Dra. Ana Echarri Piudo
Complejo Hospitalario Universitario de Ferrol
Dr. Leopoldo López Roses
Hospital Universitario Lucus Augusti. Lugo
Consists of the endoscopic removal of pedunculated or sessile polyps with the help of electric current, generally using snare polypectomy.
The preferred method for performing the technique is related to the appearance and size of the polyp. Polyps can be described as pedunculated, sessile or flat1,2.
• Polypectomy snares. They are made of braided steel wire in different shapes and sizes, generally for single use. The standard polypectomy snare has a snare that is 6-cm long and 3 cm wide, and the smallest snare is available in 3 x 1 cm measurements. The diameter of the wire is important, since a thin wire snare will cut the polyp faster (with less time to perform coagulation properly) than a snare with thicker wire. Before using a snare, we must check that it opens and closes correctly. They open up to 2 or 3 cm in diameter and have an insulating sheath with a handle at the end, enabling a gradual and controlled closing1-3.
Types of snares:
– Shape: oval, round, hexagonal, half-moon and asymmetrical (Fig. 1).
– Size: mini (11–13 mm wide, generally for small polyps treated with a cold snare). Various sizes between 11–33 mm.
– Special: barbed (to hold the skin, preventing slippage between the snare in sessile polyps); rotatable; combined with an injection needle; paediatric with a narrower sheath for 2.3 mm-channels (Fig. 2).
• Electrosurgery unit (Fig. 3). Provides a high-frequency electric current with adjusted power and calibrations for coagulation (current waves with an interrupted pattern), cutting (continuous current) and mixed (combining both forms) currents. Using a cutting current in the polypectomy technique is not advised given the high risk for associated haemorrhage. Most endoscopists use a coagulation current, at 30–40% of the maximum power of the equipment or mixed. The EndoCut system (Erbe®), currently in widespread use, automatically controls the coagulation of small amounts of tissue that alternate with cutting cycles. Energy release must not be interrupted once the technique has begun, which is why the application of pressure on the pedal that controls the energy source must be continuous. Most of the accessories used in the procedure are monopolar. The electrical circuit is formed by a small active electrode, which is composed of a polypectomy snare (or hot biopsy forceps) and a large indifferent electrode consisting of a metal plate in contact with the patient’s skin close to the location where the treatment will be performed (Table I)1,4,5.
• Thermal or hot biopsy forceps (Fig. 4). With a larger size than the common forceps, they have an insulating sheath and are connected to the active electrode. It is one of the methods used to treat lesions 2–5 mm. The head of the polyp is snared with the hot biopsy forceps by forming a pseudo-peduncle via traction, and then passing coagulation current through it until the base is whitened, destroying it and collecting the tissue for histological analysis (Fig. 5)1-3.
• Injection needle (Fig. 6).
– Injection at the base of the polyp for haemorrhage prophylaxis.
– Treatment of post-polypectomy haemorrhage.
– Facilitate resection of the sessile polyp by lifting the lesion and separating it from the muscular/serous layer, forming a safety cushion to decrease the risk of perforation1,2,6,7.
The substances to be injected are shown in Table II. For the injection of more viscous solutions, it is important to use the 23-G needle, which is thicker than the standard needle (25-G):
• Polyp-retrieving material following polypectomy (Fig. 7): various accessories enable retrieval of the polyp for histological analysis once the polypectomy has been performed. They are inserted through the channel and extracted together with the endoscope, except in case of small polyps that can be suctioned through the suction channel.
– The same polypectomy snare is used in the procedure.
– Tripod forceps.
– Dormia Baskets.
– Roth Net.
– Polyp retrieval container, which is placed right in front of the suction bottle to catch the small polyps through the channel1-3.
• Other: endoloops, clips (Fig. 8). Material useful in preventing and treating polypectomy-related complications.
– Endoloop: nylon loop (20 and 30 mm), detachable for treatment similar to snare polypectomy. Once the polyp is properly tied, the loop is released, leaving a knot around the peduncle or base of the polyp in order to prevent bleeding when performing snare polypectomy.
– Endoclips: effective in the treatment of haemorrhages and perforations when closing the bleeding vessel or small mucosal damages after resection1,2,8,9.
• Proper colon preparation is important.
• Once the lesion is located, find the best position possible to perform the polypectomy where there is a good view and the open snare can easily be placed over the polyp. Patient or colonoscopy manoeuvres may be necessary.
• Once the lesion is tied with the polypectomy snare, you must advance the distal end of the insulating sheath to the base of the peduncle before beginning to close the snare. When closing the snare, you must remain 15 mm away to leverage the effect of the snare shears that will help cut the polyp (Fig. 1, Fig. 2).
