Transanal Endoscopic Microsurgery

Theodore John Saclarides

Transanal endoscopic microsurgery (TEM) was first developed by Professor Gerhard Buess (1) and manufactured by the Richard Wolf Company almost 30 years ago. Several modifications have been proposed by others since the 1980s, which are all based upon Buess’s original vision of improving the visibility and reach of transanal surgery by employing superior optics, carbon dioxide (CO₂)-induced rectal distention, and longer instruments. The number of TEM manuscripts published since the 1980s has greatly increased and training courses have become available at a number of centers across the globe. Indeed, most of the early publications were authored by Buess himself and in these he described his personal journey of first using the instruments on an animal model (2). He then reported his clinical experience on an ever-increasing volume of human patients at a time when the concept of minimally invasive surgery, which he called “minimally aggressive but accurate,” was capturing the attention of all surgeons. As more surgeons learned and practiced TEM, the number of publications increased, but it has been slow to catch on. Buess’s training courses were spread over several days, taking the students through a step-by-step process of cutting and sewing felt cloth, to an open bovine model, and then finally to a closed but distended segment of bovine bowel. Time was needed to master the technique since the initial participants had minimal experience in endoscopic or laparoscopic surgery. In contrast, today’s TEM students learn the techniques and master the learning curve much more quickly because of laparoscopic and video skills acquired early during their surgical career.

TEM represents a unique blend between the old and the new. Although transanal excision of rectal tumors has been part of the surgeon’s armamentarium for almost a century, surgeons have been somewhat restricted by the suboptimal exposure and limited reach afforded by conventional instruments. TEM circumnavigates these restrictions, however, having the technology is not license to use it inappropriately. While virtually any adenoma can be removed with TEM, strict selection criteria must be used when addressing malignant lesions in order to not compromise cure and adversely affect patient outcome. By virtue of its longer reach, better exposure, and enhanced visibility, TEM has placed itself in the category of minimally invasive surgical procedures. Some lesions in the mid and upper rectum, which may have required a laparotomy and radical resection for removal, may now be addressed with a less invasive approach. As such, less postoperative pain, shorter recovery period, and a faster return to normal function are real and attainable goals. This is especially so when one considers the high morbidity
associated with the Mason and Kraske procedures where wound infection and fecal fistulas can be disastrous for the patient.

Indications/Contraindications

Indications

As stated above, most adenomas regardless of size, location, and degree of circumferential involvement can be removed with TEM instrumentation. Provided the lesion can be reached with a rigid scope and is visible in its entirety, it can be removed. If the lesion extends around the rectosigmoid junction or if the curvature of the sacrum prohibits passage of a rigid scope up to the lesion, then perhaps TEM is not the best approach. Lesions which encompass 360 degrees of the wall circumference can be successfully removed with TEM and intestinal continuity reestablished with a hand-sewn end-to-end anastomosis performed transanally.

Proper patient selection must be followed when considering TEM for malignant lesions. These selection criteria require that the lesion have only superficial penetration of the rectal wall (preoperative staging with either endorectal ultrasound or magnetic resonance imaging (MRI) is essential), well to moderately well differentiation, lack perineural and lymphovascular invasion, and perhaps also lack a mucinous component, although this last feature is controversial. Budding tumor cells at the leading edge of the lesion has also been considered an ominous feature and a potential contraindication for transanal excision. If these criteria are not met, the risk of lymph node metastases is increased and such nodes would potentially go untreated by any method that locally removes a tumor and does not incorporate mesorectal excision in its plan. Large tumor size (greater than 3–4 cm) has been considered a relative contraindication for transanal excision of rectal cancer, primarily because difficult exposure with conventional instruments could lead to inadequate removal, positive resection margins, and higher recurrence rates. TEM, however, eliminates larger size as a contraindication for transanal excision. If one is contemplating TEM for a rectal cancer, previous endoscopic biopsies should be reviewed with an experienced pathologist for the above features and the lesion should be imaged to determine the depth of penetration and the presence of nodal metastases. If favorable histologic features are present, there is no evidence of enlarged lymph nodes, and the lesion does not penetrate beyond the submucosa, then one can consider TEM. The surgeon, however, should adopt the mentality that such an excision is in reality an excisional biopsy, and that further therapy may be indicated after histologic review of the entire lesion has been performed. If, in fact, the lesion is a pT1 tumor, then many would consider TEM sufficient treatment; however, local excision alone is not an appropriate treatment for any tumor that has penetrated into the muscularis propria or beyond. This will be discussed elsewhere in this chapter.

