idiopathic factors This type of edema is a syndrome whose cause is unknown or whose cause may be more than one, which is more common in women and is often related to the periodicity of menstruation.

(8) Edema caused by connective tissue disease is common in lupus erythematosus, scleroderma and dermatomyositis.

2. Local edema

(1) Lymphatic Primary lymphedema, such as congenital lymphedema, early-onset lymphedema; secondary lymphedema, such as tumor, infection, surgery, elephantiasis of filariasis, epidemic Mumps caused by chest edema.

(2) Venous occlusive tumor compression or metastasis, local inflammation, venous thrombosis, thrombophlebitis, varicose veins of the lower limbs, etc. Can be divided into chronic venous insufficiency, superior vena cava obstruction syndrome, inferior vena cava obstruction syndrome and other venous obstructions.

(3) Inflammation is the most common local edema. Seen in local edema caused by erysipelas, bloated, cellulitis, etc.

(4) Allergic reactions such as urticaria, serum diseases, food, drugs, etc.

(5) Vascular nerves are allergic or neurogenic, and can be induced by insects, mechanical stimuli, warm environments, or emotional excitement. Some cases are genetically related.

Edema check

Depending on the cause of the edema, the laboratory tests required are different. Common clinical edema is often caused by diseases of important systems or organs. Therefore, in addition to the general laboratory examination of edema, it is necessary to check the primary disease to determine the treatment of edema and estimate the prognosis of edema. The following laboratory tests should be considered for patients with systemic edema.

1. Determination of total plasma protein and albumin

If the total plasma protein is less than 55 g / L or albumin is less than 23 g / L, it means that the plasma colloid osmotic pressure is reduced. Among them, the reduction of albumin is particularly important. When it is lower than 25g / L, ascites is easily produced. Decreased plasma total protein and albumin are common in cirrhosis, nephrotic syndrome and malnutrition.

2. Urine test and renal function test

When there is systemic edema, check for protein, red blood cells and casts in the urine. If there is no proteinuria, the edema is probably not caused by heart or kidney disease. Patients with heart failure often have mild or moderate proteinuria, while persistent severe proteinuria is characteristic of nephrotic syndrome. Persistent proteinuria, increased red blood cells and casts in the urine, and significantly reduced renal function often indicate that edema is caused by kidney disease; although heart failure patients can also have the above manifestations, the changes in urine examination and renal function Generally lighter. Renal function tests related to edema, phenol sulfophthalate also known as phenol red test, urine concentration and dilution test, urea clearance test, etc. are often used to detect renal excretory function.

3. Determination of red blood cell count and hemoglobin content

If the red blood cell count and hemoglobin content are significantly reduced is anemia, it should be considered that this edema may be related to chronic kidney disease.

4. Calculate daily intake and discharge of water and sodium salts

Calculate the daily intake and discharge of water and sodium salts, and if necessary, determine the sodium chloride content in the plasma to help understand the water and salt retention in the body.

Edema diagnosis

Diagnosis is based on etiology, clinical manifestations, and laboratory tests.

Edema treatment

Because there are many causes of edema, the treatment of edema caused by each cause is different, and there is no unified treatment method. But the basic principle is: symptomatic treatment according to the cause of the situation. Treatment of etiology, elimination of edema, maintenance of vital signs stability. For example, cardiogenic edema, once the diagnosis is clear, heart failure (diuresis, vasodilation, heart strengthening, etc.) should be treated. After the heart failure is controlled, the edema naturally subsides; liver edema, if caused by cirrhosis caused by hepatitis B, is large Some are edema of hypoproteinemia. At this time, anti-cirrhosis treatment is needed, such as hepatitis B antiviral treatment, liver protection, nutritional support, and treatment of ascites. There are also many causes of renal-derived edema, mainly due to the treatment. If it is Nephropathy can be treated with glucocorticoids and immunosuppressants. After the kidney disease is controlled, the edema subsides naturally. The edema caused by other causes follows the basic principles of treating primary diseases and maintaining vital signs.