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Oesophagus - Pathology (view source)

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==Introduction==
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*The [[Oesophagus - Anatomy & Physiology|oesophagus]] is the part of alimentary tract that tends to go wrong least often.
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==Functional Anatomy==
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*The [[Oesophagus - Anatomy & Physiology|oesophagus]] is a fibromuscular tube, lined by stratified squamous epithelium and lubricated by mucus, salivary, nasal and bronchial secretions, which acts to transport ingesta from the [[Pharynx - Anatomy & Physiology|pharynx]] to the [[Forestomach - Anatomy & Physiology|stomach]].
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*Failure of [[Oesophagus - Anatomy & Physiology|oesophageal]] function results in obstruction and in failure of ingesta to pass to the [[Forestomach - Anatomy & Physiology|stomach]].
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*In the bovine there may also be failure of [[Eructation - Anatomy & Physiology|eructation]] and [[tympany]] may develop.
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==Defence Mechanisms==
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*The [[Oesophagus - Anatomy & Physiology|oesophagus]] has '''no serosa''' and is covered by the fibrous tissue of the neck and mediastinum, from which it derives its blood supply.
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*Consequently, infection spreads easily and healing is more difficult.
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*[[Oesophagus - Anatomy & Physiology|Oesophageal]] disease is therefore difficult to treat and is consequently very serious.
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==Developmental Pathology==
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===Congenital Achalasia - Megaoesophagus===
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[[Image:Megaoes.gif|left|thumb|125px|<small><center>Megaoesophagus (Courtesy of Alun Williams (RVC))</center></small>]]
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*This condition has been termed achalasia but this implies (in man) a cardiac sphincter defect, which is not found in the dog.
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*A functional rather than a [[#Traumatic Pathology|physical blockage]]
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*Inherited disorder in several breeds:
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**Autosomal recessive in Fox Terrier.
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**Also in Miniature Schnauzer, Great Dane, German Shepherds and others.
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**Also in Siamese cats.
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====Clinical====
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*See at approx. 6-7 months of age when growing quickly.
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*Eats food, [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|vomits]], eats again and [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|vomits]] again because [[Oesophagus - Anatomy & Physiology|oesophagus]] has no tone to it.
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*[[Oesophagus - Anatomy & Physiology|Oesophagus]] may become extremely dilated producing a megaoesophagus. 
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*Can affect the whole length of [[Oesophagus - Anatomy & Physiology|oesophagus]].
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====Pathogenesis====
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*Appears to be due to due to delay in maturation of [[Oesophagus - Anatomy & Physiology|oesophageal]] innervation, either:
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**in upper motor neurones of central swallowing centre or
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**in the afferent sensory arm of the reflex involved with [http://en.wikipedia.org/wiki/Peristalsis| peristalsis].
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*If dog eats from raised bowel may be satisfactory as food goes down by gravity.
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*Once in [[Forestomach - Anatomy & Physiology|stomach]] it is passed on normally.
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===Megoesophagus Secondary to Dextra-Aorta===
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[[Image:Praa.gif|right|thumb|125px|<small><center>Dextra-aorta (Courtesy of Alun Williams (RVC))</center></small>]]
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*Vascular rings are congenital abnormalities of the aortic arch system which interfere with [[Oesophagus - Anatomy & Physiology|oesophageal]] function. Normally, the aortic arch, pulmonary artery and ductus arteriosus (ligamentum arteriosum) all lie on the left side of the [[Oesophagus - Anatomy & Physiology|oesophagus]].
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*However, when there is anomalous development of the aortic arch, for example in the [[right-sided arch]], the [[Oesophagus - Anatomy & Physiology|oesophagus]] becomes enclosed within a ring formed by the '''heart base''', '''aorta''', '''ductus arteriosus''' and '''pulmonary artery'''.
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*The compression and stricture produced by the “ring” presents passage of solid food beyond the heart base and food accumulates rostral (cranial) to the obstruction, resulting in dilatation or megaoesophagus.
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*In most cases food is eventually regurgitated undigested.
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*The condition is seen in pups just after weaning and if these are presented for treatment before severe dilatation occurs, then surgical correction of the ring (if possible) offers a good prognosis.
