Pathopedia-India.com: Hemodynamic Disorders 3

Subcutaneous Edema may be diffuse or mainly at the dependent part of the body e.g. legs when standing, sacrum when recumbent (influenced by gravity). This is characteristically seen in congestive heart failure.

Renal edema due to nephrotic syndrome is more severe and affects all parts of the body equally. However, initially it may affect loose connective tissue, such as eyelids causing periorbital edema.

Finger pressure displaces interstitial fluid and leaves finger shaped depression, called pitting edema.

Pulmonary Edema is typically seen in - ( Visit: Pulmonary Edema )

Diagram showing pathogenesis of Pulmonary Edema: click here

i) Left ventricular failure, but also seen in

ii) Over transfusion,

iii) Inhalation of poisonous gas,

iv) Nephritic syndrome

v) Adult respiratory distress syndrome, ( Visit: Acute Respiratory Distress Syndrome )

vi) Infections and

vii) Hypersensitive reactions.

Fluid not only accumulates in tissue spaces but also in lung alveoli. As a result gaseous exchange is interfered leading to death.

Gross features: Lungs are two to three times normal weight. Sectioning reveals a frothy blood tinged mixture of air and edema fluid.

Microscopic features : Widening of alveolar septal wall with congestion of the alveolar capillaries. Protein-rich edema fluid in the alveoli are almost cell-free.

Renal edema: 2 types-

1. Nephritic edema in acute nephritis: Edema is not extensive, does not depend on the gravity and protein content is low. Moderate edema is seen as puffiness of face and eyelids. This is due to the retention of Na+ and water due to oliguria resulting from damage of glomeruli. Na+ retention causes increased secretion of renin followed by angiotensin and aldosterone. Congestive cardiac failure is due to associated hypertension, also contribute to edema. (Visit: CONGESTIVE HEART FAILURE )

2. Nephrotic edema in nephrotic syndrome: Hypoproteinemia due to massive proteinuria causes low osmotic pressure of plasma resulting in edema. Associated hyper-aldosteronism releases renin-angiotensin-aldosterone in the system causing edema.

Cerebral edema:

It may be:

1. Localized to the site of injury (Example: abscess, neoplasm) or

2. Generalized ( Example: encephalitis, hypertensive crisis, obstruction to the venous outflow of brain ).

Grossly, brain is swollen with narrowing of sulci and flattening of gyri due to pressure of swollen brain against the skull.

Cardiac edema: (Visit: Cardiac Path Online )

Cardiac edema is due to congestive cardiac failure. Edema is influenced by gravity and is seen in the depending parts of the body (i.e. dorsum of the foot, ankle). Protein content of the edema fluid is low (2%). (Visit: CONGESTIVE HEART FAILURE )

Mechanisms: 3 factors-

1. Reduced left heart output (forward failure) causes diminished renal blood flow producing increased aldosterone secretion with retention of Na+ and water followed by increased blood volume resulting in edema.

2. Right ventricular failure (backward failure) causes increased capillary hydrostatic pressure with increased outflow of fluid from capillary and diminished absorption of tissue fluid producing edema.

3. Retention of tissue metabolites increases tissue osmotic pressure produce edema.

Difference between exudate and transudate:

Exudate -1

1. Inflammatory extra-vascular fluid due to increased capillary permeability.

2. Straw color, coagulates spontaneously due to high protein content.

3. Specific Gravity : more than 1020.

4. Protein content: more than 4%.

5. Inflammatory cells, bacteria - present.

Transudate-

1. Filtrate of plasma due to high hydrostatic pressure with normal capillary permeability.

2. Pale watery.

3. Specific Gravity : Less than 1012.

4. Protein content: Less than 2%.

5. A few endothelial cells may be present.

Pulmonary Hemorrhage
Influenza
Cytomegalovirus infection
Tuberculosis
Varicella