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Extravasation of fluid into interstitial space
Can be mild to life threatening
e.g. – edema after minor trauma in extremities to pulmonary edema

ANASARCA= Severe, generalized edema of the whole body.

HYDROTHORAX= Excessive fluid in the pleural cavity.

HYDROPERICARDIUM= Excessive fluid in the pericardial cavity.

HYDROPERITONEUM= Excessive fluid in the peritoneal cavity. Also called ASCITES

Distribution of water in human body

2/3rd law:
Total water: 2/3rd of lean body weight
ICF: 2/3rd of total body water
ECF: 1/3rd of total body water
Interstitial fluid: 2/3rd of ECF
Plasma: 1/3rd of ECF

Pathophysiologic Classification of Edema

Increased Hydrostatic Pressure
Impaired venous return
Congestive heart failure
Constrictive pericarditis
Venous obstruction or compression
External pressure (e.g., mass)
Lower extremity inactivity with prolonged dependency
Arteriolar dilation
Neurohumoral dysregulation

Reduced Plasma Osmotic Pressure (Hypoproteinemia)
Nephrotic syndrome
Liver cirrhosis
Protein losing enteropathy

Lymphatic Obstruction

Sodium Retention
Excessive salt intake with renal insufficiency
Increased tubular reabsorption of sodium
Renal hypoperfusion
Increased renin-angiotensin-aldosterone secretion

Acute inflammation
Chronic inflammation


Gross – pitting and non-pitting
Pitting – Extra lymphatic cause
Non-pitting – Lymphatic cause

edema fluid is reflected primarily as a clearing and separation of the extracellular matrix elements with subtle cell swelling
Any organ or tissue in the body may be involved-- subcutaneous tissues, lungs, and brain with potential spaces (pleural, pericardial and peritoneal) are the most common ones

Usually seen in dependent areas of the body due to gravity. Also, when pressure applied by finger the fluid is displaced leaving a finger-shaped depression, called PITTING EDEMA.Initially seen in areas with loose connective tissue such as periorbital area.
Weight of the lungs is 2-3 times the normal weight. Edema fluid can be removed from the lungs by suction and can be blood-tinged with extravasated RBCs.

Gyri are distended ,flattened and sulci narrow.
Brain herniation can occur and when in the foramnen magnum area can cause compromise of the cardiopulmonary center with DEATH.

Edematous lung

Edematous lung parenchyma
Edematous white matter on the side of tumor