Types of edema
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edema
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edema types pitting nonpitting localized generalized causes
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Edema is abnormal accumulation of fluid in the interstitial tissues.
Types of edema
1. Based on distribution
| Type | Description | Common examples |
|---|---|---|
| Localized edema | Involves one organ or body part | DVT causing unilateral leg swelling, inflammation, allergy/angioedema, lymphedema |
| Generalized edema (anasarca) | Widespread swelling of subcutaneous tissues, often with fluid in body cavities | Heart failure, nephrotic syndrome, renal failure, cirrhosis, severe malnutrition |
| Dependent edema | Occurs in dependent areas due to gravity | Feet and ankles in ambulant people; sacrum in bedridden people |
| Peripheral edema | Involves limbs, sacrum, face, scrotum, etc. | Cardiac, renal, hepatic, venous, or lymphatic disease |
| Organ-specific edema | Fluid in a particular organ or space | Pulmonary edema, cerebral edema, ascites, pleural effusion |
Peripheral edema can be localized or generalized, and peripheral plus nonperipheral edema can coexist. Frameworks for Internal Medicine, p. 219.
2. Based on response to pressure
| Type | Features | Common causes |
|---|---|---|
| Pitting edema | Firm finger pressure leaves a persistent indentation temporarily | Heart failure, renal disease, cirrhosis, venous insufficiency, DVT, low serum albumin |
| Nonpitting edema | No indentation after pressure | Lymphedema, myxedema due to hypothyroidism, chronic fibrotic edema, lipedema |
Pitting is caused by displacement of relatively mobile interstitial fluid. In long-standing lymphedema, fibrosis and fat deposition may make initially pitting edema become nonpitting. Frameworks for Internal Medicine, p. 219.
3. Based on pathophysiology
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Increased capillary hydrostatic pressure
- Fluid is pushed out of capillaries.
- Causes: heart failure, venous insufficiency, DVT, portal hypertension, pregnancy, renal sodium retention.
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Reduced plasma oncotic pressure
- Low plasma proteins, especially albumin, reduce fluid reabsorption into capillaries.
- Causes: nephrotic syndrome, liver failure, protein-losing enteropathy, severe malnutrition.
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Increased capillary permeability
- Proteins and fluid leak from capillaries into tissues.
- Causes: inflammation, sepsis, burns, trauma, allergic reactions, angioedema.
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Lymphatic obstruction or impaired drainage
- Protein-rich interstitial fluid cannot be cleared.
- Causes: malignancy, lymph-node surgery or radiotherapy, filariasis, congenital lymphatic disorders.
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Sodium and water retention
- Expands intravascular volume and contributes to elevated hydrostatic pressure.
- Causes: renal failure, heart failure, excess salt intake, some medicines.
Fluid balance is governed by hydrostatic pressure, oncotic pressure, capillary permeability, and lymphatic drainage. Frameworks for Internal Medicine, p. 219.
4. Important special forms
- Pulmonary edema: fluid in lung interstitium/alveoli. May be cardiogenic or noncardiogenic.
- Cerebral edema: may be cytotoxic, vasogenic, interstitial, or ionic.
- Angioedema: acute localized swelling of deeper skin/mucosa, commonly lips, tongue, face, or airway.
- Lymphedema: chronic, often asymmetric limb swelling from lymphatic dysfunction.
- Myxedema: nonpitting edema due to mucopolysaccharide deposition, classically in hypothyroidism.
- Ascites: fluid accumulation in the peritoneal cavity.
- Pleural effusion: fluid in the pleural space.
Clinical warning: sudden unilateral painful leg swelling can indicate DVT; acute swelling of the tongue/lips, stridor, or breathlessness can indicate airway-threatening angioedema; acute breathlessness with frothy sputum may indicate pulmonary edema. These need urgent assessment.
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