Page 291 - Clinical Manual of Small Animal Endosurgery

Small Exotic Animal Endosurgery 279

an endotracheal tube. Intermittent positive-pressure ventilation (IPPV)
should be provided as birds usually hypoventilate under anaesthesia and
with increasing anaesthetic duration, so there is an increased likelihood
of a fatal hypercapnia developing. Capnography is far more useful in
monitoring avian anaesthesia than pulse oximetry.

Tracheoscopy
Tracheoscopy is useful for syringeal Aspergillus species fungal granulo-
mas, which usually manifest in parrots as a sudden ‘change in voice’,
and small foreign bodies such as inhaled seeds, that typically lodge at
the tracheal bifurcation. It is of course essential to adequately stabilise
these patients, which may be in respiratory distress, before undertaking
anaesthesia and endoscopic examination. The major hurdle to tracheos-
copy in birds is the narrow tracheal lumen which tapers towards the
tracheal bifurcation, where pathology often occurs, and the relative
length of the trachea. However, while tracheal occlusion and asphyxia-
tion would be a real risk in small mammals, birds have the advantage
that a coelomic air-sac tube can be inserted to allow ventilation and
anaesthesia, even if the tracheal lumen is completely obstructed by the
endoscope. A coelomic air-sac tube can be inserted into the same left
lateral coloemic location as coelioscopy is performed (see below). Some
practitioners do not insert an air-sac tube, choosing very brief intermit-
tent tracheoscopy periods. However, it should be remembered that – as
most patients are being examined via this method because of respiratory
distress or disease – there are high risks with anaesthesia, which should
be explained to owners. In smaller parrots a 1.9 mm, 18 cm-long endo-
scope is needed. This has the disadvantages of being fragile, and giving
a smaller image; also, due to its thin and hence sharp nature, it can also
cause traumatic injury to the trachea. In larger birds the 2.7 mm or even
4 mm endoscope can be used, but in these cases prior placement of a
coelomic air-sac tube is strongly advised. These larger-diameter endo-
scopes also allow the opportunity for a brief initial coelioscopy to evalu-
ate any lower air-sac or pulmonary disease before tracheoscopy. In
raptors it should be noted that tracheal nematodes such as Syngamus
spp. or Capillaria spp. may be encountered, and these can be pushed by
the inserted endoscope to form an obstructive tracheal plug, with sub-
sequent asphyxiation on recovery.

Cloacoscopy
Cloacoscopy is useful in birds for haematochezia/haematurea, in visualis-
ing typical cauliflower-shaped cloacal papillomas, cloacitis (which may
manifest as raised or pseudomembranous plaques), salpingitis and
enteritis. Biopsy techniques need to be careful, as exuberant taking of
biopsies can result in cloacal perforation and resultant coelomitis. A
sheathed endoscope may be used for inflation with warmed saline for