Our study involved almost one hundred patients operated on by the same transanal technique with the novel proctoscope. The surgery was performed in an acceptable surgical time, less than 70 minutes on average, with low rates of postoperative complications, low instances of recurrence and no deaths.
One disadvantage of TEM is the visualization of very low tumors. The novel proctoscope allows the surgeon to easily remove adenomas <5 cm from the anal verge. TEO has a shorter learning curve, similar to our proctoscope. However, a 3D optical system is not used, TEO experience is limited, and studies about this technique are scarce (7, 12). TAMIS is a safe technique with a short learning curve for laparoscopic surgeons already proficient in single-port procedures, and it provides effective oncological outcomes (13). However, it has limitations in that the rectoscope cannot be mobilized at the injury site, rectal lesions located behind a rectal valve can be more difficult to access and remove, and an assistant is required to hold and manipulate the laparoscope during the surgery. Our proctoscope can be mobilized during the procedure and can remove lesions with low difficulty levels behind the rectal valves.
We found a mean operative time of 65.3 ± 41.7 minutes. Compared to other surgeries, the technique using the proctoscope was associated with a shorter operative time (14-17). Our study presented a conversion rate for open surgery oftechnical difficulties resulting from the extension of the lesion (10 and 15 cm). The conversion rates vary from 1% to 13%. Conversion to low anterior resection occurred in 6% of cases due to difficult access to the lesion and lack of progress in another series (14). Another study showed that in 6.7% of cases, the TEM procedure was discontinued because complete excision could not be completed endoscopically. In this series, the tumor extended up into the anterior wall of the upper rectum, similar to our study (15). Some authors described a 13% rate of conversion to Park’s transanal technique (18), mainly due to the proximity of the anal border and the difficulty in maintaining the pneumorectum (17). This did not occur in our study because there was no need for a pneumorectum in our proctoscope.
Our study showed rates of intraoperative and postoperative complications of 1% and 5%, respectively, which is lower than those described by other techniques (15, 18). Some authors reported that up to 20% of patients experienced postoperative complications (15), half of them due to postoperative peritonitis due to intra-abdominal perforation. The authors also reported postoperative bleeding, with some cases requiring blood transfusion. Some studies showed no intraoperative complications after surgery; however, the postoperative complication rates were higher than those in our study (9.7%), mainly due to hemorrhage (12). Another study had a postoperative complication rate of 10% (17), with complications including urinary retention, bleeding (requiring return to the operating room for urgent treatment) and suture line dehiscence. None of our patients presented with urinary retention or postoperative hemorrhage.
Our study showed a recurrence rate of 19% during the mean follow-up of 80 ± 61.5 months. To our knowledge, our study has the longest postoperative follow-up time after transanal polyp resection. The majority of studies have lower recurrence rates but a shorter median follow-up period. Recurrence is mainly related to compromised margins and can be detected in short- or long-term follow-ups. In our study, the margins were compromised or could not be evaluated due to piece fragmentation in approximately 40% of patients. In a review of 18 studies involving TEM-resected adenomas with a minimum follow-up of 12 months, the relapse rate was 0% to 15%, and relapse predominated in cases of positive or uncertain margin resection (5), similar to our results. Another study showed that during a median follow-up period of 15 months, two cases of recurrence occurred (12). Similar results were reported in another study, concluding that histological evaluation of the resected adenoma was an important predictor of recurrence and had the potential to guide follow-up strategies after surgery (19). In a systematic review of 266 procedures, the authors observed positive margins in 5% of cases, and margins could not be defined due to tissue fragmentation in almost one-third (31%) of the surgical specimens (20), which was also demonstrated in our study. Of the 19 patients with relapse in our series, the majority (57.9%) underwent a second transanal resection, and 36.8% of patients with recurrent lesions underwent rectosigmoidectomy due to a high adenoma location or cancer.
Another advantage of the new proctoscope is with regard to cost. The proctoscope used in this study is inexpensive compared with other technologies. In addition, other techniques, such as TEO, require a learning period (21). In addition, TEM has not gained wide acceptance in the surgical community and is routinely performed in only a few dedicated centers, mainly because of the long and challenging learning curve, high instrumentation costs, and relatively limited number of patients who are suitable for the procedure (8, 22). The initial cost of specialized TEM equipment is perceived by some surgeons as a limiting factor for the widespread adoption of this technique (23). The proctoscope used in this study is cheap (approximately U$ 300), and conventional and laparoscopic surgical instruments can be used without the need for gas insufflation, providing a three-dimensional view and allowing greater accessibility for surgeons (10, 11, 24).
Our study has several limitations. First, although a prospective database was used, this study was limited by its retrospective nature. However, it has the longest follow-up period to date. Second, this study was limited by the number of patients included, mainly because the surgical indication (large polyps in the rectum) was restricted. However, it is one of the largest national cohorts in terms of the number of patients. Third, the data were heterogeneous with regard to the size and location of the polyps. Therefore, further longitudinal studies using a more representative sample are needed to analyze the outcomes among patients with the same kind of polyps or similar disease stages. However, our series included only patients with rectal adenomas, which can compensate for this disparity in relation to the size and location of polyps. Finally, we compared our results with those of other techniques, even with the same study population (rectal adenoma patients). It is difficult to compare different transanal techniques, mainly due to the retrospective nature, with heterogeneous groups and many indications, in many studies. However, there are no data using our proctoscope, as it is a new device used in a single reference center.