A colonoscopy is a common screening procedure that allows a doctor to examine the entire large intestine using a flexible tube with a camera. The primary goal of this examination is to detect and remove polyps, which are abnormal growths on the lining of the colon. While most polyps are benign, certain types can develop into colorectal cancer over time, making their removal a crucial step in cancer prevention. The techniques used for removing these growths, collectively known as polypectomy, are varied and depend entirely on the characteristics of the polyp itself.
Determining the Appropriate Removal Method
The endoscopist first conducts a careful assessment of any identified polyp to determine the safest and most effective removal technique. This initial evaluation focuses on several characteristics, including the polyp’s size, its location within the colon, and its morphology, or shape. Polyps are typically classified as either pedunculated, meaning they grow on a stalk like a mushroom, or sessile, which means they are flat or slightly raised with a broad base on the colon wall.
The assessment also includes evaluating the surface pattern and vascular appearance of the polyp, often enhanced by specialized light or dye spray. Visualizing the boundaries of the growth is important to ensure a complete resection. The combination of size, shape, and visual features determines whether a standard technique will be used or if a more advanced method is necessary to safely lift the tissue before cutting.
Standard Polypectomy Techniques
For the vast majority of small and medium-sized polyps, standard polypectomy techniques are highly effective. Very small polyps (typically less than 3 millimeters) may be removed using cold biopsy forceps. The forceps grasp the growth and snip it away from the colon wall, avoiding the use of electrical current.
For polyps up to about 10 millimeters, the preferred method is often the cold snare polypectomy (CSP). A thin wire loop, called a snare, is looped around the base of the polyp. The snare is then closed rapidly, mechanically severing the polyp without applying electrocautery, which reduces the risk of deep thermal injury to the colon wall.
The hot snare polypectomy technique is reserved for larger polyps, typically those exceeding 10 millimeters or pedunculated polyps with a thicker stalk. With this method, the snare is looped around the base, and an electrical current is passed through the wire as it closes. This current simultaneously cuts the polyp and cauterizes the blood vessels at the resection site, helping to prevent immediate bleeding.
Addressing Large or Difficult Polyps
Polyps that are large, broadly sessile, or otherwise challenging to remove with a standard snare require more specialized techniques to ensure a complete and safe removal. Endoscopic Mucosal Resection, or EMR, is the technique most commonly used for these lesions, particularly those over 2 centimeters in size. EMR involves injecting a solution, often a saline mixture, into the submucosal layer directly beneath the polyp.
This injection creates a fluid cushion that lifts the polyp away from the deeper muscle layer of the colon wall, allowing safe removal using a snare, often with electrocautery. For very large lesions, the polyp may need to be removed in multiple smaller pieces, known as piecemeal resection. This technique is used when the lesion is too wide for a single snare application, ensuring the entire base of the growth is fully excised.
Immediate Steps After Polyp Removal
Once the polyp has been successfully detached, the endoscopist immediately focuses on managing the resection site to control any bleeding. For small polyps removed with cold techniques, the site often seals itself and requires no further intervention. If a hot snare was used, the electrocautery generally provides sufficient sealing of the small vessels.
In cases of larger polyps, or if there is visible bleeding after removal, the endoscopist may apply additional cauterization or close the mucosal defect with endoscopic clips. These small, metallic clips are deployed to pinch the edges of the wound together, sealing the site to prevent immediate or delayed bleeding. The removed polyp tissue is then retrieved and sent to a pathology laboratory. The pathologist examines the sample to determine the precise type of polyp and whether it contains any precancerous or cancerous cells.