We included 5 randomized clinical trials (RCTs), totalizing 461 patients. Among them, 151 were treated with bougie dilation and 225 underwent balloon dilation. Regarding symptomatic relief, recurrence, bleeding, and perforation rates, there were no differences between the methods. Concerning postprocedure pain, patients submitted to balloon dilation had less intense pain (RD 0.27, 95% IC −0.42 to −0.07, P = 0.007).
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We searched for randomized clinical trials (RCTs) published from insertion to November 2017, using MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, LILACS, and grey literature. After the data extraction, a meta-analysis was performed. The main outcomes were symptomatic relief and recurrence rate. The secondary outcomes were bleeding, perforation, and postprocedure pain.
The use of bougies and balloons to dilate benign esophageal strictures (BES) is a consolidated procedure. However, the amount of evidence available in scientific literature supporting which is the best technique is very low, despite the great prevalence and importance of such pathology. This systematic review with meta-analysis aims at comparing both techniques, providing good quality of evidence.
Despite all these theoretical advantages, there is no consensus in the available scientific literature to favor balloons over bougies [ 5 , 6 ]. Also, there is no systematic review comparing both methods in patients with BES. Therefore, we developed this study to comprehensively search and compile all available data regarding this topic and ultimately provide practitioners with the most reliable evidence.
Balloon dilatation catheters were traditionally designed to treat patients with achalasia. In the early 1980s, they were introduced for the treatment of BESs. To dilate, the balloon should stand exactly at the stricture, in most cases secured by a guidewire. Then, it applies a radial pressure on the ring and ideally carries a lower risk of perforation. Other hypothetical advantages of the balloons are a greater precision (since it dilates only the exact narrowing) and the possibility to visualize the dilation process endoscopically as it occurs [ 4 ].
Modern bougies are made of polyvinyl chloride. The dilation procedure consists in passing a guidewire through the narrowing of the esophagus (fluoroscopy-guided or not) followed by bougination with gradually thicker dilators. This process generates an axial pressure on the stricture ring and theoretically poses a higher risk of esophageal perforation compared to the balloon dilation [ 3 ].
Benign esophageal strictures (BESs) are defined as any type of nonmalignant narrowing of the esophageal lumen. The physiopathological mechanisms of BESs are diverse and may entail embryonary defects, inflammatory injuries, and iatrogenesis. Also, there are several etiologic causes that may result from the combination of different mechanisms [ 1 ]. The most common clinical presentation is dysphagia, but others as retrosternal pain, regurgitation, and odynophagia might be present [ 1 ]. The impact on quality of life is usually remarkable since the patient frequently suffers from weight loss and aspiration pneumonia [ 2 ].
This systematic review and meta-analysis was performed according to the PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and was registered in PROSPERO (International Prospective Register of Systematic Reviews) under the registry number CRD42018085541.
If I [ 2 ] was higher than 50%, we searched for outlier studies through the funnel plot. Articles outside the limits of the funnel were excluded, and heterogeneity was reassessed. If the sample became homogenous (I 2 < 50%), the excluded studies were considered true outliers and were permanently removed. If we did not find an outlier, we considered true heterogeneity and switched from fixed to random effect analysis.
We used the method of inverse variance and fixed effect model to provide the forest plots. Heterogeneity was assessed with the Higgins test [ 8 ](I 2 ), and values higher than 50% were considered highly heterogeneous. Funnel plot analyses were also employed to assess publication bias across studies.
We used the RevMan software version 5.3 to perform all analyses and employed mean or absolute risk difference. We applied the Mantel-Haenszel test for categorical variables and considered statistically significant results with 95% confidence interval (CI) and P < 0.05.
In our meta-analysis, we included only studies providing complete data in the text, tables, or figures. If necessary, we assessed supplementary data available in online platforms (e.g., Clinical Trials or PROSPERO) or tried to contact the authors by email.
