Introduction

Rectal resection combined with total mesorectal excision1 represents the gold standard for the surgical treatment of mid and low rectal cancers, with a 4 % local recurrence rate and a 78 % tumor-free survival rate at 10 years in patients with operable and non-metastatic rectal cancer2.

With increasing use of sphincter-sparing surgery, the need for an abdominoperineal resection (APR) in the treatment of rectal cancer has decreased during the last two decades. However, APR is mandatory in up to 30 % of cases,3 and a temporary diverting stoma is performed in 50–100 % of sphincter-saving procedures4. In addition, radical rectal resection through an abdominal approach is burdened by significant postoperative morbidity,5 including sexual and urinary dysfunction,6–9 stoma-related complications, and changes in body image and depression due to the presence of a stoma10.

The development of transanal endoscopic microsurgery (TEM)11 during the last 30 years has led to the evolution of the treatment of rectal neoplasms. TEM has revolutionized the technique and outcomes of transanal surgery. While transanal local excision with retractors is associated with a high incidence of local recurrence particularly for tumors in the proximal rectum12, 13, TEM affords the advantage of a less invasive transanal approach with low recurrence rates secondary to a more precise dissection due to enhanced visualization of the surgical field.

Currently, TEM represents the standard treatment modality for large rectal adenomas14, 15 and a surgical option in selected early rectal cancers16, 17. Its potential role in the treatment of more invasive cancer in combination with neo-adjuvant therapies is currently under evaluation18–20.

In this report, we describe our technique of performing a TEM procedure for rectal neoplasm.

Indications

At our institution, indications for TEM include rectal lesions with a preoperative histological diagnosis of adenoma which are judged unsuitable for endoscopic removal and staged uT0 N0 by preoperative transanal endoscopic ultrasound (EUS) or adenocarcinomas preoperatively staged uT1 N0 M0. More invasive or metastatic rectal cancers are treated by TEM with palliative intent only. Recently, after approval from the local Ethical Committee, we have expanded the indications for TEM to include in selected cases, and after informed consent of the patient, uT2 N0 M0 adenocarcinomas treated by neoadjuvant radiotherapy with either down-staging or down-sizing of the lesion. Although inadvertent opening of the peritoneum is not to be considered an intraoperative complication, rectal lesions are considered suitable for TEM only when the proximal extent is located within 12 cm from the anal verge on the anterior aspect, 15 cm from the anal verge on the lateral walls, and 18 cm from the anal verge on the posterior wall.

Although technically challenging, circumferential full-thickness excision for benign lesions with an end-to-end anastomosis can be achieved by TEM (Table 1).

Table 1 Indications and outcomes of transanal endoscopic microsurgery
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Preoperative Work-Up

The preoperative work-up includes clinical evaluation, complete colonoscopy to exclude synchronous colonic lesions, rigid proctoscopy to locate the lesion along the circumference and to measure the distance of the upper and lower limits from the anal verge, EUS to assess the level of invasion, pelvic magnetic resonance imaging to detect potential lymph node metastases, chest and abdominal computed tomography to exclude distant metastases, and serum carcinoembryonic antigen assay.

Because of the absence of a lymphadenectomy, accurate preoperative evaluation is essential to obtain satisfactory oncologic results with TEM. In particular, it is crucial to accurately evaluate the depth of tumor invasion and lymph node metastasis. Technological improvements in EUS probes have led to a progressive reduction in staging discrepancies from a rate of almost 50 % in the early 1990s to less than 15 % in the last 5 years. Due to an approximate 5 % risk of over-staging by EUS if there is a discrepancy between clinical evaluation (soft and mobile lesion) and EUS staging (uT2) for a large adenoma, we utilize TEM as the means to assess the exact diagnosis and depth of penetration.

Technique

Patient Preparation

All patients are asked to commence a low-fiber diet the week before TEM, and a rectal enema is performed 12 and 2 h preoperatively. Intravenous antibiotics, such as a second-generation cephalosporin and metronidazole, are administered before insertion of the proctoscope and continued for 24 h at 12-h intervals. Deep venous thrombosis prophylaxis is not administered.

Equipment

Prior to 2008, we routinely used the original Richard Wolf (Knittingen, Germany) TEM equipment. However, after 2008, we performed TEM with transanal endoscopic operation (TEO) instrumentation by Karl Storz GmbH (Tuttlingen, Germany), according to the standard technique described by Buess.11 TEO instrumentation includes a 7 or 15 cm rectal tube which is 4 cm in diameter and has three working channels (12, 5, and 5 mm) for dedicated or conventional laparoscopic instruments, plus a 5 mm channel dedicated to a 30° 2D optic (Fig. 1). The proctoscope is connected to the operating table via a holding arm consisting of three joints and a single screw (Fig. 2). The system is used in combination with standard laparoscopic units. Camera imaging is projected on-screen, and insufflation is obtained by a conventional CO2 thermo-insufflator which is connected to the proctoscope via a Luer lock connector. The shape of the tip of the proctoscope allows manipulation and suturing of the rectal wall on a 360° surface. Therefore, most patients are kept in a supine position, thereby reducing the need for time-consuming patient repositioning on the operating table.

