Megaesophagus

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Megaesophagus
Classification and external resources
Chagas megaseophagus
ICD-9	530.0
DiseasesDB	31519

Megaesophagus is a condition in humans, cats and dogs where peristalsis fails to occur properly and the esophagus is enlarged. Normally, when the animal's esophagus is functioning properly, it acts as a muscle and pushes the food down the esophagus into the stomach. However, when an animal has megaesophagus, the esophagus stays enlarged and does not push the food down to the stomach. Therefore, the food fails to enter the stomach and often stays in the esophagus, and is eventually regurgitated, or enters the lungs through breathing, or decays in the esophagus.

In human pathology a condition known as achalasia may predispose a person to slowly develop megaesophagus. Achalasia is due to the loss of ganglion cells of the myenteric plexus. It occurs mostly in middle aged adults. There is a marked lack of contraction within the muscles involved in peristalsis with a constant contraction of the lower esophageal sphincter. Dilation of the esophagus results in difficulty swallowing. Retention of food bolus is also noted. Chagas disease is one cause of megaesophagus in humans. Achalasia also predisposes to esophageal carcinoma.

Megaesophagus can also be a symptom of another disease in dogs called 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.

Myasthenia gravis occurs when acetylcholine receptors (nicotinic acetylcholine receptors or AChRs) fail to function properly. Due to the inability of the nerve receptors to function appropriately, the muscles fail to have a stimulus that causes them to contract.

An important distinction in recognizing megaesophagus is the difference between when a dog regurgitates or vomits. Regurgitating is a common symptom of megaesophagus while vomiting is not necessarily associated with megaesophagus. 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 "spill out" of its throat.

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 afterwards or is held in a sitting up or begging position. This requires that all food and liquid intake be closely monitored and specifically administered to the dog in regular intervals (sometimes as often as 2–3 hours) in smaller quantities. Obviously, if smaller quantities of food and water are administered, one needs to take the necessary precaution to ensure the dog has a sufficient caloric and water intake. According to many specialists, this disorder has a guarded prognosis, however, since 2004 many owners have found a number of successful management techniques, one of which is vertical feeding (see "Bailey Chair megaesophagus").

Breeds Affected

An extensive list of breeds affected via known familial predisposition may be found at Genetic Predisposition

External links

Digestive system, Digestive disease, Gastroenterology (primarily K20–K93, 530–579)

Upper GI tract

Esophagus	Esophagitis Candidal Herpetiform Rupture Boerhaave syndrome Mallory-Weiss syndrome UES Zenker's diverticulum LES Barrett's esophagus Esophageal motility disorder Nutcracker esophagus Achalasia Diffuse esophageal spasm Gastroesophageal reflux disease (GERD) Laryngopharyngeal reflux (LPR) Esophageal stricture Megaesophagus

Stomach	Gastritis Atrophic Ménétrier's disease Gastroenteritis Peptic (gastric) ulcer Cushing ulcer Dieulafoy's lesion Dyspepsia Pyloric stenosis Achlorhydria Gastroparesis Gastroptosis Portal hypertensive gastropathy Gastric antral vascular ectasia Gastric dumping syndrome Gastric volvulus

Lower GI tract:
Intestinal/
Enteropathy

Small intestine (Duodenum/Jejunum/Ileum)	Enteritis Duodenitis Jejunitis Ileitis Peptic (duodenal) ulcer Curling's ulcer Malabsorption: Coeliac Tropical sprue Blind loop syndrome Small bowel bacterial overgrowth syndrome Whipple's Short bowel syndrome Steatorrhea Milroy disease bile acid malabsorption

Large intestine (Appendix/Colon)	Appendicitis Colitis Pseudomembranous Ulcerative Ischemic Microscopic Collagenous Lymphocytic Functional colonic disease IBS Intestinal pseudoobstruction / Ogilvie syndrome Megacolon / Toxic megacolon Diverticulitis/Diverticulosis

Large and/or small	Enterocolitis Necrotizing IBD Crohn's disease Vascular: Abdominal angina Mesenteric ischemia Angiodysplasia Bowel obstruction: Ileus Intussusception Volvulus Fecal impaction Constipation Diarrhea Infectious Intestinal adhesions

Rectum	Proctitis Radiation proctitis Proctalgia fugax Rectal prolapse Anismus

Anal canal	Anal fissure/Anal fistula Anal abscess Anal dysplasia Pruritus ani

GI bleeding/BIS

Accessory

Liver	Hepatitis Viral hepatitis Autoimmune hepatitis Alcoholic hepatitis Cirrhosis PBC Fatty liver NASH Vascular Budd-Chiari syndrome Hepatic veno-occlusive disease Portal hypertension Nutmeg liver Alcoholic liver disease Liver failure Hepatic encephalopathy Acute liver failure Liver abscess Pyogenic Amoebic Hepatorenal syndrome Peliosis hepatis Metabolic Disorders Wilson's Disease Hemochromatosis

Gallbladder	Cholecystitis Gallstones/Cholecystolithiasis Cholesterolosis Rokitansky-Aschoff sinuses Postcholecystectomy syndrome Porcelain gallbladder

Bile duct/ Other biliary tree	Cholangitis PSC Secondary sclerosing cholangitis Ascending Cholestasis/Mirizzi's syndrome Biliary fistula Haemobilia Gallstones/Cholelithiasis Common bile duct Choledocholithiasis Biliary dyskinesia Sphincter of Oddi dysfunction

Pancreatic	Pancreatitis Acute Chronic Hereditary Pancreatic abscess Pancreatic pseudocyst Exocrine pancreatic insufficiency Pancreatic fistula

Abdominopelvic

Hernia	Diaphragmatic Congenital Hiatus Inguinal Indirect Direct Umbilical Femoral Obturator Spigelian Lumbar Petit's Grynfeltt-Lesshaft Undefined location Incisional Internal hernia

Peritoneal	Peritonitis Spontaneous bacterial peritonitis Hemoperitoneum Pneumoperitoneum

M: DIG

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noco/cong/tumr, sysi/epon

proc, drug (A2A/2B/3/4/5/6/7/14/16), blte

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