Colonoscopic Polypectomy: Techniques and New Method_Juniper Publishers
Authored by
Fabio Monica
Abstract
Colorectal polypectomy is an efficacy method for the
prevention of colonrectal cancer, indeed, removing cancer precursor,
reduces CRC incidence e mortality. Several techniques has been developed
to remove polyps and are chosen according to the polyp size, shape and
type. The goals of colonoscopic polypectomy are complete resection and
retrieval of precancerous lesions in a safe way.
Introduction
Colorectal polypectomy is an efficacy method for the
prevention of colonrectal cancer, indeed, removing cancer precursor,
reduces CRC incidence e mortality [1,2].
Despite proven effectiveness, polyp resection techniques are limited by
lack of evidence and are based on expert opinion and uncontrolled
observational studies [3-5].
Proper removal of polyp needs not only skillness by experienced
endoscopist but a complete knowledge of the characteristics of
endoscopic instruments and accessories, according to morphology and size
of the colorectal polyp, in order to avoid complications and to reduce
the occurrence of incomplete polypectomy, which is one of the major
cause of interval colon cancer [6,7].
In the CRC screening era, detection and resection of
all polypoid lesions are the main goals of quality colonoscopy and the
successful polypectomy has to be effective in complete resection,
efficient in retrieval all lesions, safe in minimizing the risk of
complication such as perforation or bleeding. Furthermore, the resection
must provide an accurate histological diagnosis with evaluation of the
margins and the base for possible infiltration of the underlying layers.
Polypectomy Techniques
There are several techniques to remove polyps and
these are classified according to accessories used with or without use
of electro surgery. The choice of technique depends on the morphology,
the size, the location of polyps and the experience of the endoscopist [8,9].
Nowadays the superficial neoplastic lesions of
gastrointestinal tract are stratified in three categories by Paris
endoscopic classification: protruded (type 0-I), superficial (type 0 to
II) and excavated (type 0 to III). The protruded lesions are subdivided
into pedunculated (0-Ip), if polyps have a head connected with a stalk,
sessile (0-Is), if polyps are broad based without a connecting stalk and
semipeduncolated (0-Isp) [10,12].
Based on size it's possible to identify three types of polyps: achieved
in 90% of diminutive polyps and 100% of polyps <3mm in size when
performed with chromoendoscopy diminutive: <5mm, intermediate:
between 6-9mm and large: >10mm.
The optimal method to polypectomy is removing polyps
in one piece ("en bloc resection") but, if the size of polyp is larger
than 2cm, it can be required to remove in multiple pieces ("piecemeal
resection"). For the diminutive lesion (<5mm) the technique that
should be chosen is cold forceps biopsy with standard forceps or use
jumbo forceps. It consists to grasp polyp and remove it with a firm pull
with high retrieval rate and low complication rate [13].
A recent prospective study shows that forceps ensure 96% of cases
complete resection for polyps between 1 and 3mm and 76% of cases for
polyps between 4 and 5mm [14]. Another study has shown that complete resection was and washing and postresection examination [15].
Hot forceps biopsy consists in thermal ablation of
polyps with coagulation current through electrosurgical unit, so it's
similar to cold forceps except it uses electrocautery to remove polyp
tissue. However, it can make difficult the histological diagnosis and
has a risk of delayed bleeding or hypercoagulation syndrome [16-18] so hot biopsy forceps is not recommended as a standard method.
For polyps 5mm [19,20]
snare excision is commonly used. There are several types of wire loop
snaresthe choice of them is usually due to endoscopist's preference as
there are no controlled trials demonstrating superiority of any one
device over another.
For polyps 6-9mm in size cold snare polypectomy (CSP)
is recommended. This method consists in cutting the polyp with only the
mechanical strength of the snare closed to guillotine the tissue
capturing also 1 to 2 mm of normal tissue around the polyp. CSP seems
better for polyps 5mm as shown in a recent study in which it is adequate
for complete and safe removal and shorten withdrawal time of the
colonoscopy procedure [21]. It allows efficient resection of polyp tissue in a single piece with lower rate of incomplete resection than biopsy [22] and is almost without risk [23], except insignificant bleeding that usually stops in few seconds [21]. Repici et al. [24]
in an observational study demonstrated the safety of cold snare for
polyps less than 10mm, with low rate of bleeding (1,8%) and no delayed
bleeding or perforation. In every case some bleeding, especially in
patients taking anticoagulants, is immediately displayed and can be
endoscopically treated. For these reasons, recently, the ESGE guidelines
recommends against the use of cold biopsy forceps (CBF) excision
because of high rates of incomplete resection. Only in the case of a
polyp sized 1-3mm where cold snare polypectomy is difficult or not
possible, cold biopsy forceps may be used [25].
The predominant technique for polyps 10-19mm in size
is standard snare excision with electrocautery: hot snare polypectomy
(HSP). It is effective and safe and may be aided by the saline lift
technique: the saline solution can be injected into the submucosa under
the polyp with suitable needle. This method increases the distance
between the polyp and the submucosa ensuring a complete removal of the
polyp and reducing the risk of perforation [26].
Furthermore, the most of endoscopists use dilute epinephrine (1:10000
or 1:20000) to reduce the risk of bleeding taking advantage of
vasoconstrictor properties.Unfortunately, the saline solution is rapidly
absorbed so alternative agents have been studied with or without
epinephrine including hyaluronic acid [27], dextrose solution [28], succinylated gelatin [29], hydroxyethyl starch [30], and recently polidocanol [31].
The electrosurgical is commonly used endoscopic tool for cutting or
coagulating tissue and is responsible for almost all the complications
associated with polypectomy [32].
Despite of this long history, the application of electrocautery in
snare polypectomy has not yet been standardized due to lack of large
controlled trials.
