TO THE EDITOR
Anastomotic stenosis is a relatively common complication after colorectal surgery with a corresponding incidence that ranges from 3% to 30%[1,2]. Other than the surgical procedure itself, multiple factors have also been found to be associated with the pathogenesis of this complication such as male sex, neoadjuvant treatment, obesity, sepsis, leakage, pelvic infection, and radiotherapy[1,2]. The target of treatment is to relieve obstructing symptoms by reestablishing luminal continuity. Surgical revision is feasible but it is better used in refractory cases as its use has been associated with high morbidity[1,2]. Therefore, therapeutic endoscopy has been recently introduced as a minimally invasive approach for the management of this postoperative complication. Traditionally, anastomotic stenosis is treated with electrical incision, endoscopic balloon dilation, and placement of fully-covered self-expandable metal stents (FCSEMS). However, these techniques cannot be directly used in cases of complete anastomotic occlusion (CAO)[1,2].
In their article, Chi et al[3] presented a novel method for the recanalization of CAO cases with the use of two endoscopes, one for performing electrical incision of the obstructed anastomosis and the second for guide light. Although this technique was found to be associated with various positive outcomes, such as reduced invasiveness, rapid recovery, and shortened hospital stay, it cannot be applied in all cases. This is mainly because the presence of a proximal stoma is a prerequisite for bilateral endoscopic advancement and two experienced endoscopists are required to ensure the safety and effectiveness of the procedure. However, these inherent limitations were not discussed by the authors. Considering these limitations and the absence of a standardized guideline-based procedure for the management of CAO, we reviewed the available literature in an effort to delineate the role of therapeutic endoscopy in the management of this postoperative complication and provide clinicians with the necessary knowledge to improve their daily practice.
Techniques for treating completely occluded benign anastomotic strictures
Throughout the literature, recanalization was found to be a complex procedure with endoscopic guidance playing a pivotal role in the successful outcome[1-3]. Irrespective of the selected technique, treatment is applied in different steps with the first step being the histological confirmation of the absence of malignancy in the CAO[1,2]. All reported techniques that have been used for recanalization are outlined in the following sections.
Combining electrical penetration with mechanical dilation
In this technique, electrical current is applied in repeated, short bursts, making shallow radial incisions in the center of the stenosis at different sites. Electrosurgical knives designed for endoscopic submucosal dissection such as hook and dual knives (Olympus Medical Systems Corp., Tokyo, Japan) are generally preferred for the initial perforation of the obstructed anastomosis over conventional papillotomy or pre-cutting needle knives, as they allow the endoscopist to directly feel and control the incision[4-16]. Anterograde or retrograde incision can be performed. Successful penetration into the proximal colon and absence of immediate complications should be confirmed right after incision[4-16]. The use of two endoscopes can increase the safety of the procedure as the first is used for the incision and the second for guiding and monitoring the intervention. However, this is not always feasible such as in cases where a second endoscopist is not readily available, where the second endoscope cannot reach the stenosis, or where there is a single barrel ileostomy. In these cases, the procedure is performed with one endoscope, and successful penetration is confirmed fluoroscopically[4-16]. After confirmation of the passage into the proximal enteral lumen, a definite treatment of the stenosis can be performed. Throughout the literature, in the majority of cases reported, it was found that the placement of a FCSEMS that remains in situ from 4 to 60 days after hydrostatic balloon dilation of the initial incision site to allow placement of the stent, is an effective and safe therapy[4-16]. Alternatively, in the article by Chi et al[3], the authors presented a case where recanalization was achieved with electrical stricturotomy and subsequent dilation with the tip of the scope. In this approach, potential perforation and bleeding during the procedure is the most feared complication. Although none occurred in the reported case, single electrocautery treatment can increase the risk of procedure-related complications secondary to tissue retraction in inexperienced hands, leaving this approach to more experienced endoscopists.
