Removal of Large Colon Polyps: EMR, ESD, and Full-Thickness Resection — A Patient Guide

REMOVAL OF LARGE COLON POLYPS

A polyp is a growth on the lining of the colon. Most are harmless at the time they are found, but many types can, over years, gradually turn into colon cancer. The most common type of precancerous polyp is called an adenoma. Removing colon adenomas prevents them from turning into a cancer.

Small polyps are removed routinely during a standard colonoscopy. Larger polyps — generally 20 mm and above, and often flat or carpet-like rather than on a stalk — need a dedicated procedure and a different set of techniques. This is typically why a person with large colon polyps mayb be referred to the BIDMC Center for Advanced Endoscopy.

Why you have been referred

A large polyp was found, and it was left in place rather than removed on the spot. Removing a large flat polyp succesfully well requires specific equipment, more time than a routine colonoscopy allows, and experience with these techniques. Incomplete or repeated partial attempts make the polyp harder to remove later, because scarring forms underneath it.

In almost all cases these polyps can be removed through the colonoscope, without an operation and without removing any part of the colon. This is now the preferred approach and avoids the risks and recovery of surgery.

Being referred does not mean cancer has been found. Most large polyps, even sizeable ones, are still precancerous. Occasionally the tissue examined afterward shows an early cancer, and if so it is usually a very early one caught at a curable stage.

Three techniques

All are done through the colonoscope. Which technique is used depends on the polyp's size, shape, location, the appearance of its surface, and whether it has been operated on before.

Endoscopic mucosal resection (EMR). Fluid is injected underneath the polyp, lifting it away from the muscle wall of the colon on a cushion. A dye is usually mixed in, turning the cushion blue, which makes the boundary between the polyp and the deeper layers easy to see. The polyp is then removed with a wire snare, either in one piece or, for larger ones, in several overlapping pieces — a technique called piecemeal resection. The base is then treated to destroy any microscopic cells at the edges, which lowers the chance of regrowth.

EMR is the standard treatment for large flat polyps. It is quicker, and carries a lower risk of tearing the colon wall than the alternatives.

Endoscopic submucosal dissection (ESD). Instead of snaring the polyp, a fine electrical knife is used to cut underneath it and dissect it off the wall in a single intact piece. This takes considerably longer — often one to several hours — and demands a higher level of technical skill.

The advantage is that the polyp comes out whole. That means the pathologist can assess the edges and the depth precisely, and the chance of the polyp regrowing is lower than after piecemeal EMR. The trade-off is a longer procedure and, in some series, a higher risk of making a hole in the colon wall, particularly on the right side of the colon.

Full-thickness resection (FTRD). Some polyps cannot be lifted on a fluid cushion. This happens most often when a previous attempt at removal has left scar tissue tethering the polyp to the deeper wall, and also when a polyp sits at the opening of the appendix or in a pouch (diverticulum) where a snare cannot safely reach.

For these, a specialized device can be used. A cap carrying a clip and a built-in snare is mounted on the tip of the colonoscope. The polyp and the underlying wall are drawn into the cap, the clip is closed beneath them to seal the wall, and the snare then cuts above the clip. The full thickness of the colon wall is removed, and the clip holds the site closed. It stays in place for some weeks and then passes on its own.

This is a genuinely different approach from the other two: instead of shaving off the lining, it takes the whole wall. That is what makes it possible in scarred or tethered areas, and it also gives the pathologist a complete specimen including the deepest layers, which is valuable when there is a concern about early cancer.

The main limitation of the FTRD technique is polyp size. The cap can only hold so much tissue, so this technique suits lesions roughly under 20 to 30 mm; complete removal with clear margins becomes less reliable above about 20 mm. In some cases EMR is used first to remove the bulk of a larger polyp, with the device then used on the difficult part that remains.