Our search strategy for MEDLINE (PubMed) was (Esophageal stenosis OR Esophageal Stenoses OR Esophageal Stricture) AND (Balloon OR dilatation OR savary OR bougie OR pneumodiltation OR pneumodilation). For other databases, we employed a simpler strategy: (Esophag ∗ AND (Balloon OR dilatation OR savary OR savary-gilliard OR bougie OR bougienage OR pneumodilatation OR pneumodilation).
The selected trials were developed in several countries from different continents and enrolled a great variety of patients and clinical presentations. However, all patients underwent esophageal dilation at least up to 15 mm. summarizes the studies' characteristics.
Assessing risk of bias, we identified issues during randomization and blinding processes but adequate intention to treat analysis in most of the included trials. Therefore, we assigned fair quality to all studies. Figures and synthesize the risk of bias assessment.
Two trials [ 10 , 13 ] reported postprocedure pain incidence. A total of 65 patients were enrolled (33 in the bougie group and 32 in the balloon dilation group). This analysis was highly homogenous (I 2 = 0%). The balloon group had a significantly lower incidence of pain after the procedure (RD 0.27, 95% CI 0.08–0.47, P = 0.007). shows the forest plot regarding postprocedure pain incidence.
For this analysis, we included five RCTs [ 9 – 13 ]. A total of 461 patients were enrolled, 190 treated with bougie and 271 with balloon dilation. Again, the meta-analysis identified highly homogenous data (I 2 = 0%) with risk difference between groups of −0.01 (95% CI [−0.03, 0.02]). Therefore, we found no difference concerning perforation rates ( ).
Two RCTs [ 11 , 13 ] enrolling a total of 282 patients reported bleeding rates. Among them, 104 patients were allocated for the bougie group and 178 for the balloon group. This analysis was highly homogenous (I 2 = 0%), and the risk difference was −0.02 (95% CI [−0.06, 0.02]). Therefore, we found equivalence of methods regarding bleeding rates ( ).
Four studies [ 10 – 13 ] reported the recurrence rate at 12 months. The risk difference was 0.03 (95% CI [−0.05, 0.10]) with I 2 = 59% ( ). After the funnel plot analysis, we identified and removed an outlier (Saeed et al.) ( ). Then, we pooled data again and found a decrease in heterogeneity (I 2 = 20), but still no difference between the methods ( ).
Systematic reviews and meta-analyses are statistic tools used to pool data from different studies, aiming at improving the level of evidence available. Regarding the treatment of BESs, we identified the absence of high-quality randomized clinical trials, particularly in the last 20 years. Most published articles are case series, which are fairly reliable in terms of level of evidence. Therefore, this is the most trustworthy study available concerning the endoscopic treatment of BESs [14].
This systematic review included all 5 RCTs [9–13] available in the literature, which were all published before the 2000s. This fact demonstrates the lack of current evidence, which is necessary to guide treatment and management of such complex disease. Usually, the scientific community stops researching about a specific theme when steady data is found and we achieve a consensus. However, our systematic review clearly found conflicting results when comparing techniques, and therefore refuses any kind of consensus. In 2015, the World Society of Emergency Surgery published a consensus [15] observing that there was no clear advantage of any of the methods in peptic esophageal strictures, but Savary dilators would be more reliable and effective due to the possibility to “feel the resistance to dilation under the operators hands”. However, such statement was not supported by any good quality study, being rated as level 4 recommendation.
Our meta-analysis included 461 patients with different etiologies for the BESs, such as peptic, Schatzki ring, postradiation, postanastomotic, and caustic. Also, different kinds of bougies (e.g., Savary-Gilliard and Puestow) and balloons (e.g., CRE, Rigiflex, and Bard) were used for dilation in the studies. These factors probably explain the high heterogeneity found in the recurrence rate analysis. Particularly, Saeed et al. was the main cause for the high heterogeneity and therefore was excluded as an outlier. The remainder were homogenous, but the result still showed equivalence of methods.
The employment of different bougies, each with particular physicochemical characteristics, may also be a confounding factor. To date, no randomized clinical trial compared thermoplastic (Savary-Miller) to metallic (Eder-Puestow) bougies. In our personal experience, the metallic ones carry higher perforation rates while handling is more challenging. Thus, we no longer employ such dilator in our daily practice.
