QUESTIONS

1. The muscle layer of the esophagus is striated through what percentage of the esophagus in the dog?  In the cat?
    
2. What type of epithelium is present in the esophagus?
    
3. True or False:
   
   Mucus producing glands exist in the submucosa of the esophagus all the way down in the dog. How about in the cat?
    
4. The spirurid worm which incites tremendous tissue reaction in the
   esophagus (which can actually transform into a fibrosarcoma about 2% of the time) is _______________.
   
   It's intermediate host is a _______________ but dogs usually get it from eating the paratenic host which is a ______________.
    
5. The medical term for failure of a sphincter to open is _______________. What does this have to do with canine megaesophagus?
    
6. The three places in the esophagus where foreign bodies are most likely to catch are:
   
   a) _______________
   b) _______________
   c) _______________
    
7. The most common vascular ring anomaly is: _______________
   
   In this anomaly, the aorta forms from the right aortic arch  instead of the left aortic arch and the esophagus gets trapped between:  the trachea (ventrally), the ligamentum arteriosum (dorsally), the aorta on the right and _______________ on the left. 
   
   (by the way, what in the hell is a ligamentum arteriosum?)
    
8. Sequellae to esophagitis which one most hopes to avoid are _______________ & _______________.
    
9. Normally one would expect a dog with a megaesophagus to be rather hungry. What two conditions do you susupect when your patient suddenly loses his appetite?
    
10. Why is it a very bad idea to endoscope a suspected esophageal perforation?
     
11. In esophageal strictures we used to treat via a method called
    _______________ but now  we use (like the cardiologists) _______________.
     
12. Is the prognosis generally considered worse for congenital megaesophagus or aquired idiopathic megaesophagus?
     
13. What is the #1 tumor of the esophagus?
     
14. In the esophageal peristalsis neural pathway, fill in the blanks:
    
    afferents in the pharynx ---tractus solitarius ---to the swallow center of the the lateral reticular formation (which keeps you from trying to breathe while you are swallowing) ---- to the nucleus _______________ ---- efferent nerves which make the esophagus contract & relax travel in the _______________ nerve.
    :)
    
    
    
    
     

ANSWERS

1. The muscle layer of the esophagus is striated in 100% of the canine esophagus (FYI: also in the bovine esophagus) but only in the upper 2/3 (66%) of the cat's (and horse's) esophagus.
   
   
   
   
    
2. The esophageal epitheliumis stratified squamous (it's even cornified in herbivores).
   
   
   
   
    
3. True for the dog and false for the cat (only the upper part of the
   esophagus produces mucus in species other than dogs).
   
   
   
   
    
4. The notorious worm is Spirocerca lupi.  Its intermediate host is the beetle but the paratenic host is the chicken.  It actually migrates from the aorta directly into the adjacent esophagus and may rupture the aorta in doing so.
   
   
   
   
    
5. The term I meant to be asking about is "Achalasia," which actually has nothing to do with canine megaesophagus except that in olden times it was thought to be involved. (It was thought that there was a cardiac sphincter achalasia but we now know there isn't; the cardiac sphincter is plenty open.)  Actually, in the 2000 ACVIM Proceedings cardiac sphincter achalasia is mentioned as an entity that really does exist but it is very rare and not a major player in the megaesophagus situation. Treatment for true cardiac sphincter achalasia is ``lower esophageal cardiomyotomy."
   
   
   
   
    
6. The three places where esophageal foreign bodies hang up are the thoracic inlet, the base of the heart & the cardia.  This also makes these areas prime targets for stricture formation. CVT13 notes that in large dogs, esp near the cardiac sphincter, an endoscope might pass through a stricture w/o the operator noticing as the whole esophagus can be pretty big and the narrowing might not be obvious.
   
   
   
   
    
7. The most common vascular ring anomaly is "persistent right aortic arch." The esophagus is trapped by the pulmonary artery on the left.
   
   
   
   
    
8. The bad news after esophagitis is STRICTURE.  The even worse news is PERFORATION. Treatment of esophagitis typically centers on removing  the primary cause if possible, antacids to yield less damage to the esophagus when stomach contents hit, and  motility modifiers to keep the stomach contents moving away from the esophagus. H2 blockers may be OK for mild or moderate esophagitis but it takes a proton pump inhibitor to really create neutral stomach contents. It also seems to be felt that reglan might not be as effective as cisapride in the motility modifier business. Many feel that metoclopramide only works well when the stomach contents are liquid (ie doesn't work for solid stomach contents)
   
   
   
   
    
9. If the megaesophagus patient suddenly has a poor appetite, take x-rays for aspiration pneumonia. Also, rule out esophagitis due to gastric reflux (very painful).
   
   
   
   
    
10. Never scope a suspected perforation because to scope you will need to insufflate air into the esophagus. If there is a perf, all this air will go right into a pneumothorax.
    
    Prognosis in perf. depends on time between perf & treatment (surgery). Within 24-48 hours there will be pleuritis & effusion.
    
    
    
    
     
11. The old technique is bougienage. The new method uses balloon catheters.
    
    
    
    
     
12. The prognosis is generally considered worse for adult patients.  Some feel as many as 40% of congenital megaesophagus cases will resolve. FYIL: Megaesophagus is an autosomal recessive trait in the wire fox terrier and an autosomal dominant trait in the miniature schnauzer. Congenitally affected dogs usually are clinically affected by age 12 weeks but milder cases may not be obvious until age one year.  In the schnauzer situation, most pups are much better or even normal by age 6-12 months. Other commonly affected breeds are the Dane, German Shepherd dog, Lab, Newfie, Shar pei, & Irish Setter..
    
    
    
    
     
13. #1 esophageal tumor = squamous cell carcinoma.
    
    
    
    
     
14. Efferent signals travel from the lateral reticular formation to the
    nucleus ambiguus.  Efferent fibers from there go to the esophagus via the vagus nerve.
    
    
    For laughs, here is a list of causes of megaesophagus:


Myopathy

Neuropathy

Myasthenia gravis (accounts for 25-30% of acquired megaesophagus cases making it the most common cause of acquired megaesophagus. Remember, MG can be generalized w/other muscles involved, or focal w/only the esophagus involved)

Dermatomyositis

Dysautonomia

Esophagitis

Addison's disease (black poodes esp suspicious)

Spirocerca lupi

Tumor

The hypothyroidism issue is still up in the air.