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New page: {{review}} {{toplink |linkpage =General Pathology |linktext =General Pathology |maplink = General Pathology (Content Map) |pagetype =Pathology |sublink1=Circulatory Disorders - Pathology ...
{{review}}
{{toplink
|linkpage =General Pathology
|linktext =General Pathology
|maplink = General Pathology (Content Map)
|pagetype =Pathology
|sublink1=Circulatory Disorders - Pathology
|subtext1=CIRCULATORY DISORDERS
}}
<br>
==Introduction==
* Oedema is NOT a disease.
**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."'''
* Small amounts of fluid are normally present to lubricate cavities and viscera - this is not oedema.
* Excess fluid may accumulate in:
** '''Subcutaneous tissue and between muscle'''.
** '''Serous cavities'''.
*** Depending on the cavity, this has different terms.
**** Thorax - hydrothorax.
**** Pericardium - hydropericardium
**** Abdomen - hydroperitoneum (ascites).
*** '''Anasarca''' is when there is generalised body cavity accumulation plus subcutaneous involvement.
** '''Lungs'''.
==Local oedema==
* 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.
** '''Outwards Forces''' - arteriolar
*** Vasuclar hydrostatic pressure - 35 mmHg
*** Interstitial osmotic pressure - 3 mmHg
** '''Inwards forces''' - venular
*** Plasma protein osmotic pressure - 25 mmHg
*** Interstitial hydrostatic pressure - 4 mmHg
* May be of inflammatory or non-inflammatory origin.
===Types of Local Oedema===
====Inflammatory oedema====
* Generated by one or more of the following:
*# Increased vascular permeability
*# Increased arteriolar blood pressure
*# Breakdown of tissue protein or transfer of plasma proteins into ECF.
*#* Results in raised osmotic pressure of tissue fluid.
*# Obstruction to lymphatic drainage.
*#* Usually by fibrin.
====Lymphatic oedema====
* Results in accumulation of high protein fluid.
* May provoke a [[Chronic Inflammation - Pathology#Granulation Tissue|granulation]] or fibrous tissue response.
* Due to:
*# '''Lymphangitis/ lymphadenitis '''
*#* [[Acute Inflammation - Pathology|Acute inflammation]] of lymphatics/ lymph nodes. R
*#* Caused by stasis in lymphatics and/or bacterial infection.
*#* E.g. “Monday Morning leg” in horses.
*# '''Chronic inflammation''' caused by persistent or granuloma-producing bacterial infection.
*#* E.g. [[Intestines Proliferative Enteritis - Pathology#Paratuberculosis (Johnes disease)|Johne's disease]], [[Actinobacillus species|actinobacillosis]].
*# '''Tumour spread'''.
*#* [[Neoplasia - Pathology#Dissemination of Malignant Neoplasia|Metastasis]] of tumour cell plugs lymphatics and nodes
*#* e.g. mammary carcinoma.
*# '''Parasitic migration'''
*#* Larvae may be following their normal pathway (e.g. Schistosomiasis), or may be aberrant.
====Local venous obstruction====
* Obstruction to venous drainage may be mechanical or inflammatory-mediated.
** Causes raised hydrostatic pressure.
** Endothelial permeability increases due to hypoxia.
** There may be inflammatory damage.
* '''Mechanical obstruction''', e.g.
** [[Intestine Physical Disturbances - Pathology#Positional Changes/ Displacements|Torsions of bowel]]
** Misplaced organs.
** Pressure from outside vein from adjacent structures.
*** [[Neoplasia - Pathology|Tumours]].
* '''Venous inflammation (phlebitis)'''
** May be associated with [[Thrombosis - Pathology#Introduction|thrombosis]] (thrombophlebitis).
===="Allergic" oedema====
* Results from immediate (Type I ) or delayed (Type IV) hypersensitivity.
* Vasular permeability is increased due to release of histamine and vaso-dilating substances.
* E.g.
** Insect stings (immmediate).
** Vaccination (delayed).
** Food reaction (delayed).
====[[Lungs Circulatory - Pathology#Pulmonary oedema|Pulmonary oedema]]====
* In the normal state, pulmonary alveoli are kept dry by three mechanisms:
*# Normal "push-pull" mechanism at capillary level.
*# Efficient lymphatic drainage by rhythmic pumping action near airways.
*# Integrity of the alveolar epithelial basement membrane is relatively impermeable.
*#* Unlike the capillary basement membrane, which is relatively permeable.
