Megaesophagus is a condition characterised by a widening (or dilation) of the esophagus, which is a muscular tube which connects the throat to the stomach.
Normally, when the cat eats, the esophagus senses the force of the food on the walls, which initiates the process of muscle contraction, pushing the food down to the stomach, this is known as peristalsis.
Megaesophagus is a multi-factoral disorder in which nerves and/or muscle dysfunction which affects the ability of the esophagus to constrict and push food from the throat to the stomach. Dysfunction of the muscular contractions is known as dysmotility. As a consequence, when the cat eats, food builds up in the esophagus, eventually causing regurgitation (passed back out).
Not only is the cat not receiving adequate nutrients, but the presence of food sitting in the throat also predisposes him to aspiration pneumonia, where the regurgitated food is accidentally inhaled during an episode of regurgitation.
Megaesophagus can be mild, with only a small portion of the esophagus affected, or the entire esophagus is affected.
What is the difference between regurgitation and vomiting?
Regurgitated food tends to look the same as before it was consumed, vomited food is more sausage-like in appearance.
Vomiting appears effortless, the cat opens his mouth and out it comes, compared to vomiting which is an active process, which will consist of gagging, retching and the sides will heave.
What causes megaesophagus?
The condition may be congenital, meaning present at birth, or acquired. It may be permanent or may be transient (such as with tick paralysis). Siamese and related breeds are predisposed to congenital megaesophagus.
Acquired megaesophagus may be primary or secondary and has several possible causes. Remember that the esophagus is a muscular tube, so any condition which affects the muscles can cause megaesophagus.
Vascular ring anomality (persistent right aortic arch) – A congenital disorder in which a fetal blood vessel known as the right aortic arch fails to disappear as they should post birth. This vessel passes close to the esophagus and can cause it to become compressed, blocking the flow of food to the stomach.
Myasthenia gravis – A congenital or acquired neuromuscular disorder which is characterised by muscle weakness. All muscles are controlled by their own nerve. The nerve doesn’t directly connect with the muscle, there is a small gap between the two which is known as the neuromuscular junction. In order for a message to be transmitted from the nerve to the muscle, a chemical messenger is necessary to bridge the gap, this is known as acetylcholine, where it travels from the end of the nerve and attaches to a receptor on the muscle called a acetylcholine receptor. Cats with with myasthenia gravis have an abnormal transmission between the two. There are two forms, congenital or acquired, in cats with acquired MG, the body’s own immune system antibodies attacks the acetylcholine receptors.
Glycogen storage disease – An inherited disorder affecting some Norwegian Forest cats characterised by an inability to metabolise glycogen, a stored form of sugar in the body. Glycogen builds up in the tissues including the muscles which can lead to muscle weakness.
Dysautonomia – A rare condition characterised by an inability of the autonomic nervous system (which works without conscious control) to function properly. The esophagus is a part of the autonomic nervous system and as such, may be affected in cats with this condition.
Addison’s disease (hypoadrenocorticism) – An endocrine disorder caused by a deficiency of corticosteroids that are produced by the adrenal glands. This disease can cause muscle weakness in cats.
Inflammation of the esophagus.
Lesions on the esophagus.
Thymoma – A tumour arising from the thymus gland in the chest.
Certain toxins which cause paralysis including botulism, tetanus, paralysis ticks, Australian tiger snake.
Lead and thallium poisoning.
Esophageal obstruction. Foreign body, hiatal hernia, tumour or stricture.
Hypothyroidism (extremely rare in cats).
Congenital or acquired idiopathic (no known cause).
What are the symptoms of megaesophagus in cats?
Symptoms can vary depending on the area affected. In cats with congenital megaesophagus, symptoms usually appear at the onset of weaning although in some cases nursing kittens may also regurgitate milk through their nose, this is known as milk nose.
Regurgitation of food
Coughing and/or gagging
Stunted growth in kittens
If aspiration pneumonia occurs, your cat may experience additional symptoms including:
How is megaesophagus diagnosed?
Your veterinarian will obtain a medical history from you including the onset of symptoms, what the vomit looks like, how soon after eating does your cat vomit, if your cat has any known medical conditions.
Diagnosis is twofold, diagnose megaesophagus and the underlying cause. This may include:
Routine tests including complete blood count, biochemical profile and urinalysis can’t diagnose megaesophagus, but may be of help in identifying an underlying cause.
Xray of the esophagus and chest which may reveal an enlarged esophagus filled with gas, fluid or food, persistent right aortic arch, blockages, tumours and foreign body.
Barium contrast sudy is a test in which barium is swallowed by the cat and then a series of x-rays are performed to visualise the esophagus. Barium is a radio-opaque, meaning that it shows up as bright white on x-rays making it easier for the veterinarian to visualise the esophagus.
Fluoroscopy is another test your veterinarian may choose to carry out to evaluate the esophagus. This test uses x-rays in real time to evaluate the esophagus.
Esophagoscopy is a procedure in which an endoscope, which is a flexible, thin plastic tube with a lens at one end and a video camera at the other, is inserted into the mouth and used to examine the interior of esophagus as well as look for blockages, lesions, inflammation, tumours and foreign objects.
Additional testing will be required to determine if there is an underlying cause based on your veterinarian’s index of suspicion.
Blood test to look for antibodies directed towards acetylcholine receptor in cats suspected of having Myasthenia gravis.
ACTH stimulation test which measures the ability of the adrenal glands to respond to a hormone known as adrenocorticotropic hormone (ACTH) which is made by the pituatry gland. This hormone travels through the blood stream to the adrenal glands where it stimulates the secretion of hormones such as hydrocortisone. The ACTH stimulation test measures the levels of cortisol after an injection of a synthetic form of ACTH.
ACTH stimulation test: This test measures the ability of the adrenal glands to respond to a hormone known as adrenocorticotropic hormone (ACTH) which is made in the pituitary gland, travelling through the bloodstream to the adrenal glands where it stimulates the secretion of other hormones such as hydrocortisone from the cortex. The ACTH stimulation test measures levels of cortisol in the blood before and after an injection of synthetic ACTH. – See more at: http://www.cat-world.com.au/addisons-disease#sthash.ltJuLzcg.dpuf
How is megaesophagus treated?
Treatment depends on the underlying cause if one can be established. In some cases, once the underlying condition is treated, the megaesophagus may resolve.
In emergency cases, a temporary feeding tube may be placed in your cat to provide nourishment.
For cats with megaesophagus which can’t be reversed by treatment, the aim is to prevent aspiration pneumonia and ensure adequate nutrition. This may include:
Feeding cats in an upright position to help gravity move down the esophagus. The recommended angle is 45-90 degrees from the floor and the cat should remain in that position for 10-15 minutes after eating. Some suggestions include placing the bowl on a table which is too small for your cat to sit on so he has to eat standing up, holding your cat in an upward position while you, or somebody else feeds him, I have even seen one cat held upright in a sling.
Feeding a high-calorie liquid slurry instead of firmer food.
Feeding smaller but more frequent meals 3-4 times a day.
Metaclopramide or Cisapride are medications which can help to increase motility in the esophagus.
For cats suffering from aspiration pneumonia, additional antibiotics and supportive care such as oxygen therapy will be required.
What is the prognosis for cats with megaesophagus?
This depends on the underlying cause. For cats with aquired megaesophagus, if the condition can be treated, the outcome is positive. For cats with idiopathic or congenital megaesophagus, the prognosis is guarded.
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