• Make sure that the snare only grasps the base of the polyp, as far as possible from the implantation wall, ensuring that the head of the polyp is free from contact with anything else.
• For pedunculated polyps, it is recommended that the cut be made close to the head of the polyp, especially in cases where there are short peduncles, to avoid perforation.
• Moving the polyp and snare together before performing the polypectomy is advised in order to ensure that no other structures have been caught and the head is free so that it cannot transmit the current from the snare.
• The time it takes to cut the peduncle varies, based on its thickness. Care must be taken when cutting, in order to avoid rushing or making sudden tugging motions with the snare in order to ensure proper haemostasis in the section area, thus retrieving the polyp for histological analysis1,2.
• The endoscopic resection of sessile polyps larger than 15 mm with a snare is associated with a high risk of extensive burns and perforation, therefore submucosal injection at the base of the lesion with saline (Fig. 6), which forms a protective cushion, or the piecemeal removal of the lesion, consisting of resecting the polyp in several fragments is advised10,11.
• When performing the submucosal injection of a flat and wide lesion, we advise beginning at the distal edge of the polyp, and in some cases it is effective to perform a retroflexion manoeuvre for access.
• If the lesion is not lifted properly, it can be a sign of deep-layer infiltration, and endoscopic treatment of the lesion must be ruled out.
• Prior to injection, some endoscopists mark the edges of the polyp via little touches with the tip of the snare, since a distorted lesion after injection can be problematic for locating the edges of the polyp.
• To reduce the recurrence of these lesions (20–30%), once removal with the snare is complete, it is effective to use the coagulation method with argon in the edges of the eschar to destroy any remaining small adenomatous tissue (Fig. 9)12.
• For small polyps (<5 mm), classic polypectomy can be associated with eschars that are too large for the size of the polyp, which can be avoided by performing cold snare polypectomy, meaning snare polypectomy without the need to apply a coagulation current, since small polyps have small nutrient vessels and the resulting haemorrhage is generally insignificant, or by performing it by pulling with biopsy forceps (preferably with a central needle) or hot forceps for hot biopsy (Fig. 4).
• Haemorrhage. Is the most common complication (1–2%). This is most common
in cases with large polyps or thick peduncles, or in elderly patients. There are two types: immediate and late (up to 2 weeks afterwards). In most cases in which bleeding occurs immediately, effective haemostasis can be achieved simultaneously via various endoscopic methods. If there is a peduncle remaining, one should try to tie it by applying pressure with the snare for a few minutes. If blood reappears when releasing, you can try applying small coagulation current pulses with the snare closed, but without sectioning. In other cases in which a peduncle remains, you can tie it with an endoloop or one or several clips (Fig. 8).
If the peduncle is retrieved, diluted adrenaline injection, bipolar electrode thermocoagulation (BICAP) or argon coagulation is used.
• Perforation. Is a less common complication but it has higher morbidity and fatality. This occurs especially after removing large sessile lesions, even if they are submucosal and located in the right colon, which has the thinnest wall. The treatment is surgical, although in cases in which they occur insidiously and late, due to a small perforation, these can be self-limited with a treatment similar to the treatment for post-polypectomy syndrome, in which they are subject to under strict observation. In some specific situations, perforations can be resolved endoscopically via the placement of clips (Fig. 10).
• Post-polypectomy syndrome or transmural burn. Less common than the above mentioned complications. This generally occurs 12–24 hours after a difficult or prolonged polypectomy. Transmural burn of the wall does not cause any free perforation, but the inflammatory reaction makes it adhere to the mesentery. This is treated via hospitalization, discontinuing oral intake, and antibiotics, in which the symptoms self-limit in 2 or 3 days.
ENDOSCOPIC MUCOSAL RESECTION. MUCOSECTOMY
Technique for removing early or superficial neoplastic lesions that do not surpass the muscular area of the mucosa, since in this case the risk of lymphatic metastases is very low (2%)10,13,14.
• Identify and mark the resection margins. Before starting the resection, it is important to properly identify its margins (chromoendoscopy techniques) and in certain cases, mark the identified margins of the resection with an electro-cutting device (hot forceps, tip of the closed snare).
• Submucosal injection. Raise the lesion.
A sclerosis needle is used with the various above-mentioned substances (Table II).
• Elevating and cutting. Surrounding the previously raised lesion with a polypectomy snare. A double-channel colonoscope can be used, in which the polyp is tractioned with forceps that keep the tissue elevated while the lesion is removed with a diathermal snare (Fig. 11).
