Transanal endoscopic microsurgery (TEM) is the most standardized method for the local excision of benign or early malignant rectal neoplasms [1]. This method involves resection of the rectal wall via the rigid operating proctoscope with the aid of carbon dioxide insufflated into the bowel lumen, which provides optimal visualization of the operating area [2]. Though TEM carries the risk of a higher recurrence rate for rectal carcinomas compared to radical surgery, it has an asset of better functional results and quality of life (QoL) due to avoidance of stoma, preservation of the rectal capacity, and anal transitional sensitive zone [3].

Despite obvious advantages in terms of organ preservation, local excisions of rectal lesions by means of TEM are not completely free from undesirable functional sequela. A trauma of anal sphincters caused by inserting of the operating proctoscope and prolonged stretching of anal canal during the surgery can impair continence. On the other hand, a large wound of the rectal wall and particularly those involving transitional zone can result in low anterior resection syndrome (LARS) of some degree [4].

Thus, the selection of the most vulnerable category of patients who have a high risk of major loss of function seems to be an important task. This article is a single-center audit of the functional results after TEM aimed at elucidation of risk factors for the QoL.

The audit encompassed functional results of TEM obtained from January 2019 to March 2020. Only fully continent patients with rectal adenomas, who had TEM, were included. The Ethics Committee of State Scientific Centre of Coloproctology approved the study protocol before its beginning (No. N85A, 18.08.2018). All participants provided written informed consent prior to enrolment in the study. The study was registered on ClinicalTrials.gov (identifier: NCT03675243).

All surgeries were performed by 3 surgeons (EK, SC, and ER), who had passed the learning curve of the method (> 100 cases). Antibiotics prophylaxis was performed 30 minutes before the surgery using intravenous antibiotics of the fluoroquinolones or third generation cephalosporins. The surgeries were performed under combined spinal anesthesia with intravenous sedation, for long-term surgeries total intravenous anesthesia with muscle relaxation and artificial lung ventilation was used. The TEO equipment of Karl Storz was used as a platform for surgeries. After the patient was discharged, follow-up was carried out every 3 months after surgery by one of the 3 mentioned above surgeons in the outpatient setting.

Anorectal manometry was performed before the surgery and in 3, 6, and 12 months after the surgery using a nonperfusion water filling sensor and skin electrode at the WPM Solar gastroenterological complex in the Netherlands. Phosphate microenema was used before examination for rectal cleansing.

Anorectal manometry was carried out, with a patient on the left side position. The calibrated manometric sensor was inserted into the anal canal and stayed indwelled for 3 to 4 minutes with the aim of the patient’s adaptation and attenuation of the anal reflex caused by the sensor. The range of bioelectric activity signal, average resting, and average squeezing anal pressure were recorded simultaneously. Reference values of anorectal manometry were as follows: average resting pressure, 43 to 61 mmHg and 41 to 63 mmHg; average squeezing pressure, 121 to 227 mmHg and 110 to 178 mmHg for male and female patients, respectively [5].

Wexner fecal incontinence score was used to evaluate the degree of anal incontinence before the surgery and in 3, 6, and 12 months after surgery [6].

The impact of surgery on QoL was assessed using the Fecal Incontinence Quality of Life (FIQL) scale [7] scale for 4 domains: lifestyle, coping/behavior, depression, and frustration. Additionally, all the patients were asked the resulting question of whether their QoL had changed after the surgery. The questionnaire was filled out by the patient independently without the doctor’s participation.

The study included 89 consecutive patients, who underwent TEM for benign neoplasms of the low and midrectum. Patient characteristics are presented in Table 1.

All the patients were fully continent before the surgery, the mean Wexner score was 0.9±0.8 and 1.1±0.8 for male and female patients, respectively (Fig. 1). In 3 months after TEM, the mean score changed to 4.4±2.4 and 5.2±3.0 for male and female patients, respectively (P=0.01). This difference remained significant in 6 months of the follow-up: 2.6±1.6 and 3.3±1.8 for male and female patients, respectively (P=0.01). After 12 months, the function in most patients returned to normal values and loss of statistical difference (0.90±0.90 and 1.50±1.50 for male and female patients, respectively; P=0.70).