There are instances when TEM can be used to treat cancer even though cure may not be possible or as readily obtained. Palliation of a tumor can be considered in instances where diffuse systemic metastases are present. Unfortunately, most primary tumors in these instances are large and may not be amenable to transanal excision. If the patient is medically unfit to undergo conventional surgery because of multiple comorbid factors, TEM may be considered if used in conjunction with radiation and chemotherapy. Experience in this regard is limited, therefore, caution should be exercised. Adjuvant therapy combined with TEM may also be considered for those patients who are emotionally unwilling to undergo conventional surgery that may involve a stoma. The use of TEM combined with adjuvant or neoadjuvant therapy will be discussed elsewhere in this chapter.

There are extended applications in the literature for TEM; however, for many of these conditions, experience is limited to anecdotal case reports or small series. Theoretically, TEM can be used to treat complex, supra-sphincteric or extra-sphincteric fistulas with advancement flaps. The flap should consist of mucosa, submucosa, and a
portion of the muscularis; its base should be several times the width of its apex, and there should be sufficient cephalad mobilization to avoid tension as the flap is advanced caudally. TEM has been used to treat rectovaginal fistulas (3) as well as rectourethral fistulas (4,5,6) with varying success. The author has tried using TEM instrumentation to correct circular stapler-induced rectovaginal fistulas following low anterior resection. In this regard, all three cases so attempted failed primarily because diminished rectal capacity secondary to radiation and prior resection lead to limited visibility and access. Strictureplasty can be performed with TEM instrumentation as well, the operation being done with single or multiple longitudinal incisions closed transversely or with a 180 or 270 degree transverse excision of the stricture followed by transverse closure of the defect. Such efforts are best done in the lateral and posterior portions of the extra-peritoneal rectum (7,8). TEM has been used to repair an anastomotic leak (9) and to excise retrorectal tumors (10,11).

Preoperative Planning

Preoperative Assessment and Patient Preparation

If the goal of treatment is cure, then accurate preoperative staging is paramount. Assessment begins with a digital rectal examination, which may reveal fixation or bulky extramural adenopathy. All patients must also undergo either a colonoscopy or a double contrast barium enema to evaluate for synchronous lesions. To determine local extent of disease, as previously stated, endorectal ultrasound or MRI can be used. A meta-analysis by Bipat et al. analyzed 90 studies comparing ultrasound, CT, and MRI from 1985 to 2002. Ultrasound was found to be the most accurate for determining depth of penetration, being over 90% sensitive in detecting invasion of the muscularis propria and perirectal tissue. MRI frequently over-staged T1 lesions (12). Ultrasound accuracy may decrease when used to evaluate more advanced and circumferential tumors (13). Ultrasound, CT, and MRI have comparably low sensitivities when ruling out perirectal lymph node metastases (67%, 55%, 66%, respectively) (12). The definition of what constitutes a metastatic lymph node has varied among operators and researchers. For example, one study considered any oval or circular structure greater than 5 mm to be malignant while others use 10 mm as the threshold; others have stated that any detectable node should be considered metastatic regardless of size (13). Certainly, the positive predictive value of a hypoechoic node detected within the mesorectum increases with increasing size, but it is probably best to overtreat rather than undertreat the patient and to consider any detectable node suspicious. Abdominal CT scans are usually not necessary for early, superficial cancers or adenomatous lesions, as the likelihood for distant metastases is low (14).

If a patient is referred to a surgeon for possible TEM, rigid proctosigmoidoscopy must be performed by the surgeon in order to determine the level of the lesion in the rectum and whether a rigid scope can access the lesion and reveal it in its entirety. Moreover, the exact spatial orientation of the lesion (anterior vs. posterior, right lateral vs. left lateral) must be determined as this will dictate patient position on the operating table. Informed consent should be obtained with the following considerations in mind. If bleeding is encountered or if a lesion cannot be removed, conversion to a transabdominal approach may be necessary. In addition, for anteriorly located lesions, one may inadvertently enter the peritoneal cavity. Although such an occurrence may be repaired with transanal suturing techniques, conversion to an abdominal approach may be required. Although bowel cleansing is not required for colectomy, it is still essential for TEM in order to ensure visibility and reduce the risk of infection. Moreover, if the effects of general anesthesia decline midway during the operation and the patient strains or coughs, residual stool, if present, may appear at a most inopportune time. Bowel cleansing may be accomplished with oral cathartics, enemas, or lavage solutions. General or regional anesthesia is required. Patients are positioned on the operating room
table such that the lesion is at the bottom of the optical field, for example, lithotomy for a posterior lesion. Most cases can be done on an outpatient basis or with a single overnight stay. Some patients may experience anesthesia-related nausea, urinary retention, or may require observation for bleeding. Pain is generally not an issue and patients do not usually require parenteral medications.

