Title: Megaesophagus

{{Infobox medical condition (new)
| name            = Megaesophagus
| image           = Chagas megaseophagus.JPG
| caption         = [[Chagas disease|Chagas]] megaseophagus
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| field           = [[Gastroenterology]]
| synonyms        = Esophageal dilatation
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'''Megaesophagus''', also known as '''esophageal dilatation''', is a disorder of the [[esophagus]] in humans and other [[mammal]]s, whereby the esophagus becomes abnormally enlarged. Megaesophagus may be caused by any disease which causes the muscles of the [[esophagus]] to fail to properly propel food and liquid from the mouth into the stomach (that is, a failure of [[peristalsis]]). Food can become lodged in the flaccid esophagus, where it may decay, be [[Regurgitation (digestion)|regurgitated]], or be inhaled into the lungs (leading to [[aspiration pneumonia]]).&lt;ref&gt;{{cite web |url= https://www.lecturio.com/concepts/achalasia | title= Achalasia | website= The Lecturio Medical Concept Library | date= 14 October 2020 |access-date= 26 June 2021}}&lt;/ref&gt;

==Humans==
Megaesophagus may occur secondary to diseases such as [[achalasia]] or [[Chagas disease]]. Achalasia is caused by a loss of [[ganglion|ganglion cell]]s in the [[myenteric plexus]]. There is a marked lack of contraction within the muscles involved in peristalsis with a constant contraction of the [[Cardia|lower esophageal sphincter]].  Dilation of the esophagus results in difficulty swallowing.  Retention of food [[Bolus (digestion)|bolus]] is also noted.&lt;ref&gt;{{Cite journal|last=Lewandowski|first=A.|date=2009|title=Diagnostic criteria and surgical procedure for megaesophagus--a personal experience|journal=Diseases of the Esophagus|volume=22|issue=4|pages=305–309|doi=10.1111/j.1442-2050.2008.00897.x|issn=1442-2050|pmid=19207550|doi-access=free}}&lt;/ref&gt;

==Other animals==
===Dogs===
[[File:Megaoesophagus dog marked.jpg|thumb|An x-ray of the thorax of a dog with megaoesophagus. The edges of the esophagus are shown by the yellow arrows. (In this image, the head end of the dog is to the right, and the tail end is to the left.)]]

Megaesophagus can also be a symptom of the disease [[myasthenia gravis]]. Myasthenia gravis is a [[neuromuscular disease]] where the primary symptom is weakness in various body parts of the dog. However, when myasthenia gravis occurs in older dogs it is thought of as an [[immune-mediated disease]]. Often when myasthenia gravis is diagnosed in older dogs the first symptom the dog may manifest is megaesophagus.&lt;ref&gt;{{cite journal |last1= Richardson |first1= D |date= February 2011 |title= Acquired myasthenia gravis in a poodle | journal= The Canadian Veterinary Journal | volume= 52 |issue= 2 |pages= 169–172 |pmid= 21532824 |pmc= 3022456 }}&lt;/ref&gt;

Myasthenia gravis occurs when [[acetylcholine receptor]]s (nicotinic acetylcholine receptors) fail to function properly, so that the muscle is not stimulated to contract. There is an invention known as the &quot;bailey chair&quot; that uses the force of gravity to push down liquids and food into the dog's stomach. Usually dogs are known to understand when it is time to eat in their bailey chair, and this helps prevent issues. Bailey chairs can be made and are sold.&lt;ref&gt;{{cite journal |last1= Haines  |first1= J |last2= Khoo  |first2= A |last3= Brinkman  |first3= E |last4= Thomason |first4= J |last5= Mackin |first5= A |date= 17 May 2019 |title= Technique for Evaluation of Gravity-Assisted Esophageal Transit Characteristics in Dogs with Megaesophagus |journal= [[Journal of the American Animal Hospital Association]] |volume= 55 |issue= 4 |pages= 167–177 |doi= 10.5326/JAAHA-MS-6711 |pmid= 31099601  |s2cid= 157058034 }}&lt;/ref&gt; Also, a simple chair turned upside down can be successfully used for this purpose.
[[File:Apparatus for dog megaesophagus.jpg|thumb|The apparatus for management of the dog's megaesophagus can be simply made from a regular chair turned upside down. Some soft material to protect the back and chest of the dog may be used.]]

In two unrelated incidents in [[Latvia]] and [[Australia]] megaesophagus developed in dogs that had eaten certain brands of dog food; however, no agent that could have caused the disorder has been found in lab tests of the food.&lt;ref&gt;{{cite news|last1=Mičāne|first1=Ingrīda|title=Jauns 'megaesophagus' uzliesmojuma precedents suņiem – šoreiz Austrālijā|url=http://laukos.la.lv/jauns-megaesophagus-uzliesmojuma-precedents-suniem-soreiz-australija/#comment-6910|access-date=30 March 2018|publisher=Latvijas Avīze}}&lt;/ref&gt;&lt;ref&gt;{{cite web|last=Matīse-VanHoutana |first=Ilze |title=I did my research, blew the whistle and found myself at war|url=https://www.youtube.com/watch&amp;v=uNDWvejza4c|access-date=13 December 2018|website=YouTube}}&lt;/ref&gt;&lt;ref&gt;{{cite news|last1=DONNELLAN|first1=ANGELIQUE|last2=SCOPELIANOS|first2=SARAH|title=Pet food Advance Dermocare linked to megaesophagus outbreak, research shows|url=https://mobile.abc.net.au/news/2018-12-13/pet-food-linked-to-megaesophagus-outbreak-in-dogs/10614742&amp;pfmredir=sm|access-date=13 December 2018}}{{Dead link|date=March 2020 |bot=InternetArchiveBot |fix-attempted=yes }}&lt;/ref&gt;

