Large sessile polyps and flat colorectal lesions greater than 3 centimeters may occur in as many as 5 percent of adults undergoing colonoscopy. Historically difficult to detect and remove, such lesions are of particular concern because they pose a high risk of malignancy, especially on the right side of the colon.
As recently as five years ago, most large polyps were managed surgically. But according to Timothy A. Woodward, M.D., of Mayo Clinic in Jacksonville, Fla., many of these lesions are now successfully treated using endoscopic methods.
"Advances in both imaging technology and treatment methods paved the way for endoscopic management of difficult polyps," he says. "Chromoendoscopy allowed for better identification of lesions as well as better endoscopic characterization. And a variety of endoscopes and snares made it possible to treat polyps in any part of the GI tract accessible to endoscopy, including the esophagus, stomach and duodenum."
Today, endoscopic mucosal resection (EMR) is the treatment of choice for large, flat and sessile colorectal lesions. It may be performed using electrocautery or cold snare excision, and with or without lifting agents such as saline and hydroxypropyl methylcellulose.
"Lifting agents create a cushion between the base of the polyp and healthy tissue, making removal easier and reducing the risk of perforation," Dr. Woodward says. "Our group is currently doing studies comparing snares and injectates to see whether a particular combination facilitates better removal."
Bleeding is the most common complication of EMR, occurring in about 6 to 8 percent of cases in the colon and in 11 to 17 percent in the duodenum. Generally, bleeding can be well controlled with forceps and coagulation grasping, argon plasma coagulation or endoscopic clipping. Perforation is a second major complication, but in experienced hands tends to occur in less than 5 percent of patients.
Follow-up to check for recurrence and residual disease is recommended three to five months after the procedure. Dr. Woodward notes that residual disease, which can occur in 8 to 17 percent of patients, is often successfully treated with repeat EMR.
Endoscopic submucosal dissection (ESD) is another recent advance in endoscopic therapy. Used in Japan and, increasingly, in a few large centers in the United States, EDS was developed to aid en bloc resection, which both reduces residual disease and allows for precise pathological evaluation.
"EDS requires great technical skill and is much more arduous and time-consuming than EMR," Dr. Woodward emphasizes. "After injecting fluid into the submucosal layer, the lesion is slowly and carefully removed from the base with a surgical knife. It's a very labor-intensive dissection."
The rate of complications such as bleeding and perforation also may be higher than with EMR. At Mayo Clinic in Florida, ESD is performed under the aegis of doctors well trained in the procedure.
In Japan, ESD is used to remove nearly half of early GI cancers. But Dr. Woodward says that Mayo endoscopists defer to surgeons when they suspect a lesion is cancerous. "If there is an incidental finding that is well contained and not penetrating, we may provide close and meticulous observation. More often, we refer the patient to a surgeon."
Still, the widespread use of EMR and, to a much lesser extent, ESD has greatly reduced the number of colorectal lesions requiring surgery. EMR, in particular, has proved to be a safe and often definitive therapy for large, flat polyps in the GI tract.