The pup is always hungry, always wants to eat, but cannot get enough because the food it eats does not go to the stomach.

In megaesophagus that develops later, it is really difficult to find the etiology. Etiologies are examined under the following headings:

• Primary (most common) (Idiopathic)

Secondary causes include;

• Neuromuscular diseases;

-Myasthenia Gravis (MG): It can be seen focally (only in the esophagus) or generalized. It covers 25% of acquired cases.

-Systemic lupus erythematosus, myopathy/myositis, dysautonomia (the most common cause in cats), polyneuropathy (with vagus nerve involvement), botulism, glycogen storage diseases, muscular dystrophy and tetanus.

-It may also be associated with laryngeal paralysis due to a common pathogenesis involving the vagus nerve

• Esophageal obstructions: neoplasia, parasitic granuloma (Spirocerca lupi), vascular ring anomaly, stricture, esophageal foreign bodies are among the conditions causing obstruction. Esophagitis and, rarely, gastroesophageal reflux may cause megaesophagus due to predisposition.

• Endocrine disorders: hypoadrenocorticism, hypothyroidism

• Hiatal disorders: hiatal hernia, gastroesophageal invagination

• Toxicology: lead, organophosphate

• Distemper: due to demyelination

• Thymoma is associated with megaesophagus in approximately 25% of cats.

• Achalasia-like syndrome of the lower esophageal sphincter - the sphincter remains closed when swallowing is triggered.

Some studies have reported megaesophagus after diaphragmatic hernia surgery. Bilateral vagal nerve lesions due to surgery, inflammation, or trauma may also affect esophageal motility, causing megaesophagus.

What are the clinical findings of megaesophagus?

The physical examination of the animal may be normal; in cases, regurgitation is typically seen; ptyalism, mouth smacking and dysphagia may be added. Other complaints include cough, aspiration pneumonia, musculoskeletal weakness and weight loss despite the animal having a good appetite. Sometimes, swelling can be palpated in the dilated area of the cervical esophagus due to food accumulation.

Since megaesophagus is often accompanied by aspiration pneumonia, the cause of death in many patients is aspiration pneumonia.

What is the difference between vomiting and regurgitation?

In regurgitation, swallowed food is ejected directly, without any effort. It contains undigested food, foam, saliva or a combination of all. Vomiting, on the other hand, requires active abdominal effort and the vomit may contain digested food as well as yellow-green bile.

How is megaesophagus diagnosed?

Diagnosis can often be made with direct X-ray. Diagnosis can be made with diffuse expansion of the esophagus (visualization of it filled with air, liquid or food) on L/L radiography (Figures 1 and 2). In cases where diagnosis cannot be made with direct radiography, indirect methods can also be used. For this purpose, diagnosis can be made by evaluating the residence time of barium sulfate or iodinated contrast materials in the esophagus and the diameter of the esophagus. While the contrast material administered orally should reach the stomach within seconds under normal conditions, the contrast material can remain in the esophagus for minutes in patients with megaesophagus. If fluoroscopy is available, direct swallowing reflex and esophageal motility can be evaluated.

In severe cases, ventral deviation of the trachea in L/L view and lateral deviation in V/D view can be seen on X-ray.

If the patient has aspiration pneumonia, pulmonary infiltration also accompanies.

The presence of a cranial mediastinal mass should raise suspicion for megaesophagus associated with thymoma. Esophagoscopy may also be used to evaluate for strictures, masses, or other obstructive lesions.

What laboratory tests should be performed for diagnostic purposes?

Diagnostic tests attempt to find the etiology. Tests should include complete blood count, biochemistry profile, thyroid hormone test, and Addison's disease screening. In addition to these, acetylcholine receptor antibody test, distemper titer, and ANA test for lupus erythematosus can be performed for myasthenia gravis.

What should be the treatment protocol for megaesophagus?

There are two main goals in the management of megaesophagus. The first is to determine and treat the underlying cause; the second is to try to reduce the amount of regurgitation, thereby reducing the incidence of aspiration pneumonia and ensuring adequate nutritional intake.

Medical Treatment

1) Antibiotics should be used if aspiration pneumonia is present.

2) Acid blockers can be used if esophagitis is present (Omeprazole, 1 mg / kg, PO, BID)

3) The use of prokinetics such as metoclopramide and cisapride is controversial. While some researchers recommend it because it increases esophageal motility, others have reported that it increases the risk of aspiration pneumonia because it tightens the lower esophageal sphincter.

4) If the cause of megaesophagus is myasthenia gravis, pyridostigmine (1-3 mg/kg, PO, BID, TID) can be used. It would be good to repeat the antibody titer after 4-6 weeks; if the titer is within the reference ranges, the drug can be stopped. Since estrus and pregnancy can trigger myasthenia gravis, it is recommended to neuter animals with a history of MG.

5) In a study conducted at Washington State University and the results of which were published in 2022, it was found that the use of sildenafil (1 mg/kg, PO, BID) in patients diagnosed with megaesophagus reduced the frequency of regurgitation and increased the rate of emptying the esophagus.

6) In cases where medication is not a solution, it is recommended that animals be fed in an upright position and kept in this position for at least 10-15 minutes after food intake to benefit from the effect of gravity. There are also commercially available high chairs designed for this purpose.

7) Situations that require surgical treatment of megaesophagus are vascular ring anomaly, foreign bodies that cannot be removed endoscopically, stenoses that do not resolve with balloon dilatation, and resection of esophageal masses.

The prognosis of megaesophagus is variable and difficult to predict; recovery rates vary between 20-46%. Animal owners should be warned that aspiration pneumonia can be a fatal complication. The likelihood of recovery can increase with early diagnosis and appropriate dietary management.

You may contact us for references.