====Diagnosis====

An important distinction in recognizing megaesophagus is the difference between when a dog regurgitates or vomits. When a dog regurgitates there is usually not as much effort involved as when a dog vomits. Often when regurgitating, the dog will tip its head down and the liquid and/or food will almost appear to &quot;spill out&quot; of its throat.{{cn|date=June 2021}}

One of the primary dangers to a dog with megaesophagus is [[aspiration pneumonia]]. Because the food stays lodged in the throat, it can often be inhaled into the lungs causing aspiration pneumonia. One way to avoid this is to make sure that every time the dog eats or drinks anything, that the dog sits for at least 10 minutes afterward or is held in a sitting up or begging position. This disorder has a guarded prognosis, however, a successful management technique is vertical feeding in a Bailey chair.&lt;ref&gt;{{Cite web|url=http://vcahospitals.com/know-your-pet/megaesophagus|title=Megaesophagus|website=vca_corporate|language=en|access-date=2019-12-29}}&lt;/ref&gt;

==== Affected breeds ====
{{Col-begin}}
{{Col-2}}
* [[Basset Fauve de Bretagne]]
* [[Bernese Mountain Dog]]
* [[Bichon Frise]]
* [[Boston Terrier]]
* [[Chihuahua (dog)|Chihuahua]]
* [[Cocker Spaniel]]
* [[Dachshund]]
* [[English Springer Spaniel]]
* [[French Bulldog]]
* [[German Shepherd]]
* [[German Spitz]]
* [[Golden Retriever]]
* [[Great Dane]]
* [[Greyhound]]
* [[Irish Setter]]{{Col-2}}
* [[Irish Wolfhound]]
* [[Italian Greyhound]]
* [[Labrador Retriever]]
* [[Miniature Schnauzer]]
* [[Newfoundland dog]]
* [[Rottweiler]]
* [[Shar Pei]]
* [[Shih Tzu]]
* [[Welsh Corgi]]
* [[Welsh Terrier]]
* [[Wire Fox Terrier]]
* [[Yorkshire Terrier]]
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===Cats===
Affected breeds:
* [[American Shorthair]]
* [[Persian (cat)]]
* [[Siamese (cat)]]

===Horses===
Megaesophagus is rare in horses.&lt;ref&gt;{{cite journal|last1=Broekman|first1=LE|last2=Kuiper|first2=D|title=Megaesophagus in the horse. A short review of the literature and 18 own cases|journal=The Veterinary Quarterly|date=December 2002|volume=24|issue=4|pages=199–202|doi=10.1080/01652176.2002.9695136|pmid=12540136|s2cid=40515417|doi-access=free}}&lt;/ref&gt; It is more frequently reported in [[Friesian horse]]s than in other breeds.&lt;ref&gt;{{cite journal|last1=Ploeg|first1=M|last2=Gröne|first2=A|last3=Saey|first3=V|last4=de Bruijn|first4=CM|last5=Back|first5=W|last6=van Weeren|first6=PR|last7=Scheideman|first7=W|last8=Picavet|first8=T|last9=Ducro|first9=BJ|last10=Wijnberg|first10=I|last11=Delesalle|first11=C|title=Esophageal dysfunction in Friesian horses: morphological features|journal=Veterinary Pathology|date=November 2015|volume=52|issue=6|pages=1142–7|doi=10.1177/0300985814556780|pmid=25367366|doi-access=}}&lt;/ref&gt; [[Birth defect|Congenital]] megaesophagus is usually identified when a foal begins to eat solid food from the ground; prior to this, as the foal nurses milk from its mother, the milk passes easily down into the stomach.&lt;ref name=&quot;McAuliffe 2013&quot;&gt;{{cite book|last1=McAuliffe|first1=Siobhan Brid|title=Knottenbelt and Pascoe's color atlas of diseases and disorders of the horse.|date=2013|publisher=Elsevier Saunders|isbn=9780723436607|pages=23–24|edition=2nd|chapter=Esophageal dilatation/megaesophagus}}&lt;/ref&gt; The most common signs are difficulty swallowing ([[dysphagia]]) and inhalational pneumonia.&lt;ref name=&quot;McAuliffe 2013&quot;/&gt;

==References==
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== External links ==
{{Medical resources
|   DiseasesDB     = 31519
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|   ICD9           = {{ICD9|530.0}}
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* [http://www.caninemegaesophagus.org/ Canine megaesophagus]

{{Digestive system diseases}}

[[Category:Dog diseases]]
[[Category:Esophagus disorders]]