Long‐term outcomes of open versus closed rectal defect after transanal endoscopic microscopic surgery

Management of the rectal defect after transanal endoscopic microsurgery (TEM) is a matter of debate. Data are lacking on long term outcomes and continence of patients with open or closed rectal defect. We sought to analyse these in a retrospective cohort study.


INTRODUC TI ON
The incidence of early rectal cancer (ERC), defined as lesions limited to bowel wall and not extending beyond submucosa (T1) or muscularis propria (T2) without lymph nodal involvement, has increased in the recent times, possibly due to widespread introduction of screening programmes and impressive improvements in diagnosis, staging and treatment modalities of rectal cancer over the last two decades.
It is thought to constitute approximately 40% of all colorectal cancer diagnoses [1]. While the 5-year survival rate is approximately 95%, management of ERC remains controversial. TEM presents a less invasive alternative option with reported postoperative clinical morbidity rates of less than 10%, no genitourinary/sexual changes and a low mortality rate [2][3][4]. Lack of lymphadenectomy makes it only suitable for selected T1 cancers [5].
While more and more centres adopt the technique and develop expertise, endoluminal suturing of the rectal defect remains a particularly difficult skill to master and the data around leaving the defect unsutured or otherwise remain scanty. Recently, some studies, including randomised controlled trials, have shown no difference between leaving the defect open or sutured close for various shortterm outcomes. However, no study has assessed long-term outcomes of these two approaches. We, therefore, aimed to look at long term outcomes in terms of recurrence, structural healing and impact on continence in patients who had rectal defect closed or left open after TEM.

ME THODS
All patients undergoing full thickness rectal excision using TEMS from January 2012 to December 2019 referred from the Regional

RE SULTS
During the study period, 198 TEM procedures were carried out.
Patients who required subsequent TME rectal resections post-TEM (n = 22) due to poor prognostic features on final histology (tumour > T1Sm3, poor differentiation, lymphovascular invasion, tumour budding and tumour at resection margins R1) and those who underwent salvage surgery were excluded. No patient had neoadjuvant chemoradiotherapy and those who had radiotherapy for prostate cancer before diagnosis of rectal polyps were also excluded.  Table 1.
Final histology revealed 44% of the total lesions to be benign (70/170) and the rest were found to be malignant (100/170). Of the 100 malignant lesions, the majority were identified as adenocarcinoma (92/100), with 82% staged as pT1 (Sm1 = 23/82, Sm2 = 27/82, Sm3 = 32/32/82). Eight malignant tumours were found to be pT2 and two were staged as pT3 on final histology. Table 2  Assessment of rectal defect after TEM was recorded using lower GI endoscopy. A total of 80% of patients had flexible sigmoidoscopy within 6 months of the initial procedure and 92% had lower GI endoscopy (flexible sigmoidoscopy/colonoscopy) within 12 months.
Endoscopic findings from post-TEM assessment of rectal defect endoscopically were categorised into three categories: healed scar-site, unhealed/sinus formation and stricture/narrowing (   Table 4.

DISCUSS ION
This is the first study to look at the long-term outcomes of rectal de- LGD 11 15 LGD+HGD 18 26 Abbreviations: HGD, high grade dysplasia; LGD, low grade dysplasia.

