Practical Gastrointestinal Endoscopy

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CHAPTER 7
process. Snaring has the advantage over hot-biopsy of squeezing
the polyp base, so reducing the area and depth of electrocoagulation
damage to the remaining mucosa and underlying blood vessels.
Some endoscopists go further and advocate ‘cold snaring’
without electrocoagulation, particularly in the proximal colon,
physically pulling through the base of the small snared polyp in
order to avoid any risk of heat ulceration and delayed bleeds.
Snaring very small polyps can be technically difficult and the specimens
are not infrequently lost. Use of the filtered suction trap for retrieval
is a significant improvement over the older mucus aspiration
trap (designed for bronchoscopy or neonatal care), because
each specimen is trapped in a separate numbered compartment
and the incorporated filter prevents specimen loss even if excess
fluid has to be aspirated. Putting a gauze in the suction line is
cheaper for single polyps.
‘Hot biopsy’
(a)
(b)
(c)
Fig. 7.29 (a) Hot biopsy forceps
grasp the small polyp and pull
up… (b)…then coagulate until
there is ‘snow on Mount Fuji’…
(c)…pull off the biopsy sample,
leaving the coagulated polyp
base.
Hot biopsy forceps are a quick and effective way of destroying
the smallest (1–4·mm) polyps (Fig. 7.29a), in spite of some bad
press due to occasional bleeding complications. They have the
particular virtue of yielding over 95% of interpretable histology—compared
with the frequent specimen losses after snaring.
Histology is potentially important in managing a patient
because the total number of adenomas is the most important
predictor offuture risk of neoplasm, so should influence advice
on follow-up (see below). The hot biopsy forceps are only different
from conventional diagnostic forceps in having a plastic insulation
outer sheath and a handle with electrical connection to
the electrosurgical unit, the circuit connecting back via a patient
plate, just as for polypectomy. The same low-power ‘coag’ setting
(15–25·W or equivalent) is used as for snaring a small polyp. The
specimen taken (often only 10–20% of the whole polyp) is protected
from current flow within the forceps jaws, so is unheated
(unless by thermal conduction resulting from over-lengthy
current application). By contrast, provided that the technique
is properly performed, within 1–2 seconds there is intense local
heating of the tissues and blood supply beneath, resulting in
surprisingly dramatic but superficial ulceration—which heals
over the next two weeks.
Safe hot biopsy depends on localizing the heating effect by careful
attention to details of technique:
1–Select only a suitably small polyp—and don’t be too proud to
abandon hot biopsy and change to (mini-) snaring if the polyp
proves to be bigger than expected.
2–Only the apex of the small polyp is grasped in the jaws of the hotbiopsy
forceps (Fig. 7.29b), deliberately not forcing them into the
colon surface below, as is normal in taking a mucosal biopsy.