Transanal endoscopic microsurgery (TEM)Medical editor Arild Nesbakken MD
Oslo University Hospital
Using transanal endoscopic microsurgery (TEM) tumors in the rectum can be removed with far greater precision and overview than other endoscopic or conventional transanal techniques allow. This provides greater confidence of complete removal of the lesion and that local recurrences are avoided. Complete resection also provides a correct histological diagnosis.
Cancer in the head of pedunculated polyp
- For T1 tumor in pedunculated polyp, Haggitt level 1 and 2, removed by endoscopic snare resection with macro- and microscopic definitely free resection margins, the treatment is considered as completed. (Similarly in colon.)
- For Haggitt level 3 the resection margins is often questionable. In rectum a resection of the area can then be performed by TEM, and histology will clarify whether this is adequate treatment. (In colon a formal resection must be performed.)
- Haggitt level 4 is treated as a sessile tumor.
Cancer of sessile polyp
TEM is the main method for removing large premalignant polyps in the rectum. Polyps up to 10-12 cm in diameter may be removed by TEM, including polyps growing around the circumference of the intestine, and are located in the area of the dentate line up to about 15 cm above the anal opening.
For infiltrating cancer local excision by TEM is a good option for curative treatment if the following criteria are met:
- The tumor is less than 2.5 to 3 cm in diameter
- The tumor is high or moderately differentiated
- The tumor does not invade deeper than the upper part of the submucosa (Kikuchi sm1)
- For sm1 there is an agreement that TEM excision is curative when performed adequately
- For sm2 there is no agreement that TEM is sufficiently radical and these patients must be considered individually
- There are no signs of infiltration in vessels or lymphatic infiltration
- The location of the rectal tumor is in an area where performing a full wall resection is possible, and one cm free margin laterally is achievable (in mucosa/intestinal wall surrounding the tumor)
It is being attempted to ascertain whether these criteria are met at the preoperative staging assessment, but a final and correct answer is only available after histological examination of the TEM sample. The TEM procedure is therefore often called a diagnostic excision biopsy and histological response will decide whether the procedure is sufficiently radical.
If all criteria are met, the risk of local recurrence is less than 10%. Patients must be carefully controlled by rectal exploration, endoscopy and possibly rectal ultrasound. Any recurrence may then be detected at an early stage, and a curative reoperation can be performed.
If all criteria are note met, patients in good general condition should be reoperated with total mesorectal excision (TME) within a few weeks. The patient should have information and be aware of this before the TEM operation.
In very old patients and patients with poor general condition TEM may be appropriate as a compromise operation also for deep T1 and at T2 tumors. The risk of local recurrence is approximately 30% for this group, but if radiation therapy is given additionally it will be reduced, possibly in combination with chemotherapy. This should be assessed individually based on the risk of side effects. Disadvantage of TEM is that the surgery usually requires general anesthesia, and therefore is more straining for the patient than other endoscopic techniques.
- A operating rectoscope ,4 centimeter in diameter and 15 or 25 centimeter in length, is used. This is fixed on a movable holder mounted to the operation table.
- The optical system is put into place, there is binocular optics with six times magnification and a good three-dimensional image. A camera for view on a screen (2D) may also be connected.
- There are three working channels for grasping forceps, diathermy knife/needle holder and suction.
- Thorough preoperative bowel emptying is necessary. Oral laxative is administered the day before the surgery and water enema the day of surgery.
- Thrombosis- and antibiotic prophylaxis are administered. The patient needs a urinary catheter.
- The patient is positioned on the operating table depending on the location of the tumor around the circumference. The position does not change during the procedure, but the operating table can be tilted if necessary.
- The operation is usually performed under general anesthesia and with full muscle relaxation. Exceptionally the operation is performed under spinal anesthesia.
- The rectoscope is put in place and a intraluminal pressure of approximately 10 mm Hg is being established.
- A suction is inserted to remove smoke after diathermy, fluids and possibly blood.
- With grips pliers in the left hand and dissecting instruments or needle holder in the right hand, resection and suture of the defect in the intestinal wall are performed.
- If the patient is fully relaxed with low intraabdominal pressure in order to distend the rectum and the polyp is not too big, a good visualization of the operation field is usually possible. If the polyp is growing very exophytic, and possibly has a large diameter (> 5.6 centimeters) the lumen will often be filled out after some dissection and this will complicate the overview.
TEM is technically difficult because of the small space in the rectoscope with three working intruments which easily collide with each other. When the rectoscope is mounted, there is a limited area of access to the rectal wall. It is therefore necessary to move and angle the rectoscope repeated times to reach the areas to be dissected or sutured.When everything functions optimally there is however good overview, and the different layers of the bowel wall are defined and it is possible to dissect submucosa or between the muscle layers in the muscularis propria or perirectal fat tissue (full wall resection).
Full wall resection is the quickest and most simple method and is preferred in the areas of the rectum where the entire wall can be removed. Distally, the external sphincter will be damaged and cranially on the anterior rectal wall, the abdominal cavity will be opened with a full wall resection. In these two areas, only a mucosal resection should be performed.
When operating for cancer a full wall resection is always the intention.
The patient may begin to drink, eat and mobilize immediately after surgery. The catheter is removed as soon as the patient is mobilized and no later than the first postoperative day.
Oral analgesics is administered if required. There is usually minimal pain associated with the postoperative phase, but sutures in and close to the dentate line may be painful.
Patients are usually discharged on the first postoperative day. For very large resections or increased risk of infection the patient stays hospitalized for three-four days for observation.
- Serious complications after TEM are rare.
- Moderate fever (up to 38.5 ° C) and CRP increase to 200 is normal and does not indicate a complication.
- Infection originating from the perirectal pocket that appears after suture of the intestinal wall may occur. An abscess usually drains itself through the sutures and antibiotics for some days are sufficient treatment. In rare cases (1-2 %), the patient gets a serious perirectal infection, possibly with sepsis.
- Postoperative bleeding in the form of blood seepage is common. Hematoma in perirectal pocket often leads to infection. In some cases (about 5 %) a major bleeding may occur 6-10 days after surgery and a doctor should be consulted.The bleeding usually stops spontaneously.
- Postoperative perforation of the intestine to free abdominal cavity is very rare. The condition usually requires reoperation and construction of a stoma.
Control for TEM for cancer
The patients should have follow- up controls at the surgical ward which carried out the operation.
There should be controls at least every six months for three years. Thereafter annually up to the fifth follow-up year. At every control a rectal examination, endoscopy and possibly rectal ultrasound are performed. This is sufficient if R0 resection with good margins at T1 sm1 is performed.
If a TEM is performed as a compromise at deep T1 or T2 tumor, and new treatment is relevant in case of local-regional recurrence, a control with MRI of the pelvis should be considered, particularly if the tumor was above the level that can be reached with the fingers during exploration. Additionally the CEA may be controlled. CT for detection of distant metastases may be considered individually.