Colon polyps are small, abnormal growths that form on the inner lining of the large intestine. Most polyps are benign, but they represent the starting point for nearly all colorectal cancers if left untreated. The vast majority of people with these growths do not experience symptoms, which makes regular screening an important preventative measure. Bleeding is one of the most common signs of a polyp, ranging from barely detectable to obvious blood loss. This symptom often prompts a medical visit, leading to discovery and removal.
Understanding Colon Polyps
Polyps are broadly classified into two main groups based on their potential to become cancerous: non-neoplastic and neoplastic. Non-neoplastic polyps, such as hyperplastic and inflammatory polyps, are generally considered harmless and rarely progress to cancer. Hyperplastic polyps are extremely common and have a very low malignant potential, especially when small and located in the lower colon.
Neoplastic polyps are considered precancerous and carry a risk of developing into colorectal cancer. The most common type is the adenomatous polyp (adenoma), which accounts for the majority of polyps found. Serrated lesions, including sessile serrated lesions, also fall into this higher-risk category and can be difficult to detect due to their flat appearance.
The physical structure of a polyp influences its risk. Polyps are described as either sessile (flat and directly attached to the colon wall with a broad base) or pedunculated (attached by a narrow stalk). Larger polyps, generally those measuring 10 millimeters or more, and those with a villous or tubulovillous cellular structure, are associated with a greater risk of turning into cancer.
The Mechanism of Polyp Bleeding
Colon polyps cause bleeding because their surface tissue is often more delicate and fragile (friable) than the normal lining, lacking robust protective mucosal layers. As stool passes through the colon, physical friction can easily scrape or erode the fragile surface, causing a small injury.
The size and shape of the growth also contribute significantly to the bleeding risk. Larger polyps, especially sessile ones with a broad base, tend to have a greater concentration of blood vessels feeding them. Peristaltic movements, the natural muscular contractions that push waste along, can also induce surface erosion and subsequent bleeding.
Bleeding from a polyp is typically slow, intermittent, and low-volume, meaning the blood loss is often not immediately visible. This slow, chronic bleeding can lead to the gradual development of iron-deficiency anemia. Anemia can cause symptoms like fatigue and weakness.
Symptoms and Diagnostic Steps
Bleeding caused by a polyp can manifest in several ways, depending on the location and size of the growth. Rectal bleeding may appear as bright red blood mixed with the stool or visible on the toilet paper. If the polyp is located higher up, the blood may be partially digested by the time it reaches the rectum, leading to black or dark, tarry stools.
Since many other common conditions, such as hemorrhoids or anal fissures, also cause visible rectal bleeding, self-diagnosis should be avoided. Any noticeable blood should prompt a consultation with a healthcare professional for a complete evaluation. A slow bleed that is not visible can be detected through a fecal occult blood test.
The definitive method for diagnosing polyps and determining the cause of bleeding is a colonoscopy, which involves inserting a long, flexible tube with a camera to view the entire inner lining of the colon. The physician can visually inspect the size, shape, and location of any polyps present.
During the examination, the physician can remove the polyps, a process called polypectomy, using specialized tools passed through the scope. Removing the growth serves both a diagnostic and therapeutic purpose, as it stops the bleeding and prevents the tissue from developing into cancer. The removed tissue is then sent to a laboratory for analysis to confirm its specific type and determine if any cancerous cells are present.