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|linkpage =General Pathology
|linkpage =General Pathology
|subtext1=CIRCULATORY DISORDERS
|subtext1=CIRCULATORY DISORDERS
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==Introduction==
==Introduction==
Oedema is NOT a disease; it is the sign of a disease state.
* Oedema is defined as :'''"The swelling of tissues resulting from accumulation of excess fluid in the intercellular tissue spaces and serous cavities."'''
* Oedema is defined as :
'''"The swelling of tissues resulting from accumulation of excess fluid in the intercellular tissue spaces and serous cavities."'''
* Small amounts of fluid are normally present to lubricate cavities and viscera - this is not oedema.
* Small amounts of fluid are normally present to lubricate cavities and viscera - this is not oedema.
==Local oedema==
==Local oedema==
* Local oedema is the local accumulation of excess interstitial fluid.
* Local oedema is the local accumulation of excess interstitial fluid.
* Caused by disturbance of the balance betwen fluid extravasation and resorption at the level of the capillaries.
* Caused by disturbance of the balance betwen fluid extravasation and resorption at the level of the capillaries.
===Types of Local Oedema===
===Types of Local Oedema===
====Inflammatory oedema====
====Inflammatory oedema====
* Generated by one or more of the following:
* Generated by one or more of the following:
*# Increased vascular permeability
*# Increased vascular permeability
====Lymphatic oedema====
====Lymphatic oedema====
* Results in accumulation of high protein fluid.
* Results in accumulation of high protein fluid.
* May provoke a [[Granulation Tissue|granulation]] or fibrous tissue response.
* May provoke a [[Granulation Tissue|granulation]] or fibrous tissue response.
====Local venous obstruction====
====Local venous obstruction====
* Obstruction to venous drainage may be mechanical or inflammatory-mediated.
* Obstruction to venous drainage may be mechanical or inflammatory-mediated.
** Causes raised hydrostatic pressure.
** Causes raised hydrostatic pressure.
===="Allergic" oedema====
===="Allergic" oedema====
* Results from immediate (Type I ) or delayed (Type IV) hypersensitivity.
* Results from immediate (Type I ) or delayed (Type IV) hypersensitivity.
* Vasular permeability is increased due to release of histamine and vaso-dilating substances.
* Vasular permeability is increased due to release of histamine and vaso-dilating substances.
====[[Lungs Circulatory - Pathology#Pulmonary oedema|Pulmonary oedema]]====
====[[Lungs Circulatory - Pathology#Pulmonary oedema|Pulmonary oedema]]====
* In the normal state, pulmonary alveoli are kept dry by three mechanisms:
* In the normal state, pulmonary alveoli are kept dry by three mechanisms:
*# Normal "push-pull" mechanism at capillary level.
*# Normal "push-pull" mechanism at capillary level.
=====Pathogenesis=====
=====Pathogenesis=====
# The pumping efficiency of the lymphatics is exceeded.
# The pumping efficiency of the lymphatics is exceeded.
# Fluid accumulates in connective tissue adjacent to airways.
# Fluid accumulates in connective tissue adjacent to airways.
=====Haemodynamic type=====
=====Haemodynamic type=====
* Fluid leaks into alveoli via junctional complexes BUT the alveolar basement membrane remains intact.
* Fluid leaks into alveoli via junctional complexes BUT the alveolar basement membrane remains intact.
** I.e. is due to elevated pulmonary venous pressure.
** I.e. is due to elevated pulmonary venous pressure.
=====Permeability type=====
=====Permeability type=====
* Fluid fills the alveoli following damage to cells or junctional complexes, or permanent ionic alteration of the alveolar basement membrane.
* Fluid fills the alveoli following damage to cells or junctional complexes, or permanent ionic alteration of the alveolar basement membrane.
* Irreversible.
* Irreversible.
==General oedema==
==General oedema==
* General oedema involves subcutaneous and tissue spaces/body cavities.
* General oedema involves subcutaneous and tissue spaces/body cavities.
* Indicative of severe upset of overall body fluid balance.
* Indicative of severe upset of overall body fluid balance.
===Types of General Oedema===
===Types of General Oedema===
====Cardiac oedema====
====Cardiac oedema====
* Seen in heart failure.
* Seen in heart failure.
** Shows that cardiac output fails to meet the demands of the tissues throughout the body.
** Shows that cardiac output fails to meet the demands of the tissues throughout the body.
====Renal oedema====
====Renal oedema====
* Kidney malfunction induces oedema as a consequence of deranged sodium and water handling.
* Kidney malfunction induces oedema as a consequence of deranged sodium and water handling.
** There is often secondary cardiac involvement.
** There is often secondary cardiac involvement.
====Protein-losing enteropathies====
====Protein-losing enteropathies====
* Mucosal damage leads to loss of ability to absorb and retain proteins.
* Mucosal damage leads to loss of ability to absorb and retain proteins.
** Plasma proteins, especially albumin are lost.
** Plasma proteins, especially albumin are lost.
====Hepatic oedema====
====Hepatic oedema====
* Associated with severe [[Liver - Anatomy & Physiology|liver]] damage.
* Associated with severe [[Liver - Anatomy & Physiology|liver]] damage.
** Liver damage may be:
** Liver damage may be:
==Composition of oedema fluid==
==Composition of oedema fluid==
* Inflammatory oedema which produces an exudate.
* Inflammatory oedema which produces an exudate.
** This is a protein rich fluid containing many inflammatory cells.
** This is a protein rich fluid containing many inflammatory cells.