Esophageal Dilations for Esophageal Strictures

The mainstay of treatment for benign esophageal strictures is dilation. Although dilation usually results in symptomatic relief, recurrent strictures do occur. In order to predict which types of strictures are most likely to recur, it is important to differentiate between esophageal strictures that are simple and those that are more complex.

Simple esophageal strictures are defined as focal and straight, and most have a diameter that is sufficient to allow the passage of a normal diameter endoscope. These strictures are amenable to the standard technique of bougie or balloon dilation. Common etiologies include peptic injury (60-70% of cases), but also a Schatzki’s ring or a web. In most patients with simple esophageal strictures, 1-3 dilations are required to relieve symptoms, with an additional 25-35% of patients requiring repeat dilations.

Strictures that are long (>2 cm), tortuous, or associated with a diameter that precludes passage of a normal diameter endoscope are defined as complex esophageal strictures. The most common causes include caustic ingestion,radiation injury, anastomotic stricture, photodynamic therapy-related stricture and severe peptic injury. The latter can occur in patients in the intensive care unit or in mentally disabled people. Complex esophageal strictures are more difficult to treat than simple esophageal strictures, require at least three dilation sessions to relieve symptoms, and are associated with high recurrence rates. If complex strictures cannot be dilated to an adequate diameter allowing passage of solid food, recur within a time interval of 2-4 weeks, or require ongoing (more than 7-10) dilation sessions, they are considered to be refractory. Novel treatment modalities for refractory strictures include temporary stent placement and incisional therapy Three types of dilators are currently in use. These include bougies filled with mercury or tungsten (e.g. Maloney dilators [Medovations, Inc., Germantown, WI]), wire-guided polyvinyl dilators (e.g. Savary-Gilliard® [Wilson-Cook Medical]) and Through-The-Scope (TTS) balloon dilators (Controlled Radial Expansion [CRETM] dilation balloon, with or without guidewire [Boston Scientific]). Of these, the Savary-Gilliard® and TTS balloon dilators are currently by far the most frequently used. The main difference between these two dilators is their mechanism of action. A Savary-Gilliard® dilator exerts a radial force as it is passed down, but some of its dilating force is transmitted longitudinally because of its shearing effects. By contrast, longitudinal forces are not transmitted with balloon-type dilators. Nonetheless, no clear advantage has been demonstrated for either one of these two dilator types.The only exceptions include conditions in which a longitudinal shearing force should be avoided, such as strictures caused by epidermolysis bullosa, or in cases in which a tracheoesophageal puncture voice prosthesis is present. Savary-Gilliard® dilators are more cost-effective as they can be reused, whereas TTS balloon dilators are intended for single use only.

The main complications associated with esophageal dilation include perforation, hemorrhage and bacteremia. The reported rate of perforation and massive bleeding is 0.3%: this risk is higher when complex strictures and caustic strictures are dilated. It is generally believed that the risk of perforation is minimal if the ‘rule of three’ is applied, meaning that dilation diameters should not increase by more than 3 mm per session. Pre-dilation diameter and stricture length are established factors that influence the number of dilations required for symptom relief and the need for additional dilations.

Various investigators have examined whether the injection of steroids into the stricture can prevent recurrence of dysphagia. Most of these studies, however, were, small, uncontrolled and involved strictures with a diverse etiology. One randomized trial has been published in full. A total of 30 patients with recurrent peptic stricture were randomly allocated to TTS dilation to 15-18 mm followed by 4-quadrant 0.5 cm triamcinolone injections (40 mg/cm3) or to TTS dilation to 15-18 mm alone. After a follow-up of at least 1 year, two patients in the steroid group (13%) and nine in the sham group (60%) required repeat dilations. This finding suggests that steroid injections could have a role in patients with recurrent peptic strictures after prior dilation therapy. The utility of intralesional injections for strictures with a different etiology needs further elucidation.

Complex Strictures. Circular or nearly circular benign esophageal strictures are most frequently seen after radiation therapy for malignancies in the chest, head or neck. Most of these strictures are amenable to dilation, although fluoroscopic guidance is often required to monitor guidewire passage through the stricture. Endoscopic management of these strictures can, however, be challenging, particularly when a guidewire cannot be advanced, which sometimes occurs in the proximal esophagus. In these cases, an ‘endoscopic rendezvous’ approach can be employed. This is accomplished by introducing a smalldiameter endoscope through a mature PEG tract and advancing it in a retrograde fashion into the esophagus until the stricture is identified. In some patients, the guidewire, be it stiff or floppy, can be passed through the stricture, but in others a thin membrane is present that precludes its passage. In these patients, the guidewire, or a needle knife, can be used to puncture the membrane. The puncture should be aided by a second flexible endoscope or rigid laryngoscope approaching the stricture in an antegrade fashion. Subsequently, the stricture is dilated over the guidewire using a balloon dilator (retrograde) or Savary-Gilliard® dilator (antegrade). As these post-radiation strictures need repeat dilations, a nasogastric feeding tube should be placed to maintain luminal access for future dilations.
Stents

It is not surprising that the successful application of metal stents for the palliation of esophageal malignancies indicated that there might be a role for these devices in the management of recurrent benign strictures. In the initial clinical series of patients with benign esophageal strictures refractory to conventional therapy, however, the partially uncovered self-expandable metal coil stents used were associated with some major complications.The most common of these complications was the ingrowth of (benign) granulation tissue through the stent mesh as a reaction to the radial force placed by the stent onto the esophageal wall, and this ingrowth started to occur as early as 2-6 weeks after stent placement. This ingrowth of granulation tissue resulted in recurrent obstruction in up to 40% of patients.

