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Achieving the perfect end-to-end single-stapled anastomosis in low anterior resection for rectal cancer: technical aspects
Technical Note Technical tips or video clip Achieving the perfect end-to-end single-stapled anastomosis in low anterior resection for rectal cancer: technical aspects
Department of Colorectal Surgery, Singapore General Hospital, Singapore
Correspondence to: Cherylin Wan Pei Fu, MBBS, FRCS(Ed), MMed(Surg) Department of Colorectal Surgery, Singapore General Hospital, Outram Rd, Singapore 169608 Email: cherylinfu@gmail.com
• Received: April 13, 2025 • Revised: May 1, 2025 • Accepted: May 16, 2025
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
The cornerstone of successful low anterior resection (LAR) for rectal cancer, aside from achieving optimal oncological clearance, is the integrity of the colorectal anastomosis. This factor directly influences functional outcomes and postoperative complications. Among potential complications, anastomotic leak (AL) is particularly devastating [1]. Meticulous surgical technique is crucial to constructing the “perfect” colorectal anastomosis, potentially eliminating the need for a defunctioning stoma.
A known risk factor for AL is the intersection of staple lines and the presence of “dog-ear” corners established by the conventional double-stapled technique (DST) [2–4]. To avoid this, side-to-end anastomosis and modified DST—incorporating the corners of the rectal stump into the circular stapler—have been proposed [2–4]. Single-stapled anastomosis (SSA) is another method that eliminates these problems and has been associated with lower rates of AL [5–8]. Due to the adoption of techniques such as natural orifice specimen extraction (NOSE), transanal total mesorectal excision (taTME), and transanal transection and SSA (TTSS), SSA has emerged as a compelling alternative to DST [5, 6, 9, 10]. This report discusses surgical approaches and technical considerations for performing end-to-end SSA using a single circular stapler in LAR for rectal cancer.
TECHNIQUE
Achieving an ideal end-to-end SSA in LAR involves careful execution of 4 technical steps: (1) the approach to rectal transection; (2) creation of the distal rectal purse-string; (3) use of the circular stapler; and (4) reinforcement of the completed anastomosis. These steps are illustrated in Supplementary Videos 1–5.
Intracorporeal versus transanal rectal transection
In preparation for SSA, the rectum distal to the tumor is typically transected using scissors, cautery, or an energy device, rather than linear staplers. This creates an open rectal stump that is subsequently closed with a purse-string suture, facilitating a double purse-string SSA. Rectal transection can be performed intracorporeally under laparoscopic visualization or transanally, either under direct vision (the TTSS approach) or laparoscopic vision (the taTME approach). The appropriate option depends on factors such as the distal extent of the tumor, to ensure an accurate distal resection margin. For tumors located in the upper rectum (8 to 10 cm from the anal verge) that are clearly identifiable after TME mobilization, the rectum can be occluded distally with surgical tape, followed by distal rectal washout before laparoscopic intracorporeal transection (Supplementary Video 1). However, for smaller rectal tumors or lesions that have regressed after neoadjuvant therapy, transanal transection offers direct visualization of the tumor, ulcer, or scar, ensuring a definite macroscopic transection margin of at least 5 mm (Supplementary Video 2). Following rectal transection, the NOSE technique can be employed when appropriate, enabling transanal removal of the specimen and avoiding an abdominal incision. The stapler anvil is subsequently introduced extracorporeally into the proximal colon.
Laparoscopic intracorporeal versus transanal extracorporeal rectal purse-string
Unlike DST, achieving SSA with a single circular stapler requires manual closure of the open rectal stump with a purse-string suture prior to stapling. This can be executed either intracorporeally via laparoscopic suturing or extracorporeally via transanal suturing, using a continuous circumferential suture around the rectal cuff (“in-out, out-in” or “over-and-over”). A monofilament nonabsorbable suture like Prolene 2-0 (Ethicon) is suitable, minimizing tissue drag while providing sufficient strength to be securely tied onto the stapler anvil without breaking. The choice between intracorporeal and extracorporeal purse-string placement often depends on the level of the rectal tumor and the resulting length of the rectal stump. A laparoscopic approach is feasible when the stump is long (>6 cm from the anal verge), allowing the purse-string to be tied intracorporeally onto the stapler’s spike (Fig. 1). Conversely, for shorter stumps (<6 cm), a transanal approach may be preferred due to the technical difficulty of laparoscopic suturing deep within the pelvis. Additionally, achieving an airtight purse-string laparoscopically is challenging with a short rectal stump due to tension from the pelvic floor muscles holding the stump open. In the transanal technique, the purse-string can be hand-tied directly onto the anvil (which is already secured to the proximal colon) before engaging the anvil with the stapler shaft (Fig. 2); alternatively, it may be tied onto the long spike of the circular stapler. A securely tied purse-string incorporating the entire circumference of the distal rectum is crucial for ensuring a complete distal tissue donut upon stapler firing, which creates a robust staple line and minimizes leakage risk [9]. Applying a second purse-string is often advisable to secure a leak-proof seal.
