Practical Gastrointestinal Endoscopy

THERAPEUTIC COLONOSCOPY 187
peritoneal (below the peritoneal reflexion) and may sometimes
be better removed by local proctological techniques, which often
produce a single large specimen for optimum histology—rather
than the chaos of fragments resulting from endoscopic piecemeal
snaring. Anesthesia allows anal dilation and a two-handed
approach for injection and scissor-excision, with the potential to
ligature or suture bleeding points if necessary. A failed endoscopic
attempt to remove such rectal polyps forms scar tissue,
which hinders submucosal epinephrine injection and excision
by the proctologist, so the endoscopist’s decision to refer should
be made on the basis of visual assessment alone. Only 1·:·200·000
epinephrine solution is used in the rectum (compared with 1·:
·10·000 solution in the colon) because very large volumes may
be needed and there is risk of communication to the systemic
circulation, and danger of serious cardiac dysrhythmias. Sessile
polyps more than 12·cm above the anal margin can alternatively
be reached with a Buess operating sigmoidoscope (transanal
microsurgery or TEMS), where this is available, but will more
often be managed by the flexible endoscopist using injection and
piecemeal removal with argon plasma coagulation.
Smaller rectal polyps close to the anal canal can be snared in retroversion
after local anesthetic injection, unless the polyp is very small
and quick to snare (perhaps by ‘cold-snaring’). The distal 3–5·cm
of the rectal ampulla is otherwise difficult to visualize properly
and is also richly supplied with sensory nerves, a heat burn causing
the same pain as it would on exterior skin.
Large stalked polyps
The ‘large’ size of a polyp is sometimes an illusion because the
visual judgment of size is made relative to the diameter of the
colon lumen. Proximal colon and cecal polyps thus tend to be
larger than they look at first sight. In the narrowed lumen of diverticular
disease, polyps that appear large may prove on snaring to
be significantly smaller.
In snaring a large stalk, extra electrocoagulation is needed to
minimize the increased chance of bleeding from the relatively
large plexus of stalk vessels, and extra care (and time) should be
taken to optimize things before starting:
1– Check that an epinephrine-filled injection cannula can be rapidly
available in case of bleeding, and probably a clipping device and
nylon EndoLoop® as well.
2–Palpate and move the stalk around using the closed snare to
judge its diameter, length and mobility.
3–Get the best view possible; if necessary rotate the endoscope or
change patient position (Figs 7.21 and 7.37).
4 –Place the snare optimally on the narrowest part of the stalk to ensure
maximal current density.
(a)
(b)
Fig. 7.37 (a) Bad view of a polyp?
(b) Change the patient’s position
to let gravityhelp.