**2. TEM instrumentation and technique**

The TEM system consists of a beveled rigid rectoscope of 4 cm in diameter and available in two sizes: 12 cm – short – or 20 cm – long – (**Figure 1**), depending on the preoperative location of the rectal lesion.

The rectoscope is fixed to the operating table with a multidirectional bearing, the Martin's Arm, and a constant pneumorectum is obtained by an insufflation unit providing carbon dioxide insufflation, suction, and irrigation (**Figure 2**).

The removable faceplate of the rectoscope has a port system to accommodate long curved instruments, the suction and coagulation cannula, and for placing the stereoscope with gas sealing (**Figure 3**). Through the stereoscope the surgeon obtains a magnified, three-dimensional vision of the rectal lesion with high-intensity lighting.

**Figure 1.** *Rectoscope © Richard Wolf GmbH. All rights reserved.*

#### **Figure 2.**

*Martin's Arm and insufflation system © Richard Wolf GmbH. All rights reserved.*

#### **Figure 3.**

*Port System and Stereoscope © Richard Wolf GmbH. All rights reserved.*

The stereoscope can also be connected to a laparoscopic video unit, for procedure recording and teaching purposes.

Given the instrumentation design, the lesion must always be located in the inferior part of the operative visual field. Therefore, a precise preoperative assessment of the rectal tumor position is of upmost importance because the patient's position on the operative table depends on the localization of the rectal lesion: for anteriorly located lesions, a prone jack-knife position (**Figure 4**) is required, whereas a lithotomy position is needed for posterior lesions (**Figure 5**). These positions may have to be coupled with a lateral tilt of the operative table on one side or the other in case of lesions that are located on the lateral rectal wall. The patient's position and the instrumentation settings may sometimes have to be changed during the procedure; therefore, an excellent supporting working team is fundamental.

**Figure 4.** *The prone jack-knife position for anterior lesions.*

**Figure 5.** *The lithotomy position for posterior lesions.*

Once the correct patient position and lesion exposure are obtained, the surgeon gets a magnified view of the distended rectum and can take advantage of a wide set of angled instruments (monopolar grasping forceps, scissors, needle holder, hook, silver clip applier, suction/irrigation, and coagulation cannula) to excise the lesion with adequate margins. The surgeon may therefore perform a full-thickness resection of the rectal lesion including the perilesional mesorectal fat, if necessary, and to close the residual defect with a running suture.
