- When the esophageal muscles do not function properly, megaesophagus may develop.
- Megaesophagus in dogs falls into two broad categories: primary and secondary.
- Primary is inherited genetically and secondary typically develops due to other underlying causes.
- The most common symptoms include regurgitation of undigested food and failure to gain weight.
- Primary megaesophagus and secondary esophagus is often managed and not cured.
The canine digestive tract is relatively similar to the human digestive tract. Dogs take in food through their mouths. This food then travels to the stomach via a muscular tube known as the esophagus. From the stomach, food moves to the small intestine and then the large intestine, before finally exiting the body.
Within the esophagus, unconscious muscle contractions move food from the mouth to the stomach. In addition to this muscular tissue, there are sphincters at each end of the esophagus: the upper esophageal sphincter regulates the movement of food from the mouth to the esophagus, while the lower esophageal sphincter regulates the movement of food from the esophagus to the stomach.
In order for food to move properly from the mouth to the stomach, normal esophageal function is required. When the esophageal muscles do not function properly, a condition known as megaesophagus may develop. This is one of the most common esophagus problems in dogs.
What is Megaesophagus?
Megaesophagus in dogs is a condition in which the esophagus (the muscular tube leading from the mouth to the stomach) loses the ability to push food towards the stomach in a normal manner and becomes dilated or distended.
This leads to the accumulation of food and liquid within the esophagus. This accumulation can cause dogs to regurgitate. Dog regurgitation is somewhat similar to vomiting, except regurgitated food is undigested and expelled in a passive process. In contrast, vomiting involves the active expulsion of digested or partially-digested food.
Megaesophagus is an inherited condition in Miniature Schnauzers and Wirehaired Fox Terriers. Other breeds that are predisposed to megaesophagus include German Shepherds, Newfoundlands, Great Danes, Greyhounds, Irish Setters, Labrador Retrievers, and Shar-Peis.
Megaesophagus Causes in Dogs
Megaesophagus in dogs falls into two broad categories: primary megaesophagus (inherited) or secondary megaesophagus (which occurs as a result of another medical disorder).
Primary megaesophagus is a genetic condition. Dogs with primary megaesophagus often begin to demonstrate signs at an early age, staring at the time that they are weaned onto solid food. In rare cases, however, primary megaesophagus may not be apparent until adulthood.
Secondary megaesophagus typically develops later in life and it can have a number of possible causes. Direct injury to the esophagus, such as an obstructing foreign body that leads to esophageal damage, or esophageal disease, such as a tumor, can affect the function of the esophageal muscles. This esophageal muscle damage can lead to megaesophagus.
Diseases that affect the brain or the nerves that travel from the brain to the esophagus can interfere with the nerve signals responsible for normal function of the esophagus.
Other potential causes of secondary megaesophagus include:
- Myasthenia gravis (affects signals between nerves and muscles)
- Inflammatory myopathy
- Persistent right aortic arch
- Addison’s disease
- Canine distemper virus
- Snake envenomation (venom from a snake bite)
- Lead toxicity
- Organophosphate toxicity (poisoning from insecticides, medications, nerve agents)
Symptoms of Megaesophagus in Dogs
Dogs with megaesophagus have difficulty moving food from their mouths to their stomachs. For this reason, the most common signs include regurgitation of undigested food and failure to gain weight. You may also notice trouble swallowing or excessive salivation.
In some cases, regurgitated food and water may enter the lungs, resulting in aspiration pneumonia. This often leads to trouble breathing, fever, and other signs of pneumonia.
Signs that may be associated with megaesophagus in dogs include:
- Regurgitation (passive expulsion of undigested food)
- Failure to gain weight
- Weight loss
- Muscle weakness
- Increased salivation
- Bad breath
- Difficulty eating
If your dog has been diagnosed with megaesophagus and develops the following signs of aspiration pneumonia, contact your veterinarian immediately:
- Rapid breathing
- Changes in lung sounds
Aspiration pneumonia is a medical emergency and requires prompt treatment.
How to Diagnose Megaesophagus in Dogs
If your dog presents to the veterinarian with signs of megaesophagus, your veterinarian will first perform a full physical exam. In some cases, the veterinarian may be able to palpate (feel) the esophagus distended with air and food when rubbing your dog’s neck. The veterinarian will also look for signs of aspiration pneumonia and rule out other conditions that may cause similar clinical signs.
Your veterinarian may also recommend blood tests. Although there is no blood test that can specifically be used to diagnose megaesophagus, blood tests can help detect underlying conditions that may cause megaesophagus and can also rule out other medical conditions that could cause signs similar to megaesophagus.
Megaesophagus is typically diagnosed with radiographs (X-rays). In a dog with megaesophagus, radiographs typically show an enlarged esophagus filled with air or food. In some cases, your veterinarian may need to administer an oral contrast medium to your dog, to better outline the appearance of the esophagus on radiographs. In especially challenging cases, more advanced imaging techniques such as fluoroscopy (a live-action, X-ray movie) may be used.
Once your veterinarian has diagnosed your dog with megaesophagus, additional tests may be recommended to look for possible underlying causes of the condition. It is essential to look for the underlying cause of suspected secondary megaesophagus, because treating the underlying disease may cure the dog’s megaesophagus.
How to Treat Canine Megaesophagus
In cases of secondary megaesophagus, treatment depends upon the underlying cause.
The treatment of primary megaesophagus, however, consists entirely of supportive care. Dogs with megaesophagus should be fed from elevated food and water bowls, so gravity can help the esophagus move food and water towards the stomach. The dog should be fed in a standing position, with the head above the heart, and kept in that position for at least 10 minutes.
A Bailey chair for dogs can be used to assist with positioning. This megaesophagus chair functions like a child’s high chair, keeping the dog entirely upright during feeding.
While there is no specific megaesophagus dog food, many pet parents do find that dietary modifications can aid in the treatment of megaesophagus.
First, focus on feeding small, frequent, calorie-dense meals throughout the day. These are often better-tolerated than a single large meal. Next, experiment with different foods and consistencies. Some dogs will do best with a gruel, while others are more successfully able to eat small meatballs of food.
Can Megaesophagus in Dogs Be Cured?
Some cases of megaesophagus can be cured, depending on the dog’s underlying disease. Cases associated with toxicity, myasthenia gravis, hypothyroidism, polyradiculoneuritis, and a persistent right aortic arch have the best prognosis for cure.
Primary megaesophagus, or secondary esophagus due to other underlying causes, is often managed and not cured.
Medications to Treat Megaesophagus in Dogs
Sildenafil is an oral tablet that may be used to treat dogs with megaesophagus. This drug is given twice daily to relax the lower esophageal sphincter, allowing food to pass more easily from the esophagus into the stomach.
Other medications may be used to treat the underlying cause of megaesophagus or secondary aspiration pneumonia.
General Cost to Treat This Condition
The cost to treat megaesophagus varies considerably, depending on the severity of the condition. In some cases, megaesophagus may be manageable with simple feeding changes, with minimal associated financial expenses.
In dogs with aspiration pneumonia, hospitalization and aggressive treatment may be needed, costing thousands of dollars.
How to Prevent Megaesophagus in Dogs
While there is no genetic test for primary megaesophagus, the best method to prevent this condition is to avoid breeding affected dogs and avoid repeating matings that produce affected puppies.
Prevention of secondary megaesophagus relies upon the prompt diagnosis and treatment of conditions that may cause secondary megaesophagus.
- Aspiration pneumonia
- Myasthenia gravis