F I G U R E 1
The difference between the two groups in terms of short-term outcomes is illustrated. No statistical difference between the two groups was identified (p > 0.05) without increasing complications or compromising continence [8].
However, a more recent study has postulated that open management of the rectal defect after TEM may be associated with more postoperative complications (19% vs. 8.4%) but it does pose a viable approach in patients where the defect does not compromise the peritoneal cavity [9]. Another subject of concern has been association of management of TEM defect with increased postoperative pain. This gained popularity after a study in 2011 concluded that postoperative pain after sutured closure of the rectal defect in TEM was associated with a high readmission rate and also high incidence of wound dehiscence [10]. However, a more recent multicentre RCT has nullified these results, exhibiting no difference in postoperative pain between sutured or open defect management. Findings from this trial reassure us that when the mesorectum is intact, open management of a rectal defect does not compromise postoperative recovery [11]. Another study found increased risk of bleeding with open rectal defects but no significant difference overall between the two techniques [12]. Our results also demonstrated no difference between the two groups in terms of infection, bleeding, postoperative pain, urinary retention, urinary tract infection, reinterventions, length of stay and bleeding.
No study in the past has commented on long-term endoscopic surveillance and long-term complications. Approximately 16% of our patients developed sinuses/strictures on surveillance. Significantly more strictures were seen in the closed group. This was independent of the size of the resected lesion. Our findings are in line with a study that investigated development of strictures after TEM. They found that the risk was highest with circumferential lesions (75%) and that the overall incidence in those more than 5 cm was only 3%. No stenoses were witnessed in lesions measuring less than 5 cm [13]. Mucosal ischaemia and lack of mucosal apposition could both account for stricture formation. There is some evidence that circumferential mucosal deficit is an independent risk factor [14,15]. However, we found more strictures in the closed group than open and therefore it is not apparent if these two factors are indeed the most likely culprits. It is safe to say that development of stenosis after TEM is a multifactorial process. Thankfully, most patients do not develop symptoms and those who do are easily amenable to local therapies.
Faecal incontinence is not uncommon after TEM, with a reported incidence of up to 30% [16] and prevalence of around 2%-12% [17].
It is reasonable to assume that insertion and repositioning of the rectoscope during the procedure may damage the internal anal sphincter (IAS), while larger excisions may negatively impact rectal capacity and sensation [18]. There is data from studies reporting anorectal function and manometry in patients with TEMS. Effects demonstrated are a decrease in anal squeeze pressure and rectoanal inhibitory reflex, as well as a persistent reduction in rectal perception and compliance [18].
Defects in IAS have also been found post-procedure in up to 30% of patients, leading to a reduction in anal resting and squeeze pressures [19]. It has also been deduced that resecting more than 50% of rectal circumference is also adversely associated with rectoanal inhibition reflex and sphincter reflex contractions [19]. We saw a significant TA B L E 4 FISI scoring pre-and postoperative (n = 114) difference in continence scores in our patient cohort before and after the procedure and while we did not perform a multivariate analysis to assess the risk factors for this, many studies have already alluded to that and identified old age, full thickness excisions and malignant lesions to be independent risk factors [16,20].
Another important driver promoting closure of the rectal defect is to develop the technical skills which would be needed if a breach to the peritoneal cavity was to happen, particularly in anteriorly placed neoplasms. These breaches are not uncommon (approximately 6%) [21,22] and must be sutured. If routinely closing the defects is employed, surgeons performing the procedures must have the required skillset to do so when it is needed, particularly in situations when suturing is quite challenging. It has been feared that suturing a rectal defect leads to an increase in operating times and lengthens the procedure. However, Lee et al. [12] found no significant difference in the operating time (82 vs. 85 min) between suture closure and open rectal defects. Median time taken for suturing a rectal defect is 12 min (range 5-30 min) in our own experience. The flip side to this is recognition of defects that will not be amenable to closure, or will have a high risk of dehiscence if closed. These have been reported to occur in up to 30% of procedures [8]. Such defects can be safely managed as open wounds and closure is best avoided in such circumstances.
Our study is limited by its retrospective nature, although data were retrieved from a prospectively maintained database. This is a single, albeit regional, centre experience and therefore, is subject to inherent selection biases and the usual disadvantages that a retrospective analysis brings, despite the careful and rigorous follow-up performed herein.
In conclusion, management of the rectal defect after TEM remains a matter of debate and largely at the discretion of the operating surgeon, and long-term outcomes and delayed complications should be expected and actively followed up. Patients should be adequately and appropriately counselled for the deterioration in bowel function and continence.

CO N FLI C T O F I NTE R E S T
None to declare.

FU N D I N G I N FO R M ATI O N
No funding was sought for this project.

AUTH O R CO NTR I B UTI O N
KA, DS, SG and AK undertook data collection. KA performed analyses, analysed data and wrote the manuscript. SA and SS provided surgical expertise for the project, where TA oversaw the histological aspects of the project.

E TH I C S A PPROVA L
Local hospital ethics approval was sought for and granted for the purpose of this study.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data that support the findings of this study are available from the corresponding author upon reasonable request.