All 89 patients completed the FIQL questionnaire at baseline, 3, 6, and 12 months after surgery (Table 2). The major decrease of QoL was observed in women in 3 months after the surgery in terms of lifestyle and frustration domains (3.60 and 3.64 points, respectively), but even those differences were not significant (all P>0.05). The main changes in QoL of male patients were noted after 3 months in the frustration domain (3.70 points). Noteworthy that in 5 patients impare of QoL persisted for 6 months (1, male and 4, female). In a year of the follow-up QoL was regained in all the patients, though only 2 female patients gave positive reply to the resulting question. A direct correlation was found between the decrease in functional and manometric results in the studied category of patients (r=0.77, P=0.001).

The average resting and squeezing pressure before TEM were in reference values of anorectal manometry in all patients. In 3 months after the surgery, there was a significant decrease in resting pressure both in male and female patients: 55 mmHg (range, 34–72 mmHg) and 49 mmHg (range, 24–62 mmHg), respectively (P=0.01) (Fig. 2). This difference remained significant in 6 months after the surgery; 57 mmHg (range, 34–75 mmHg) for male patients and 50 (range, 27–62 mmHg) for female patients, respectively (P=0.01). In 12 months after the surgery, resting pressure returned to preoperative level in most patients (P=0.50).

The same tendency was observed in squeezing pressure. There was significant decrease in 3 months (145 mmHg [range, 60–229 mmHg] and 124 mmHg [range, 66–222 mmHg], P=0.028) and in 6 months after TEM (146 mmHg [range, 68–229 mmHg] and 128.5 mmHg [range, 72–225 mmHg], P=0.04) in male and female patients, respectively (Fig. 3).

At the same time, in 3 patients the manometric decrease of pressure persisted for a year after the surgery. This fact was reflected in the QoL in 5 patients (5.6%).

The significant decrease in contraction pressure in 6 months after the surgery was associated with the surgery time (r=0.24, P=0.026). Reducing resting pressure noticed as linear relationship with low tumors (r=0.31, P=0.003) and increase in size of the formation (r=0.22, P=0.039).

A significant decrease of manometric parameters appears when the surgery time is more than 55 minutes (Youden index, 0.56; area under the ROC curve [AUC], 0.742; P=0.05), the tumor localization is lower than 3 cm from the anus (Youden index, 0.38; AUC, 0.724; P=0.03) and the tumor size is over 3 cm (Youden index, 0.39; AUC, 0.745; P=0.001) (Fig. 4).

TEM is the method of choice for the treatment of benign lesions and early carcinomas of the rectum [1]. The full-thickness excision of the rectal wall allows to scrutinize pathology and avoid unnecessary radical surgery, which is associated with certain morbidity and functional impairment. However, despite the minimally invasive nature of the local excision, according to some authors, TEM also affects the QoL of patients and causes LARS in up to a third of patients.

According to van Heinsbergen et al. [4], in series of 55 patients treated for rectal cancer, 16 patients (29.1%) had severe LARS and 14 had mild functional disorders after TEM. The high rate of LARS reported by the authors can be explained by the administration of neoadjuvant chemoradiotherapy in some patients, which exacerbates anorectal function and worsens LARS (P=0.037). In this context, the results of this study could not be extrapolated to the entire population of the corresponding category of patients. Additionally, female sex (P = 0.024) and depth of resection (P=0.023) were identified as risk factors of worse functional results.

In accordance with the presented study, the most significant risk factors for the development of functional disorders after TEM were surgery time of over 55 minutes (P=0.05), tumor localization less than 3 cm from the anus (P=0.03), and tumor size exceeding 3 cm (P=0.001). Independently of each other, these factors have already been reported in the literature, which confirms the reproducibility of our results [8–10].