Fig. 1
figure 1

Long (left) and short (right) proctoscope with three working channels

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Fig. 2
figure 2

TEO instrumentation in place. a Rectal tube; b working channel; c camera; d holding arm; e connector for CO2 insufflation; f monopolar hook cautery; g grasper

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Recently, single cases and small series of patients treated by TEM performed using equipment for single incision laparoscopic surgery (SILS) have been reported. There is a lower cost for the single disposable SILS equipment compared with each single reusable TEM proctoscope. However, no comparative studies aimed at evaluating the cost of TEM in high-volume centers over long periods of time have been published.

Positioning of the Patient on the Operating Table

The TEM procedure is usually performed under general anesthesia. The patient is placed either prone or supine in order to keep the lesion as close to the 6-o’clock position as possible, even with lateral lesions. Different from what was originally described by Buess, we avoid placing the patient in the lateral decubitus position, as this is extremely difficult and the benefit is minimal. Patients with lateral lesions are usually placed in the supine position, unless the lesion is predominantly located in the right or left upper quadrant (i.e., 12- to 3-o’clock position or 9- to 12-o’clock position).

With circumferential lesions, the patient is always positioned prone due to the higher risk of entering the peritoneal cavity and the consequent need to reduce the descent of small bowel loops into the surgical field while repairing the opening itself.

Surgical Technique

Step 1: Dissection

After insertion of the proctoscope, the lesion is identified and the proctoscope is fixed in the correct position. However, the position is adjusted throughout the procedure in order to ensure optimal visualization and access to the margins of the lesion. High-flow carbon dioxide (CO2) insufflation is required, and endoluminal pressure is generally maintained at 8 mmHg, although, it might need to be increased up to 16 mmHg. Dissection is usually started at the right lower border of the tumor (Fig. 3a). A macroscopic margin of at least 5 mm from the neoplasm needs to be obtained with both benign and malignant lesions. Tumor excision is performed by monopolar hook cautery. In difficult cases, especially if a partial mesorectal excision is recommended for malignancy, ultrasonic shears (Johnson and Johnson Medical, Cincinnati, OH) or an electrothermal bipolar vessel sealing system (Valleylab, Covidien, Boulder, CO) may be helpful. Dissection is continued circumferentially around the lesion to the perirectal fat (Fig. 3b, c). Due to the uncertainty of the preoperative diagnosis and staging, full-thickness resection with adequate margins of clearance should be performed. The specimen is retrieved transanally and is pinned on a corkboard before fixation in 10 % buffered formalin in order to preserve the margins of normal mucosa surrounding the tumor. The specimen is analyzed by permanent section.

Fig. 3
figure 3

Dissection of the rectal neoplasm

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Step 2: Wall Defect Suturing

After the parietal defect is disinfected with iodopovidone solution, the rectal wall is always closed with one or more Maxon 3-0 (Codisan ® S.p.A.) running sutures secured with dedicated silver clips (Richard Wolf, Knittingen, Germany). These clips serve to anchor the suture in place, since knot-tying during TEM is challenging. As an alternative, the Endo Stitch™ single-use suturing device can also be used.

At this stage, the endoluminal pressure may be reduced to allow better compliance of the rectal wall. Suturing is performed with particular attention to the integrity of the rectal lumen. Therefore, when suturing large defects, a midline stitch to approximate proximal and distal margins is placed (Fig. 4). At the end of the procedure, patency of the rectum is carefully verified through the TEM proctoscope.

Fig. 4
figure 4

Suture of the rectal wall defect

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Post-operative Management

Patients are mobilized the same day as surgery. The urinary catheter placed at the time of surgery is removed 24 h after surgery (48 h if the anterior wall was involved). Postoperative analgesia is ensured by intravenous paracetamol for 24 h. Oral intake is allowed the day after flatus is reported.

Results

Perioperative Outcomes

Peritoneal perforation (PP) is a serious and challenging intraoperative event that may occur during TEM. It is frequently reported as a complication, and therefore tumors of the upper rectum, especially those located on the anterior or lateral wall, are considered a contraindication to TEM. The learning curve and the case volume of the surgical center are two main factors that influence the treatment strategy adopted when PP occurs. Conversion to laparotomy is reported in 50–100 % of cases of PP in series with less than 100 patients, whereas it ranges between 0 % and 40 % in larger series.

