What is it?Megaoesophagus is a dilation (stretching) of the oesophagus (food pipe) which is believed to occur due to problems with the nerve supply, although this is poorly understood at present. This makes it difficult for food to travel from the mouth into the stomach correctly (this is called dysmotility) and results in food sitting in the oesophagus.
Why is it important?It is one of the most common causes of regurgitation in dogs. Megaoesophagus can be a congenital condition (the dog is born with a dilated oesophagus) but more often it is acquired and there may be an underlying disease which requires treatment. It can cause severe malnourishment as well as life threatening complications such as aspiration pneumonia (see below).
What’s the risk?
Although congenital megaoesophagus is rare a family predisposition has been suggested in some breeds e.g. Irish Setters, Great Danes, German Shepherd and Labrador Retrievers.
There are a variety of diseases which can result in acquired megaoesophagus. The neuromuscular disorder myasthenia gravis accounts for 25-30% of these cases but other conditions include hypoadrenocorticism (Addison’s), Lupus myositis, polymyopathies, polyneuropathies, dysautonomia, lead poisoning and some severe forms of oesophageal ulceration. However, an underlying condition is not always found, in these cases we say the disease is “idiopathic” (no known cause) or “spontaneous”.
What happens to the animal?
Regurgitation is the most frequent clinical sign reported by owners, and needs to be differentiated from vomiting. Vomiting is an active process, compared to passive regurgitation where food just “falls out” of the mouth, often seeming to almost catch the dog by surprise. The frequency and timing of regurgitation after eating varies considerably but the process is always passive. Symptoms in puppies with congenital megaoesophagus typically start after they are weaned. Patients are typically underweight with signs of malnourishment.
Changes in breathing and a fever may be present if the dog has aspiration pneumonia. This occurs when the dog regurgitates food/saliva and particles are accidentally breathed into the lungs, causing an infection. Aspiration pneumonia is a common secondary complication of megaoesophagus and can be life-threatening so requires prompt emergency treatment.
Additional symptoms depend on the underlying cause of megaesophagus (where relevant), and include muscle pain with a stiff gait (polymyositis), generalized weakness, exercise intolerance (neuromuscular disease), and other gastrointestinal symptoms such as diarrhoea (lead toxicosis, hypoadrenocorticism).
How do you know what’s going on?
Any dog with an ongoing history of regurgitation will be assessed for megaoesophagus. X-rays are taken of the chest and neck to assess for dilation of the oesophagus as well as any associated complications such as aspiration pneumonia. Sometimes contrast material is fed to the patient immediately before taking an x-ray to help show the outline of oesophagus. In high risk patients or when the answer is unclear fluoroscopy may be used to get a live video x-ray of the dog eating, however this is usually only available at specialist referral centres.
Other tests to assess for underlying causes of megaoesophagus are carried out. These may include blood tests to assess for hormone disorders (e.g. hypoadrenocorticism/Addison’s), blood tests to check for toxins (e.g. lead, tetanus), antibody blood titres for myasthenia gravis, and/or biopsies (tissue samples) of skin/muscle/organs to assess for other neuromuscular diseases.
If all the additional testing is negative then the megaoesophagus is classified as idiopathic/spontaneous.
What can be done?
If an underlying cause of the disease can be found then this should be treated. However, this may not necessarily fix the megaoseophagus, especially if there is already significant dilation. Dogs with underlying myasthenia gravis are reported to have a better response to treatment and a better prognosis. Dogs with idiopathic acquired megaoesphagus sadly have a generally poor long-term prognosis.
Megaoeophagus is managed by trying different food consistencies (liquid/dry/wet) and feeding the patient from a height, preferably with them sat up (like a human) to help food pass down into the stomach. Each patient will have different foods which work better for them as well as optimal times for remaining in an upright position after eating. A ‘Bailey chair’ to support your dog in this position is frequently recommended.
Any secondary conditions such as aspiration pneumonia (lung infection) are also treated and the patient will need close monitoring for repeat problems which are common. Patients with severe malnourishment or with repeated bouts of aspiration pneumonia may benefit from a temporary or permanent feeding tube which allows owners to feed their dog directly into their stomach. Although this is a more labour intensive way of feeding it is effective as it bypasses the oesophagus completely. However, it does not completely stop the patient from regurgitating saliva or water which can still be aspirated. Feeding tubes require careful management and this option should be discussed with your vet if it is an avenue you wish to pursue.