How the choice is made. EMR is the default for most large flat polyps, where a piecemeal removal is entirely adequate and the recovery straightforward. ESD is favored when there is a suspicion that the polyp may already contain an early cancer, because an intact specimen is then essential for deciding whether anything further is needed, and for very large polyps and certain surface patterns. Full-thickness resection is reserved for smaller polyps that will not lift, recurrences on scar tissue, and lesions in awkward positions such as the appendix opening. In some centers a variation of EMR performed underwater, without a fluid cushion, is used for certain polyps. The final decision is sometimes only made once the polyp has been inspected directly.

What the procedure involves

1. Careful inspection first. The polyp is examined in detail using high-definition equipment and special light filters, and often dye sprayed onto its surface. Its size, borders, and surface pattern are assessed. Certain features suggest the polyp is entirely superficial and can be safely snared; others raise the possibility of deeper involvement and change the technique chosen. This assessment determines the plan, and takes time.

2. Removal. By EMR, ESD, or full-thickness resection, as described above. The goal at this stage is to remove all visible polyp tissue in one session, in the safest minimum number of pieces.

3. Closing and treating the site. Small metal clips are often placed on the resulting defect, particularly on the right side of the colon, to reduce the risk of bleeding afterward. They cause no symptoms and fall off on their own within a few weeks. A permanent ink mark is sometimes placed nearby so the site can be located again at follow-up.

4. Pathology. Everything removed is sent for examination. The result usually takes a week or two, and determines what follows.

Sedation is used, as with any colonoscopy. Most people go home the same day. Bowel preparation is the same as for a standard colonoscopy.

Risks

These are real but uncommon, and generally manageable without surgery.

Bleeding after the procedure is the most common problem, affecting roughly 2 to 5 in 100 people. It usually appears within the first two weeks, as blood in the stool. Most cases settle on their own or are treated at a repeat colonoscopy.

A hole in the colon wall (perforation) is uncommon — well under 1 in 100 for EMR in experienced hands, and somewhat higher with ESD, in the region of a few in 100. Most are recognized during the procedure and closed with clips there and then. A small number require surgery.

Post-polypectomy syndrome — abdominal pain and sometimes a mild fever from irritation of the colon wall, without a hole — occurs in around 1 to 2 in 100 and is treated with rest, fluids, and antibiotics.

Blood thinners and antiplatelet medications need to be discussed beforehand, as some are stopped temporarily and for a period afterward.

Call the same day about heavy or repeated rectal bleeding, severe or worsening abdominal pain, fever, or persistent vomiting.

Recovery

Most people feel normal within a day or two. Light activity is fine immediately; strenuous exercise and heavy lifting are usually deferred for about a week. There is no need for a special diet, though a lighter diet on the first day is often more comfortable. Long-haul travel is best avoided for a short period afterward, since the small risk of bleeding is highest in the first two weeks.

What the pathology result means

A precancerous polyp, completely removed. The common outcome. Nothing further is needed beyond follow-up colonoscopy.

An early cancer confined to the superficial layer, completely removed. Endoscopic removal alone is usually curative, with closer follow-up.

Cancer extending more deeply, or with unfavorable features. Surgery to remove that segment of colon, or in some cases further treatment, may then be recommended. This is a minority of cases, but it is the reason the specimen is examined so carefully.

Follow-up

Follow-up after removal of a large polyp is more frequent than after an ordinary colonoscopy, for two reasons: a small amount of polyp tissue can regrow at the site, and people who form one large polyp often have others elsewhere in the colon.

After a large polyp removed in pieces, the usual schedule is a colonoscopy at about 6 months, then 1 year after that, then at 3 years, assuming each is clear. When the polyp came out in a single intact piece, the interval is longer. Some guidelines allow 6 to 12 months for the first check depending on the polyp's features.

At each follow-up, the site of the previous removal is examined closely using enhanced imaging, and samples are usually taken from the scar even when it looks normal. The rest of the colon is also inspected carefully.

Regrowth occurs in a small proportion of cases after endoscopic removal. When it does, it is nearly always tiny, found at the first follow-up, and removed at that same visit. It is an expected part of this process rather than a setback.