Practical Gastrointestinal Endoscopy

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CHAPTER 7
Fig. 7.38 ‘Leak’ current can
result in contralateral burns.
Fig. 7.39 A large area of contact
reduces the risk of contralateral
burn, but also reduces current
flow and heat coagulation in the
lower stalk.
5–Consider ‘pre-snaring’ lower down the stalk in order to extend
the zone of electrocoagulation. Squeeze the snare gently for this
preliminary stalk heating, so that transection doesn’t occur and
the snare is easy to release and replace higher up the stalk for
conventional polypectomy.
6–Electrocoagulate the stalk for longer than usual, until visible
swelling and whitening indicate that it is safe to start transection.
7– Consider using a higher than usual current setting, especially if,
in the process of transection, the core desiccates and the snare
will not make the final cut. Resist the urge to ‘pull through’ the
snare. The thickest arteries are the last to sever, so it is safer to
raise the current setting further and let current heating help to
make thecut.
In snaring large stalked polyps, complications, especially
bleeding, need to be anticipated (and so often avoided). Large
polyps inevitably have larger, thicker-walled and more numerous
feeding vessels. Epinephrine and an injection catheter
should be available for immediate use if required, and it is
highly desirable to have EndoLoop® and clipping devices also.
By employing a careful ‘slow cook’ polypectomy technique, the
precautionary methods described below and the crisis-control
(or prevention) accessories, we have experienced no serious immediate
hemorrhage after polypectomy for manyyears. Delayed
bleeds, however, do continue to happen unpredictably.
Contralateral burns are essentially a ‘non-problem’
. During snar-
ing of a large stalked polyp, the head will flop about, inevitably
touching the bowel wall in several places. ‘Leak’ currents flow at
each point of contact, which results in inefficient heating of the
stalk (Fig. 7.38) and the possibility of a contralateral burn—often
out of the field of view. The burn hazard is mainly theoretical and
the possibility can be avoided by moving the snared polyp head
around during coagulation, which ensures that no one point gets
all the heat. Alternatively make sure that the area of contact between
the head and the opposite wall is large, so that resistance
is low and heating insignificant.
During a difficult polypectomy try to keep a view of the snared stalk,
especially if only part of the polyp can be seen, and ensure that
adequate visible coagulation occurs below the snare loop before
transection. (If leak currents do flow up the stalk to a contact
point at the head, electrocoagulation can occur primarily above
the snare (Fig. 7.39) and bleeding could result from inadequately
coagulated vessels in the lower part of the stalk.)
If there is any doubt about stalk electrocoagulation when the
polyp head has severed and if the stalk remnant shows too little
visible electrocoagulation whitening, or visible vessels at the
center, it may be wise to ‘post-snare’ lower down, squeezing the
stalk gently and electrocoagulating further (without transection)
before reopening and removing the loop.