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| | ==[[Local Oedema|Local oedema]]== | | ==[[Local Oedema|Local oedema]]== |
| − | * Local oedema is the local accumulation of excess interstitial fluid.
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| − | * Caused by disturbance of the balance betwen fluid extravasation and resorption at the level of the capillaries.
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| − | ** '''Outwards Forces''' - arteriolar
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| − | *** Vasuclar hydrostatic pressure - 35 mmHg
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| − | *** Interstitial osmotic pressure - 3 mmHg
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| − | ** '''Inwards forces''' - venular
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| − | *** Plasma protein osmotic pressure - 25 mmHg
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| − | *** Interstitial hydrostatic pressure - 4 mmHg
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| − | * May be of inflammatory or non-inflammatory origin.
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| − |
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| − | ===Types of Local Oedema===
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| − | ====Inflammatory oedema====
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| − | * Generated by one or more of the following:
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| − | *# Increased vascular permeability
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| − | *# Increased arteriolar blood pressure
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| − | *# Breakdown of tissue protein or transfer of plasma proteins into ECF.
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| − | *#* Results in raised osmotic pressure of tissue fluid.
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| − | *# Obstruction to lymphatic drainage.
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| − | *#* Usually by fibrin.
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| − |
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| − | ====Lymphatic oedema====
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| − | * Results in accumulation of high protein fluid.
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| − | * May provoke a [[Granulation Tissue|granulation]] or fibrous tissue response.
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| − | * Due to:
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| − | *# '''Lymphangitis/ lymphadenitis '''
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| − | *#* [[:Category:Acute Inflammation|Acute inflammation]] of lymphatics/ lymph nodes. R
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| − | *#* Caused by stasis in lymphatics and/or bacterial infection.
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| − | *#* E.g. “Monday Morning leg” in horses.
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| − | *# '''Chronic inflammation''' caused by persistent or granuloma-producing bacterial infection.
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| − | *#* E.g. [[Johne's Disease|Johne's disease]], [[:Category:Actinobacillus species|actinobacillosis]].
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| − | *# '''Tumour spread'''.
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| − | *#* [[Neoplasia - Pathology#Dissemination of Malignant Neoplasia|Metastasis]] of tumour cell plugs lymphatics and nodes
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| − | *#* e.g. mammary carcinoma.
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| − | *# '''Parasitic migration'''
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| − | *#* Larvae may be following their normal pathway (e.g. Schistosomiasis), or may be aberrant.
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| − |
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| − | ====Local venous obstruction====
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| − | * Obstruction to venous drainage may be mechanical or inflammatory-mediated.
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| − | ** Causes raised hydrostatic pressure.
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| − | ** Endothelial permeability increases due to hypoxia.
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| − | ** There may be inflammatory damage.
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| − | * '''Mechanical obstruction''', e.g.
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| − | ** [[Torsion, Intestinal|Torsions of bowel]]
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| − | ** Misplaced organs.
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| − | ** Pressure from outside vein from adjacent structures.
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| − | *** [[Neoplasia - Pathology|Tumours]].
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| − | * '''Venous inflammation (phlebitis)'''
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| − | ** May be associated with [[Thrombosis#Introduction|thrombosis]] (thrombophlebitis).
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| − |
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| − | ===="Allergic" oedema====
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| − | * Results from immediate (Type I ) or delayed (Type IV) hypersensitivity.
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| − | * Vasular permeability is increased due to release of histamine and vaso-dilating substances.
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| − | * E.g.
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| − | ** Insect stings (immmediate).
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| − | ** Vaccination (delayed).
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| − | ** Food reaction (delayed).
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| − |
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| − |
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| − | [[Category:Circulatory Disorders - Pathology]]
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| − |
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| − |
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| − | ====[[Pulmonary Oedema|Pulmonary oedema]]====
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| − | * In the normal state, pulmonary alveoli are kept dry by three mechanisms:
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| − | *# Normal "push-pull" mechanism at capillary level.
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| − | *# Efficient lymphatic drainage by rhythmic pumping action near airways.
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| − | *# Integrity of the alveolar epithelial basement membrane is relatively impermeable.
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| − | *#* Unlike the capillary basement membrane, which is relatively permeable.
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| − |
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| − | =====Pathogenesis=====
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| − | # The pumping efficiency of the lymphatics is exceeded.
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| − | # Fluid accumulates in connective tissue adjacent to airways.
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| − | # The alveolar walls fill with fluid.
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| − | # The alveoli abruptly and severely fill with fluid.
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| − | #* Associated with the disintegration of alveolar epithelial junctional complexes.
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| − |
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| − |
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| − | =====Haemodynamic type=====
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| − | * Fluid leaks into alveoli via junctional complexes BUT the alveolar basement membrane remains intact.
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| − | ** I.e. is due to elevated pulmonary venous pressure.
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| − | * Potentially reversible.
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| − | * Causes:
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| − | *# '''Cardiogenic'''
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| − | *#* Usually left ventricular failure.
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| − | *#* Also occurs with cardiac overload due to valvular disease.
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| − | *# '''Mechanical'''
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| − | *#* Large primary pulmonary tumours.
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| − | *#* Severe metastatic disease.
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| − | *#* Granulomatous infections may raise pulmonary venous pressure.
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| − | *# '''Neurogenic'''
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| − | *#* Seizures or CNS disorder.
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| − | *#* Rare in domestic species.
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| − |
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| − | =====Permeability type=====
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| − | * Fluid fills the alveoli following damage to cells or junctional complexes, or permanent ionic alteration of the alveolar basement membrane.
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| − | * Irreversible.
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| − | * Causes:
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| − | *# '''Toxins'''
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| − | *#* Bacterial
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| − | *#** [[:Category:Pseudomonas and Burkholderia species|''Pseudomonas'']]
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| − | *#** [[:Category:Pasteurella and Mannheimia species|''Pasteurella'']]
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| − | *#** [[:Category:Staphylococcus species|''Staphylococcus'']]
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| − | *#* Chemical
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| − | *#** Paraquat.
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| − | *# '''Aspiration/inhalation'''
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| − | *#* Gastric contents (low pH)
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| − | *#* Smoke.
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| − | *#* Excess ozone.
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| − | *#* Oxygen.
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| − |
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| − | * There may be a combination of haemodynamic and permeability types in electrocution syndromes and "shock" lung.
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| − | ** E.g. in Adult Respiratory Distress Syndrome (ARDS).
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| − |
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| − | [[Category:Circulatory Disorders - Pathology]]
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| | ** '''Ventral subcutaneous oedema''' | | ** '''Ventral subcutaneous oedema''' |
| | * Seen in heart failure in horses and cattle. | | * Seen in heart failure in horses and cattle. |
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| | + | [[Pulmonary Oedema]] |
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| | [[Category:Circulatory Disorders - Pathology]] | | [[Category:Circulatory Disorders - Pathology]] |
| | + | [[Category:Cardiology Section]] |