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Megaoesophagus/megaesophagus (MO/ME) in dogs
The oesophagus (gullet) is a muscular tube that actively propels food from the mouth to the stomach. Most diseases that affect the oesophagus lead to widening of the tube hence ‘megaoesophagus’.
The classic presenting clinical sign of oesophageal disease is regurgitation. This is the passive return of food (often in a sausage shape) or saliva (‘whipped egg whites’), often many hours after eating. Sometimes gurgling and sloshing of oesophageal contents can be heard. Regurgitation is distinguished from vomiting; an active process accompanied by signs of nausea and rhythmic retching. Because normal protective reflexes are not initiated during regurgitation, food content may enter the airway leading to aspiration pneumonia, so breathing difficulties, fever and coughing may be seen in dogs with MO.
Megaoesophagus in dogs may occur when there is a physical obstruction, such as in puppies with an abnormal development of the vessels in the chest leading to a ‘vascular ring anomaly’, with lumps within the chest cavity or with strictures. Alternatively, megaoesophagus in dogs may be seen with generalised diseases causing muscle weakness, such as hormone deficiency states. Irritation of the lining of the oesophagus (oesophagitis) may be a primary cause or a consequence. Diseases of the nerves, the nerve-muscle junction or the muscle of the oesophagus form the final group of causes. Often a definitive cause is not proven, which is designated ‘idiopathic’.
Confirmation of megaoesophagus in dogs may require radiographic studies (see figure showing outline of air-filled oesophagus and pneumonia). These should be obtained without sedation or anaesthesia to avoid misdiagnosis. Blood tests look for metabolic disease and evidence of response to infection. A blood test for myasthenia gravis (a disease of the nerve-muscle junction) is often indicated. Abnormal oesophageal function may be studied by real-time X-ray (fluoroscopy).
Endoscopy may be indicated to determine whether there is irritation of the oesophagus or other gastrointestinal disease. Tests for muscle disease may include EMG (testing for abnormal electrical activity) or, in some cases, biopsy.
If a specific disease is diagnosed, then this should be treated, although that may not result in the return of normal oesophageal function. Physical obstructions are surgically treated if possible. Aspiration pneumonia is treated with aggressive antibiotic treatment and supportive care as necessary. The mainstay of management is feeding to minimise the potential for regurgitation. Food is typically fed from raised bowls. Some patients cope best with a ‘slurry’ type preparation of food, whereas others are better with more solid food such as hand-moulded balls of tinned diet. Trial and error is the only way to determine what works best. Holding the patient upright after feeding is also indicated.
In some circumstances e.g. prior to surgical management in a debilitated animal, by-pass of the oesophagus may be needed for short term nutritional support and may be achieved by surgical or, if appropriate, endoscopic placement of a gastrostomy tube. If the oesophageal disorder is permanent and oral alimentation is not possible, placement of a permanent gastrostomy feeding tube can be considered; the success rate of this approach is not documented.
The outlook for patients with megaoesophagus in dogs (MO) is variable. Some do very well but others either continue to regurgitate despite treatment or succumb to pneumonia. Outlook is, unfortunately, unpredictable.
If you are concerned about the health of your pet you should contact your veterinary surgeon.