Equipment

TEM utilizes a closed endoscopic system that allows for the instillation and retention of CO₂ gas; this creates constant rectal distention, which facilitates exposure and visualization of the lesion, excision of the tumor, control of bleeding, and subsequent closure of the wound defect. Other distinguishing features of TEM are the long reach of the instruments and the unique stereoscopic magnified image. A combined multifunctional endosurgical unit regulates suction, irrigation, intrarectal pressure, and gas insufflation. Suction removes fluid, blood, waste, and smoke. Irrigation helps maintain a relatively clean operative field and can rinse the end of the scope. CO₂ insufflation maintains distention of the rectum throughout the procedure and flow can be increased as high as 6 l/minute. The intrarectal pressure is set at a desired level (usually 10–15 cm H₂O) and the four functions mentioned above are regulated to achieve a constant steady state at that level. The surgeon may choose at various times during the operation to increase the suction; when this occurs, the endosurgical unit will increase flow of CO₂ to maintain a steady state. If intrarectal pressure does not rise or if the rectum does not distend, there is likely a leak in the system and the surgeon should be able to systematically check the set up for air leaks. This is probably the most frequently encountered problem that the surgeon must learn to troubleshoot.

The operating rectoscopes are beveled and are approximately 4 cm in diameter. A straight, nonbeveled rectoscope is also available and may be preferable for the very distal lesions where the lower lip of a beveled scope could slip exterior to the patient allowing for the escape of CO₂ and collapse of the operative field. Since the end of a beveled scope must face downward at the lesion, patients are variably positioned, depending upon where the lesion is located along the anterior–posterior dimensions of the rectal wall. For example, if a patient has an anterior lesion, he or she should be placed in the prone position with the legs spread apart to permit close access to the perineum. After the legs are placed upon and secured to long and well-padded long-arm boards, the foot of the table is dropped to allow the surgeon to sit close to the patient. Alternatively, stirrups placed parallel to the floor and coming off the end of the table can be used to support the legs in the prone position. For a posterior lesion, the patient is placed in the lithotomy position and if the lesion is laterally located, the patient is placed in the appropriate lateral decubitus position. The end of the rectoscope is covered with a sealed facepiece, which has airtight rubber seals and sealed working ports through which the long-shafted instruments necessary for the dissection are inserted. The suction catheter can be electrified and in this way a bleeding vessel can be coagulated while the blood is being aspirated. In a similar way, the tissue graspers can be electrified for control of a bleeding vessel. Vision is obtained through a binocular stereoscopic eyepiece, which provides a unique image yet magnifies at the same time. An accessory scope may be inserted for video recording and transmission of the image to a video monitor for viewing by surgical assistants, medical students, and surgical residents. The binocular eyepiece provides 6× magnification and has a 50 degree downward view and a 75 degree lateral field of view. In contrast, the accessory scope has a 40 degree downward view and a reduced lateral view. Because of the discrepancy, the image seen through the accessory scope and the video monitor is reduced in its scope relative to the binocular eyepiece.

Most of the bleeding occurring during full-thickness TEM dissections is encountered when one traverses the mesorectum. The standard TEM cautery may be insufficient in stemming the flow of brisk bleeding, the surgeon may
then have to work with a tissue grasper in each hand, working them in a hand-over-fist manner to get to the bleeding vessel, grasp it, and then coagulate it. This can be somewhat cumbersome. At those points during an operation when bleeding is likely to occur, the surgeon may chose to use an alternative energy device for hemostasis such as a harmonic scalpel (15). Studies have shown that a harmonic scalpel reduces operative time and bleeding. Ayodeji et al. compared harmonic dissection with the standard TEM cautery unit in a nonrandomized fashion, correcting for differences in tumor size between the two groups. The harmonic dissector reduced operative time by 26%; however, in 50% of the harmonic group, the surgeon used a hybrid approach and used cautery for portions of the case (16). Hermsen et al. showed that when the long harmonic shears are used, a further reduction in operative time can be achieved as well as a significant reduction in blood loss (17). Caution should be exercised. In rare instances, pelvic sepsis has occurred following cases, which used the harmonic dissectors possibly as a result of prolonged application of energy to the tissue. When cautery is used to traverse the mesentery, the energy is imparted in short bursts at very focal and precise areas. In contrast, when a harmonic dissector is used, tissue is grasped and energy imparted over a longer period of time until the tissue separates.

