Megaoesophagus

Toby O’Brien

2 Year Old Male Neutered Pug

History 6 week history of vomiting

Trial treatment with metronidazole, amoxicillin, maropitant and omeprazole

Gastric and intestinal biopsies taken –NAD

Endoscopy – fluid in oesophagus

Further questioning: Toby had mostly been regurgitating. He was bringing up food/fluid appeared frothy and contained undigested food

Differences between Vomiting and Regurgitation

Vomiting Regurgitation

Prodromal Nausea Yes No

Retching Yes No

Substance of food Digested food or bile Often undigested/fliud and froth. No bile

pH Acidic or Alkali Alkali

Time related to feeding Anytime Anytime but often related to feeding

Common Ddx for Chronic Regurgitation

Megaoesophagus (Acquired or Congenital) Vascular Ring Anomaly

Oesophagitis

Foreign Body

Stricture

Thoracic Radiographs

Patient should be preferably unsedated

Some sedative agents can cause dilation of the oesophagus and therefore can imitate a megaoesophagus.

Can use contrast medium (barium) but care needs to be taken as if this is aspirated difficult for lungs

Vascular Ring Anomaly

Dilated Oesophagus cranial to aortic arch

Persistent Aortic Arch

Generalised Megaoesophagus

Dilated Oesophagus

Dorsal Tracheal Stripe

Toby’s Thoracic Radiographs

Tracheal Stripe

Dilated Oesophagus

Trachea

Megaoesophagus

Fluoroscopy

Useful to visualise the motility of the oesophagus and to assess for any strictures

Megaoesophagus

Primary/Idiopathic

Congenital Acquired

Secondary/Acquired

• Myasthenia Gravis• Hypoadrenocorticism

(Addison’s)• Canine

Dysautonomia• Polyradiculoneuritis• Myopathy

Further Tests

Once ruled out Ring and presence of strictures

Start investigating for cause of megaoesophagus

Ach Antibodies to test for Myasthenia Gravis (takes several days to come back)

Basal Cortisol levels or an ACTH Stim Test to test for Addison’s

T4 and TSH levels to check for hypothyroidism

CK and AST levels (muscles damage)

Toby’s Results

Haematology Mild leucocytosis with mild neutrophilia

Biochemistry Mild hypoalbuminaemia

T4 26.1

TSH – 0.09

Basal Cortisol – 39

Because low did ACTH stim test Pre – 33

Post – 271

NOT Addison’s

ACH receptor Antibodies: 072 – High therefor diagnosis of Myasthenia gravus made

Complications of Megaoesophagus

Aspiration Pneumonia

This should be checked for on the initial radiographs.

If present:

Treat with IV antibiotics

If not present:

Risk of developing AP in future thereforewater anf food must ge biven from a height and dog must be monitored for signs of development of an aspiration pneumonia (cough) and mucopurulent discharge

The most common reason for death in dogs with megaoespophagus

Approx 48% of dogs with megaoesopahgus will have aspiration pneumonia

Back To Toby….

Normal Basal Cortisol levels

ACTH Stim Test negative

But…

ACTH Antibodies above ref range

Therfore diagnosed with focal myasthenia gravis

Myasthenia Gravis Can be Congenital or Acquired

Can be focal or diffuse

Congenital present less than a year old – caused by lack of Ch receptos

Acquired – An immue mediated disorder in which Autoantibodies form against the nicotinic Acetylcholine receptors at the neuromuscular junctions

Dogs have striated muscle the entire length of the oesophagus and therefore it can be focally affected

Diffuse causes exercise intolerance

Can be caused by Thyoma (mass in cranial mediastinum on thoracic radiograph)

Treatment: hhjhjhjhjh

Prognosis

Poor Prognostic Factors for Acquired Myasthenia Gravis

Over 13 months old

Aspiration Pneumonia present

Good

If responds to dietary

If the underlying cause can be treated

Management

Feed from height while waiting in test results

Uses gravity to aid food passing down oesophagus to stomach

Food consistency – Try meatballs or more liquid type food

Pyridostigmine bromide

Kept in for 24 hours to monitor for signs of side effects to treatment.

Famotidine

Plan

Recheck in 2 weeks to see how he is getting on (still regurg or no)

Reassess antibodies in a 3 months to look for evidence of remission

Re radiograph to look for signs that the oesophagus is less dilated

References Shelton et al (1990) Acquired Myasthenia Gravis. Journal of Veterinary

Internal Medicine, 4: 281–284.

Webb et al (1997) Focal myasthenia gravis in a dog. Can Vet J 38: 493-495

Richardson (2011) Acquired myasthenia gravis in a poodle. Can Vet J.52(2): 169–172.

Foy et al (2011) Cholinergic crisis after neostigmine administration in a dog with acquired focal myasthenia gravis. Journal of Veterinary Emergency and Critical Care 21(5) , pp 547–551

McBrearty et al (2011) Clinical factors associated with death before discharge and overall survival time in dogs with generalized megaoesophagus. Journal of the American Veterinary Medical Association Vol. 238, No. 12, Pages 1622-1628

BSAVA Manual of neurology Chapter 7 pages 43-47

Elwood (2006) Diagnosis and management of canine oesophageal disease and regurgitation In Practice 28: 14-21

Questions?