This document provides an overview of edema, including its definition, types, pathogenesis, and examples of important types of edema. Edema is defined as the abnormal accumulation of free fluid in interstitial tissue spaces or body cavities. It can be localized to an organ or limb, or generalized throughout the body. The pathogenesis of edema involves mechanisms that interfere with fluid balance, plasma oncotic pressure, capillary hydrostatic pressure, lymphatic flow, and sodium and water retention. Examples of important types of edema discussed include renal edema, cardiac edema, pulmonary edema, cerebral edema, hepatic edema, nutritional edema, and myxoedema.

1. ODEMA
Presented by :
Dr. Ajay Kirti Jain ,MD (Ayurveda)
Asso. Prof and H.O.D

2. ODEMA-DEFINITION
The Greek word oidema means swelling. Oedema may be defined as abnormal and
excessive accumulation of “free fluid” in the interstitial tissue spaces and serous cavities.
The presence of abnormal collection of fluid within the cell is sometimes called
intracellular oedema but should more appropriately be called hydropic degeneration.
• 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), and hydropericardium or pericardial effusion (if in the pericardial cavity).
• Free fluid in interstitial space:
The oedema fluid lies free in the interstitial space between the cells and can be displaced
from one place to another. In the case of oedema in the subcutaneous tissues,
momentary pressure of finger produces a depression known as pitting oedema. The
other variety is non-pitting or solid oedema in which no pitting is produced on pressure
e.g. in myxoedema, elephantiasis.

3. ODEMA-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.
Depending upon fluid composition, oedema fluid may be:
transudate which is more often the case, such as in oedema of cardiac
and renal disease; or exudate such as in inflammatory oedema.

4. PATHOGENESIS OF OEDEMA
Oedema is caused by mechanisms that interfere with normal fluid balance of
plasma, interstitial fluid and lymph flow.
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
6. Sodium and water retention.

5. Differences between Transudate and Exudate.

6. Mechanisms
involved in
oedema by sodium
and water
retention.

7. PATHOGENESIS AND MORPHOLOGY OF
IMPORTANT TYPES OF OEDEMA
As observed from the pathogenesis of oedema just described, more than
one mechanism may be involved in many examples of localised and
generalised oedema. Some of the important examples are described below:-
• Renal Oedema
• Cardiac Oedema
• Pulmonary Oedema
• Cerebral Oedema
• Hepatic Oedema
• Nutritional Oedema
• Myxoedema

8. RENAL OEDEMA
Generalised oedema occurs in certain diseases of renal origin such as in
nephrotic syndrome, some types of glomerulonephritis, and in renal
failure due to acute tubular injury
Differences between Nephrotic and Nephritic Oedema.

9. CARDIAC OEDEMA
Generalised oedema
develops in right-sided
and congestive cardiac
failure. Pathogenesis of
cardiac oedema is
explained on the basis
of the following
hypotheses-

10. PULMONARY OEDEMA
Acute pulmonary oedema is the 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.
Mechanisms involved in the pathogenesis of pulmonary
oedema

11. 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.
Cerebral oedema can be of 3 types:
1. VASOGENIC OEDEMA
2. CYTOTOXIC OEDEMA
3. INTERSTITIAL OEDEMA.

12. Hepatic Oedema
The mechanisms involved in causation of oedema of the legs and
ascites in cirrhosis of the liver is as under:
• There is hypoproteinaemia due to impaired synthesis of proteins by
the diseased liver.
• Due to portal hypertension, there is increased venous pressure in the
abdomen, and hence raised hydrostatic pressure.
• Failure of inactivation of aldosterone in the diseased liver and hence
hyperaldosteronism.
• Secondary stimulation of renin-angiotensin mechanism promoting
sodium and water retention.

13. Nutritional Oedema
Oedema due to nutritional deficiency of proteins (kwashiorkor,
prolonged starvation, famine, fasting), vitamins (beri-beri due to
vitamin B1 deficiency) and chronic alcoholism occurs on legs but
sometimes may be more generalised. The main contributing factors are
hypoproteinaemia and sodium-water retention related to metabolic
abnormalities.

14. Myxoedema
Myxoedema from hypothyroidism is a form of non-pitting oedema
occurring on skin of face and other parts of the body as also in the
internal organs due to excessive deposition of glycosaminoglycans in
the interstitium. Microscopically, it appears as basophilic
mucopolysaccharides.

15. Thank you
:- Reference book,
Textbook of Pathology by Harsh
Mohan