=====Pathogenesis=====
# The pumping efficiency of the lymphatics is exceeded.
# Fluid accumulates in connective tissue adjacent to airways.
# The alveolar walls fill with fluid.
# The alveoli abruptly and severely fill with fluid.
#* Associated with the disintegration of alveolar epithelial junctional complexes.
=====Haemodynamic type=====
* Fluid leaks into alveoli via junctional complexes BUT the alveolar basement membrane remains intact.
** I.e. is due to elevated pulmonary venous pressure.
* Potentially reversible.
* Causes:
*# '''Cardiogenic'''
*#* Usually left ventricular failure.
*#* Also occurs with cardiac overload due to valvular disease.
*# '''Mechanical'''
*#* Large primary pulmonary tumours.
*#* Severe metastatic disease.
*#* Granulomatous infections may raise pulmonary venous pressure.
*# '''Neurogenic'''
*#* Seizures or CNS disorder.
*#* Rare in domestic species.
=====Permeability type=====
* Fluid fills the alveoli following damage to cells or junctional complexes, or permanent ionic alteration of the alveolar basement membrane.
* Irreversible.
* Causes:
*# '''Toxins'''
*#* Bacterial
*#** [[Pseudomonas aeruginosa and Burkholderia species|''Pseudomonas'']]
*#** [[Pasteurella species and Mannheimia haemolytica|''Pasteurella'']]
*#** [[Staphylococcus spp.|''Staphylococcus'']]
*#* Chemical
*#** Paraquat.
*# '''Aspiration/inhalation'''
*#* Gastric contents (low pH)
*#* Smoke.
*#* Excess ozone.
*#* Oxygen.
* There may be a combination of haemodynamic and permeability types in electrocution syndromes and "shock" lung.
** E.g. in Adult Respiratory Distress Syndrome (ARDS).
==General oedema==
* General oedema involves subcutaneous and tissue spaces/body cavities.
* Indicative of severe upset of overall body fluid balance.
** Usually one or more vital organ system is abnormal.
* Requires one or more of the following conditions:
*# General increase in arteriolar hydrostatic pressure.
*# Decrease in osmotic pressure of blood.
*# Increase in tissue fluid osmotic pressure.
*#* E.g. sodium retention in renal disease.
*# Increased capillary permeability.
*#* E.g. due to hypoxic damage.
===Types of General Oedema===
====Cardiac oedema====
* Seen in heart failure.
** Shows that cardiac output fails to meet the demands of the tissues throughout the body.
** Left-side failure gives pulmonary congestion.
*** Leads to pulmonary oedema.
** Right-side failure gives systemic congestion.
*** Leads to generalised oedema.
* Chronic venous congestion develops when cardiac output fails to keep pace with venous return to the heart.
* Fluid balance is further complicated by secondary renal impairment.
** Sodium is retained, triggering the renin-aldosterone loop with further sodium retention.
====Renal oedema====
* Kidney malfunction induces oedema as a consequence of deranged sodium and water handling.
** There is often secondary cardiac involvement.
*** Due to via renin effect on heart and myocardial depressant factor.
* Causes:
*# '''Acute glomerulonephritis'''
*#* Reduction in glomerular filtration rate results in systemic hypertension and retention of excess sodium and water.
*# '''Nephrotic syndrome'''
*#* A glomerular filtration defect gives selective heavy loss of plasma proteins (especially albumin)
*#** Reduction of plasma osmotic potential results in oedema.
*# '''Acute renal tubular necrosis'''
*#* Tubules can no longer selectively reabsorb sodium and other electrolytes.
*#** Water retention with the sodium and urea produces oedema.
*# '''Fibrosing glomerulonephritis'''
*#* Causes systemic hypertension and secondary cardiac failure with oedema.
====Protein-losing enteropathies====
* Mucosal damage leads to loss of ability to absorb and retain proteins.
** Plasma proteins, especially albumin are lost.
*** Circulating plasma proteins area therefore reduced, leading to oedema.
* E.g.
** Johne's disease in cattle and sheep.
** Ulcerative colitis or regional enteritis in dogs.
* For more on protein-losing enteropathies, see [[Intestines Protein-Losing Diseases - Pathology|Protein-Losing Diseases]].
====Hepatic oedema====
* Associated with severe [[Liver - Anatomy & Physiology|liver]] damage.
** Liver damage may be:
*** '''Actue'''
**** E.g. due to acute fascioliasis or canine viral hepatitis.
**** Lymphatics and blood vessels of the [[Liver - Anatomy & Physiology|liver]] and [[Peritoneal cavity - Anatomy & Physiology|peritoneal caivity]] are damaged.
