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| − | ==Bloat/Tympany==
| + | [[Bloat]] |
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| − | * When [[Eructation - Anatomy & Physiology|eructation]] fails, the [[The Rumen - Anatomy & Physiology|rumen]] becomes distended due to the accumulation of gas produced by the fermentation process. This distension is known as '''bloat''' or '''tympany'''.
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| − | ===Clinical===
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| − | *The disease is acute and progressive and will result in death in a matter of hours.
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| − | ===Pathology===
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| − | * In severe bloating, that the [[The Rumen - Anatomy & Physiology|rumen]] almost fills the abdomen.
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| − | ** Diaphragm is displaced forwards, compressing the lungs.
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| − | ** Posterior vena cava (lying dorsally) is also compressed, reducing the venous return to the heart.
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| − | ** Respiration is depressed and animals die from anoxia.[[Image:oesophageal bloat line.jpg|thumb|right|150px|Oesophageal "bloat line" (Courtesy of Elspeth Milne)]]
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| − | *** Blood is dark (hypoxic) and clots poorly.
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| − | * The anterior parts of the body are often characteristically acutely congested.
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| − | ** Oedema and subcutaneous haemorrhage of head and neck tissues.
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| − | ** [[Oesophagus - Anatomy & Physiology|Oesophageal]] "bloat line" at thoracic inlet.
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| − | *** Congested and haemorrhagic cranially, pale caudally.
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| − | ===Pathogenesis===
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| − | * There are two forms of bloat:
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| − | ** '''Frothy bloat/ Primary bloat'''
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| − | *** Occurs following ingestion of large amounts of succulent green plant material. This is highly fermentable and produces large amounts of gas.
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| − | *** Material contains high levels of soluble proteins. These act as foaming agents by reducing surface tension but increasing surface viscosity of rumenal liquids and a stable rumenal foam forms.
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| − | *** The [[Volatile Fatty Acids - Anatomy & Physioogy|volatile fatty acids]] of the plant material consumed lower pH, optimising conditions for formation of froth.
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| − | *** Gas present in bubble form is insufficient to trigger eructation, and so the [[The Rumen - Anatomy & Physiology|rumen]] becomes distended.
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| − | ** '''Free gas bloat/ Secondary bloat'''
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| − | *** May be:
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| − | **** '''Acute'''
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| − | *****Due to sudden [[Oesophagus - Anatomy & Physiology|oesophageal]] obstruction, for example by a solid foreign body (e.g. a piece of potato or turnip).
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| − | **** '''Chronic'''
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| − | ***** Results from partial [[Oesophagus - Anatomy & Physiology|oesophageal]] obstruction/ compression, or from interference with the normal eructation mechanism, e.g. with:
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| − | ****** partially obstructive foreign bodies
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| − | ****** actinobacillosis in the oesophagus or [[Oesophageal groove|oesophageal groove]]
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| − | ****** [[Oesophagus - Anatomy & Physiology|oesophagus]] or groove tumours
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| − | ****** chronic inflammatory or adhesive disease of the [[The Reticulum - Anatomy & Physiology|reticulum]]
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| − | ***** Some passage of gas is possible, so gas build-up and distenesion is more prolonged.
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| − | ***** Interference with cardiac and respiratory function is seldom life threatening.
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