Comparison of anal function and quality of life after conformal sphincter preservation operation and intersphincteric resection of very low rectal cancer: a multicenter, retrospective, case–control analysis

Patient selection

The clinical data of patients who underwent CSPO and ISR for very low rectal cancer was collected in Changhai Hospital Affiliated to Naval Medical University (n = 117) and Huashan Hospital Affiliated to Fudan University (n = 66), respectively, from August 2011 to April 2020. This study was approved by the Ethics Committee of the First Affiliated Hospital of Naval Medical University (committee’s reference number CHEC2022-021) and followed the precepts established by the Helsinki Declaration. Each patient signed the informed consent. The work has been reported in line with the STROCSS criteria [8]. This research was retrospectively registered in the Chinese Clinical Trial Register (ChiCTR2300070971).

The inclusion and exclusion criteria for patients undergoing CSPO were described previously by Sun et al. [4]. The inclusion criteria are briefly described as follows: (1) diagnosis of rectal adenocarcinoma by digital rectal examination, colonoscopy, and biopsy; (2) the tumor does not infiltrate the intersphincteric space; (3) good anal function before surgery evaluated by Wexner incontinence score in combination with the digital rectal examination during consultation; (4) distance between the lower tumor edge and the dentate line is within 2 cm or the distance of the lower tumor edge from the anal verge is less than 4–5 cm; (5) the diameter of the tumor is less than 3 cm with no more than 1/3 circumference of the intestinal lumen; (6) the American Society of Anesthesiologists Score (ASA) is ≤ 3.

The following patients were excluded: (1) Distant metastasis (including lymph node metastasis outside of the mesorectum); (2) patients not able to tolerate the operation (ASA > 3).

Surgical methods

All CSPO procedures were conducted at Changhai Hospital, while all ISR procedures took place at Huashan Hospital. The surgeons performing ISR or CSPO were experienced colorectal surgeons with similar levels of expertise. Both hospitals are tertiary institutions situated in the same city, Shanghai. All clinical treatments adhered to the same guidelines. We give patients preoperative chemoradiotherapy in case of preoperative stage T3–T4 or N+, or mesorectal fascia (MRF) involvement in MRI assessments after communication with patients.

CSPO procedures

The key steps of CSPO were as follows [4, 5]: the sigmoid colon was mobilized in the standard manner to decrease the tension during the later anastomosis. The origin of the inferior mesenteric artery was ligated. The rectum was dissected according to the TME (total mesorectal excision) principle with autonomic nerve preservation. The rectum was dissected up to the hiatal ligament which is the sequence of the anococcygeal raphe body [9]. After the hiatal ligament was cut off, further dissection into the intersphincteric space was not performed to prevent damage to the nerve structure, which is different from ISR. The intestine was transected at the rectosigmoid junction with the proximal resection margin length > 15 cm. The anus was dilated to 3–4 fingers wide, through which the rectum was pulled out. In case of difficult eversion from the rectum due to a fatty mesorectum or a narrow pelvic cavity, transanal resection like TaTME (transanal total mesorectal excision) was utilized without eversion of the rectum. A conformal resection line was designed according to the position and shape of the tumor: the rectal wall, dentate line, and internal anal sphincter were retained as much as possible on the opposite side of the tumor (Fig. 1). The distal resection margin length was at least 1 cm under direct vision. For patients who received preoperative chemoradiotherapy, we maintained a distal resection margin length longer than 1 cm, as observed with the naked eye during the operation [10]. Intraoperative frozen pathological examination was utilized to ensure a safe distal resection margin. The rectal stump was closed manually with interrupted sutures. A 25-mm circular stapler was inserted through the anus, and the anastomosis was made on the side with more rectal wall, dentate line and internal sphincter retained. In case the left rectal stump was too short to insert a circular stapler, manual anastomosis was used. For the manual anastomosis, absorbable threads (size 3–0) were utilized to make four sutures at the top, bottom, left, and right sides. After fixation of the four sutures, two 3–0 sutures with barbs were used in succession, with each suturing half a circle. A prophylactic ileostomy was created routinely.

Fig. 1figure 1

Surgical procedures for CSPO (red line); total, subtotal, and partial ISR (blue lines). Adapted with permission from Sun et al. [4]

ISR procedures

In the ISR procedures, first, the sigmoid colon was mobilized in the standard manner to decrease the tension for later anastomosis. After TME was completed and the anococcygeal raphe was cut off transabdominally, the intersphincteric space was mobilized through the pelvic approach, exposing the puborectalis muscle, cutting the hiatal ligament, and entering the intersphincteric space through the lateral and posterior approaches and dissecting for about 2–4 cm caudally. Some joint longitudinal muscles in the sphincteric space were cut off. The anus was dilated and exposed with a Lonestar retractor.

