Rectal Polyp: Causes, Symptoms and Treatment

What Is a Rectal Polyp?

A rectal polyp is an abnormal growth of tissue arising from the inner lining (mucosa) of the rectum, which is the final section of the large intestine located just above the anal canal. Polyps may be pedunculated (attached by a stalk) or sessile (flat, without a stalk). In most cases, rectal polyps are initially benign; however, certain types -- especially adenomatous polyps -- carry a significant risk of transforming into colorectal cancer over time. Early detection and removal are therefore essential for cancer prevention.

Causes and Risk Factors

The exact causes of rectal polyp formation are not fully understood. However, several well-established risk factors have been identified:

• Age: The risk increases significantly after the age of 50.
• Genetic predisposition: Hereditary conditions such as familial adenomatous polyposis (FAP) and Lynch syndrome greatly increase the risk.
• Diet: A diet high in red and processed meat and low in dietary fiber is considered a contributing factor.
• Obesity and physical inactivity: A high body mass index (BMI) and sedentary lifestyle are associated with an increased risk of polyp formation.
• Smoking and alcohol consumption: Both are recognized risk factors for the development of colorectal polyps.
• Inflammatory bowel disease: Conditions such as Crohn's disease and ulcerative colitis can promote polyp formation.

Types of Rectal Polyps

Rectal polyps are classified by their tissue structure into several types:

• Adenomatous polyps (adenomas): The most common type with the highest risk of malignant transformation. Subtypes include tubular, villous, and tubulovillous adenomas. Villous adenomas carry the greatest cancer risk.
• Hyperplastic polyps: Generally benign with a very low risk of malignancy.
• Serrated adenomas: A subgroup with an elevated cancer risk that requires careful monitoring.
• Inflammatory polyps (pseudopolyps): Arise as a response to chronic mucosal inflammation, often in patients with inflammatory bowel disease.
• Hamartomatous polyps: Primarily associated with genetic syndromes such as Peutz-Jeghers syndrome.

Symptoms

Rectal polyps frequently cause no symptoms and are discovered incidentally during a routine screening examination. When symptoms do occur, they may include:

• Blood in the stool or on toilet paper (rectal bleeding)
• Changes in bowel habits such as diarrhea or constipation
• Mucus discharge during bowel movements
• A feeling of incomplete bowel emptying
• Rarely: cramping or abdominal discomfort

Because these symptoms can also indicate other conditions, it is important to consult a doctor if any of these signs appear.

Diagnosis

The most reliable method for diagnosing rectal polyps is colonoscopy, during which a flexible endoscope is inserted through the anus to directly visualize the bowel lining. Any polyps identified can be removed during the same procedure and sent for histological examination (tissue analysis).

Additional diagnostic methods include:

• Proctoscopy and sigmoidoscopy: Examination of the lower bowel segments.
• CT colonography (virtual colonoscopy): A computed tomography-based imaging of the colon.
• Fecal occult blood test (FOBT): Used as an initial screening tool, but not sufficient for definitive diagnosis.

Treatment

The standard treatment for rectal polyps is endoscopic removal (polypectomy) during colonoscopy. Depending on the size and characteristics of the polyp, different techniques may be used:

• Snare polypectomy: The polyp is removed using a wire loop, often with electrocautery.
• Endoscopic mucosal resection (EMR): Used for flat or broad-based polyps.
• Endoscopic submucosal dissection (ESD): Suitable for larger flat lesions or early cancerous changes.
• Surgical resection: Required in cases where polyps are too large or cannot be safely removed endoscopically.

After removal, the tissue is examined histologically to determine whether the polyp was benign or showed signs of malignancy. Follow-up colonoscopies are then scheduled at intervals based on the findings.

Prevention and Follow-Up

Since rectal polyps are often asymptomatic, colorectal cancer screening plays a critical role in their detection. In many countries, routine colonoscopy is recommended starting at age 45 to 50 for average-risk individuals. People with a family history of colorectal cancer or known genetic risk syndromes are advised to begin screening earlier and at more frequent intervals.

After a polyp has been removed, regular surveillance colonoscopies are important, as the risk of developing new polyps remains elevated. The recommended follow-up interval depends on the number, size, and histology of the removed polyps.

References

1. World Health Organization (WHO): Global Cancer Observatory -- Colorectal Cancer Fact Sheet. Geneva: WHO, 2022.
2. Leitlinienprogramm Onkologie (AWMF, German Cancer Society): S3 Guideline Colorectal Cancer, Version 2.1 (2019). AWMF Registration No. 021-007OL.
3. Tanaka S. et al. - JGES guidelines for colorectal endoscopic submucosal dissection/endoscopic mucosal resection. Digestive Endoscopy, 2020.