Page 298 - Clinical Manual of Small Animal Endosurgery

286 Clinical Manual of Small Animal Endosurgery

Just as in birds, the choanae themselves in the dorsal roof of the oral
cavity can be examined with the endoscope in a retrograde manner.

Tracheoscopy
Tracheoscopy can be performed, as in birds, with a long, slender endo-
scope. Many chelonia have a trachea that bifurcates cranially, behind the
head. This allows retraction of the head into the shell without resultant
kinking or compression of the trachea. Combined with tortuous primary
bronchi, this makes tracheoscopy difficult in these patients. The trachea
of snakes can be particularly long and narrow, and it is often not possible
to reach the lung lumen by this method. The outer surface of the lung
can be visualised by coelioscopy; surgical endoscopy of the interior of
the faveolar lung is also possible (see below, under coelioscopy). Tor-
toises, like birds, have complete tracheal rings, making the trachea much
more susceptible to trauma if endotracheal tubes are cuffed. In contrast,
lizards and snakes have C-shaped tracheal cartilage rings, similar to
mammals.

Otoscopy
Similar to birds, otoscopy has very limited application in reptiles. Lizards
have a shallow, wide external ear canal, if any, with a tympanic mem-
brane that is easily visible to the eye. Tortoises have a tympanic mem-
brane flush with the skin and no external ear canal at all, and snakes
have no ears. Skin mites could be visualised in the ear, but are usually
easily demonstrated elsewhere on the body by simpler means. Endo-
scopic examination of the middle ear can be used after a myringotomy
has been performed in lizards and tortoises to remove an ear abscess,
to help visualise whether all necrotic and purulent material has been
removed.

Oral endoscopy or stomatoscopy
While the majority of reptiles have relatively widely opening mouths,
and hence are easily visualised in comparison to birds and small exotic
mammals, oral endoscopy can be used to enhance visualisation of the
back of the mouth in small chelonians, and can help visualise the entrance
to the Eustachian tube which may contain caseous material in tortoises
with middle-ear infections and abscessation.

Rigid endoscopy of the upper gastrointestinal tract
As in birds, a sheathed endoscope can be used to examine the pharynx,
oesophagus and stomach, and insufflation can be provided with a syringe
of air attached to the sheath, or a visual space created by instillation of
warm fluid. Rigid oesophagoscopy and gastroscopy is particularly useful