To prevent recurrence due to ingrowth of granulation tissue, the completely covered Polyflex® stent made of silicone and polyester was evaluated in three retrospective series.[40-42] In the first two series, the experience was favorable. In one series, relief of dysphagia occurred in 17 of 21 patients (81%) after a median follow-up of 21 months, especially in those with caustic and hyperplastic (due to partially covered stent placement) strictures;in the other series, relief occurred in 12 of 15 patients (80%) with caustic, post-radiation, anastomotic or peptic strictures after a median follow-up of 22.7 months. No complications were mentioned in the first series, whereas in the other study recurrent dysphagia was seen in 33% of patients, which was due to mucosal hyperproliferation in four patients and stent migration in one patient.

Less optimistic results on Polyflex® stents have since been reported. Holm et al.[42] placed 84 Polyflex® stents in 20 patients, most with benign or anastomotic strictures. Migration was the most frequent complication, noted in 18 of 29 patients (62%) and for 53 of 83 stent placements (64%). In addition, hyperplastic tissue growth and stricture formation around the stent was seen in 5 patients (17%) after 15 procedures (18%). Remarkably, only 5 of 83 procedures (6%) resulted in long-term symptom relief after stent removal, which is in line with the experience at my institution.

The management of patients who have refractory hypopharyngeal strictures after chemoradiation and/or surgery can be unsatisfactory as normal diameter stents placed in this location can cause a foreign body sensation, severe pain, fistula formation or perforation. Patients with refractory hypopharyngeal strictures who have undergone stent placement sometimes end up with a feeding tube, but experience difficulties in degutting saliva. To prevent the need for a feeding tube and to allow patients to eat, a cervical Niti-S stent was developed that has a body diameter of 10 mm, 12 mm or 14 mm. This stent is available with or without a flare that is 2 mm wider than the body diameter and is covered or uncovered. This stent effectively improved dysphagia in a small series of seven patients.[43] As six of the seven patients developed stent migration and/or granulation tissue ingrowth or overgrowth, additional new stents were placed a median of 3 months after the previous stent placement. Hypopharyngeal strictures have a high recurrence rate, and prolonged stent placement with periodic stent exchanges at intervals of 6 weeks to 3 months is, therefore, indicated.

In conclusion, Polyflex® stents have originally been advocated to be a promising stent type for the treatment of complex benign strictures. However, recent experience has questioned this optimistic view and further studies are required to select the most optimal patient population. Apart from stent migration, another disadvantage of using Polyflex® stents is that the stent applicator is large and stiff compared with the applicators used for metallic stents. Dilation before stent placement is, therefore, often required. Another drawback to using Polyflex® stents is the need to load the stent into the introduction catheter to avoid prolonged folding of the stent and prevent it from becoming deformed. For these reasons, at my institution we also use metal stents, particularly partially covered Ultraflex™ stents, to treat benign esophageal strictures, and retrieve the stents 4-6 weeks after placement. In our experience, Ultraflex™ stents have the advantage that they are less likely to migrate than Polyflex® stents. For patients with complex hypopharyngeal strictures, my group prefers to use the modified Niti-S stents. In our experience, the best results can be obtained with the 10 or12 mm cervical Niti-S stent types that are flared and fully covered.

A recommended technique of stent removal is to grasp the nylon loop that is attached to the proximal end of most stents. This decreases the stent diameter and facilitates pulling the stent out. Yoon et al.[44] designed a special hook to grasp this loop and to remove the stent under fluoroscopic control. Although they reported that this technique was successful in the removal of 127 of 130 stents (98%), it is the experience at my institution that these loops quite often break during stent removal. We therefore prefer to grasp the proximal end of the stent with a polyp snare, or a rat-toothed forceps if a fully covered type of stent, such as the Polyflex® stent, has been used. Partially covered stents, such as the Ultraflex™ stent, can be removed more easily by grasping the distal end of the stent with rat-toothed forceps, which will result in invagination of the stent into itself.
Incisional Therapy

Refractory anastomotic strictures that occur after gastrointestinal surgery are common, with a reported incidence of 2-30%.[23,45,46] Anastomotic strictures usually are secondary to tissue ischemia, leakage or radiation therapy.[23,45] As an alternative to repeat dilation therapy, incisional therapy using electrocautery,[47] argon plasma coagulation in combination with electrocautery,[48] or endoscopic scissors[49] have been reported to be successful in patients with anastomotic strictures. In the largest reported series,[47] 20 patients with persisting anastomotic strictures after three endoscopic dilations were treated with a session of needle knife electrocautery until the endoscope could easily pass the stricture (Figure 6). Twelve patients who had a stricture shorter than 1 cm were free of dysphagia after a single treatment. In the remaining eight patients who had a stenosis of 1.5-5 cm, a mean of three electrocautery sessions was required for them to become symptom free. No complications such as perforation and hemorrhage were observed. In patients with recurrent Schatzki’s rings, the same technique was also reported to be moderately successful after a median of three endoscopic dilations.[50] These results show that in patients with a firm fibrotic stricture, such as can be found at an anastomotic site, incisional therapy could be a safe alternative treatment modality in cases refractory to endoscopic bougie or balloon dilation.