***** Results in "overflow" of fluid into the [[Peritoneal cavity - Anatomy & Physiology|peritoneal cavity]].
**** Additionally, hepatocyte damage may result in inadequate inactivation of aldosterone.
***** Increases sodium retention giving further water accumulation in the abdomen
*** '''Chronic'''
**** E.g. metastatic neoplasia or fibrosing hepatopathy (cirrhosis).
**** Failure to produce plasma proteins leads to osmotic imbalance in the peripheral circulation.
**** This is seen as subcutaneous oedema.
***** E.g. "bottle jaw".
==Composition of oedema fluid==
* Inflammatory oedema which produces an exudate.
** This is a protein rich fluid containing many inflammatory cells.
* Non inflammatory oedema which produces a transudate.
** This fluid is low in protein and cells.
* Transudates and exudates are distinguished by the following criteria:
{| border="1" cellspacing="0" cellpadding="5" align="center"
! '''Criteria'''
! '''Transudate'''
! '''Exudate'''
|-
| '''Appearance'''
| Clear/ pale yellow ("straw coloured")
| Dark yellow, red or brown. Often cloudy or opaque.
|-
| '''Consistency'''
| Thin, serous
| Viscous
|-
| '''Protein content'''
| 0.05 - 0.5%, mainly albumin
| Usually 2 - 4%
|-
| '''Coagulability'''
| No fibrinogen, no coagulation
| Contains fibrinogen, coagulates
|-
| '''Specific gravity'''
| Low (< 1.012)
| High (1.012 - 1.020) +
|-
| '''Cell content'''
| Very low. mesothelial cells, some macropahges and lymphocytes/monocytes.
| High. Often macrophages, neutrophils, lymphocyes etc. Depends on cause and chronicity
|}
* Examples of transudates:
** '''Ascites'''
*** Excessive fluid in abdominal cavity.
** '''Hydrothorax'''
*** Excessive fluid in the thorax.
** '''Hydropericardium'''
*** Excessive fluid in the pericardium.
** '''Anasarca'''
*** Generalised tissue oedema most noticeable in subcutaneous tissues.
** '''Ventral subcutaneous oedema'''
* Seen in heart failure in horses and cattle.
{{toplink
|linkpage =General Pathology
|linktext =General Pathology
|maplink = General Pathology (Content Map)
|pagetype =Pathology
|sublink1=Circulatory Disorders - Pathology
|subtext1=CIRCULATORY DISORDERS
}}
<br>
==Introduction==
* Oedema is NOT a disease.
**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."'''
* Small amounts of fluid are normally present to lubricate cavities and viscera - this is not oedema.
* Excess fluid may accumulate in:
** '''Subcutaneous tissue and between muscle'''.
** '''Serous cavities'''.
*** Depending on the cavity, this has different terms.
**** Thorax - hydrothorax.
**** Pericardium - hydropericardium
**** Abdomen - hydroperitoneum (ascites).
*** '''Anasarca''' is when there is generalised body cavity accumulation plus subcutaneous involvement.
** '''Lungs'''.
==Local oedema==
* 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.
** '''Outwards Forces''' - arteriolar
*** Vasuclar hydrostatic pressure - 35 mmHg
*** Interstitial osmotic pressure - 3 mmHg
** '''Inwards forces''' - venular
*** Plasma protein osmotic pressure - 25 mmHg
*** Interstitial hydrostatic pressure - 4 mmHg
* May be of inflammatory or non-inflammatory origin.
===Types of Local Oedema===
====Inflammatory oedema====
* Generated by one or more of the following:
*# Increased vascular permeability
*# Increased arteriolar blood pressure
*# Breakdown of tissue protein or transfer of plasma proteins into ECF.
*#* Results in raised osmotic pressure of tissue fluid.
*# Obstruction to lymphatic drainage.
*#* Usually by fibrin.
====Lymphatic oedema====
* Results in accumulation of high protein fluid.
* May provoke a [[Chronic Inflammation - Pathology#Granulation Tissue|granulation]] or fibrous tissue response.
* Due to:
*# '''Lymphangitis/ lymphadenitis '''
*#* [[Acute Inflammation - Pathology|Acute inflammation]] of lymphatics/ lymph nodes. R
*#* Caused by stasis in lymphatics and/or bacterial infection.