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==Erosive & Ulcerative Pathology==
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==Vesicular Pathology==
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==Neutrophilic Inflammation==
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==Granulomatous and pyogranulomatous Inflammation==
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==Eosinophilic Inflammation==
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==Necrotizing Inflammation==
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==Lymphocytic and plasmacytic Inflammation==
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==Immune Mediated Pathology==
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===Autoimmune===
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====Myasthenia Gravis====
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*Animals develop antibodies to nicotinic acetylcholine receptors.
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*Results in generalised muscle weakness and or megaoesophagus.
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====Key-Gaskell syndrome====
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*Autonomic polyganglioneuropathy in cats
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*Abnormal function of the sympathetic and parasympathetic system.
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*Whole autonomic system involved – affected animals usually die.
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**Similar to [[Intestines - physical disturbances#Equine dysautonomia, or grass sickness|grass sickness]] in horses.
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=====Clinical===== 
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*Cats show:
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**Mega-oesophagus
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**Dilated pupils
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**Whole gut is involved (very little peristalsis)
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**Constipation.
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*Generalised autonomic effects:
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**Reduced salivation
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**Reduced lachrymation
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**Bradycardia
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**Constipation
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**Pupillary dilatation
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=====Pathology=====
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*Histologically there is marked reduction in the number of neurones in all autonomic ganglia in the ventral horn of all levels of spinal cord accompanied by proliferation of non-neuronal cells.
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*Similar changes in brain stem nuclei of cranial nerves.
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=====Pathogenesis=====
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*Acquired disease - outbreaks occurred in the past, now only occasionally seen but seems to be getting more common again.
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*Possibly toxic cause.   
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*Possibly in dry food or in vaccine? 
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*Agent not really known, but produces general damage to autonomic nervous system.
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===Hypersensitivity===
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==Proliferative Pathology==
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===Hyperplastic===
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===Papular===
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====Bovine Papular Stomatitis====
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[[Image:BPSOES.gif|right|thumb|125px|<small><center>Oesophageal lesions of BPS (Courtesy of Alun Williams (RVC))</center></small>]]
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Lesions of [[Cavity & Gingiva - Pathology#Bovine Papular stomatitis|Bovine Papular Stomatitis]] may also be found in the [[Oesophagus - Anatomy & Physiology|oesophagus]].
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===Neoplastic===
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====Upper Alimentary Tract Carcinoma Complex====
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=====Aetiology=====
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*The most important [[Oesophagus - Anatomy & Physiology|oesophageal]] neoplasm is squamous cell carcinoma in the cow.
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*This tumour is seen as part of a more general syndrome of upper alimentary tract neoplasia in adult cattle grazing rough pasture on which the '''bracken fern''' (Pteridium aquilinum) is present.
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*The syndrome is seen in various part of the world including the Western Highlands of Scotland, Brazil and Kenya.
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*In affected animals, squamous carcinomas may be present in the [[Oral Cavity - Oropharynx - Anatomy & Physiology|oropharynx]], [[Oesophagus - Anatomy & Physiology|oesophagus]] and [[The Rumen|rumen]] and there may also be [[intestinal adenocarcinomas]] and bladder tumours, or the condition known as [[enzootic bovine haematuria]].
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=====Pathogenesis=====
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*Experimentally, the feeding of bracken to laboratory animals will result in alimentary and [[Bladder - Anatomy & Physiology|bladder]] tumours.
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*However, in many naturally-occurring cases of upper alimentary carcinoma in cattle there are coexisting viral papillomata, some of which show malignant change.
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*The relationship between the ingestion of bracken and the presence of virus in the aetiology of the malignancies is currently the subject of intensive investigations.
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*It may be that both are involved in the carcinogenesis.
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=====Macroscopically=====
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*These upper alimentary squamous carcinomas are most often seen as:
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**large
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**fungating
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**often superficially-necrotic
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**protruding into the lumen of the [[Alimentary - Anatomy & Physiology|alimentary tract]];
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*There is often a marked scirrhous reaction.
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*The tumours are locally aggressive and may permeate local lymphatics and metastasise to local lymph nodes.
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=====Microscopically=====
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The tumour consists of cords or groups of squamous cells, which may form keratin.
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Individual or multiple papillomata may be found in association with the carcinomata.
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*The presence of the tumours interferes with normal alimentary function
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**there may be difficulty in chewing and [[Deglutition|swallowing]] or in cudding and [[Eructation - Anatomy & Physiology|eructation]].
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====Squamous Cell Carcinoma of Other Species====
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*Squamous cell carcinomas of the [[Oesophagus - Anatomy & Physiology|oesophagus]] are occasionally seen in other species, notably in the cat, where the tumour tends to infiltrate around the oesophageal wall resulting in a “'''ring carcinoma'''”.