The TEM needle holder is self-righting. The needle can be grasped when in an inverted position, yet the needle holder will automatically place it in the upright position when the locking mechanism is activated. Sutures are started and finished with silver shots applied to the thread with a specially designed applicator. Traditional instrument knot tying is too tedious to perform on a constant basis.

Surgery

Technique

Once the anesthetic has been administered, the patient is positioned according to the location of the tumor. The buttocks and perineum are washed with antiseptic solution, sterile drapes are placed, and the rectoscope is inserted up to the lesion under direct vision aided by the manual insufflations of air. The scope is then secured to the operating room table with the adjustable, double-jointed Martin arm and the facepiece is locked into place on the end of the scope. The Martin arm is moved multiple times during the procedure in order to keep the lesion and the area of dissection in the center of the optical field. Rubber sleeves, covered by rubber caps with a hole in their center are placed onto the working ports of the facepiece. The long shafted instruments are inserted and the tubing necessary for CO₂ insufflation, saline irrigation, and pressure monitoring are connected. The binocular eyepiece and the accessory scope are inserted.

The technique of excision will vary according to preoperative histology, suspicion that a “benign” lesion may contain an occult cancer, and the location of the lesion within the rectum. Small adenomas may be removed by dissecting within the submucosal plane; this is especially appropriate for an anterior lesion in a woman where the anterior peritoneal reflection is unpredictable in its location and a full-thickness excision may be hazardous. For a submucosal excision of a small adenoma, a 5-mm margin of normal appearing mucosa is marked around the lesion, the mucosal edge is lifted with the tissue grasper, and the lesion is excised without entering the muscularis. Larger adenomas may contain invasive cancer and are excised using a full-thickness technique whereby the dissection is taken down into the mesorectal fat. If the peritoneum is violated, it should be repaired promptly and the operation completed as planned, conversion to laparotomy is not necessary. Before the patient is extubated, the abdomen should be examined in the event a large pneumoperitoneum needs needle decompression. Cancers are removed with a full-thickness excision after a 1-cm margin has been marked around the lesion. To help orient the pathologist to the deep and lateral margins, the specimen should be sutured or pinned to a flat surface such as cork board or a piece of Telfa paper. Wounds are closed transversely with a 3-0 running monofilament suture and SH needle. TEM surgeons frequently debate whether or not the wound needs to be closed. Small submucosal excisions can certainly be left open; however, larger open wounds are more likely to cause a longer period of tenesmus, bleeding, and mucous discharge during the days or weeks
after surgery. Ramirez prospectively randomized TEM patients into a group that underwent wound closure and a group that did not. Wound closure extended surgery by 16 minutes but this was not significantly significant. In fact, no significant differences were noted with respect to intraoperative bleeding, length of stay, and early or late complications (18). This author’s belief is that closure should be attempted in all mainly to maintain one’s skills in suturing. There will be instances where suturing is mandatory such as in cases of peritoneal entry or following excision of circumferential lesions.

Technical pearls are as follows:

Sutures of short length are preferable in order to be able to pull the suture tight yet stay within the narrow confines of the rectum.
Crossover of instruments should be avoided, rather, they should be manipulated in parallel.
One should avoid dropping the needle. It is far better to pass it from instrument to instrument otherwise time will be wasted looking for the needle.
One should avoid high-power settings on the cautery unit as excessive heat will fog the lens and create unnecessary smoke. Moreover, the end of the scope should be kept at a distance from the lesion in order to avoid splatter and debris from hitting the lens.
The surgeon should become adept at knowing where air leaks in the system are likely to occur and how to fix them.
The scope should be repositioned several times during the course of the dissection in order to keep the operative field in the center of the optical field.
All of the instruments including the shaft of the eyepiece should be lubricated with mineral oil to facilitate passage and reduce wear and tear on the rubber seals of the facepiece.
For large wound defects, one should use multiple sutures of short length. When closure is complete, one should be sure that the rectal lumen has not been inadvertently closed by passing a rigid proctoscope through the area.