What does the esophagus do?
The canine esophagus is the tube that connects the throat to the stomach. It plays a vital part in the transportation of food through coordinated contractions. So, what happens when the esophagus isn’t working as it should? A disease called Canine Megaesophagus can occur. But what is this and what can you do about it? Take a read below!
What is Megaesophagus in dogs?
Megaesophagus is not a single disease. It is a combination of disorders. At the end resulting in esophagus dilation and losing its motility.
The esophagus is a complex muscular tube. It consists of two layers of skeletal muscles with two sphincters on each end. The one closest to the mouth remains closed at all times, except when the dog swallows. The other one. Closest to the stomach. It is not a true sphincter, it can be closed by surrounding tissue.
Neurological reflexes cause the contractions of the esophagus and the opening of sphincters. When these reflexes get interrupted the esophagus can no longer transport the food. Instead, it loses tone and dilates. This flaccid and air-filled esophagus is megaesophagus.
Common causes of Megaesophagus in dogs
Megaesophagus can either be congenital (the dog is born with it) or acquired.
In congenital cases, the puppies are born with megaesophagus. But, it often isn’t discovered until they start eating solid food. In mild cases, it might not be diagnosed until they’re a year old. The pathophysiology is unclear, but research suggests that it is in part due to a fault with the Vagus nerve.
The most common signs are regurgitation and failure to thrive.
Some breeds seem to have a higher prevalence of the conditions, these include:
- Miniature Schnauzers
- Great Danes
- German Shepherds
- Labrador retrievers
With acquired megaesophagus, the condition is often discovered later in life. Often in young adults and middle-aged animals. There are several potential causes.
Myasthenia Gravis is a neurological disease. It is the most common reason for megaesophagus in dogs. Myasthenia gravis is an immune system condition. Here the immune system destroys the junctions between the muscles and nerves. The muscles in the esophagus simply don’t receive the signals from the nerves.
Any dog breed can get Megaesophagus. But some have an increased risk for developing myasthenia gravis. These include:
- German shepherds
- Labrador retrievers
Other conditions that can cause Megaesophagus in dogs are:
- Strictures: Scarring or tumors in the esophagus can cause strictures. This is however not true megaesophagus, as the muscles are still working.
- Addison’s disease: A disease causing deficiency of cortisone. Normally produced in the adrenal gland. This alters the metabolism of esophageal muscles and they become smaller.
If possible, the underlying diseases need identifying. But, the majority of cases of megaesophagus in dogs are idiopathic.
In cases with acquired megaesophagus, the most common symptom is regurgitation. It is important to distinguish between true vomiting and regurgitation.
Vomiting is when stomach contents get expelled from the stomach. This happens through the active movement of the abdominal muscles. Often accompanied by retching. Bile will also only be present in vomit.
Regurgitation is a passive motion producing food and/or liquid. This can happen straight after a meal or several hours later. Often the food is a tubular shape but is not digested.
Other symptoms may be ptyalism (drooling), halitosis (bad breath), or vomiting.
When regurgitation occurs the food can move into the trachea. This can cause aspiration pneumonia. If this has developed, associated symptoms can be:
- Nasal discharge
In the dogs where Myasthenia gravis is the cause for Megaesophagus, symptoms vary. They depend on which form of the disease is causing Megaesophagus. Local Myasthenia gravis may only affect the esophagus. With megaesophagus being the only symptom. Generalized Myasthenia gravis may display generalized muscle weakness.
Are there diagnostic tests for megaesophagus?
When a sick animal is brought to the clinic, a physical exam must always be the first step. The animals can be either bright and alert, if not yet badly afflicted. Or, they can be lethargic. Especially if the condition has developed into aspiration pneumonia. Some patients may also present with significant weight loss.
To diagnose Megaesophagus the veterinarian will need to do x-rays/radiographs. Often it can be diagnosed on plain film. The clinician should, if possible, avoid using barium contrast. If the condition is present, it can be aspirated into the lungs. However, this can sometimes be the only way to definitely make the diagnosis.
Looking at the same x-rays, it is also important to try and determine whether the dog has aspirated any food or liquid into the lungs. This is to diagnose whether aspiration pneumonia is already happening. Remember: Even though the chest x-rays are clear, it does not mean that aspiration pneumonia cannot happen in the future.
When Megaesophagus is confirmed, an underlying cause is investigated. But, despite a variety of diagnostic tests available, the majority of Megaesophagus cases are idiopathic. Meaning no underlying cause is found.
How is Megaesophagus in dogs treated?
If no underlying cause can be confirmed, Megaesophagus is not curable. But, the symptoms can be alleviated. Remember to always contact your veterinarian before administering any kind of medicine.
It’s important to first determine whether the dog will do better on a different diet. Some dogs experience milder symptoms when on a liquid diet rather than solids. Or vice versa. If liquids are an issue water can possibly be given as ice cubes.
Dogs with Megaesophagus are often undernourished. Protein supplements can be necessary to ensure enough protein in the diet.
Elevated feeding and the chair
To combat the effects of gravity on regurgitation, elevated feeding can help. Place the food on a raised platform. This will force the dog to stretch its neck upwards when eating. This means gravity will allow the food to descend into the stomach, instead of regurgitating it back up.
Sometimes elevated feeding isn’t possible. Often due to the dog being unwilling to eat in that position. A Bailey-chair is an option. Looking similar to a baby chair. The dog is placed in the chair, sitting on its butt with its back straight. This allows for easier feeding. It also restrains the patient for the mandatory post-feeding waiting period. These can either be homemade by the owner or bought.
If elevated feeding or the chair isn’t an option, a gastric feeding tube can be necessary. The tube is placed on the side of the dog, where it is comfortable. This allows the food to be placed directly into the stomach. The dog will still regurgitate saliva, but food regurgitation should be minimal.
Some medications can be given to minimize the symptoms of Megaesophagus.
- Sildenafil: Known also as viagra. Will help the sphincter between the esophagus and the stomach stay open. Allowing the food to get into the stomach.
- Sucralfate: An antacid. It protects the lining of the esophagus from any stomach acid that may be pushed into it.
Megaesophagus is in most cases a chronic condition. It needs long term treatment and monitoring of the individual patient.
Megaesophagus is at times a complicated disease. It can be debilitating for the dogs regurgitating food and liquids. It can also be difficult to manage for the owner. But, with the right therapy and plenty of owner compliance, many dogs can live long and happy lives!
Catharina is a Veterinary Medicine student from Uni of Copenhagen. When she isn’t making camp in the library, stuck to the books, she’s also a writer and avid photographer. Capturing everything from buildings to dogs – especially her poodle Bailey is a frequent subject.