Rectal Adenocarcinoma
The most common cancer of the rectum, starting in its glandular lining
Quick Facts
- Type: Cancer of the large intestine
- Origin: Gland cells lining the rectum
- Common symptom: Rectal bleeding, change in bowel habits
- Screening: Colonoscopy can find it early or prevent it
Overview
Rectal adenocarcinoma is cancer that starts in the gland cells lining the rectum, which is the last several inches of the large intestine before the anus. It is the most common form of rectal cancer and is closely related to colon cancer; together they are often called colorectal cancer.
Most rectal cancers begin as small growths called polyps, which can slowly turn cancerous over years. Because this process is gradual, screening tests such as colonoscopy can find and remove polyps before they become cancer, or catch cancer early when it is most treatable.
Symptoms
Early rectal cancer may cause no symptoms, which is why screening is important. When symptoms do appear, they can include:
- Bleeding from the rectum or blood in the stool
- A change in bowel habits, such as new diarrhea, constipation, or narrower stools
- A feeling that the bowel does not empty completely
- Cramping or pain in the lower abdomen
- Unexplained weight loss
- Fatigue or weakness, sometimes from anemia caused by slow bleeding
These symptoms can have many causes, including hemorrhoids, but persistent or unexplained changes should always be evaluated.
Causes
Rectal adenocarcinoma develops when cells lining the rectum acquire genetic changes that make them grow uncontrollably. Most cancers arise from polyps that gradually become cancerous over time.
The exact reason these changes occur is usually unknown, but a mix of inherited factors, lifestyle, and chronic inflammation contributes. A minority of cases are linked to inherited conditions that greatly increase risk. The journey from a normal cell to cancer usually takes many years, which is what makes screening so valuable: there is often a long window during which precancerous polyps can be found and removed before they ever become cancer. This is why doctors emphasize regular screening even for people who feel completely well.
Risk Factors
- Older age
- A personal or family history of colorectal cancer or polyps
- Inherited syndromes such as Lynch syndrome or familial polyposis
- Long-standing inflammatory bowel disease (Crohn's disease or ulcerative colitis)
- Diets high in red and processed meats and low in fiber
- Obesity, physical inactivity, smoking, and heavy alcohol use
Diagnosis
Diagnosis combines examination, direct visualization, and tissue testing.
- Colonoscopy: a scope used to view the entire colon and rectum and to take a biopsy of any suspicious area
- Biopsy: examining tissue under a microscope to confirm cancer
- Imaging: MRI of the pelvis, CT scans, and sometimes ultrasound to determine the depth of the tumor and whether it has spread
- Blood tests: including markers that can help monitor the cancer
Staging the cancer guides the treatment plan.
Treatment
Treatment is tailored to the stage and location of the tumor and usually involves a team of specialists.
- Surgery: the main treatment for most rectal cancers, removing the tumor and nearby tissue
- Radiation therapy: often used before surgery to shrink the tumor, especially for cancers low in the rectum
- Chemotherapy: may be given before or after surgery, or for advanced disease, to destroy remaining cancer cells
- Targeted and immune therapies: options for certain advanced cancers based on tumor features
Many people are cured, particularly when the cancer is found early, and ongoing follow-up helps detect any recurrence.
Prevention
- Get screened starting at the recommended age, or earlier if you are at higher risk
- Remove polyps found during colonoscopy
- Eat a diet rich in fiber, fruits, vegetables, and whole grains, and limit red and processed meats
- Stay physically active and maintain a healthy weight
- Avoid smoking and limit alcohol
When to See a Doctor
See a doctor if you notice rectal bleeding, blood in your stool, a lasting change in bowel habits, or unexplained weight loss. Do not assume bleeding is only from hemorrhoids. Seek prompt evaluation for:
- Rectal bleeding that is new, persistent, or heavy
- A change in bowel habits lasting more than a few weeks
- Persistent abdominal pain or a feeling of incomplete emptying
- Unexplained tiredness, weakness, or weight loss
If you are due for colorectal cancer screening, talk with your doctor about scheduling it even if you feel well.
Frequently Asked Questions
What is the most common symptom of rectal cancer?
Rectal bleeding or blood in the stool is one of the most common signs, often along with a change in bowel habits. Because early rectal cancer may cause no symptoms at all, regular screening is the best way to catch it early.
How is rectal cancer found early?
Colonoscopy is the main screening test. It can detect and remove precancerous polyps before they turn into cancer and find cancer at an early, more treatable stage. Talk to your doctor about when to start screening.
Is rectal cancer curable?
Yes, many cases are curable, especially when found early. Treatment usually combines surgery with radiation and chemotherapy, tailored to the tumor's stage and location, and a large share of people are cured with appropriate care.
Can I lower my risk of rectal cancer?
Yes. Getting screened and having polyps removed is the most effective step. A high-fiber diet, limiting red and processed meats, staying active, maintaining a healthy weight, not smoking, and limiting alcohol all help lower risk.
Does rectal bleeding always mean cancer?
No. Bleeding is most often caused by hemorrhoids or anal fissures, which are not cancer. However, because bleeding can also signal cancer, any new, persistent, or unexplained rectal bleeding should be evaluated by a doctor.
References
- American Cancer Society. Colorectal Cancer.
- National Cancer Institute (NCI). Rectal Cancer Treatment.
- MedlinePlus, U.S. National Library of Medicine. Rectal cancer.
- Centers for Disease Control and Prevention (CDC). Colorectal Cancer.