Similarly, there are no high-quality studies comparing high- to low-complacency balloons. Theoretically, the highly complacent ones pose a higher risk of perforation due to their capacity to mold according to the shape of the stricture. This mechanism results in overpressure beyond the narrowing, which might result in esophageal perforation. However, there is no concrete literature supporting this hypothesis.
Regarding the cause of BESs, the lack of literature is even more impressive. Some etiologies such as peptic present a better response to dilation because the inflammatory process is usually limited to superficial layers and spares the muscularis propria [16]. Moreover, the efficacy of PPI treatment decreased the number of patients suffering from peptic strictures. Controversially, other etiologies such as postradiation and caustic carry full-thickness inflammation and fibrosis. In these cases, the symptomatic relief after dilation is usually shorter [16]. Therefore, it is always imperative to consider not only the technique but also the etiology of the BES when analyzing outcomes.
Concerning the interval between sessions, some authors advise early redilation regardless of symptoms, while others recommend dilation according to the patient's complaints [17]. Again, there is no current consensus regarding this topic, and each trial included in our meta-analysis may have employed a different interval between sessions. This fact might be considered another confounding factor.
Strictures can occur at any level of the gastrointestinal tract (GIT) from the esophagus to the colon. The causes of GIT strictures are numerous, such as reflux disease, congenital webs, caustic ingestion, malignancy, anastomotic, radiation, Schatzki’s rings, pyloric stenosis, nonsteroidal anti-inflammatory drug (NSAID) use, diverticulitis, or inflammatory bowel disease. In addition, these strictures are difficult to treat at times as each intervention may lead to further scarring and worsening stricture formation. As one may expect with such various etiologies and locations, there are many modalities of treatment. Historically, the first treatments involved dilation with fixed diameter bougies. As anesthesia and the field of surgery progressed, more invasive surgeries were developed that would allow for the resection of the diseased area. More recently, adjunctive endoscopic therapies such as stent placement, intralesional injections and electrosurgery have evolved to help solve this complex disease process.
The earliest treatments were focused on the esophagus as it was the most accessible of areas. In the mid-1600s, Dr. Thomas Willis described using a thick sponge on the end of a whalebone bougie and in the 1700s, some doctors in Europe were recording the use of ivory bougies to dilate esophageal strictures (1). Over the past 150 years, various types of dilators have been used. Initially these were placed blindly, but fluoroscopic guidance has become a useful adjunct to aid with visualization during dilation. As the field of surgery progressed, retrograde dilators were able to be used by having the patient swallow a string which was then attached to a dilator through a gastrostomy site and pulled in a retrograde fashion through the esophagus. Another technique that has been used was using string guidance, whereby a patient swallowed a weighted string and after this passed into the distal esophagus past the stricture, GIT dilators were then passed over the taut string.
The most common blind bougie dilators in use today are the Hurst and Maloney dilators (Figure 1). Both are filled with tungsten and push type dilators that exert a shearing and radial force as they are pushed through a stricture. One point of differentiation with these two dilator types is that the Maloney dilators have a tapered type tip while the Hurst dilators have a blunt style tip. Another option that allows for slightly more control are Savary-Gilliard, American Dilation System and Tucker dilators that have an internal channel that allows for wire guidance. The Savary-Gilliard and American Dilation System dilators are push type dilators while the Tucker dilators are of the pull type. Tucker dilators have a loop on both tapered ends. They are pulled both antegrade and retrograde across a stricture. The Savary-Gilliard dilators have a radiopaque marking at the end of the taper point that is the maximum diameter whereas the American Dilation System dilators are totally radiopaque. Finally, anorectal Hegar dilators are stainless steel dilators with rounded ends. They are short and tend to be used for anorectal strictures. These dilators all have fixed maximum diameter and exert both radial and longitudinal shearing forces on the stricture during dilation.
Figure 1 Examples of a Hurst (left) and Maloney (right) bougie dilator.