We recently reported an overall PP rate of 5.8 % in 481 consecutive patients, with a trend toward a higher rate of PP over the last 4 years compared with the preceding period (8.5 % versus 4.3 %), reflecting the extension of indications to larger and more proximal lesions.21 The extension of indications for TEM is derived not only from increased surgical experience and dexterity, but also from the use of the TEO instrument (Karl Storz GmbH) which, secondary to the particular shape of the tip of the proctoscope, allows manipulation and suturing of the rectal wall on a 360° surface. In addition, due to the discrepancy between preoperative and postoperative histology and staging, our policy is to perform a full-thickness excision, even with anterior wall lesions, in order to obtain a complete specimen and enable a correct pT staging.

No cases of pelvic sepsis or infectious complications after PP have been observed.

PP does not seem to influence oncologic outcomes. With a median follow-up of over 4 years, all patients in whom a PP occurred during TEM for adenoma or pT1 rectal cancer are disease-free, with no sign of peritoneal seeding of adenomatous or cancerous tissue.

In line with previous studies that reported postoperative complication rates between 2 % and 15 %,16 we observed an early postoperative complication rate of 7.7 % in our initial series of 300 patients22 which decreased to 4 % in the following 200 patients, despite an expansion of the indications for TEM to include more complicated cases. No deaths occurred. In most cases, common local complications, such as bleeding and suture dehiscence, can be managed conservatively. Four patients developed rectovaginal fistulas; while all were successfully treated by transvaginal surgical suture, this highlights that special care should be taken when performing an anterior full-thickness resection in female patients (Table 1).

Oncologic Outcomes

Large Adenomas

Among surgical techniques, TEM represents a valid surgical alternative to conventional transanal surgery in the treatment of large rectal adenomas. TEM has the advantage of combining a less invasive transanal approach which has benefits in terms of postoperative functional outcomes and quality of life and low recurrence rates for adenomas and selected early rectal cancers due to enhanced visualization of the surgical field allowing precise dissection.

In our series of 293 rectal adenomas23 over a median follow-up period of 110 (range, 12–216) months, the recurrence rate was 5.6 %, with more than 75 % of recurrences detected within 12 months after TEM (Table 1). Since over 75 % of recurrences occurred within the first 12 months, we suggest an intensive follow-up protocol including proctoscopy every 3 months for the first year, then every 6 months if there were positive margins at final pathology or the adenoma was ≥5 cm.

Adenocarcinomas

For over 20 years, TEM has been proposed for treatment of early rectal cancer. The depth of submucosal invasion for pT1 cancers is an important prognostic factor. Therefore, a precise evaluation of the depth of tumor invasion and lymph node metastases is crucial for the appropriate patient selection.

Our series of 48 pT1 patients demonstrated a significant difference in recurrence rates between pT1 sm1 (0 %) and sm2-3 (22.7 %)24 (Table 1).

The role of TEM in the treatment of more invasive rectal cancer is controversial. One of the main disadvantages of transanal excision concerns the lymphadenectomy. The incidence of lymph node metastasis is very low for T1 sm1, but, for T1 sm2-3 and for T2, it increases up to 25 %. In these cases, especially T2 tumors, TEM alone does not represent an adequate therapy, being burdened by a significantly higher recurrence rate compared with abdominal surgery. Therefore, transanal excisions should be limited to those lesions previously staged as uT2 that demonstrate significant down-staging or down-sizing.

Functional Results

As TEM requires the transanal insertion of a 40-mm diameter rigid proctoscope with continuous endorectal CO2 insufflation and full-thickness excision of a portion of the rectal wall, both gas and fecal continence may be compromised. In a series of 100 patients prospectively evaluated by standardized questionnaires and manometry25, postoperative manometric values at 3 months were lower than at baseline but had returned to preoperative values at 12 months. Tumor size ≥ 4 cm was the only factor that significantly (P = 0.008) affected the rectal sensitivity threshold, the urge to defecate threshold, and the maximum tolerated volume at 3 months after TEM. A significant improvement was noted in various clinical and quality of life scores at 12 and 60 months.

Transient worsening of fecal continence and a higher rate of urgency are the reasons for a temporary reduction of quality of life; however, these completely resolve by 1 year. On the other hand, urological and sexual dysfunction that frequently occurs after abdominal surgery for rectal cancer is rare after TEM.

Conclusions

During the last three decades, TEM has been increasingly used in the treatment of rectal neoplasms. Designed as a means to excise benign rectal neoplasms with very low morbidity, the indications for TEM have since expanded to include malignant neoplasms that are histologically confirmed as pT1 sm1 carcinomas. At present, patients with T1 sm2-3 and T2 lesions should be treated with TEM only if they are enrolled in a clinical trial and in combination with neoadjuvant therapy. In line with these observations, accurate preoperative staging is essential for appropriate patient selection. Furthermore, TEM does not have long-term effects on anorectal function or quality of life. We feel that patients with a clear indication for TEM should be referred to specialized medical centers at which surgeons, endoscopists, gastroenterologists, and pathologists are experienced with the technique.