During the dissection process and during the suturing, precise manipulation of two instruments is mandatory. Monocular vision provides less precise information because of the parallel movement of the instruments. Subsequently, the triangulation effect that provides spatial information is not available. The optical system provides a natural stereoscopic view in combination with a high-resolution image. A third rod lens optic has been introduced into the stereoscopic optic that is connected to a video camera. Images are displayed on a screen to provide useful information to the entire operative team and for teaching purposes.
By means of TEM, together with optimal coagulation systems, it is possible to provide mucosectomy, partial or full wall excision and segment resection, with preservation of an adequate safety margin between the tumour and the line of resection.
The most frequent indications of TEM are as follows:
- sessile adenomas
- large broad-based pedunculate polyps
- early carcinoma (pTl) in good or with medium differentiation adenomas within the extraperito-neal portion of the rectum
- carcinoma (pT2) in elderly, high-risk patients
- benign rectal tumours (lipoma, leiomyoma)
- diagnosis and centesis of haemorrhages
- correction of rectal stenosis
- closure of fistulas
TEM has been developed mostly for lesions out of reach from the transanal approach. It could be used also for large benign lesions above the peritoneal reflection.
Favourable T1 lesions have equivalent local recurrence rate and 5-year survival compared to radical surgery. Unfavourable T1 lesions have higher local recurrence (10-15%). TEM+radiation therapy on T2 tumours have local recurrence of 25-46%.
Most larger mid-rectal and high rectal polyps have recently been managed by means of gas-filled endo-rectal excision, using the TEM technique. Although this technique has many advocates in Europe, in the USA it has mostly been ignored . But from time to time there are also reports from the USA describing first experiences with TEM . They succeeded in providing excision of rectal lesions with negative margins in 97% of cases with minimal morbidity and short-duration hospital stay. Their follow up was too brief to evaluate recurrences, but the thoroughness of resection of the tumour in a high proportion of cases was promising.
Endoscopic microsurgery is at the moment the most advanced procedure in the field of intraluminal surgery . At the same time, endoscopic microsurgery, which has been in the clinical routine since 1983 , was the first complex endoscopic operation to be routinely applied in gastrointestinal surgery. The procedure is performed using the operative rectosco-pe. A number of endoscopic instruments have been designed for TEM. CO2 insufflation must be performed by use of various systems, dealing recently with TEM. Also very special combinations of instruments exist for the dissection. They allow optimal handling and electronically controlled switching between the bipolar and cutting mode and the monopolar coagulation mode. The most modern electrosurgical systems come from Germany. They are constructed to be multifunctional (ERBE TEM 400), uniting bipolar cutting, monopolar coagulation, suction and irrigation. There is no need to change instruments during the operation as there was several years ago. The cutting needle extends automatically when the cutting function is activated and retracts automatically at the end of cutting. This ensures safe cutting (Fig. 5). Synchronous and intermittent suction and irrigation facilitate the surgical procedure. Suction is always provided due to the roller pump.
Their advantages are:
- streamlined surgery via a multifunctional instru-
ment with cutting, coagulation and suction/irrigation functions
- shorter procedural time
- shorter operations
- less morbidity (infection, incontinence)
Other sophisticated improvements are described every year. One of them is dye-enhanced selective laser ablation , which uses a diode laser, operating at a wavelength of 805 nm. Indocyanine green (ICG) has a maximum energy absorption of a wavelength of approximately 800 nm. The effect of the diode laser as a laser knife can be significantly enhanced with an injection of ICG. The dye-enhanced photothermal effect was investigated by the Japanese. Their experiences with resection of 5 rectal tumours by means of TEM were very good due to precise hae-mostasis and its excellent tissue cutting effect.
As mentioned above, TEM involves the use of expensive equipment, which is not widely available, while posterior approach techniques have lost their popularity due to the high incidence of post-operative complications .
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