In the study by Allaix et al. [8], which is based on the results of 93 TEMs for rectal adenomas and early carcinomas, only tumor size of >4 cm significantly affected functional outcomes in 3 months after surgery (P<0.05). In 12 months after surgery, anal pressure and QoL assessed by the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire Core 30 returned to baseline in most patients.

Tumors located close to the anal canal were identified as a risk factor for functional disorders in the analysis of 201 cases of TEM published by Mora López et al. [9]. Though this factor lost its significance in multivariate analysis, it should not be neglected in clinical practice.

In a small study by Kennedy et al. [10], a direct relationship between surgery time of TEM and functional outcomes (r=0.39, P=0.047) was found. The decrease of preoperative mean resting anal pressure from 104±32 cmH₂O to postoperative 73±30 cmH₂O was detected (P=0.0009). At the same time, there were no significant changes in squeezing anal pressure, transmission time within pudendal nerve or threshold rectal volume.

According to some studies [11, 12], the internal anal sphincter (IAS) is a critical structure in terms of damage during TEM. A dilatation of anal sphincter complex caused by the insertion of rigid proctoscope of a large diameter and exposure of smooth muscle to prolonged stretching leads to direct trauma and interruption of the rectoanal inhibitory reflex (RAIR). Zhang et al. [13] confirmed this by the endorectal ultrasound, which was done in patients with anal incontinence after repeated TEM. A disruption of the IAS was detected in 8 of 21 patients (38.1%), while integrity of the external anal sphincter was preserved in all cases.

The other factor not evaluated in our study but also which may affect the function is open or closed management of the rectal defect after TEM. In spite of no difference in the functional outcomes, Altaf et al. [14] noticed a significant difference in post-TEMS Fecal Incontinence Severity Index scores with worsening function in patients with closed rectal defect (P=0.02).

Though all these studies are apparently statistically underpowered, the authors agreed that, regardless of risk factors, dysfunction in most patients is temporary, and anal function recovers within a few months after surgery. It was demonstrated in a systematic review of the literature, which includes 29 studies with results of treatment of 1,297 patients, who were operated on by means of TEM or transanal minimally invasive surgery (TAMIS). Almost unanimously, the researchers come to the conclusion of the minimal effect of TEM on the QoL. Undesirable functional sequelae are regarded as temporary in most patients. However, even temporary dysfunction can affect QoL and should not be underestimated. The authors of the systematic review reported the infeasibility of a meta-analysis due to significant heterogeneity of studies and the absence of a comparison group [15].

As additionally follows from this review, TAMIS theoretically can be an alternative to TEM in terms of function preservation since SILS ports (Covidien) which are used for TAMIS are potentially associated with less trauma to the anal sphincter [16].

Endoscopic submucosal dissection (ESD) is another alternative technique for en bloc removal of rectal neoplasms. It has similar rates of R0 resection and recurrence of at least rectal adenomas but theoretically is associated with less trauma of the anal sphincter due to smaller diameter of endoscope compared to TEM platform, though ESD is more time-consuming technique [17]. There is a lacuna in direct head-to-head randomized clinical trials comparing results of ESD versus TEM. In this context, comparative studies with a secondary end-point of functional outcomes look very interesting.

A significant limitation of our study is the retrospective design, though the data were collected from patients, who were enrolled in the study prospectively. Another drawback of the study is the lack of the results of some manometric outcomes: RAIR, rectal compliance, and rectal sensitivity.

In conclusion, some patients who underwent TEM had a risk of anal function impairment which can affect QoL. The most significant risk factors for the development of functional disorders after TEM are surgery time of over 55 minutes (P=0.05), tumor localization at less than 3 cm from the anal verge (P=0.03), and tumor size of more than 3 cm (P=0.001). Though undesirable sequelae are temporary and most patients recover within 6 months after surgery, they should be informed about possible functional disorder.