• CAP or cap-assisted mucosal resection. By placing a clear, rigid plastic cap on the tip of the endoscope. This cap has an inner edge in the exterior circumference that enables the placement of an open polypectomy snare. Once the snare is prepared inside of the cap, it is supported over the lesion and the lesion is suctioned while the snare closes, applying a coagulation-cut combination to complete the resection (Fig. 12)15.
• Haemorrhage. Is the most common complication, ranging between 1–3%. It can be treated endoscopically, preferably with endoclips.
• Perforation (0,2%). In some cases, the complication can be resolved via the placement of endoclips.
ENDOSCOPIC SUBMUCOSAL DISSECTION
Endoscopic mucosal resection has a size limit for obtaining pieces as a unit that are larger than 2 cm. If lesion removal is performed piecemeal, post-resection recurrence is very high. Endoscopic submucosal dissection (ESD) with cutting needles permits the early treatment of larger neoplasms or those with scarred or retracted areas, with removal of the lesion as a unit, thus minimizing the risk of local recurrence and increasing the percentage of lesion-free margins. Also, it enables the treatment of ulcerated lesions or recurrent tumours after endoscopic mucosal resection, since submucosal fibrosis is not a hindrance for the procedure.
The primary limitations of the technique include the high degree of experience it requires and the high incidence of associated complications10,13,16.
Specific instrument material is used to dissect the submucosal layer as a unit: various types of needles called high-frequency surgical needles have been developed.
• Electro-surgical needles (Fig. 13):
– Needle-knife. Devices with a sharp tip that enable deep, narrow incisions.
– Insulation-tipped knife (IT-knife and IT-knife2). Is a needle-knife equipped with a ceramic ball that covers the tip, allowing for an easer and safer dissection of the submucosa.
– Hook-knife. Has a tip curved at a right angle, which permits traction of the submucosa before dissection.
– Flex-knife. With a rounded, adjustable-length tip covered with a protective plastic.
– Dual knife.
– Triangle-tip knife..
– Hybrid Knife, Flush Knife or Splash Needle: allows for the injection of fluid with the proper instrument, thus achieving a quicker dissection.
– Mucosectomy with insulated tip: enables rotation with a single cutting side for a more precise dissection.
• CAP. Enables viewing and stability of the lesion during dissection.
Since there can be significant bleeding during the procedure, it is recommended that prophylactic haemostasis of the vessel be performed while the piece is dissected.
1. Identifying and marking the margins. Applying dyes to delimit the lesion and marking the edges with a diathermal device (needle) can be useful. It is recommended that marks be made every 2 mm, situated 5 mm from the external edge of the lesion.
2. Submucosal injection. A sclerosis needle is used to inject a solution that separates the submucosal layer from the muscular layer. Injection must begin outside of the marks made. The solution can be glycerol 10%, hyaluronic acid 4%, or a mixture of serum, glycerine, IC and adrenaline. Another option is to elevate the lesion is by using the Hybrid Knife that, when applying slight pressure over the mucosa, enables fluid to be directly applied in the submucosa, forming a “water pillow” that enables dissection.
3. Dissecting the lesion. With the pre-cutting needle, a 1–2 mm cut should be made in the edge of the tumour: if the lesion is very big, more than one cut may be necessary.
Once the muscular layer of the mucosa is surpassed, the IC previously injected in the submucosa can be seen, which serves as a guide to know that the proper depth has been reached. Next, an insulated-tip knife (IT-knife or Hybrid knife) is inserted through the orifice made and a circumferential dissection is done following pre-marked points. It is usually advised that adequate power be used with the EndoCut or DryCut dissection method
(Table III). After having completed the cut of the edge of the lesion, the remaining submucosa under the lesion is injected again, with the intention of continuing to raise the submucosa. Dissection of the submucosa continues with a careful tangential motion of the needle. It is recommended that dissection be done before continuing to make cuts, given the progressive loss of elevation over time. When resection has been completed, the sample is removed with forceps.
4. Treating the residual ulcer. Since there can be significant bleeding during the procedure, it is recommended that prophylactic haemostasis be performed in the vessels while the piece is dissected. Electrocauterization can be performed by using hot forceps (Fig. 4), a bipolar probe or even, for small vessels, the same dissection needle.
5. Processing the removed piece. The sample must be laying flat and fixed with needles on blotting paper before submerging it in formalin.
• Haemorrhage. This is the most common, ranging between 1–6%. Since there can be significant bleeding during the procedure, it is recommended that prophylactic haemostasis be performed in the vessels while the piece is dissected, with the same dissection needle or with hemostats.
• Perforation. It occurs more often than in the case of mucosal resection, with rates ranging between 1–8%. In the case of microperforations, placing endoscopic clips
is usually helpful (Fig. 10).
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