Practical Gastrointestinal Endoscopy

172
Practical Gastrointestinal Endoscopy: The Fundamentals, Fifth Edition
Peter B. Cotton, Christopher B. Williams
Copyright © 2003 by Blackwell Publishing Ltd
7
Therapeutic Colonoscopy
EQUIPMENT
The equipment requirements for endoscopic polypectomy are
few, and in many ways the fewer the better. It adds significantly
to safety to be completely familiar with one electrosurgical unit,
and only a few accessories, since from this familiarity it becomes
easy to recognize when polypectomy is going right and when it
is not.
Snare loops
Use one commercial
snare type for familiarity.
Fig. 7.2 Mark the handle when
the loop is fully closed.
Fig. 7.3 Polyp tissue can be
trapped in the snare, reducing its
efficiency.
Be familiar with the type of snare used. For anyone doing a limited
number of polypectomies it is advisable for endoscopist and
assistant to be familiar with one or two snare types only. Several
makes of snare loop are available, and different handle characteristics
and wire thicknesses greatly affect control of polypectomy.
Single-use snares have the advantage of always being in
good condition and predictable. Reusable snare loops and wires
can become deformed or may be reassembled into non-standard
plastic outer tubes. Many endoscopists prefer to use a standard
larger snare (2.5·cm diameter) and a ‘mini-snare’ (1·cm diameter
for smaller polyps) and specialist spiked, barbed or stiffer snares
are available for sessile polyps (Fig. 7.1). Various configurations
of snare loop or variations of handle are available, but are mainly
a matter of personal preference.
With any snare there are several points that should be checked
before starting polypectomy:
1–Mark the snare handle with a pencil or indelible pen at the point that
the snare is just closed to the tip of the outer sheath (Fig. 7.2). This
is arguably the single most important safety factor in polypectomy.
It allows the assistant to stop snare closure before the wire
closes too far into the tube and there is danger of a smaller stalk
being cut off by ‘cheese-wiring’ mechanically without adequate
electrocoagulation; it also warns if the stalk is larger than apparent
or head tissue has become entrapped (Fig. 7.3). Marking
can also, but less conveniently, be performed after insertion by
looking for the moment when the wire emerges from the snare
catheter. Many snare handles have marker numbers moulded
in or printed on, but making a physical mark is safer—because
the mark proves that the point of wire closure has been exactly
checked, and it is easier to see.