In 1971, Lilly et al. reported the first endoscopic guided dilation which allowed a whole new avenue of therapies and began the use of balloon expandable dilators (2). These dilators come in various sizes ranging from 5 to 20 mm in diameter and exert only a radial force. By using the endoscope for guidance, it is possible to access strictures throughout the GIT as compared to the prior available dilators. They are designed to pass through the therapeutic channel of an endoscope with or without wire assistance. If inflated with radiopaque contrast, one is able to observe the dilation throughout the length of the stricture (Figure 2). The balloons are single use devices which can add to the cost of the procedure compared to bougie dilators. A handheld device to inject liquid is used to inflate the balloon, which then allows the proceduralist to monitor the pressure used during the dilation in addition to observing it through the endoscope. Over the years, a few trials have investigated comparing fixed diameter bougie dilators with endoscopic guided balloon dilators, mostly in the treatment of esophageal strictures as these are the most accessible to both treatment modalities. On a recent meta-analysis, no difference was noted in symptomatic relief, recurrence at one year, bleeding or perforation. However, patients who had balloon dilation did experience less severe post procedure pain (4).
Figure 2 Depiction of a fluoroscopic-guided balloon dilation of a pyloric stricture with the characteristic “waist” indicating the location of the stricture followed by further balloon dilation until the waist and stricture disappear (Depiction of a fluoroscopic-guided balloon dilation of a pyloric stricture with the characteristic “waist” indicating the location of the stricture followed by further balloon dilation until the waist and stricture disappear ( 3 ). Available online: http://www.asvide.com/article/view/32545
Although the majority of strictures can be effectively managed with endoscopic dilatation, additional measures can also be considered in the management of strictures depending on the etiology. Stent placement is one of the most common adjunctive modalities to maintain lumen patency, particularly with malignant strictures. Stents act by exerting radial force on the stricture; there are a variety of stents available depending on the location, length, material and diameter (Figure 3) (5).
Figure 3 Examples of a biodegradable stent, fully covered self-expandable metal stent and self-expandable plastic stent. (A) Biodegradable stent (ELLA-CS, Czech Republic) composed of polydioxanone monofilament; (B) fully covered Evolution® stent composed of nitinol silicone coating (Cook, United States); (C) fully covered silicon constructed Polyflex® stent (Boston Scientific, United States). Figure care of Baishideng Publishing Group (Examples of a biodegradable stent, fully covered self-expandable metal stent and self-expandable plastic stent. (A) Biodegradable stent (ELLA-CS, Czech Republic) composed of polydioxanone monofilament; (B) fully covered Evolutionstent composed of nitinol silicone coating (Cook, United States); (C) fully covered silicon constructed Polyflexstent (Boston Scientific, United States). Figure care of Baishideng Publishing Group ( 5 ).
Uncovered stents are generally used in patients with poor survival and in areas with expected high likelihood of stent migration such as the duodenum and colon because of its benefit of flexibility to exert high pressure on angulated strictures in these regions (6). However, due to the risk of tumor and tissue in-growth with uncovered metal stents that can lead to re-obstruction and symptom recurrence, the majority of stents used for malignant strictures are either partially-covered or fully-covered metal designs, which have both been found to be equally effective and safe (7). Although fully-covered stents are more resistant to tumor and tissue in-growth, one of their disadvantages is that they are more prone to stent migration which can require re-intervention. Strategies to reduce the risk of stent migration include the use of large-sized stents and anchoring of the stents using clips at the stent margin or endoscopic sutures (8). Partially-covered stents do offer some of the advantages of both uncovered and fully covered stents; however, in benign pathologies, partially covered stents are not recommended due to the proliferation of granulation tissue through the proximal and distal uncovered stent edges which can make removal difficult. As such, fully-covered metal or self-expanding plastic stents are commonly used for benign strictures as a temporary treatment strategy which has the benefit that they are more easily removed compared to uncovered stents that can be more challenging to remove due to tissue ingrowth. To prevent excessive tissue in- or overgrowth, it is generally recommended that stents be removed by 6–10 weeks after treatment (9). Techniques for stent removal include using endoscopic rat tooth forceps to pull the purse-string suture at the proximal stent edge, double forcep graspers through a double-channel endoscope, stent-in-stent technique of temporary placement of a new stent within the first stent to facilitate removal and stent inversion of grasping the distal end of the stent and inverting it through itself. There is new evidence supporting the use of biodegradable stents which are typically made of polydioxanone that would not require removal; a recent multi-center randomized control trial found that biodegradable stent placement was associated with a significantly longer median time to first dilation with improved symptom control and higher level of activity compared to dilation alone with no difference in adverse events (10). However, further studies are still required to define the role of biodegradable stents in the treatment of benign strictures. Regardless of stent type, there was no significant difference found between stent types in the treatment of benign strictures, with an approximate success rate of 40% in benign esophageal strictures (11). The role of endoscopic stent placement will also be further discussed in another article in this series.