*#* E.g. “Monday Morning leg” in horses.
*# '''Chronic inflammation''' caused by persistent or granuloma-producing bacterial infection.
*#* E.g. [[Intestines Proliferative Enteritis - Pathology#Paratuberculosis (Johnes disease)|Johne's disease]], [[Actinobacillus species|actinobacillosis]].
*# '''Tumour spread'''.
*#* [[Neoplasia - Pathology#Dissemination of Malignant Neoplasia|Metastasis]] of tumour cell plugs lymphatics and nodes
*#* e.g. mammary carcinoma.
*# '''Parasitic migration'''
*#* Larvae may be following their normal pathway (e.g. Schistosomiasis), or may be aberrant.
====Local venous obstruction====
* Obstruction to venous drainage may be mechanical or inflammatory-mediated.
** Causes raised hydrostatic pressure.
** Endothelial permeability increases due to hypoxia.
** There may be inflammatory damage.
* '''Mechanical obstruction''', e.g.
** [[Intestine Physical Disturbances - Pathology#Positional Changes/ Displacements|Torsions of bowel]]
** Misplaced organs.
** Pressure from outside vein from adjacent structures.
*** [[Neoplasia - Pathology|Tumours]].
* '''Venous inflammation (phlebitis)'''
** May be associated with [[Thrombosis - Pathology#Introduction|thrombosis]] (thrombophlebitis).
===="Allergic" oedema====
* Results from immediate (Type I ) or delayed (Type IV) hypersensitivity.
* Vasular permeability is increased due to release of histamine and vaso-dilating substances.
* E.g.
** Insect stings (immmediate).
** Vaccination (delayed).
** Food reaction (delayed).
====[[Lungs Circulatory - Pathology#Pulmonary oedema|Pulmonary oedema]]====
* In the normal state, pulmonary alveoli are kept dry by three mechanisms:
*# Normal "push-pull" mechanism at capillary level.
*# Efficient lymphatic drainage by rhythmic pumping action near airways.
*# Integrity of the alveolar epithelial basement membrane is relatively impermeable.
*#* Unlike the capillary basement membrane, which is relatively permeable.
=====Pathogenesis=====
# The pumping efficiency of the lymphatics is exceeded.
# Fluid accumulates in connective tissue adjacent to airways.
# The alveolar walls fill with fluid.
# The alveoli abruptly and severely fill with fluid.
#* Associated with the disintegration of alveolar epithelial junctional complexes.
=====Haemodynamic type=====
* Fluid leaks into alveoli via junctional complexes BUT the alveolar basement membrane remains intact.
** I.e. is due to elevated pulmonary venous pressure.
* Potentially reversible.
* Causes:
*# '''Cardiogenic'''
*#* Usually left ventricular failure.
*#* Also occurs with cardiac overload due to valvular disease.
*# '''Mechanical'''
*#* Large primary pulmonary tumours.
*#* Severe metastatic disease.
*#* Granulomatous infections may raise pulmonary venous pressure.
*# '''Neurogenic'''
*#* Seizures or CNS disorder.
*#* Rare in domestic species.
=====Permeability type=====
* Fluid fills the alveoli following damage to cells or junctional complexes, or permanent ionic alteration of the alveolar basement membrane.
* Irreversible.
* Causes:
*# '''Toxins'''
*#* Bacterial
*#** [[Pseudomonas aeruginosa and Burkholderia species|''Pseudomonas'']]
*#** [[Pasteurella species and Mannheimia haemolytica|''Pasteurella'']]
*#** [[Staphylococcus spp.|''Staphylococcus'']]
*#* Chemical
*#** Paraquat.
*# '''Aspiration/inhalation'''
*#* Gastric contents (low pH)
*#* Smoke.
*#* Excess ozone.
*#* Oxygen.
* There may be a combination of haemodynamic and permeability types in electrocution syndromes and "shock" lung.
** E.g. in Adult Respiratory Distress Syndrome (ARDS).
==General oedema==
* General oedema involves subcutaneous and tissue spaces/body cavities.
* Indicative of severe upset of overall body fluid balance.
** Usually one or more vital organ system is abnormal.
* Requires one or more of the following conditions:
*# General increase in arteriolar hydrostatic pressure.
*# Decrease in osmotic pressure of blood.
*# Increase in tissue fluid osmotic pressure.
*#* E.g. sodium retention in renal disease.
*# Increased capillary permeability.
*#* E.g. due to hypoxic damage.
