Pedunculated (stalked) polyps are more common in the left colon than the right. They may be positioned in the sigmoid colon in areas of marked angulation. Repositioning the patient may improve exposure of the polyp head and stalk. A skilled endoscopist should be able to remove essentially all pedunculated colon polyps. Ensnaring a very large polyp is often facilitated by the use of an extra-large (jumbo) snare. The closed snare should be positioned near the polyp head or at least two thirds of the distance from the base of the stalk to the polyp head. This leaves residual stalk that can be snared if there is immediate bleeding. On the other hand, some have argued that if the polyp looks as though it may be malignant, it is preferable to close on the base of the stalk126
in order to improve the chance of a clear resection margin. If the tip of the polyp head touches the contralateral colon wall, current may pass through that wall and produce a burn (Fig. 149-9
). Gentle movement of the snare during application of cautery will dissipate this burn on the contralateral
wall and eliminate the risk for perforation. Most experts hold the colonoscope shaft in position with their right hand during application of cautery, or pin the scope against the bed with their hip to prevent scope movement if manipulation of the snare during cautery is needed. An assistant generally closes the snare. If, before passing the snare down the instrument, a mark is placed on the snare handle at the point of closure where the snare tip just enters the plastic sheath, then the distance from the mark to the closing portion of the snare provides an estimate of the amount of tissue in the snare. If this distance is excessive (more than 1 to 1.5 cm), then careful inspection or remanipulation of the snare is prudent to ensure that no portion of the normal wall or the polyp head is in the snare.
FIGURE 149-9. Current dissipation through the contralateral colonic wall. The electrosurgical snare is around the stalk of a pedunculated polyp. The polyp head is in contact with the contralateral wall. Leaking current during cautery may cause thermal injury to the contralateral wall (arrows). Significant injury is easily averted by moving the polyp head during application of electrocautery whenever the polyp head touches the contralateral wall.
The risk for perforation with pedunculated polyps is exceedingly low, so that application of current can usually be liberal and mechanical closure slow. A white coagulum should be endoscopically visible adjacent to the snare before mechanical closure begins. Current should be applied continuously because intermittent application allows cooling of the snare and may seal it to the tissue (“stuck snare”).
The most common complication of endoscopic transection of pedunculated polyps is bleeding, which can be either immediate or delayed. Some experts preinject the stalk with epinephrine and saline. However, the risk for immediate bleeding overall is low, particularly if coagulation current is used. Thus, the use of an injection catheter and epinephrine routinely for colon polyps is not cost-effective. A time-honored approach to immediate hemorrhage is to regrasp the stalk with the snare and hold the stalk for 10 to 15 minutes. No additional cautery is applied, yet this method is consistently effective. Alternatively, epinephrine can be injected into the stalk if immediate bleeding occurs, followed by bipolar coagulation of the transection site on the stalk. A recent innovation, proved effective in a randomized trial,127
that appears to prevent both immediate and delayed bleeding is a detachable snare, which is placed on the polyp stalk before transection (Fig. 149-10
). The snare subsequently sloughs up to 1 week later. The detachable snare can also be placed on the stalk after transection. Attempted application to semi-pedunculated polyps before or after transection is often unsuccessful. An alternative is to place a metal clip across the base of the stalk.
FIGURE 149-10. Resection of a pedunculated polyp with a detachable snare. A: The loop of a detachable snare is placed around the stalk of the polyp, tightened, and then detached from the handle. B: A cautery snare is placed above the loop and transects the stalk by electrocoagulation.
More than 95% of colon polyps can be successfully retrieved. Small pedunculated polyps can be suctioned through the colonoscope into a trap. If the polyp is not visible in the trap after suctioning, it is usually impacted in the umbilical cord of the instrument. Water can be suctioned from a syringe inserted into the suction or biopsy inlet of the instrument through the umbilical cord to flush the polyp into the trap. Larger pedunculated polyps are most easily retrieved by gently regrasping the transected polyp head. If 2 to 3 cm of the snare is left outside the colonoscope tip, then examination can continue while the polyp is being delivered. If additional small polyps are encountered, the large polyp is dropped in the lumen, the small polyps are removed and suctioned, the large polyp is regrasped, and the examination then continues. Combined cautery and retrieval snares have been recently described.128
Large pedunculated colon lesions with overlying normal mucosa are usually lipomas. The diagnosis is confirmed by the “cushion” or “pillow” sign of easy deformability with probing; by the yellow hue, which is sometimes present; and if necessary, by EUS. These tumors are usually asymptomatic but can produce intussusception. Endoscopic snare resection is often unsuccessful. Fat has low water content and resists the desiccation necessary for easy mechanical transection.
