Villous Adenoma

Overview

A villous adenoma is a type of polyp, a growth that develops from the inner lining of the colon or rectum. Adenomas are considered precancerous because, given enough time, some can develop into colorectal cancer. Villous adenomas have a distinctive finger-like, frond surface and are important because they carry a higher risk of containing or turning into cancer compared with other common polyp types.

Most villous adenomas grow slowly and cause no symptoms, so they are often discovered during a colonoscopy done for screening or another reason. Less commonly, large villous adenomas can produce large amounts of mucus, which in rare cases leads to significant loss of fluid and salts. Because of the cancer risk, these polyps are removed and the bowel is then watched with regular surveillance.

Symptoms

Many villous adenomas cause no symptoms and are found incidentally. When symptoms occur, they may include:

• Blood in the stool or rectal bleeding
• A change in bowel habits
• Passing mucus with bowel movements, sometimes in large amounts with bigger polyps
• A feeling of incomplete emptying or, with large rectal polyps, the sensation of needing to pass stool
• In rare cases of very large polyps, symptoms of dehydration and low potassium from heavy mucus secretion

Because rectal bleeding and changes in bowel habit can have many causes, including cancer, these symptoms should always be evaluated.

Causes

Villous adenomas, like other adenomas, develop when cells in the bowel lining grow abnormally and form a polyp.

• Gradual cellular changes: Over years, changes in the bowel lining cells can lead to polyp formation and, in some cases, progression toward cancer.
• Age and lifestyle: The risk increases with age and is influenced by diet, weight, smoking, and alcohol.
• Inherited factors: A family history of polyps or colorectal cancer, and certain inherited syndromes, increase the tendency to form adenomas.

The villous type is defined by its microscopic structure, which is associated with a higher chance of harboring cancerous change.

Risk Factors

• Older age
• A personal or family history of colon polyps or colorectal cancer
• Certain inherited polyp syndromes
• A diet low in fiber and high in red or processed meat
• Obesity, smoking, and heavy alcohol use
• Long-standing inflammatory bowel disease

Diagnosis

Villous adenomas are diagnosed by examining the bowel and looking at the polyp under a microscope.

• Colonoscopy: The main test, allowing the doctor to see polyps throughout the colon and rectum and remove them.
• Biopsy and pathology: Examining the removed tissue confirms it is a villous adenoma and checks for any cancerous change.
• Other tests: Stool tests for blood and, in some cases, imaging studies may prompt a colonoscopy.

Treatment

Because of their cancer potential, villous adenomas are removed whenever possible.

• Removal during colonoscopy: Many polyps can be taken out at the time of colonoscopy.
• Specialized removal: Larger polyps may need advanced endoscopic techniques or, occasionally, surgery, especially for large rectal lesions.
• Treating cancer if found: If the polyp contains cancer, further treatment is guided by how deep and advanced it is.
• Correcting fluid and salt loss: Rarely, large polyps causing heavy mucus loss require fluid and electrolyte replacement.

After removal, regular surveillance colonoscopy is recommended because people who have had adenomas are more likely to form new ones.

Prevention

• Attending recommended colorectal cancer screening, which can find and remove polyps before they become cancer
• Eating a fiber-rich diet with plenty of vegetables, fruit, and whole grains
• Limiting red and processed meat and alcohol
• Maintaining a healthy weight and staying active
• Not smoking
• Following the surveillance schedule advised after any polyp is removed

When to See a Doctor

See a doctor if you have rectal bleeding, blood in the stool, a persistent change in bowel habits, or large amounts of mucus in your stool, as these need evaluation. Talk with your doctor about when to begin colorectal cancer screening based on your age and family history. Seek prompt care for heavy rectal bleeding, severe weakness, or signs of dehydration, which can rarely occur with very large polyps.

Related Topics

Frequently Asked Questions

References

1. American Cancer Society. Understanding your pathology report: Colon polyps.
2. National Cancer Institute (NCI). Colorectal cancer prevention.
3. MedlinePlus, U.S. National Library of Medicine. Colorectal polyps.