Intracorporeal versus extracorporeal stapling method
The method of anastomosis typically aligns with the purse-string creation method. If performed intracorporeally, the circular stapler is introduced transanally into the rectal stump, the purse-string is tied laparoscopically onto the spike, the anvil in the proximal colon is engaged, and the stapler is fired intracorporeally (Supplementary Video 3). If the purse-string was created extracorporeally (transanally), it is usually tied directly onto the anvil extracorporeally. Then, the anvil is engaged with the transanally introduced stapler shaft, and the stapler is fired under direct extracorporeal vision (Supplementary Video 4). Alternatively, the rectal purse-string may be tied onto a long spike or tube extension before advancing the stapler shaft through the rectal stump under laparoscopic visualization and engaging it with the anvil for intracorporeal anastomosis [4]. Regardless of the method, meticulous inspection of both excised tissue rings (“donuts”) after firing is critical to confirm completeness. Incomplete donuts strongly suggest a potential anastomotic defect, necessitating thorough inspection of the staple line. A reverse air leak test (immersing the anastomosis with water/saline while insufflating the abdomen) may help identify leaks, as traditional intra-abdominal air leak tests can be of limited utility for low anastomoses that are difficult to visualize intra-abdominally.
Reinforcement of the anastomotic staple line
Reinforcing the SSA staple line is a crucial step for reducing AL risk and potentially avoiding a diverting stoma, even after neoadjuvant therapy or in ultralow resections. This involves placing interrupted absorbable sutures (e.g., PDS II 3-0, Ethicon) circumferentially along the staple line (Fig. 3, Supplementary Video 5). Reinforcement serves several purposes: it distributes tension more evenly, helps seal microscopic staple holes, potentially narrows interstaple gaps, mitigates staple line bleeding [1, 11], and, crucially, may repair defects arising from incomplete donuts. Furthermore, suture reinforcement of the LAR staple line can anchor the anastomosis to the adjacent pelvic floor muscles, reducing the risk of anastomotic stricture, as evidenced by the endoscopic appearance of a well-healed SSA (Fig. 4). Combined with other preventative measures, including meticulous SSA technique and intraoperative perfusion assessment using indocyanine green (ICG) fluorescence, reinforcement appears promising for achieving very low leak rates [12].
Ethics statement
This study was approved by the Centralised Institutional Review Board of SingHealth (No. 2024-3487). Waiver of consent for publication of the research details and clinical images was applicable as all data was de-identified and anonymized.
DISCUSSION
While not a novel concept, SSA has seen renewed interest largely due to the adoption of advanced techniques such as NOSE, taTME, and TTSS [5, 6, 9, 10]. A primary theoretical advantage of SSA over DST is the avoidance of intersecting staple lines and the elimination of “dog ears,” both considered potential weak points prone to ischemia and leakage [2–4]. For very low rectal cancers requiring transection deep in a narrow pelvis, DST often necessitates multiple linear stapler firings, a factor consistently associated with increased rates of AL [4]. Clinical outcomes comparing AL rates between SSA/TTSS and DST have been mixed, but several studies favor SSA, as shown in Table 1 [3, 5, 6, 8, 13, 14]. Notably, Foppa et al. [6] reported a significantly lower 90-day AL rate for SSA (6.48%) versus DST (15.28%) after minimally invasive TME for low rectal cancer, while Spinelli et al. [5] found that TTSS was associated with a 62% lower AL risk compared to DST. A recent meta-analysis also concluded that SSA corresponded to a lower AL rate than DST (odds ratio, 0.79; 95% confidence interval, 0.33–1.25; P<0.001) [8]. This potential for reduced AL rates with SSA, potentially augmented further by reinforcement [1, 11], raises the possibility of safely omitting diverting stomas in selected patients without significant comorbidities or intraoperative instability. Avoiding a stoma offers considerable benefits: reduced stoma-related morbidity, improved quality of life, lower healthcare costs, and potentially fewer anastomotic strictures from disuse. Staple line reinforcement, easily performed transanally, is a cost-effective measure that may improve the integrity of low colorectal or coloanal anastomoses [11]. Preclinical research has confirmed that reinforcement increases anastomotic burst pressure [1], and clinical evidence supports its role in reducing bleeding and leaks, especially in high-risk cases [11].
