Practical Gastrointestinal Endoscopy

184
CHAPTER 7
Piecemeal removal is
safer (although less satisfactory
for the pathologist).
submucosal injection can be used to elevate the polyp tissue
before snaring (see below).
Move the closed snare to andfro as a measure of safety having snared
all or part of a sessile polyp; if the mucosa moves, but not the bowel
wall, there is no danger. If the colon moves with the snare, the full
thickness of the wall has been ‘tented’ dangerously (Fig. 7.32b)
and the snare should be repositioned to take only a smaller part.
If the base of a protuberant polyp is over 1.5·cm in diameter, with
no stalk, the safe course is to take the head piecemeal in a number
of bits (Fig. 7.33); each bit can be cut through with no risk of fullthickness
burns and little risk of bleeding, since the vessels of
the head are much smaller than those in the stalk. With the submucosal
injection technique describedbelow, however, it may be
possible to remove flat sessile polyps up to 1.5–2·cm in diameter
in a single specimen, and much larger ones piecemeal.
Injection polypectomy
(a)
(b)
(c)
Fig. 7.34 Injection polypectomy.
(a) A small sessile polyp … (b)…
is elevated by submucosal saline
injection … (c)… and snared off
in one piece.
Submucosal saline injection elevates sessile polyps for easier removal,
a technique common in proctology and originally described
for colonoscopic use in 1973. Injection has become a frequent
routine, initially with the intention of obtaining small sessile
polyps (flat adenomas) as a single histopathological specimen
(Fig. 7.34). ‘Injection polypectomy’ or endoscopic mucosal resection
(EMR), as it is often called, can also be invaluable for the
removal of much larger polyps, having the double advantage of
creating a bloodless plane for transection and a ‘safety cushion’
of engorged submucosal stroma that protects the bowel wall
from heat damage. Injection can also be with normal saline
(0.9%) or 1·:·10·000 epinephrine in 0.9% saline, but this absorbs
in 2–3 minutes, so snaring needs to be reasonably quick. To
make the injected bleb last longer, a hypertonic solution can
be injected (2·N saline, 20% dextrose or hyaluronic acid have
all been used, with or without epinephrine). Some experts add
a few drops of methylene blue when making up the solution,
the blue showing up the extent of the submucosal bleb. With
a 10·mL syringe attached, the sclerotherapy needle is either
jabbed tangentially into the mucosal surface adjacent to the
polyp or directly through the polyp tissue. A relatively slow,
low-pressure injection gives time, if necessary, to withdraw the
needle slightly until a submucosal bleb is seen to be forming.
The ‘plane of separation’ in the submucosa for successful injection
is surprisingly superficial and the tendency is to inject too
deep, although there is no hazard involved should the needle or
solution pass into the peritoneum (or the peritoneal cavity). An
injection of 1–3·mL should be enough to raise the submucosa
below a small polyp for immediate snaring, but 20–30·mL may
be needed for larger polyps.