Improvements in technology have seen the introduction
of more sophisticated electrosurgical generators in which Endocut mode
(ERBE) has been widely used for its better quality for polypectomy
because rapidly modifies the current in response to changes in the
tissue impedance [33].
Alternating cutting and coagulation cycles allow performing a
controlled cutting with sufficient hemostasis during the entire cutting
process and minimizing depth and spread of thermal injury. For removing
large pedunculated polyp, it need apply energy early and closing the
snare slowly, it will help to avoid complications such as bleeding. The
electrocautery snare should be placed around the stalk approximately
one-half to one-third the distance between the polyp head and the colon
wall, allowing sufficient resection margin in case of malignancy and
leaving residual and visible stump of stalk after resection that can be
grabbed in the event of bleeding.
To prevent bleeding in pedunculated polyp with head
≥20mm or a stalk ≥10mm in diameter, it's useful pretreatment of the
stalk with injection of dilute adrenaline and/or to place a nylon loop
(endoloop) [34] around the stalk below the resection point or hemoclips across the polypectomy stalk [25].
Now, for resection of large sessile lesion and flat colorectal
laterally spreading tumors (LSTs) ≥20mm advanced techniques are been
developed as endoscopic mucosal resection (EMR) and endoscopic
submucosal dissection (ESD).
When performing endoscopic polypectomy with snare,
the polyp should be always place in the 5 to 7 o'clock position and it's
important to identify polyp's margins through high definition/
resolution endoscopes with electronic chromo-endoscopy (NBI, FICE, LBI,
iSCAN) which helps for clear visualization of polyps' margins. Adding
biologically inert blue dye (methylene blue or indigo carmine) to the
saline used to lift the polyp helps in defining the borders of a
flat/sessile lesion. Then the infiltration of the submucosa must be
always started in the proximal part (anatomically) of the polyp base, so
that the polyp will rise from the side of the vision and will not tip
over.
When electrocautery is used the endoscopists should
minimize the duration of energy delivery to limit the damage to the
colonic wall. Every part ensnared should be lifted away from the wall:
this can be done by tenting the polyp toward the center of the lumen
just before application of current to prevent deep perforation. If
islets of adenomatous tissue between resected pieces or margins of
polypectomy remain should be used the argon plasma coagulation to
electrocute but the efficacy is unclear because this method is however
associated with polyp recurrence [11,35].
After polypectomy if the pieces are relatively small they can be suctioned through the suction channel [23]
otherwise an endoscopic net, wire basket or forceps can be used for
retrieval of a resected large polyp or tissue that will not pass,
especially if located in the right colon.
New Method
Recently "under-water" polypectomy has been
used during water-aided colonoscopy. For the first time this technique
has been described by Kenneth Binmoeller [36]
for removing flat colorectal lesions. The bowel lumen is filled with
water rather than air and submucosal injection of the lesion is not
required. Furthermore, this technique increases the proportion of
complete resection and reduces the possible complications: bleeding,
transmural burns, and perforation. Both cold and hot snare could be used
safely because water does not affect the conductivity of the tissue
during polypectomy. However further studies are needed to validate the
technique.
Another new method is use of carbon dioxide
insufflation during polypectomy because reduce discomfort of patient
during and after procedure since CO2 is absorbed faster than air [37,38].
Problems of Polypectomy
When we are faced with a polyp hardly approachable
due to their location in a tight turn or behind a colonic fold we could
use some ploys: lock the dials on the endoscope or ask an assistant to
hold the scope position (for polyps in tight bends), do the retroflexion
of the scope tip (only in the right colon), use a side- viewing
duodenoscope [39,40]
or cap-assisted colonoscope for polyps behind folds. However
standardized guideline doesn't exist and the choice depends on the
experience and preference of the operator.
After polypectomy surveillance intervals are based on
complete removal of all adenomas and in case of incomplete polypectomy,
residual neoplastic tissue could progress to malignancy. It has been
estimated that up to 27% of interval cancers may be due to incomplete
endoscopic resection [6,41]. In the CARE study [42]
it has been showed that residual adenoma is common after HSP and it is
variable by type and size of polyps. The authors concluded that the
rates of incomplete resection significantly varied between endoscopists
(6.5%-22.7%), suggesting that individual operator factor and an
appropriate training are the most important contributions to correct and
successfully polypectomy [43,44].
Tattoing
After polypectomy is necessary to assess the
opportunity to make a tattoo of the lesion especially when polyp has
large size, if we are not sure that removal has been completed or other
sessions will be needed to remove it and if there are indicators of
suspicious of malignancy Furthermore, if the lesion is located in the
rectum, in the cecum or near to the ileocecal valve should not be
tattooed. Tattooing consist in injection of permanent staining agent
into the gut wall to create a mark to identify the site from inside or
outside the lumen and it is typically done with at least two submucosal
injections of dye on contralateral sides of the bowel near the lesion.
It should be made few centimeters distal (3cm) to the lesion or on three
or four sites circumferentially to avoid the risk of tumor seeding [45].
A double injection with a saline injection into the
submucosa to form a bleb following by an injection of dye using a second
syringecan improve efficacy of tattooing and prevent inflammatory
complications [46,47]
because it avoids that the dye can penetrate into the colon wall. There
are many types of dye (methylene blue, indigo carmine, toluidine blue,
hematoxylin) but only two persisted for more than 24 hours: indocyanine
green and India ink [48].
These were limited by difficulties including lack of permanence,
infection because not sterile solution or complex preparation and
complication [49-54].
More recently dilute sterile and biocompatible prepackaged suspension
of pure carbon particles was developed so it's the only dye approved by
the Food and Drug Administration. However cases of peritonitis and
submucosal fibrosis have been reported by this suspension [55].
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