New Research

Advanced Colonoscopic methods for large benign polyp removal

Historically, a segmental “cancer type” bowel resection is carried out to remove adenomas of the colon that are judged not amenable to removal with a colonoscope. In this case a 7 to 10 inch length of colon is resected (the polyp is usually in the middle of the specimen) along with the lymph nodes and blood vessels supplying the bowel after which the remaining ends are rejoined. Many patients ask why so much bowel is removed to treat a benign polyp? The reason is that 10 to 15 percent of large, supposedly benign, polyps that come to surgical resection are found to contain invasive cancers. Certainly, for the 10-15 percent of patients with cancers the lengthier and more extensive resection is logical and appropriate. In regards to the remaining 85-90 percent of patients with benign polyps the cancer type resection is not necessary. If there were a way to be reasonably certain that a polyp was, in fact, benign, then, perhaps, the radical resection could be avoided.

An important method of judging a polyp is by taking multiple biopsies of it through the colonoscope. Another useful method is to inject saline into the bowel wall beneath the polyp to see if the polyp “lifts” off the deeper layers of the bowel wall. The injected fluid greatly expands the middle layer of the bowel wall that separates the inner lining from the outer muscle coating of the colon. If the polyp rises, then the lesion is not invading into the muscular layer (a characteristic of invasive cancers). This saline lift test is easily done through the colonoscope. Yet another method is endoscopic ultrasound which uses sound waves to determine whether the polyp is invading and into the deeper bowel wall layers. Simply taking a close look at a polyp can also provide important information to the surgeon. What are the alternatives to a full segmental cancer type resection for polyps judged benign by the above tests?

Some large benign polyps can be removed by resecting a small oval shaped piece of the bowel wall (part of the circumference only) that includes the polyp and a small rim of normal bowel wall. This is called a "wedge" resection. This operation avoids extensive dissection and does not include division of the blood vessels supplying the area or removal of the lymph nodes. In short, it is a much smaller and less radical operation that requires minimal dissection of the colon and removes far less tissue. The chances of having a complication after this type of surgery are lower because less has been done. Patients usually go home in 1 to 2 days as opposed to 3 to 5 days after the standard cancer type bowel resection.

The “wedge” resection is best performed laparoscopically. Using this method the polyp and adjacent bowel wall is resected with a narrow stapler that is inserted through a hollow 1 inch "port" in the abdominal wall. The specimen is removed through one of the laparoscopic port wounds in a plastic bag after which a pathologist immediately examines the polyp and carries out one or several "frozen sections" to verify that the lesion is an adenoma only. The patient remains on the operating room table asleep while the polyp is evaluated. In the unlikely situation that the frozen section reveals an invasive cancer, then a standard cancer type resection would be immediately carried out laparoscopically.

Another way to remove some of these polyps is to perform a colonoscopy in conjunction with laparoscopy in the operating room with the patient under general anesthesia. The laparoscopic instruments can be used to push on the outside of the colon wall to make it easier for the doctor driving the colonoscope to grasp the polyp with a snare. In this way, some polyps that could not be removed during a regular outpatient colonoscopy can be excised. It is also possible to use advanced Colonoscopic polypectomy methods to remove these polyps. One such method is called ESD or Endoscopic Submucosal Dissection. In this method a thin wire connected to an electric cautery machine is passed through an insulated sheath through the colonoscope and used to make an incision around the polyp (like a knife). Then other Colonoscopic tools are used to lift and dissect beneath the polyp in order to fully detach it. If successful, at the end, the polyp has been removed in one piece and the underlying muscle layer remains intact. If successful, this method avoids removing even a “wedge” of the entire bowel wall.