Combining mechanical penetration with mechanical dilation
To avoid electrothermal injury, previous reports showed that penetration to the oral side of the COA could be obtained mechanically[17-22]. In this technique, under direct endoscopic view, the endoscopist exerts direct mechanical force to the center of the anastomosis[17-22]. Blunt and sharp catheters including biopsy forceps, through-the-scope thin dilators such as those included in commercially available transanal drainage systems, stiffened by a reversely inserted guide wire, suprapapillary biliary puncture catheters, trocars and needles used for transjugular intrahepatic portosystemic shunt or sclerotherapy (23-25G, 4-6 mm in length) can be all used for penetration[17-22]. Successful penetration needs to be confirmed prior to continuation of the procedure[17-22]. The use of a second colonoscope as guide light in the same way it was used in the article by Chi et al[3] may be particularly helpful in this technique as it can allow endoscopists to have direct visual control of the advancement of the catheter throughout the procedure, mitigating the risk of serious complications such as perforation. However, if a second endoscopist is not available, confirmation of the intraluminal position of the catheter can be sought fluoroscopically. Subsequently, a guidewire can be passed into the proximal bowel and the stenosis can be treated either with progressive pneumatic dilation with controlled radial expansion balloon dilators until a luminal diameter of 15 to 20 mm is achieved or with deployment of FCSEMS[17-22]. Special attention is required in cases where the stenosis is stiff and thick secondary to post-surgical fibrosis which can complicate the procedure. In these cases, penetration might be better performed with the use of sharp catheters or with the use of another technique. Throughout the literature, both modalities are efficient and safe, as none was found to be associated with immediate or delayed complications, whereas revision surgery was deferred in all cases[17-22]. However, compared to balloon dilation, the placement of a FCSEMS for a period ranging from 4 to 60 days may be preferable as their use was associated with a reduced need for subsequent interventions as approximately half of the patients treated with balloon dilations needed up to 4 sessions before closure of the ileostomy[17-22].
Alternative approaches
Recanalization guided by endoscopic ultrasound system: As an alternative to the abovementioned techniques, recanalization of a completely obstructed anastomosis can be performed with the use of an endoscopic ultrasound system (EUS)[12,13,23-29]. The feasibility of this technique was investigated for the first time in 2008 when a prototype front-view and forward-array echoendoscope was created to guide the process[12,13,23-29]. Under EUS guidance, penetration in the proximal bowel was performed with a 22-gauge needle and confirmed by using a SpyGlass fiberoptic probe[12]. Serial balloon dilations were then performed to establish patency with excellent results[12]. To date, this technique has been used with variations in the employed modalities[12,23-29]. These variations simplified the technique without compromising its safety[12,23-29]. The first variation refers to the modality that is used to confirm the successful penetration into the proximal bowel. The selection depends on whether a second endoscope can reach the stenosed anastomosis[12,23-29]. In cases where single barrel ileostomy or blind anastomotic ends are present or there is no access to the proximal bowel, the problem is solved with fluoroscopic guidance[12,23-29]. In all other cases, a colonoscope can be passed through the external orifice into the proximal lumen, to fill the space with water to improve visibility and accuracy. After the confirmation of successful penetration, a guidewire is passed and the needle is withdrawn, with the second variation referring to the method the endoscopist will select to achieve resolution of the stricture. Needle knives and endoscopic balloon dilators with or without the placement of a FCSEMS to maintain patency were all found to be effective and safe in the management of CAO[23-26]. However, their use can be complicated by fluid leakage, bleeding, perforation and migration[23-26]. To avoid these complications, a novel generation of stents, designed for trans-enteric drainage named lumen-apposing metal stents (LAMS) can be deployed. To date, LAMS have been repeatedly used for the management of complete anastomotic strictures with good results in terms of efficacy and safety[12,27-29]. Their deployment is relatively easy after the initial needle puncture without the need of special equipment whereas their placement was found to be associated with reduced need for re-intervention compared to the other modalities, giving LAMS an additional advantage[12,27-29].
Transanal endoscopic microsurgery: Transanal endoscopic microsurgery (TEM) is another technique that can be used in the management of complete anastomotic stenosis. In a previous report, Wolthuis et al[30] showed that TEM can be a stable platform that can provide access to the proximal bowel. The procedure requires general anesthesia for the insertion of the 20-cm TEM rectoscope with perforation of the occluded membrane occurring with a vessel-sealing device[30]. After initial perforation, the patency of the anastomosis was established with balloon dilation up to a diameter of 2 cm[30]. However, this technique was complicated by a perforation that became evident after dilation and was treated during the procedure with uneventful recovery of the patient[30]. Nevertheless, we believe that the use of a second endoscope for guide light or fluoroscopic guidance could increase the safety of this procedure, increasing its popularity in the future.
Magnetic compression: Magnetic compression is a minimally invasive method for creating surgical anastomosis dating back to 1978[31]. However, a recent anecdotal report supports the use of this technique as an alternative for the recanalization of an occluded anastomosis[31]. Based on this report, two magnets of 17.5 mm in diameter can be delivered by a combination of endoscopic and fluoroscopic guidance and placed in the proximal and distal side of an obstructed anastomosis without the need for general anesthesia[31]. Fluoroscopy can confirm that the magnets have attached to both ends of the obstructed stenosis[31]. After successful placement, the magnets are left in situ before being absorbed with a patent neo-anastomosis being induced after 7 days, uneventfully[31]. The size of the anastomosis was large enough thus making any further endoscopic or surgical intervention, unnecessary[31].
