T ransanal endoscopic microsurgery (TEM) is a surgical technique introduced in the 1980s as an answer to the technical difficulties of the resection of tumors in the ampulla of the rectum.
Traditionally, the most frequently used procedure in the treatment of tumors located in the lower third of the rectum has been endoanal exeresis, limited to a distance up to 7 or 8 cm from the anal margin. As far as visual control of the dissection limits and haemostasis are concerned, the use of this technique can lead to difficulties due to big and high tumors.
In the middle third of the rectum, the most frequent exeresis technique was usually via the sphincter, but it is less and less common due to high morbidity rates and associated morbidity. The trassacral exeresis of the rectum which allowed access to the upper third has also been abandoned because of its high morbidity and mortality rates.
When facing big adenomatous tumors, the alternative to these techniques is low anterior resection of the rectum or abdominoperineal resection. In rectum cancer, the chosen technique is this abdominoperitoneal resection with total mesorrectal excision. Thanks to these techniques, the mortality in our Hospital is inferior to 1% and morbidity is inferior to 15%, not to mention the disruption caused by the need of temporary or definitive ostomies.
The TEM (Transanal endoscopic microsurgery) was created to give an answer to these difficulties, and it is an endoscopic procedure that permits preserving the sphincter apparatus. Thanks to the excellent vision system of the proctoscope and the creation of a pneumorectum, it is possible to access rectum tumors located up to 20 cm from the anal margin. . The Transanal endoscopic microsurgery technique facilitates dissection, cutting, coagulation and suture.
The lack of circulation of the Transanal endoscopic microsurgery technique, which is only available in a very select and reduced number of clinic centers, has been determined by the need of a long and very specific knowledge curve.
The use of ultrasonic scalpel in Transanal endoscopic microsurgery facilitates tumor dissection and better control of haemostasis, therefore surgical time is reduced.
Patient selection protocol/b>
The selection of patients for TEM leads to a correct preoperative staging of rectal tumors. We perform a total colonoscopy with multifocal biopsy of the injury to all patients. Thus, we obtain details on the tumor size, the distance between its upper and lower rims to the anal margin, the location in its quadrants and the presence of other possible synchronic injuries in the rectum or colon.
The biopsies inform if we are facing adenomas, their type (tubular, tubulovillous, and villous), and the degree of dysplasia. Moreover, we can learn if they are infiltrating or intramucous adenocarcimona (in situ), and the degree of differentiation.
The endorrectal ultrasonography allows staging the injury and confirms the tumor size, the distance between its upper and lower rims to the anal margin, the location in its quadrants (front, back left or right side). It is very important to confirm the location of the injury, as it affects the position of the patient in the surgical table.
Magnetic resonance imaging of the pelvis is a very important test that complements the endorrectal ultrasonography. Although the accuracy in the staging of the tumor is not better than the endorrectal ultrasonography, it is necessary to proceed with this test in case of rectum adenocarcinoma. This is done in order to confirm the staging, but specially to confirm the absence of possible metastatic adenopathies. In our opinion, it is also compulsory in case of villous adenoma greater than 3 cm diameter because of the high percentage of malignancy, which can reach 32% of cases. More specifically, the magnetic resonance must indicate the staging of the tumor, the presence of adenopathies and the topography of the injury.
With diagnosed tumors of adenocarcinomas or in case of suspicion of this, we perform a computed tomography to rule out distant metastasis and also to determine tumor marker CEA and CA 19.9.
Patients apt for Transanal endoscopic microsurgery
Local exeresis via TEM is indicated for the following pathologies: adenoma, rectal adenocarcinoma (stages T0-1, N0 and T1-2; N0 in very specific cases) and rectal tumors at any state with a palliative orientation.
Technical limitations for Transanal endoscopic microsurgery
- Location regarding the anal margin. Unlike endoanal exeresis, in which the distance between the injuries and the anal margin is limited to 7 or 8 cm, the limitations for TEM lays in the risk derived from the location of the injury in the intraperitoneal area. This is why it is so important to know the exact location of the injury. Exeresis is feasible with reduced risks of perforation up to 18-20 cm when the location of the tumor is in the front quadrant, and up to 15 cm if it is located laterally of in the back quadrant.
- Size of the injury. Thanks to Transanal endoscopic microsurgery, the classic limitations have changed when the injury is smaller than 3.4 cm and does not take up more than a quadrant of the circumference. It is possible to obtain exeresis of injuries with up to 12 cm of diameter that occupy three quadrants of the circumference.
Postoperative morbidity and mortality
Postoperative morbidity range from 4 to 24%. Most of these cases are minor complications that require a conservative treatment. Major complications are those that require surgery, and they conform less than 5% of the cases. The most frequent one is perforation, which makes a surgical reintervention necessary
Sphincter functional alterations after Transanal endoscopic microsurgery
Traditionally, the introduction of a 4-diameter rectoscope in the sphincter apparatus has been considered to cause injuries and sphincter alterations. However, it has been demonstrated that its use does not worsen the sphincter functionality.
Control and monitoring after Transanal endoscopic microsurgery
It is advisable to closely monitor these patients performing a transrectal ultrasonography and a rectosigmoidoscopic examination with a multifocal biopsy of the scar every 4 months during the first 2 years. From the third to the fifth year, these controls are performed every 6 months, and later come regular controls. Moreover, it is necessary to control the sphincter function 3 weeks later and also 3 months after the procedure.