Esophagus

Question 1

What is the esophagus composed of ?

Answer 1

• lined by stratified squamous epithelium
• tunica muscularis consists of striated muscle in Ru & Ca
• in Fe, Eq, Sw, & primates, the distal esophagus contains smooth muscle

Question 2

How do you perform a post-mortem exam of the esophagus?

Answer 2

• open the entire esophagus & examine the mucosa for erosions & ulcers & the muscle for hypertrophy & strictures

Question 3

What is megaesophagus?

Answer 3

• (esophageal ectasia)
• dilation of the esophagus b/c of insufficient, absent, or uncoordinated peristalsis in the esophagus

Question 4

What are the clinical signs of megaesophagus?

Answer 4

• recognized clinically by regurgitation after ingestion of solid food
• on xray, the esophagus is dilated anterior to the lesion & retains radiopaque dyes
• animals are thin & may be affected by respiratory distress (aspiration pneumonia)

Question 5

what would you see on necropsy w/ megaesophagus?

Answer 5

• dilated esophagus
• putrid ingesta are sometimes found in the dilated portions of the esophagus accompanied by esophagitis
• aspiration pneumonia (may be cause of death)

Question 6

What are the causes of megaesophagus?

Answer 6

• physical obstruction/stenosis
• innervation/denervation disorders
• idiopathic

Question 7

What are physical obstructions or stenosis that can cause megaesophagus?

Answer 7

• foreign body
• fibrosis of gastric/cardial orifice (ex: chronic gastric ulceration in Sw) -> entire esophagus is affected
• external pressure (tumour, abscess, etc.) -> esophagus cranial to the lesion is affected
• persistence of R aortic arch -> esophagus cranial to the heart affected
• parasitism (Spirocerca lupi)

Question 8

What are innervation/denervation disorders that can cause megaesophagus?

Answer 8

• myasthenia gravis
• lead poisoning (waterfowl)
• vagal indigestion

Question 9

What is myasthenia gravis?

Answer 9

• congenital: inherited deficiency in acetylcholine receptors
• acquired: autoimmune disease directed against acetylcholine receptors of the neuromuscular junction

Question 10

What is a hiatal hernia?

Answer 10

• protrusion of the abdominal esophagus & cardia of the stomach through the diaphragm into the thoracic cavity, it is generally self-reducing
• sometimes a gastroesophageal intussusception occurs

Question 11

What is an idiopathic muscular hypertrophy of the distal esophagus?

Answer 11

• seen in Eq & Sw, but usually is of no clinical significance
• occasionally may be associated w/ esophageal impaction or gastric cardinal fibrosis

Question 12

What are infectious causes of esophageal erosions & ulcers in Ru?

Answer 12

• BVD, bovine papular stomatitis, IBR (neonates), FMD, Rinderpest (eradicated)

Question 13

What are infectious causes of esophageal erosions & ulcers in Fe?

Answer 13

calicivirus

Question 14

What are non-infectious causes of esophageal erosions & ulcers?

Answer 14

• reflux esophagitis often accompanied by hyperkeratosis (caused by refluxed gastric HCl acid)
• improper use of stomach tubes
• foreign bodies (ex: bones in Ca), caustic chemicals

Question 15

What is choke?

Answer 15

• choke is a clinical term referring to esophageal obstruction

Question 16

where does choke most often occur?

Answer 16

anatomic locations in which the esophagus cannot fully expand (dorsal to larynx, cranial to the first rib at the thoracic inlet, base of the heart, diaphragmatic hiatus)

Question 17

what are the causes of choke?

Answer 17

• ingestion of large foreign bodies (potatoes, apples, bones, corn cobs, or medicaments)
• neoplastic or inflammatory lesions of the esophagus or periesophageal tissues may cause obstruction

Question 18

what are the clinical consequences of choke?

Answer 18

• formation of strictures (if chronic), starvation, & aspiration pneumonia: a foreign body lodged against the mucosa for longer than 2 days causes circumferential pressure necrosis of the esophageal mucosa (in part due to ischemia due to muscular constriction), which heals w/ fibrosis & causes strictures during healing

Question 19

Are there any neoplasia’s associated w/ the esophagus?

Answer 19

papillomatosis (bovine papilloma virus)

Question 20

Answer 20

megaesophagus

Question 21

Answer 21

megaesophagus due to persistent R aortic arch

Question 22

Answer 22

Muscular hypertrophy in the distal esophagus of Eq

Question 23

Answer 23

erosive esophagitis from BVD

Question 24

Answer 24

acid reflux esophagitis in Sw

Question 25

Answer 25

esophageal ulceration due to improper stomach tubing of Eq

Question 26

Answer 26

foreign body w/ esophageal necrosis in Ca

Question 27

Answer 27

pressure esophageal necrosis due to choke in Eq

Question 28

Answer 28

esophageal papillomatosis in Bo