Edema is defined as the abnormal accumulation of free fluid in the interstitial tissue spaces and body cavities. There are two main types: localized edema affecting a single organ or limb, and generalized edema affecting the entire body. Edema can occur due to decreased plasma oncotic pressure, increased capillary hydrostatic pressure, lymphatic obstruction, or increased capillary permeability. Renal edema, cardiac edema, pulmonary edema, and cerebral edema are some common types discussed in the document, along with their causes and pathogenesis.

1. Edema

2. Definition
• e Greek word oidema means swelling.
• Defined as- abnormal and excessive accumulation of “free fluid” in
the interstitial tissue spaces and serous cavities.

3. • A. Free fluid in body cavities:
• Depending upon the body cavity in which the fluid accumulates, it is
correspondingly known as
• ascites (if in the peritoneal cavity),
• hydrothorax or pleural effusion (if in the pleural cavity),
• hydropericardium or pericardial effusion (if in the pericardial cavity).

4. • B. Free fluid in interstitial space:
• oedema fluid lies free in the interstitial space between the cells and
can be displaced from one place to another.
• Types- Pitting oedema & non-pitting or solid oedema

5. Types
2 main types:
• 1. Localised
when limited to an organ or limb
e.g. lymphatic oedema, inflammatory oedema, allergic oedema.
• 2. Generalised (anasarca or dropsy) :
when it is systemic in distribution, particularly noticeable in the
subcutaneous tissues
• e.g. renal oedema, cardiac oedema, nutritional oedema.

6. pathogenesis
• The following mechanisms may be operating singly or in combination
to produce oedema:
• 1. Decreased plasma oncotic pressure
• 2. Increased capillary hydrostatic pressure
• 3. Lymphatic obstruction
• 4. Tissue factors (increased oncotic pressure of interstitial fluid, and
decreased tissue tension)
• 5. Increased capillary permeability

8. Types
• Renal Oedema
• Generalised oedema occurs in certain diseases of renal origin - in
nephrotic syndrome, glomerulonephritis, and in renal failure due to
acute tubular injury.
• 1. Oedema in nephrotic syndrome.
• Nephrotic oedema is classically more severe and marked and is
present in the subcutaneous tissues as well as in the visceral organs.
• The affected organ is enlarged and heavy with tense capsule

9. • 2. Oedema in nephritic syndrome.
• Oedema occurs in conditions with diffuse glomerular disease such as
in acute diffuse glomerulonephritis and rapidly progressive
glomerulonephritis (nephritic oedema).
• In contrast to nephrotic oedema, nephritic oedema is not due to
hypoproteinaemia but is largely due to excessive reabsorption of
sodium and water in the renal tubules via renin-angiotensin-
aldosterone mechanism

10. • 3. Oedema in acute tubular injury.
• Acute tubular injury following shock or toxic chemicals results in gross
oedema of the body.
• The damaged tubules lose their capacity for selective reabsorption
and concentration of the glomerular filtrate resulting in increased
reabsorption and oliguria

11. Nephrotic vs Nephritic

12. Cardiac Oedema
• Generalised oedema develops in right-sided and congestive cardiac
failure.
Mechanisms involved in the pathogenesis of cardiac oedema

13. Pulmonary Oedema
• Most important form of local oedema as it causes serious functional
impairment but has special features.
• It differs from oedema elsewhere in that the fluid accumulation is not
only in the tissue space but also in the pulmonary alveoli

14. Mechanisms involved in the pathogenesis

15. Cerebral Oedema
• Cerebral oedema or swelling of brain is the most threatening example
of oedema.
• The mechanism of fluid exchange in the Brain differs from elsewhere
in the body since there are no draining lymphatics in the brain but
instead, the function of fluid-electrolyte exchange is performed by the
blood-brain barrier located at the endothelial cells of the capillaries.

16. 3 types:
• 1. VASOGENIC OEDEMA.
• This is the most common type and corresponds to oedema elsewhere
resulting from increased filtration pressure or increased capillary
permeability.
• Vasogenic oedema is prominent around cerebral contusions, infarcts,
brain abscess and some tumours.

17. • 2.CYTOTOXIC OEDEMA.
• In this type, the blood-brain barrier is intact and the fluid
accumulation is intracellular.
• Mechanism - disturbance in the cellular osmoregulation as occurs in
some metabolic derangements, acute hypoxia and with some toxic
chemicals.

18. 3. INTERSTITIAL OEDEMA.
This type of cerebral oedema occurs when the excessive fluid crosses
the ependymal lining of the ventricles and accumulates in the
periventricular white matter.
This mechanism is responsible for oedema in noncommunicating
hydrocephalus.