===Types of General Oedema===
====Cardiac oedema====
* Seen in heart failure.
** Shows that cardiac output fails to meet the demands of the tissues throughout the body.
** Left-side failure gives pulmonary congestion.
*** Leads to pulmonary oedema.
** Right-side failure gives systemic congestion.
*** Leads to generalised oedema.
* Chronic venous congestion develops when cardiac output fails to keep pace with venous return to the heart.
* Fluid balance is further complicated by secondary renal impairment.
** Sodium is retained, triggering the renin-aldosterone loop with further sodium retention.
====Renal oedema====
* Kidney malfunction induces oedema as a consequence of deranged sodium and water handling.
** There is often secondary cardiac involvement.
*** Due to via renin effect on heart and myocardial depressant factor.
* Causes:
*# '''Acute glomerulonephritis'''
*#* Reduction in glomerular filtration rate results in systemic hypertension and retention of excess sodium and water.
*# '''Nephrotic syndrome'''
*#* A glomerular filtration defect gives selective heavy loss of plasma proteins (especially albumin)
*#** Reduction of plasma osmotic potential results in oedema.
*# '''Acute renal tubular necrosis'''
*#* Tubules can no longer selectively reabsorb sodium and other electrolytes.
*#** Water retention with the sodium and urea produces oedema.
*# '''Fibrosing glomerulonephritis'''
*#* Causes systemic hypertension and secondary cardiac failure with oedema.
====Protein-losing enteropathies====
* Mucosal damage leads to loss of ability to absorb and retain proteins.
** Plasma proteins, especially albumin are lost.
*** Circulating plasma proteins area therefore reduced, leading to oedema.
* E.g.
** Johne's disease in cattle and sheep.
** Ulcerative colitis or regional enteritis in dogs.
* For more on protein-losing enteropathies, see [[Intestines Protein-Losing Diseases - Pathology|Protein-Losing Diseases]].
====Hepatic oedema====
* Associated with severe [[Liver - Anatomy & Physiology|liver]] damage.
** Liver damage may be:
*** '''Actue'''
**** E.g. due to acute fascioliasis or canine viral hepatitis.
**** Lymphatics and blood vessels of the [[Liver - Anatomy & Physiology|liver]] and [[Peritoneal cavity - Anatomy & Physiology|peritoneal caivity]] are damaged.
***** Results in "overflow" of fluid into the [[Peritoneal cavity - Anatomy & Physiology|peritoneal cavity]].
**** Additionally, hepatocyte damage may result in inadequate inactivation of aldosterone.
***** Increases sodium retention giving further water accumulation in the abdomen
*** '''Chronic'''
**** E.g. metastatic neoplasia or fibrosing hepatopathy (cirrhosis).
**** Failure to produce plasma proteins leads to osmotic imbalance in the peripheral circulation.
**** This is seen as subcutaneous oedema.
***** E.g. "bottle jaw".
==Composition of oedema fluid==
* Inflammatory oedema which produces an exudate.
** This is a protein rich fluid containing many inflammatory cells.
* Non inflammatory oedema which produces a transudate.
** This fluid is low in protein and cells.
* Transudates and exudates are distinguished by the following criteria:
{| border="1" cellspacing="0" cellpadding="5" align="center"
! '''Criteria'''
! '''Transudate'''
! '''Exudate'''
|-
| '''Appearance'''
| Clear/ pale yellow ("straw coloured")
| Dark yellow, red or brown. Often cloudy or opaque.
|-
| '''Consistency'''
| Thin, serous
| Viscous
|-
| '''Protein content'''
| 0.05 - 0.5%, mainly albumin
| Usually 2 - 4%
|-
| '''Coagulability'''
| No fibrinogen, no coagulation
| Contains fibrinogen, coagulates
|-
| '''Specific gravity'''
| Low (< 1.012)
| High (1.012 - 1.020) +
|-
| '''Cell content'''
| Very low. mesothelial cells, some macropahges and lymphocytes/monocytes.
| High. Often macrophages, neutrophils, lymphocyes etc. Depends on cause and chronicity
|}
* Examples of transudates:
** '''Ascites'''
*** Excessive fluid in abdominal cavity.
** '''Hydrothorax'''
*** Excessive fluid in the thorax.
** '''Hydropericardium'''
*** Excessive fluid in the pericardium.
** '''Anasarca'''
*** Generalised tissue oedema most noticeable in subcutaneous tissues.
** '''Ventral subcutaneous oedema'''
* Seen in heart failure in horses and cattle.