Colon polyps are small clusters of cells that develop on the lining of the large intestine, or colon. The majority of these growths are benign and remain entirely asymptomatic, often discovered during routine screening. While most polyps do not cause noticeable symptoms, they can cause diarrhea, though this presentation is unusual. Diarrhea is typically linked only to certain types of polyps or those that have grown to a substantial size. This article explains the connection between polyps and changes in bowel habits and outlines the necessary steps for diagnosis and screening.
The Specific Connection Between Polyps and Diarrhea
The occurrence of diarrhea due to a colon polyp is a rare event, almost exclusively linked to a specific subtype of growth known as a large villous adenoma. These adenomas are characterized by finger-like projections that cover a broad surface area, often exceeding four centimeters in diameter. The cells lining these large polyps can become hypersecretory, producing and releasing excessive amounts of fluid and mucus directly into the colon.
This hypersecretion leads to secretory diarrhea, where the large volume of fluid overwhelms the colon’s ability to reabsorb water. The mucus is rich in electrolytes, including sodium, chloride, and especially potassium. The rapid and chronic loss of these electrolytes can result in severe electrolyte imbalances, notably hypokalemia, or dangerously low potassium levels.
In the most profound cases, this fluid and electrolyte depletion is known as McKittrick-Wheelock syndrome, which can cause dehydration and even acute kidney dysfunction. Small, common growths like hyperplastic polyps or small tubular adenomas do not possess this hypersecretory capability. Diarrhea caused by a polyp is generally chronic, persistent, and often involves a conspicuous amount of mucus.
Other Common Signs of Colon Polyps
While diarrhea is a possibility, polyps are far more likely to cause other signs that often go unnoticed. The most common overt sign of a polyp is rectal bleeding, which may appear as bright red blood on toilet paper or mixed in with the stool. This bleeding is usually intermittent and results from stool passing over the fragile surface of the growth.
Polyps that bleed higher up in the colon can cause changes in stool color, sometimes resulting in a dark, tarry appearance. This dark color, known as melena, occurs when blood is partially digested as it travels through the intestines. Bleeding can also be occult, meaning it is not visible to the naked eye but can be detected through specific laboratory tests.
Chronic, subtle blood loss can lead to iron-deficiency anemia, a condition where the body lacks enough healthy red blood cells. Symptoms of anemia often include persistent fatigue, weakness, and shortness of breath. If a polyp grows large enough to partially block the passageway of the colon, it can cause abdominal pain, cramping, or a change in the caliber of the stool.
Steps for Diagnosis and Screening
Any persistent change in bowel habits, unexplained rectal bleeding, or the development of chronic fatigue should prompt a conversation with a healthcare professional. A physician will assess the duration and nature of the symptoms to determine the appropriate next steps. Symptoms suggestive of a polyp necessitate a thorough evaluation, even if the individual is younger than the standard screening age.
For individuals at average risk, current guidelines recommend starting routine screening for colorectal polyps at age 45. There are several screening options available, including stool-based tests like the Fecal Immunochemical Test (FIT), which checks for invisible blood in the stool. A positive result on a stool test always requires follow-up with a diagnostic procedure.
Colonoscopy remains the gold standard for both diagnosis and intervention. This procedure involves inserting a flexible tube with a camera into the rectum to examine the entire lining of the colon. Crucially, if a polyp is identified during a colonoscopy, the doctor can often remove it immediately using specialized tools passed through the scope.
The type, size, and number of polyps removed will determine the recommended timeline for future surveillance colonoscopies. For instance, a person found to have advanced adenomas may be advised to return for a repeat procedure in three to five years. Regular screening and timely removal are the most effective ways to prevent the progression of polyps into colorectal cancer.