Endoscopic intralesional steroid injections have also been considered as an adjunctive therapy either before or after dilation and are typically used for refractory benign or anastomotic strictures. It is believed that intralesional steroids inhibit stricture formation by interfering with collagen synthesis, fibrosis and chronic scarring processes to help augment the effects of dilation but the mechanism of action is not entirely clear (12). The steroid utilized is typically triamcinolone acetate or acetonide in a concentration of 10–40 mg/mL injected using a 21 to 23 gauge 5 mm long sclerotherapy needle in 0.5 mL aliquots circumferentially in four quadrants at the proximal margin of the stricture as well as in the strictured segment when possible which should be difficult to inject if in the correct position (13). Although a few small studies demonstrated symptom improvement and an overall reduction in the need for repeat dilatations for benign esophageal strictures, these were not found to be statistically significant in a more recent meta-analysis. However, it was found to be consistent across all studies that there was a significant increase in the interval between dilations indicating some efficacy of intralesional steroids when used in combination with endoscopic dilation (14). The efficacy of intralesional steroids in addition to endoscopic balloon dilation was also found to be replicated with anastomotic strictures following esophagectomy in which a small randomized control trial demonstrated a significant reduction in the total number of dilations required as well as a significant improvement in re-stricture free survival (15).
With a similar logic as intralesional steroid injections that help counter collagen synthesis, fibrosis and scarring, people have investigated topical application of mitomycin C to strictures. In an animal study, mitomycin C in a dose dependent manner showed significant ability to prevent stricture formation after caustic esophageal injury with fairly good results which was then replicated in a case series. A double-blind, randomized, placebo controlled trial showed 80% resolution of esophageal strictures with topical mitomycin C treatment compared to only 35% in the placebo group as well as less total number of dilation sessions in the treatment group (16). Mitomycin C has also been injected intra-lesionally into the submucosal space in complex recurrent esophageal strictures, in which a study found that there was a significant improvement and resolution of dysphagia symptoms in the group treated with mitomycin C compared to the placebo group with no adverse effects (17). In addition, mitomycin C was found to be effective in stricture prevention in a porcine model (53.6% low dose, 35% high dose); however, in this trial, the esophageal wall treated with high-dose mitomycin C appeared to be necrotic and eventually led to perforation. In models treated with a low dose of mitomycin C, the esophageal wall appeared re-epithelialized and healthy (18).
Another adjunctive measure to endoscopic dilations used for benign refractory and anastomotic strictures is electroincisional therapy in which electrocautery can be combined with argon plasma beam coagulation, needle-knife or endoscopic scissor techniques to incise the tissue of the stricture. The most common technique is the radial incision and cutting technique, in which the stricture is incised under direct endoscopic vison in a radial fashion parallel to the longitudinal axis to remove the rim of the stenosis (Figure 4) (19). The procedure is typically terminated once the scope can easily traverse the previously strictured segment (20). Incisional therapy can also be used in conjunction with dilation or steroid injections to reduce the need for repeated intervention. One randomized controlled trial found that electroincisional therapy was comparable in efficacy in terms of the total number of dilations and success rate when compared with Savary dilations with no increase in adverse events (19). Current evidence also suggests that incisional therapy is also most effective in the treatment of refractory benign or anastomotic strictures that have a relatively short stenosis less than 1cm in length with a success rate of approximately 80.6% and rate of recurrence of approximately 4.8% (21). As such, electroincisional therapy can be considered a safe and effective alternative method for the treatment of refractory strictures for whom multiple re-interventions have failed.
