Benign Polyp Section
There are various types of polyps that can be found in the large bowel. The most common type of colon polyp is the adenoma which is a benign tumor (premalignant) that has the potential to develop into an invasive cancer if left in place and allowed to grow for years. Very rarely, polyps are found that have already developed into small cancers; these are called polyp cancers. Some polyps have begun the transformation to cancer; in this situation, microscopically, the polyp cells more closely resemble a cancer than an adenoma yet there is no invasion beyond the innermost layer of the colon wall. These are given the name dysplastic polyps or “carcinoma in situ”.
The second most common type of polyp, usually quite small, is called a hyperplastic polyp. Although hyperplastic polyps arise in the colon they are more often found in the rectum. Thankfully, hyperplastic polyps are not capable of transforming into a cancer. A third category of polyps, inflammatory, are found in patients who have had colitis related to inflammatory bowel disease, or infection. Thankfully, these polyps do not have the capacity to turn into a cancer.
Polyps come in a variety of shapes and sizes. Some are flat and grow directly on the surface of the colon while others are like small mushrooms that protrude into the colon on thin flexible stalks. Adenomas range in size from several millimeters (1/16 of an inch) to over 10 cm (3 inches). The chances that a given adenoma polyp may contain an invasive cancer is related to the size of polyp and to the type of adenoma that is present.
It is usually not possible to distinguish between adenomas (which can turn into a cancer) and the other types of polyps just by looking at them. Therefore, when polyps are found they are removed or at least biopsied. Most polyps are small enough that they can be removed or destroyed at the time of colonoscopy. A small percentage of polyps are too large to be removed with the colonoscope. These larger polyps are removed in the operating room by resecting a portion or segment of the colon or through a combined laparoscopic and colonoscopic method.
The great majority of benign colon and rectal polyps are small or moderate sized and can be removed through the colonoscope in the outpatient setting using a variety of instruments that are passed through a narrow channel in the colonoscope. Very small polyps are destroyed with a forceps that grasps and removes small pieces of the rectal lining. Larger polyps are removed most often with a metal snare (like a noose) that is passed through a thin insulated hollow plastic tube. The snare and plastic sheath are passed through a channel in the colonoscope to the scopes tip and beyond. The snare is placed around the polyp (often shaped like a mushroom) and tightened while electric current is passed through the wire. This cauterizes the stalk of the polyp while it is being cut. If possible, the polyp is recovered and sent for pathological analysis. Polyps can also be directly burned or cauterized with heat or electric current, usually after one or several biopsies have been obtained. Larger polyps, especially the flat ones, are more difficult to treat colonoscopically.
Ideally, a polyp is removed completely and intact with a single application of the wire snare. However, this is not possible for some middle sized and larger polyps. One approach to these lesions is to remove them in pieces using the wire snare multiple times. To make it easier and safer to remove these larger polyps saline or other solutions are sometimes injected into the bowel wall via a catheter (with a needle at its tip) which is passed through the colonoscope. The injected fluid expands and swells the bowel wall making it thicker which protects the deeper muscle layers of the bowel wall from injury when the snare is used to remove parts of the polyp. In some cases it is not possible to fully remove the polyp at one colonoscopy. In this situation it is common to mark or “tattoo” the location of the polyp with India ink or another dye so that the area can be easily found. The colonoscopy is usually repeated months later at which time an attempt is made to remove the remaining polyp, usually with a metal snare, as before. It may take 3 or 4 colonoscopies to fully destroy a larger polyp using the colonoscope.
Unfortunately, when some polyps are initially found they are judged too large to be removed with a colonoscope in an endoscopy suite. Also, in some patients, after several attempts to colonoscopically remove a polyp, the gastroenterologist will make the judgement that the polyp can be fully destroyed with the scope. In these situations the patient is usually referred to a surgeon after the polyp has been tattooed with India ink.
Surgical Treatment of Large Benign Polyps
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 is 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 after the polyp’s location in the colon is marked with india ink tattoos via the colonoscpe. The india ink injections are given with a long needle catheter that is passed through the colonoscope. These marks tell the surgeon where the polyp is located and permit the wedge resection. After marking, 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 colonoscope, still in the colon, observes the process and verifies that the stapler is well positioned to remove the polyp. 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.
Our Approach at St. Luke’s Roosevelt Hospital
At St. Luke's Roosevelt Hospital our approach is to assess all patients with large benign polyps who are sent for a standard colon resection and determine if either the laparoscopic "wedge" or the combined laparoscopic / colonoscopic polypectomy methods can be utilized. The goal is to remove the polyp via the least invasive method possible. If successful, patients are home sooner with all or more of their colon in tact. Because it is not possible to be certain before surgery that a polyp can be removed via a combined laparoscopic/colonoscopic or wedge method, patients must consent to a standard colectomy in addition to the less invasive polyp removal methods. The consent states that, at the end of the procedure, the polyp will have been removed by one of the 3 methods with the standard cancer type resection being the last resort.
When the colonoscopy is performed in the operating room on the day of surgery if the polyp lifts when injected and is judged resectable via colonoscope then an attempt will be made to excise it using a variety of colonoscopic tools. If needed, the polyp can be manipulated externally with laparoscopic instruments to facilitate removal. If the polyp is successfully removed a test is done to make sure that the colon wall is not perforated after which the scopes are removed and the patient woken up.
If it is not possible to fully remove the polyp using colonoscopic methods, the borders of the polyp are marked with india ink and then an attempt is made to do a laparoscopic wedge resection of the polyp and the adjacent colon wall with a stapler. The colonoscope, still in place, views the placement of the stapler to make sure all is well. If successful, then the specimen is put in a plastic bag and removed through one of the small wounds.
However, if the polyp will not lift when injected, is judged too large for coloniscopic or wedge resection, or looks like a cancer then the standard cancer type bowel resection would be immediately performed.
If you would like further information about the above polyp removal methods or about colonoscopy, in general, please contact the Section of Colon and Rectal Surgery at St. Luke’s Roosevelt Hospital.