Endoscopic resection of a malignant pedunculated polyp is considered curative if (1) the cancer is well or moderately differentiated, (2) there is no vascular (lymphatic) invasion, and (3) the margin is clear. If these criteria are met, surgical resection is not advised. If the criteria are not met, the risk for metastasis is increased, with the extent of increase depending on the number and severity of the changes.129
If the estimated risk of operation is lower than the risk for metastasis, then surgical resection should be considered.
Sessile polyps larger than 5 mm are typically removed by snare cautery. Lesions smaller than 1.5 cm should be removed in a single piece if possible. Larger polyps may require removal in pieces.132
The snared polyp or portion of polyp is tented into the lumen to create an artificial stalk. In the right colon, lumenal deflation will thicken the wall before application of cautery.
Large sessile polyps that demonstrate surface irregularity or ulceration are usually malignant; biopsy should generally be performed to rule out cancer before attempting endoscopic resection. The rationale for biopsy is that sessile malignant lesions are a general indication for surgical resection. However, some experts consider endoscopic resection to be definitive therapy for sessile malignant polyps if they exhibit favorable histological criteria.4
In this case, a sessile polyp with some malignant features could be resected endoscopically if it could be lifted on a submucosal saline mound, indicating that no submucosal fixation is present. In general, lesions covering more than one third of the colon circumference or having a longitudinal extent of more than two haustral folds should be considered for surgical resection as primary therapy. However, in the right colon and rectum where the lumenal diameter is relatively large, much larger sessile lesions may be amenable to endoscopic resection.
Submucosal saline injection should be considered for large or flat sessile polyps. Injection begins at the proximal edge or, for smaller polyps, is made directly into the polyp center. Only injection into the submucosa will raise a mound. Injection has not been associated with a risk for tumor seeding or peritonitis, although clearly, the needle may pass through the colon wall. During injection polypectomy, the snare may close over the saline mound without grasping tissue. This effect can be countered by barbed snares (Olympus Corp, Lake Success, NY) or needle-tipped snares (Wilson-Cook, Winston-Salem, NC) that hold the snare in place. Alternatively, a circumferential incision cut with electrocautery in the saline mound but outside the polyp forms a groove that seats the snare in position around the polyp.134
In some cases, sessile adenomas are so flat (so little elevated aspect) that the lesions are unsnarable even after submucosal injection. Potentially effective treatments in this instance include ablative therapy (see later) and EMRC. EMRC has the advantage of retrieving a histological specimen. In the colon, EMRC use is best confined to the thicker-walled left colon and rectum. EMRC is performed only after submucosal saline injection, and volumes of at least 30 to 40 mL are anecdotally important to reduce the risk for perforation associated with aspiration of deep wall layers into the cap. In our experience with an American population, EMRC is needed much less frequently in the colon than the stomach and especially toward the esophagus.
Visualization of the margin of very flat polyps can be facilitated by dye spraying with methylene blue, indigo carmine, or cresol violet, or by addition of small amounts of methylene blue to the saline before injection (see earlier). Sections that are flat and that cannot be removed by saline injection can be destroyed using Nd:YAG laser, BEC, or APC. The latter two techniques are preferred because they have a lower chance of perforation.
Endoscopic localization for possible subsequent surgery is not reliable unless the ileocecal valve is in view or the polyp is in the rectum or distal sigmoid. Between these sites, large polyps should be marked by tattooing with India ink.
If a sessile polyp is removed in piecemeal fashion and the fragments are too large to be retrieved by suctioning, retrieval can be facilitated by the Roth retrieval basket. This device consists of a net on a large snare, which is repeatedly opened and closed on the fragments until all are trapped in the net.
Histological criteria to assess the need for surgical resection are less clearly applicable to sessile malignant polyps. In a review of nine studies reporting the frequency of cancer at surgery or during follow-up after endoscopic resection of a sessile malignant adenoma, polyps with favorable histology had a 4.1% incidence of residual cancer, compared with 20.6% in polyps with unfavorable histology.135
In another study, the incidence of metastasis from sessile malignant polyps was 15%.136
Thus, operative resection should be considered in any sessile malignant polyp because the risk for metastasis is several times that of pedunculated polyps with similar histological criteria.
