Page 245 - Clinical Manual of Small Animal Endosurgery

Upper Respiratory Tract 233

source, as this provides the brightest and whitest light for the coolest
temperature available. Halogen light sources are available and quite
inexpensive but the light produced is generally of a lesser intensity with
a slight yellow hue.
Irrigation fluid can be delivered via a pressure bag or gravity feed, or
via a purpose-built endoscopic irrigation pump.
The majority of rhinosinusoscopy is performed with rigid endoscopes.
The most commonly used rhinoscope in my arsenal is the 2.7 mm-
diameter, 30° paediatric cystoscope. Manufacturers commonly market
this endoscope as a ‘multipurpose rigid endoscope’. This designation is
appropriate given the multiplicity of procedures that this one endoscope
can perform. The scope can be housed in either a cystoscopy sheath or
an arthroscopy sheath. The cystoscopy sheath has a beveled, angled
distal aperture equal to the 30° angle of the optical end of the endoscope.
This allows for a more even laminar flow of irrigant over the lens of the
endoscope, providing a cleaner, debris-free image. This sheath also has
dual two-way stopcock ports for fluid ingress and egress and an instru-
ment channel port. The downside to this sheath is the slightly larger
resultant external diameter relative to the same scope in the arthroscopy
sheath. The arthroscopy sheath has a single fluid-irrigation port, but is
narrower in diameter, allowing for an easier fit into small-diameter
luminal spaces. Operator preference dictates which sheath is used. This
author uses the standard paediatric cystoscope sheath for the majority
of procedures and will employ the arthroscopy sheath for particularly
narrow spaces in smaller dogs and many cats.
Smaller-diameter rigid endoscopes with similar sheaths are also avail-
able for use in small canine and feline patients. This author rarely uses
these devices, for several reasons. Firstly, the smaller diameter results in
a small optical field of view. Secondly, these scopes are quite delicate and
susceptible to damage (I have broken more than my fair share of these
scopes!). Still, their small diameter gives them great utility in some ana-
tomical situations.
These rigid endoscopes can also be used quite effectively in endoscopy
of the frontal sinus, which will be discussed later in this chapter.
While the focus of this chapter is on rigid endoscopy of the upper
respiratory tract, a complete rhinoscopic examination does require the
use of a small-diameter flexible endoscope. These scopes are usually
found as fibreoptiscopes (rather than true video endoscopes) and range
in external diameter from 2.9 to 4.1 mm. These scopes generally have
two-way deflection and a small-diameter instrument channel with an
optional bridge that can allow for simultaneous irrigation and instru-
mentation placement. These scopes are requisite for ‘J manoeuvre’ evalu-
ation of the posterior nares and adjacent soft palate.
When rigid tracheoscopy is indicated, the previously mentioned endo-
scopes can be employed. However, the length of the scope is often the
limiting factor. In larger patients the author has employed a 5 mm
forward-view laparoscope to achieve a more distal view of the trachea.