Megaoesophagus associated to inflammatory infiltrate in the autonomous plexus in a 7-year-old Spanish Water Dog

Megaoesophagus (ME), a disorder of the oesophagus characterized by diffuse oesophageal dilation and decreased peristalsis that may be congenital or acquired. Knowledge regarding the aetiology and prognosis for canine acquired ME is currently limited with most cases being idiopathic, which is a considerable problem to implement an appropriate treatment and a potential better prognosis.

A 7-year-old, neutered, female Spanish Water Dog was evaluated for progressive weight loss, chronic vomiting and regurgitation. The patient did not present other clinical signs. The contrast radiography in the cervical zone revealed oesophageal dilation. Eventually, the endoscopy revealed a marked dilation of the oesophagus. A surgery was conducted to insert a gastrotomy feeding tube. Initially, the patient response to this treatment was positive. However, the vomiting and regurgitation reappeared after 8 days. Due to the grim prognosis the owners elected to euthanize the patient. Necropsy revealed severe oesophageal dilation. The histopathological evaluation revealed moderate erosive catarrhal oesophagitis and gastritis. The skeletal muscular layer of the oesophagus showed moderate angular atrophy of some muscular fibres and a severe infiltrate of lymphocytes with marked tropism to autonomous neuronal bodies, some of which showed severe degenerative changes with absence of Nissl corpuscles, pyknotic nuclei and eosinophilic cytoplasm. The immunohistochemical study revealed that the majority of the infiltrate surrounding neuronal bodies were CD3 + T cells. These findings are consistent with an immune-mediated megaoesophagus.

To the best of our knowledge, this is the first report describing a lymphoplasmacytic infiltrate surrounding the oesophageal myenteric plexus in an adult dog with no other clinical signs or other myopathies. With these results, the authors hope to raise awareness in the diagnostic of canine ME and include an immune-mediated cause that lean to the establishment of appropriate treatment and improve prognosis of this condition.