Endoscopic Mucosal Resection (EMR) Technique

Updated: Jun 26, 2017
  • Author: Bruce D Greenwald, MD; Chief Editor: Kurt E Roberts, MD  more...
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Technique

Approach Considerations

Before endoscopic mucosal resection (EMR) is initiated, the extent of the target lesion should be clearly established. Once resection has commenced, mucosal landmarks may be obscured. Furthermore, visible abnormalities in early neoplastic lesions are often difficult to ascertain. Saline or water irrigation is often used; spraying of 1% acetylcysteine aids in the dissipation of adherent mucus. A combination of magnification high-definition white-light endoscopy and narrow-band imaging or chromoendoscopy (see the image below) is useful.

Superficial gastric neoplasm (arrow) demonstrated Superficial gastric neoplasm (arrow) demonstrated with chromoendoscopy prior to cap-assisted endoscopic mucosal resection (EMR).

Additional techniques include confocal laser endomicroscopy and optical coherence tomography/volume laser endomicroscopy; these techniques are not yet widely available. The periphery of the lesion may be marked using superficial cautery marks.

Several EMR techniques have been developed, all of them based on the principles of “lifting” the target mucosa and resecting the lesion by applying the cautery (see the image below). The main approaches are as follows:

  • Injection-assisted EMR
  • Cap-assisted EMR
  • Ligation-assisted EMR
Principle of mucosal resection. Principle of mucosal resection.

Early work with another variant, "underwater" EMR, suggests that this approach may prove to be an effective and safe alternative to traditional EMR. [69]

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Injection-Assisted EMR

The injection-assisted (or “inject-and-cut”) technique consists of submucosal injection of an aqueous solution followed by the application of a snare cautery for lesion resection. [70]  Submucosal injection is a well-established technique that creates a submucosal cushion underneath the lesion, mitigating the risk of transmural thermal injury during the application of cautery.

The solution is delivered via a standard injection needle. The underlying principle is that the solution will “seek” the submucosal layer because of the presence of loose connective tissue within this layer. An automated pump is commercially available that facilitates uniform submucosal injection (ERBE, USA). A modification of this technique, the “inject-lift-and-cut” technique or “strip biopsy,” uses a tissue grasper passed through a second working channel to provide traction on the target mucosa during resection.

Typically, 5-50 mL of solution is injected beneath the lesion. During colonic EMR, injection of the distal margin of the lesion first often aids visualization during resection. The addition of dilute staining dyes (eg, indigo carmine or methylene blue) assists in identification of the deep and lateral resection margins. [71]

Results with saline, the most commonly used solution, are often limited by the relatively rapid absorption of the injection; thus, multiple injections are often necessary. This problem has been addressed by the invention of combination needle and snare devices, as well as the study of various injection solutions. The addition of dilute epinephrine to standard saline provides a limited increase in cushion durability.

Other solutions that have demonstrated longer-lasting cushions include hyaluronic acid, hydroxypropyl methylcellulose, glycerol, and fibrinogen solutions, though most are not widely available and are limited by cost considerations. [72, 73, 74]  It is noteworthy that injection of autologous blood has shown superior results with respect to cushion durability. [75, 76]  An increased incidence of local inflammatory reactions has been demonstrated with the use of hypertonic saline, hypertonic dextrose, and hydroxypropyl methylcellulose, limiting their use in practice.

A systematic review and meta-analysis assessed injection of normal saline against injection of other viscous and hypertonic solutions (eg, hydroxyethyl starch, sodium hyaluronate solution, 50% dextrose, and succinylated gelatin) in the setting of EMR for colorectal polyps. [77]  Compared with normal saline, other viscous solutions were associated with a significant increase in en-bloc resection and a significant decrease in residual lesions. Overall adverse events rates did not differ significantly between the two groups.

Because there were no significant outcome differences for lesions smaller than 2 cm, the authors of this study suggested that endoscopists might consider using normal saline for EMR of smaller (<2 cm) colorectal polyps and other viscous solutions for larger (>2 cm) colorectal polyps. [77]

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Cap-Assisted EMR

This technique uses a combination of submucosal injection, aspiration of tissue into a clear soft plastic cap attached to the tip of the endoscope, and snare excision. [78]

Various single-use devices that include a combination of cap and specially designed snare are commercially available. Typically, the snare is opened within the distal internal rim of the cap, tissue is aspirated within the cap and snare, the snare is closed around the captured tissue, and a standard snare cautery is applied to excise the tissue. Caps are available in various sizes and have either a flat (cylindrical) or oblique end, with the latter assisting in tissue aspiration within the tubular esophagus (see the image below).

Transparent endoscopic mucosal resection (EMR) cap Transparent endoscopic mucosal resection (EMR) cap.
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Ligation-Assisted EMR

Born from the extrapolation of tissue acquisition during variceal band ligation to EMR, this technique involves the application of bands around aspirated tissue and subsequent snare-cautery resection. In theory, the band will incorporate the mucosal and submucosal layers while leaving the muscularis propria in situ as a consequence of insufficient contractile force.