SSA is often combined with transanal techniques such as taTME and TTSS, which employ manual transection of the distal rectum rather than a linear stapler. This approach ensures superior visualization and enables precise rectal transection—vital for achieving clear margins with low or small tumors [15]. Although no studies have directly compared local recurrence rates and disease-free survival between SSA and DST, evidence suggests that SSA approaches may yield longer distal resection margins than DST [7, 14]. A less commonly mentioned advantage of manual rectal transection is that it allows direct visualization of the rectal stump mucosa, facilitating viability assessment before anastomosis to reduce ischemia and subsequent stenosis. In DST, where the rectal stump is inherently closed, perfusion assessment can only be performed using indirect methods such as intraoperative ICG imaging [12]. When combined with NOSE, SSA offers additional benefits, including reduced pain, faster recovery, lower incisional hernia rates, and improved cosmesis [16, 17]. Eliminating the linear stapler also provides considerable cost savings and permits the exclusive use of 5-mm laparoscopic ports, further supporting the minimally invasive nature of the procedure.
The functional outcome of SSA is difficult to evaluate, as it depends heavily on the associated dissection and extraction method (e.g., transabdominal, NOSE, taTME, or TTSS). A recent study comparing TTSS and DST reported lower LAR syndrome scores at 24 months after stoma closure in the TTSS cohort, despite a significantly lower anastomotic height in that group (P=0.027) [7]. Several ongoing trials—such as the Super SST trial [10] and COLOR III trial [18]—are expected to provide further insights into SSA versus handsewn and DST anastomoses.
The choice between intracorporeal and extracorporeal approaches for SSA depends primarily on the tumor’s height and visibility. Generally, upper rectal tumors (>8 cm from the anal verge) can be managed with intracorporeal transection, laparoscopic rectal purse-string formation, and intracorporeal anastomosis, whereas low rectal tumors (<6 cm from the anal verge) are best addressed with transanal transection, transanal purse-string formation, and extracorporeal anastomosis. Middle rectal tumors (6–8 cm from the anal verge) present the greatest technical challenge and may be approached with intracorporeal transection combined with transanal purse-string formation—using a circular anal dilator—followed by extracorporeal anastomosis. In very small middle rectal tumors or those reduced to a fibrotic scar after neoadjuvant therapy, transanal transection via taTME or TTSS can provide superior visualization to secure the distal margin.
Despite its advantages, end-to-end SSA is not universally suitable and thus requires careful intraoperative assessment. When the rectal wall is markedly thick or fibrotic—a condition often seen after neoadjuvant radiotherapy—and in the middle rectum, where the mesorectum is thickest, achieving a tight, secure purse-string closure around the anvil or spike can be extremely difficult. This challenge increases the risk of an incomplete distal donut and a subsequent anastomotic defect. In such situations, using a linear stapler to transect the rectal stump—as in DST—may be more suitable than performing a double purse-string SSA. Modifications to incorporate dog-ears into the circular stapler can then be attempted to avoid intersecting staple lines in the final anastomosis. Finally, surgeon expertise and high-quality preoperative imaging are crucial prerequisites for performing SSA successfully, as the procedure often involves laparoscopic intracorporeal suturing within the pelvis.
In conclusion, SSA is emerging as a valuable and often advantageous alternative to traditional DST in LAR for rectal cancer. However, achieving the “perfect” end-to-end SSA requires meticulous attention to technical details throughout the procedure, potentially incorporating preventative measures such as anastomotic reinforcement and intraoperative perfusion assessment. The choice between double purse-string end-to-end SSA and DST should be tailored to each patient’s anatomy, tumor characteristics, available resources, and surgeon expertise. Ongoing research will continue to delineate the precise indications for SSA and solidify its role in contemporary colorectal surgery.
ARTICLE INFORMATION
Conflict of interest
No potential conflict of interest relevant to this article was reported.
Funding
None.
SUPPLEMENTARY MATERIALS
Supplementary Video 1.
Intracorporeal rectal transection with natural orifice specimen extraction (NOSE).
Supplementary Video 2.
Transanal rectal transection via transanal total mesorectal excision (taTME).
Supplementary Video 3.
Intracoporeal rectal purse-string and anastomosis.
Supplementary Video 4.
Transanal rectal purse-string and extracorporeal anastomosis.
Supplementary Video 5.
Sutured reinforcement of single-stapled anastomosis.
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