Endoscopic resection of sessile polyps carries a risk for perforation, postpolypectomy syndrome, and immediate and delayed bleeding. Perforation should be managed operatively in most cases, particularly if it is recognized within the first few hours after resection. Perforations presenting later with well-localized peritoneal signs can sometimes be managed nonoperatively.137
Postpolypectomy syndrome is the result of a serosal (transmural) burn without free perforation. Patients present with localized pain and tenderness, fever, and elevated white blood cell count, but no free air on abdominal radiographs. In some instances, a water-soluble contrast enema or CT scan may be necessary
to rule out perforation. Treatment is bowel rest, antibiotics, and careful observation. Immediate bleeding is best managed by injection of epinephrine (1:10,000 in normal saline) into the polypectomy base or simply spraying the solution onto the polyp base. This can be followed by BEC or heater-probe treatment of the bleeding site. Monopolar cautery should not be reapplied. Most delayed bleeding stops spontaneously. If delayed bleeding remains active, repeat colonoscopy with epinephrine injection and bipolar cautery or heater probe treatment of the base is effective.138
Application of metal clips is an inexpensive and effective alternative for both immediate and delayed bleeding from sessile polypectomy sites.
Recurrence rates of large sessile adenomas after endoscopic piecemeal polypectomy vary from 16.5% to 50%.131
Nearly one half of recurrences occur after one negative follow-up examination, and recurrences may develop more than 1 year after the initial resection.139
It should be recalled that most current guidelines for postpolypectomy surveillance140
are derived primarily from the National Polyp Study.142
However, sessile adenomas greater than or equal to 3 cm in size were excluded from the National Polyp Study,142
and thus the conclusions derived from that study do not apply to these large polyps. Most recurrences can be successfully treated by additional endoscopic therapy.139
Repeat examinations at 3- to 6-month intervals are indicated after piecemeal resection of large sessile adenomas.139
After complete resection appears verified, another examination at 1 year is prudent.139
Several groups have reported experience with Nd:YAG laser ablation of large rectal polyps.143
A disadvantage is that tissue is obliterated and not available for histological evaluation, so that late presentation of metastatic cancer is possible. The overall success rate depends on the polyp size, with success rates as low as 56% for lesions occupying two thirds of the circumference,145
and as many as 10 treatment sessions required. Complications include bleeding, rectal stenosis, and fever. Perforation is rare owing to the retroperitoneal location of much of the rectum. Snare cautery debridement before Nd:YAG laser therapy is superior to Nd:YAG therapy alone.146
Transanal or transsacral resection should also be considered, although recurrence rates of 6% to 42% and complications in 13% follow the transanal approach, and the transsacral approach is followed by fistula formation in up to 21% of patients.148
PDT was reported to eradicate sessile villous adenomas in the rectosigmoid that had failed to respond to Nd:YAG laser.151
PDT has been reported to debulk large sessile rectal adenomas before Nd:YAG therapy.152
Debulking by snare excision, however, is the preferred approach.146
When lesions compatible with flat adenomas or cancers are identified, mucosectomy is the preferred approach because it allows clarification that the submucosa is not fixed and gives an ideal histological specimen for ascertainment of tumor-free margins.153
Endoscopic Treatment of Colorectal Cancers
The treatment of choice for cure or palliation of colorectal cancer is surgical resection. Less than 5% of patients are not candidates for surgery because of widely metastatic disease, inability to tolerate surgery, or unwillingness to undergo surgery or ostomy. In these instances, management depends on local expertise. However, Nd:YAG laser, PDT, and placement of a colonic stent may all be considerations, depending on symptoms. The Nd:YAG laser is effective for relief of bleeding, obstruction, or both.157
In rare instances in which surgery cannot be performed, Nd:YAG laser can be used to treat T1 or T2 lesions staged as N0, M0 with curative intent.162
PDT was used for 21 patients with inoperable or recurrent colorectal cancer, and 16 had evidence of necrosis, 15 had increased lumenal diameter, and 10 had relief of obstructive symptoms.165
However, the ease with which colonic stents can be placed and the need for repeated treatments with ablative therapies has made stent placement the treatment of choice for palliation of obstructing colorectal cancer.