In the simplest form of the procedure, a standard variceal band ligator device is used to aspirate the target lesion and apply a band around it (see the images below). After removal of the banding device, a separate snare is used to resect the lesion. [79, 80]

Combined cap-and-snare device. Combined cap-and-snare device.
Aspiration of tissue during ligation-assisted endo Aspiration of tissue during ligation-assisted endoscopic mucosal resection (EMR).

A submucosal injection may also be made before tissue aspiration, though this step is not universally applied. Two EMR kits are commercially available in the United States. Both include a modified multiband ligator and hexagonal snare that is passed within the working channel with the ligation device in place.

Practice variations in technique include the following [81] :

  • Use of saline lift before EMR
  • Closure of the snare above vs below the band
  • Initial application of multiple bands versus resection following the application of each band during resection of larger lesions
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Postprocedural Care

EMR is primarily performed on an outpatient basis. After the procedure, patients typically receive general instructions regarding medication use, diet, and symptom management. Patients undergoing upper EMR may be  prescribed a clear liquid diet on the day of the procedure with diet advancement as tolerated thereafter. All patients should receive high-dose proton pump inhibitor therapy after foregut lesion resections.

Infrequently, patients may experience pain that can be managed with nonnarcotic analgesia. Management of anticoagulants and antiplatelet agents should be discussed with the prescribing provider prior to the day of the procedure. These are generally stopped beforehand at an interval that allows return to normal clotting and coagulation function in advance of the procedure; they are generally restarted shortly after the procedure. Cessation of aspirin is not necessary before EMR. 

Patients should be instructed to seek medical attention if they experience fever, nausea or vomiting, hematochezia, or melena.

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Complications

EMR is generally safe in experienced centers, though several complications have been described.

Bleeding

Bleeding is the most common complication of EMR and consists of intraprocedural bleeding and delayed bleeding, which can occur from 6 hours to 7 days after EMR. Immediate bleeding has been identified as an independent predictor of delayed hemorrhage. [82, 83]

Bleeding rates vary, depending on the EMR site. Bleeding after EMR in the esophagus is uncommon, with one large study reporting significant bleeding requiring intervention, transfusion, or hospitalization in 1.2% of patients undergoing this procedure. [84, 85] Intraprocedural bleeding rates for gastric EMR range from 0% to 11.5%, with delayed bleeding occurring in approximately 5% of patients. [84] Intraprocedural bleeding rates after EMR of colorectal lesions larger than 20 mm range from 11% to 22%. Bleeding rates after EMR of large colonic polyps range from 2% to 11%. [84]

Immediate bleeding is typically managed via the application of hemostatic endoscopic clips, hot biopsy forceps, monopolar hemostatic forceps, bipolar coaptive coagulation, argon plasma coagulation, or the application of soft coagulation with the tip of a snare. 

 

Perforation

Perforation is a rare complication of EMR, with reported rates of 0.3-0.5% for esophageal and colonic EMR [86, 56]  and 1% for gastric EMR. [87] Small perforations are amenable to endoscopic closure with endoscopic clips. [88, 89, 90]  Urgent surgical consultation and intravenous broad-spectrum antibiotics are indicated for larger defects.

Endoscopic suturing of large mucosal defects, typically performed after endoscopic submucosal dissection (ESD), has also been utilized. [91] Endoscopic tissue shielding with polyglycolic acid sheets has been described in two cases of large perforations not eligible for endoscopic closure as a possible option for large perforations after esophageal endoscopic resection. [92]

Stricture

Stricture formation is a late complication following endoscopic removal of esophageal lesions and has been reported in 5-88% of patients. [93, 94, 95, 96, 97, 98, 99, 100] Esophageal strictures are more common after resection of multiple lesions and large resections occupying three quarters of the luminal circumference or resection lengths in excess of 3 cm. [97] Strictures respond well to serial endoscopic dilation. 

Ampullectomy

The most common complication associated with ampullectomy is pancreatitis, occurring in 10% of cases. Bleeding, perforation, cholangitis, and delayed papillary stenosis are also infrequently reported. Placement of prophylactic duct stents may serve to mitigate the risks of ductal occlusion. [59]

Submucosal lesions

EMR of submucosal lesions is associated with a relatively high incidence of complications, with reported rates of bleeding approaching 40% and perforation rates of 0.8%. [101]

Little comparison has been made between techniques in randomized controlled trials, although the inject-and-cut techniques are generally more technically demanding than the cap-assisted and ligation-assisted techniques. A single randomized study comparing injection with cap-assisted EMR and ligation-assisted EMR without injection within the esophagus found no significant difference in safety.

Although transient bacteremia has been reported with colonic EMR, routine antibiotic prophylaxis is not generally recommended.

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