What Is the Difference Between EMR and ESD?

Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) remove colon cancer and polyps.

The main endoscopic techniques that are available for the removal of colon (part of the large intestine) polyps or cancer are as follows:

• Endoscopic mucosal resection (EMR): This procedure removes early-stage cancer and precancerous growths from the lining of the digestive tract. It works better with superficial masses.
• Endoscopic submucosal dissection (ESD): This procedure removes large tumors from the gastrointestinal tract.
• Polypectomy: This procedure is used to remove polyps (an abnormal collection of tissue) from the inside of the colon.

• Resection: This is a surgical procedure used to remove a part of an organ or a structure, possibly because of disease or cancer (e.g., the tumor resected after chemotherapy).
• Dissection: This is a procedure of cuts apart or separates tissue for further study or diagnosis. It helps in removing a complete part that is affected by the disease (e.g., autopsy).

Endoscopic mucosal resection is performed with a target to capture the diseased tissue. An electrosurgical current is used to cut the tissue that has been grasped. 

An injection is usually administered in the submucosal space (a lining in the colon) to elevate the lesion but is not always necessary; some techniques, such as underwater endoscopic mucosal resection, do not require an injection into the submucosa. 

If the lesion is larger than 15 to 20 mm, it typically must be removed in a nonsystematic fashion. The main use of an endoscopic mucosal resection is to remove polyps that are larger than 10 mm.

An endoscopic submucosal dissection (ESD) is performed by injecting fluid into the submucosa (a lining on the colon) and creating an incision around the perimeter of the diseased part or lesion and then carefully dissecting the lesion from the deeper layers. Various specialized instruments (ESD knives) are utilized to perform the procedure. 

An ESD is endorsed for lesions that have a high likelihood of aggressive cancer that have high chances to invade other parts. It is used when lesions cannot be removed by an endoscopic mucosal resection or when lesions reoccur after the endoscopic mucosal resection procedure.

• EMR is easier to learn and perform, has a lower risk of adverse events, and carries a low-cost burden. It continues to be the more commonly performed endoscopic resection procedure.
• Endoscopists have limited experience with an ESD, and there is no reimbursement for this procedure in few parts of the world. There is limited incentive to learn and perform this more complex and high-risk procedure by endoscopists.
• Each technique has its own advantages and disadvantages. EMR is relatively simple to perform, uses a limited number of devices and has a long track record of being successful for most precancerous lesions. Its main disadvantage is that some patients who are treated with this procedure may require additional surgery. However, if they had been treated with ESD, they may have been cured. The other major disadvantage of EMR is that it has a high lesion recurrence rate in the range of 15% to 20%, which necessitates further therapy.
• The main advantage of ESD is that it allows complete dissection of any type of lesion regardless of size. Removing the entire lesion in a single piece is a basic oncologic principle and carries the benefits of accurate histological assessment and staging, determination of curative resection and a very low recurrence rate of less than 1%. However, it is technically more demanding than EMR and requires advanced endoscopy skills. Furthermore, ESD is a relatively complex procedure associated with a higher perforation rate compared with EMR. Fortunately, most perforations caused by an ESD can be successfully treated by endoscopy without the need for surgery.