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*The affected cat has progressive difficulty in eating and [[Deglutition|swallowing]].
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==Degenerative Pathology==
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===Acquired megaoesophagus===
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*Occurs spontaneously in adult in any disorder that disrupts normal reflex involved in swallowing either peripheral or central.
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*These can include:
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**Viral encephalitides
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**Peripheral neuropathies
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***Degeneration or inactivity of local myenteric nerve plexuses (Auerbach’s plexuses),
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***or to lesions in the vagus nerve or the central nucleus in the medulla of the brain which supply the [[Oesophagus - Anatomy & Physiology|oesophagus]].
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**Poisonings such as:
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***Lead
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***Tetanus
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***Botulism
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**Myopathies.
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*The result is the presence of a hypotonic [[Oesophagus - Anatomy & Physiology|oesophagus]] in which food accumulates causing distension
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*Usually the thoracic oesophagus from the thoracic inlet to the diaphragm is affected and grossly the [[Oesophagus - Anatomy & Physiology|oesophagus]] is dilated, thin-walled and hypotonic.
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==Metabolic Pathology==
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==Nutritional Pathology==
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==Traumatic Pathology==
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===Impaction===
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{| style="color:darkblue;background-color:#ffffcc;" cellpadding="10" cellspacing="0" border="1"
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|'''Upper Block'''
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|'''Lower Block'''
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|-
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| Acute vomiting
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| Gradual intestinal distention
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|-
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| Dehydration
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| Mucosal destruction
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|-
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| Alkalosis
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| Toxaemia
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|-
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| Pre-renal azotaemia
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| Peritonitis
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|}
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*Commonly in cattle, horses and dogs.
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*The most common sites of obstruction are the '''thoracic inlet''', '''the base of the heart''', and the '''hiatus oesophagus''' of the diaphragm, i.e.: the narrowest points.
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====Clinical Signs====
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====Horse====
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*With foods that expand in [[Oesophagus - Anatomy & Physiology|oesophagus]] such as haylage etc.
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*Also seen with whole apples. 
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====Cattle====
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[[Image:Bovimpaction.gif|right|thumb|125px|<small><center>Impaction of a bovine oesophagus (Courtesy of Alun Williams (RVC))</center></small>]]
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*May eat a spherical object that obstructs the [[Oesophagus - Anatomy & Physiology|oesophagus]] mostly in anterior 1/3rd of [[Oesophagus - Anatomy & Physiology|oesophagus]] and can often be palpated in live animal.
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*Potatoes can be a cheap source of feed and if fed whole can become stuck in [[Oesophagus - Anatomy & Physiology|oesophagus]]. 
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*If obstruction occurs further down can be difficult to diagnose and remove. 
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*Cattle develop bloat when [[Oesophagus - Anatomy & Physiology|oesophagus]] obstructed.
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*Apples fairly easily to dislodge.
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====Dog====
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*Usually with small bones
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*Animals that feel protective of feed may gulp food down quickly, particularly if given small chops / knuckle bones.
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*Knobbly shape may make bone lodge in [[Oesophagus - Anatomy & Physiology|oesophagus]], particularly just anterior to heart. 
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*Very difficult to dislodge (because of shape).
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*Pressure necrosis occurs very quickly around it and can erode through [[Oesophagus - Anatomy & Physiology|oesophagus]] within about 24 hours. 
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*Small bone may also lodge in [[Duodenum - Anatomy & Physiology|duodenum]] if they pass through the [[Forestomach - Anatomy & Physiology|stomach]].
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===Rupture===
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*Perforation may occur with sharp foreign bodies. This may lead to [[cellulitis]] or [[pleurisy]] and other complications.
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*Rupture of the [[Oesophagus - Anatomy & Physiology|oesophagus]] admits pathogenic organisms to the mediastinum and fascial planes of the neck. Both are composed of loose connective tissue and communicate with each other.
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*Infection spreads rapidly as a cellulitis, aided possibly by peristalsis and pulsation of the carotid arteries, and soon leads to pleurisy.
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*'''Rupture is almost always fatal.'''
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==Vascular Pathology==
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==(Other)==
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==Learning Tools==
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[[Alimentary Flashcards - Pathology#Oesophagus Flashcards|Oesophagus Flashcards]]
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