Figure 4 Illustration of an esophageal stricture prior to electro-incisional therapy (left) and following electro-incisional therapy where radial incisions are made parallel to the longitudinal axis to remove the rim of the stenosis (Illustration of an esophageal stricture prior to electro-incisional therapy (left) and following electro-incisional therapy where radial incisions are made parallel to the longitudinal axis to remove the rim of the stenosis ( 19 ).
Given that the goal of dilation is to disrupt the stricture to enlarge the lumen, mucosal tears are expected. However, significant complications can occur which can include bleeding, perforation, bacteremia and aspiration which is mostly with upper GIT strictures and also related to sedation given for the procedure. Minor bleeding following dilation, stent insertion or electroincisional therapy is relatively common and typically self-limiting not requiring any intervention as fibrotic strictures are relatively avascular; however, significant bleeding from these interventions occurs at a rate between 0.1–0.4% (19,22). With this risk in mind, the American Society of Gastrointestinal Endoscopy (ASGE) came out with guidelines to help address the added bleeding risk of therapeutic endoscopy on patients who are on anti-coagulation or antithrombotics. For high-risk procedures such as dilation or incisional therapies, anti-coagulation and thienopyridines should be held for the appropriate time frame while non-steroidal anti-inflammatory drugs, aspirin and DVT prophylaxis should be continued even in high risk procedures. Controversially, endoluminal stent placement is categorized as low risk and as such, it is recommended to continue anti-coagulation in this setting (23). Perforation is the most clinically significant complication and can occur either from complete transmural disruption or creation of a false tract (24). It is estimated that the overall risk of perforation ranges from 0.1% to 0.6% (25). Factors that are associated with an increased risk of perforation include malignancy, severe inflammation, radiation or caustic-induced strictures as well as operator inexperience. Features of strictures that also increase the risk of perforation include long-segment, significant luminal narrowing or angulated strictures (26). Bacteremia is also a known complication from endoscopic dilation; however, it is rarely clinically significant as it is equivalent with brushing and flossing and the current ASGE guidelines do not recommend routine antibiotic prophylaxis at the time of endoscopic intervention for the management of strictures (27). Ultimately, endoscopic management of strictures is generally safe and well-tolerated. The benefits and risks of each technique must be weighed against other endoscopic alternatives, surgery or medical management and discussed thoroughly with patients.
Strictures can be located throughout the GIT and can be successfully treated using endoscopic techniques such as dilation, stents, and intralesional injections with either steroids or mitomycin C or electroincisional therapy. Careful consideration should be made to characterize the stricture prior to intervention and the method used for the treatment of strictures is dependent on etiology, location, length and degree of stenosis. Each option can be repeated if necessary and used in a step-wise approach to relieve symptoms and improve the success of intervention. Overall, endoscopic management of GIT strictures is relatively safe, effective and has a favorable risk-benefit profile. Additional studies are required to better define the long-term efficacy of endoscopic options such as intralesional steroid or mitomycin C injections, biodegradable stents and electroincisional therapy.
The authors would like to thank Ryan Juza and Jeffery Marks for allowing us to participate in this special issue on surgical endoscopy.
Funding: None.
Provenance and Peer Review: This article was commissioned by the Guest Editors (Jeffrey M. Marks and Ryan M. Juza) for the series “Surgical Endoscopy: Essential Skills in Gastrointestinal Surgery” published in Annals of Laparoscopic and Endoscopic Surgery. The article has undergone external peer review.
Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/ales.2019.06.06). The series “Surgical Endoscopy: Essential Skills in Gastrointestinal Surgery” was commissioned by the editorial office without any funding or sponsorship. The authors have no other conflicts of interest to declare.
Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.
doi: 10.21037/ales.2019.06.06
Cite this article as: Johnson R, Fung EC. Dilation and adjunct therapy for strictures. Ann Laparosc Endosc Surg 2019;4:63.
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