Page 794 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Gastrointestinal system: 4.1 The upper gastrointestinal tr act 769

VetBooks.ir 4.95 4.96

Fig. 4.95 Grass-stained bilateral nasal discharge Fig. 4.96 Oesophagoscopy revealing normal
associated with an oesophageal obstruction (choke). oesophageal mucosa (distended).

until swallowing is elicited and then advanced with the pharynx to avoid retroflexion of the end of
care. Measuring scale marks can be helpful to iden- the endoscope into the oral cavity, with resultant
tify the distance of any obstruction from the nares. crushing of the end of the endoscope. This can be
When viewed from the left side of the neck the NG avoided by the placement of a Hausemann’s gag
tube can usually be seen descending the cervical for oesophagoscopy, or by passing a short wide-
oesophagus dorsal to the trachea. Severe resistance bore NG tube into the cranial oesophagus before
to the passage of the NG tube indicates an oesoph- introducing the endoscope. The lubricated scope
ageal obstruction and attempts to force the tube is passed all the way down the oesophagus, while
through, or past, the obstruction are contraindi- inflating the lumen using the air pump to inspect
cated and may lead to oesophageal wall perforation. the mucosa as far as the stomach; however, it is
The absence of a swallowing reflex may indicate the more easily viewed while withdrawing the endo-
presence of neurological dysfunction, which should scope distad to proximad. Constant irrigation will
be considered in the context of other neurological also be necessary to remove any food or mucus and
deficits. A thorough oral examination should also be to identify small mucosal lesions or perforations.
performed to check for any pharyngeal obstructions The normal oesophagus is collapsed with longi-
or causes of an oral dysphagia. tudinal folds, which flatten when it is distended.
Good distension is required to avoid missing small
Oesophagoscopy focal or longitudinal oesophageal perforations. If
Oesophagoscopy is the most effective way to exam- the oesophagus is obstructed with food, the cranial
ine the lumen of the oesophagus and is safe and end of the bolus and the type of feed can be identi-
convenient to perform in the conscious sedated fied, but visibility is poor in the presence of food
horse (Fig. 4.96). A 2 m endoscope is sufficient and saliva in the lumen. Mural or intrathoracic
to reach the cardia in most horses, although a 3 m masses such as tumours or abscesses can occlude
gastroscope can also be used for gastroscopy. Care the oesophageal lumen from externally, causing
must be taken when passing the endoscope into secondary obstruction (choke).