A purse string was sutured two times just distal to the lower edge of the tumor to close the bowel. The distal rectum was irrigated. A circular incision was made at about 1–1.5 cm distal to the purse-string suture, to cut off the internal sphincter and joint longitudinal muscle, and meet the other dissection from the pelvic approach. The rectosigmoid was transected at the rectosigmoid junction. The specimen was removed through the anus. The proximal sigmoid colon and the anal canal were anastomosed by interrupted sutures (approximately 24–32 stitches). All patients had a prophylactic ileostomy.

Data collection

The following patient characteristics were collected: age, sex, body mass index (BMI), tumor diameter, tumor position (the distance between the lower edge of the tumor and the anal verge), clinical T stage, clinical N stage, preoperative chemoradiotherapy, postoperative chemotherapy, pathological T stage, pathological N stage, and tumor differentiation.

The following surgery-related information was collected: blood loss, surgical approach, operation duration, postoperative hospital stay, distal resection margin length, and the number of retrieved lymph nodes.

Anal function evaluation

The anal function after ileostomy reversal was evaluated with the Wexner incontinence score (range 0–20, where 0 indicated perfect continence, and 20 indicated the most severe form of fecal incontinence), low anterior resection syndrome score (LARS score, range 0–42, where 0–20 indicated no LARS, 21–29 minor LARS, 30–42 major LARS), and visual analog scale of anal function satisfaction (VAS, range 0–10, where 0 indicated the lowest satisfaction, 10 indicated the highest satisfaction) [11,12,13].

Quality of life evaluation

VAS was also utilized to evaluate satisfaction with the quality of life [14, 15] (range 0–10, 0 indicating the lowest satisfaction and 10 the highest satisfaction). Detailed domains of quality of life were evaluated with the EORTC QLQ-C30 questionnaire [16] in combination with the EORTC QLQ-CR38 [17] questionnaire.

The EORTC QLQ-C30 questionnaire includes the following domains: global health (QL2), physical function (PF2), role function (RF2), emotional function (EF), cognitive function (CF), social function (SF), fatigue (FA), nausea and vomiting (NV), dyspnea (DY), pain (PA), insomnia (SL), appetite loss (AP), constipation (CO), diarrhea (DI), and financial difficulties (FI).

The EORTC QLQ-CR38 questionnaire includes the following domains: body image (BI), sexual function (SX), sexual enjoyment (SE), future perspective (FU), micturition problem (MI), chemotherapy side effect (CT), symptoms of gastroenterology (GI), male sexual problem (MSX), female sexual problem (FSX), stoma-related problem (STO), and weight loss (WL).

All the above domains in C30 and CR38 have a range between 0 and 10. A score of 0 in a particular functional domain indicates the worst function, and a score of 0 in symptom domains indicates the least severe symptoms. A score of 100 in functional domains indicates the best function, and a score of 100 in symptom domains indicates the most severe symptoms.

Statistical analysis

We used R software (version 1.4.1106, 2021) to analyze data and generate figures. Continuous variables were presented as mean ± standard deviation or median and interquartile ranges depending on whether the data were normally distributed or not. Categorical variables were analyzed with the chi-square test, and continuous data were compared with a Student’s t test or Mann–Whitney U test depending on the distribution of the data.

The Kaplan–Meier curve was used to describe the time to ileostomy reversal. Cox regression analysis was used to analyze risk factors for ileostomy reversal time between the operation and reversal. Multivariable linear regression was used to analyze factors affecting satisfaction with anal function and quality of life, and their specific domains, i.e., Wexner score, LARS score, EORTC-C30, and EORTC-CR38. For the binary categorical outcome, we used the logistic regression analysis.

The following factors which may affect ileostomy reversal, postoperative anal function, or quality of life were first included in the univariable linear regression analysis: type of operation, age, gender, BMI, tumor position, tumor diameter, tumor differentiation, pathological stage, preoperative chemoradiotherapy, postoperative chemotherapy. In the analysis of anal function and quality of life, whether ileostomy reversal was performed more than 12 months ago or not was included as a variable in the univariable regression analysis as well. Variables with a p value smaller than 0.15 in univariable analysis were selected to be included in multivariable regression analysis using the backward elimination method. A p value less than 0.05 (two-sided) was considered statistically significant in multivariable analysis.

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