You may have heard of a condition called megaesophagus, which is rarely seen in dogs let alone cats.
The megaesophagus refers to the widening (mega) of the muscular tube that carries solid food and liquids from the mouth to the stomach (the esophagus).
Normally, the esophagus pushes swallowed food and liquids from the mouth to the stomach using an action called peristalsis, but in megaesophagus, the esophagus loses its peristaltic function.
No longer able to push food into the stomach where it can be digested, the esophagus expands, so food and fluid stay there.
This leads to regurgitation.
Unlike vomiting – an active lifting process by which food is ejected from the stomach – regurgitation is passive.
It is usually not preceded by lip smacking (a sign of nausea), heaving, or retching.
On the contrary, a regurgitating animal simply opens its mouth and releases the contents of the esophagus.
Some animals are born with a megaesophagus while others acquire the disease, either secondary to a pathological process such as certain neurological, infectious, autoimmune or endocrine diseases, or to toxicities such as organophosphate or lead toxicity.
In Australia, from 2017 to 2018, there was an outbreak of megaesophagus linked to commercial dog food, which is thought to be contaminated in some way.
During this period, the incidence of megaesophagus in dogs in Australia has increased sevenfold compared to 2014.
More than 70 dogs were affected, although a contaminant was never isolated despite extensive investigations.
The most common form of acquired megaesophagus is idiopathic – which is a fancy way of saying the origin is unknown.
Chronic regurgitation is the main sign of idiopathic megaesophagus.
Affected animals typically lose their physical condition and are at increased risk of developing pneumonia by inhaling (aspirating) material, such as saliva, water, or food, instead of swallowing it.
Aspiration pneumonia can be life-threatening.
Other signs include a cough, which is usually secondary to aspiration pneumonia, increased salivation, or a runny nose.
A recent Australian study found that megaesophagus typically affects less than 1 in 100,000 dogs.
Diagnosis requires x-rays of the chest and neck area, as well as fluoroscopy (x-rays taken while an animal is swallowing).
Other tests, including blood tests, ultrasound, and advanced imaging, may be needed to rule out co-occurring conditions and underlying causes.
If an underlying cause is found and can be resolved, the outlook for affected animals is good.
If the cause is not known or treated, affected animals are at continued risk of aspiration pneumonia.
The treatment aims to minimize this risk.
Some animals do well when fed grits; others do better if their food is rolled into small balls.
Affected animals should be given smaller meals several times a day to reduce the risk of leaving food in the esophagus.
They should also be fed in an upright position, so that gravity can help move food from the mouth to the stomach.
A special chair – known as the Bailey chair – was developed for this purpose.
All of this care requires a significant commitment from owners.
And even with great care, aspiration pneumonia can still occur.
If you notice your pet regurgitating, see your veterinarian as soon as possible.
Renwick, M., et al., A case-control study to identify risk factors for idiopathic adult megaesophagus in Australian dogs, 2017-2018. BMC Veterinary Research, 2020. 16(1): p. 157.
Dr Anne quain, BVSc (Hons), MANZCVS (Animal Welfare), ECAWBM Dip (AWSEL) Ilecturer at the Sydney School of Veterinary Science and practicing veterinarian.