Colorectal Adenoma

Colorectal adenomas are abnormal growths that form in the lining of the colon or rectum. While most are harmless, they are considered precancerous because they have the potential to develop into colorectal cancer over time. About 50% of people develop these growths, but fewer than 10% of them become cancerous. Early detection through screening can prevent cancer by allowing doctors to remove adenomas before they turn dangerous.

Table of contents

• What Are Colorectal Adenomas
• Types of Adenomas
• Causes and Risk Factors
• Symptoms
• Diagnosis
• Treatment
• What to Expect After Treatment
• Prevention and Risk Reduction

What Are Colorectal Adenomas

A colorectal adenoma is a type of polyp, which is an unusual growth of cells that forms a small clump in the lining of your colon or rectum^[1][5]. The colon and rectum are parts of your digestive system that process waste. Adenomas are benign, meaning they are not cancer, but they are considered precancerous because they can transform into colorectal cancer if left untreated^[1][3].

These growths appear as raised bumps or slightly raised spots on the otherwise smooth lining of the colon. Under a microscope, they may look like tiny cauliflower heads or bumps clinging to a stalk^[1]. While most colon polyps are harmless, adenomas are the type that most often change into colorectal cancer, which is why healthcare professionals recommend removing them^[4].

Colorectal adenomas are quite common, with approximately 50 percent of people age 60 or older having one or more of these polyps. However, only about six percent of these people develop colon cancer^[7]. This shows that while adenomas carry risk, cancer development is not inevitable.

Types of Adenomas

Adenomas are classified based on how their cells grow and appear under a microscope. Understanding these differences helps doctors assess cancer risk^[1][3].

Tubular adenomas are the most common type, making up more than 80% of all colorectal adenomas^[6]. These have cells that form orderly rows of tiny tube-like structures. When they are smaller than 1.5 centimeters, only about 2% contain cancer cells^[3]. Tubular adenomas are generally considered lower risk compared to other types.

Villous adenomas have cells with finger-like or leaf-like projections on the surface^[3]. These adenomas tend to be larger and grow more quickly than tubular adenomas. They are more likely to become cancerous, with about 15% to 40% containing cancer cells, especially when they are over 4 centimeters in diameter^[3]. Villous adenomas can sometimes cause the body to produce large amounts of mucus, leading to diarrhea and loss of potassium in patients.

Tubulovillous adenomas have features of both tubular and villous types. They contain both tube-like structures and finger-like projections^[3]. These adenomas carry a cancer risk between that of tubular and villous types, with about 20% to 25% containing malignant cells^[3].

While villous adenomas appear to have higher cancer rates, this actually reflects their larger surface area due to their finger-like projections. When adjusted for surface area, all types of adenomas have similar potential to become cancerous^[3].

Causes and Risk Factors

No specific cause is known for colorectal adenomas, but certain factors increase your risk^[5][11]. Anyone can develop these growths, but your chances are higher under certain circumstances.

Age is a major risk factor. The risk increases significantly as you get older, particularly after age 50^[1][11]. Men are also at slightly higher risk than women^[1].

Family history plays an important role. If your parents, siblings, or children have colorectal cancer or polyps, you are twice as likely to develop colorectal cancer as someone without that family history^[1][8]. Certain inherited gene changes can cause rare forms of colorectal disease, such as familial adenomatous polyposis (FAP) or Lynch syndrome, which greatly increase the likelihood of developing multiple adenomas at a young age^[1][8].

Your medical history also matters. Having had colorectal cancer, ovarian cancer, or inflammatory bowel disease such as Crohn’s disease or ulcerative colitis increases your risk^[1][4][11].

Lifestyle factors that increase risk include smoking or using tobacco products, having obesity, drinking alcohol, lack of exercise, and type 2 diabetes^[1][5][11]. Diets high in animal fats and low in fiber have also been linked to higher risk^[4][11].

Symptoms

Colorectal adenomas rarely cause symptoms, which is why screening is so important^[1][4]. Many people have adenomas without knowing it. When symptoms do appear, they usually occur as the polyps grow larger^[11].

The most frequent symptom is finding painless bright red or dark red blood when you wipe yourself after a bowel movement^[1][11]. You might also notice blood in your stool or bleeding from the rectum^[7].

Other possible symptoms include changes in bowel habits, such as constipation or diarrhea lasting more than a week^[1][11]. Some people experience abdominal pain, stomach cramps, unintentional weight loss, or loss of appetite^[1][11]. Anemia, which is a low level of red blood cells, can also occur if an adenoma causes ongoing bleeding^[11].

It’s important to remember that other illnesses and conditions can cause these same symptoms. If you notice any of these changes, you should see your doctor to find out the cause^[11].

Diagnosis

Finding colorectal adenomas before they turn into cancer leads to a better chance of recovery^[11]. Most adenomas are discovered during routine screening tests for colorectal cancer^[1].

A colonoscopy is the main test used to find and diagnose adenomas^[1][11]. During this procedure, a doctor uses a thin, flexible tube with a light and camera to view the entire inside of your colon and rectum. The tube is guided through the colon using air to expand the walls and get a clear view. Images appear in real time on a video screen, and polyps usually appear as bumps or raised spots on the smooth lining^[10].

Your healthcare provider might find an adenoma while examining your rectum as part of a physical examination, though this is less common^[1]. Your doctor might also test your stool for blood. If blood is found, a colonoscopy is usually ordered^[11].

Other diagnostic methods include flexible sigmoidoscopy, which examines just the last third of the colon using a similar tube with camera, and virtual colonoscopy, which uses a CT scan to view the colon from outside the body^[10][11]. If polyps are found during these tests, a full colonoscopy is needed to remove them.

When an adenoma is found, it is usually removed during the colonoscopy. The tissue is then sent to a laboratory where it is examined under a microscope to determine if it contains cancer cells and how quickly the cells are growing^[1][7]. This information helps your healthcare team decide if further treatment is needed.

Treatment

The main treatment for colorectal adenomas is to remove them^[1][5][11]. This usually happens during the colonoscopy where the adenomas are discovered.

During the colonoscopy, your healthcare provider typically uses a wire loop or forceps to pull the adenoma loose from your colon lining^[1]. You might feel some pressure or pulling, but no pain. The provider retrieves the adenoma so it can be examined under a microscope for cancer cells. This removal procedure is often called a polypectomy.

If a polyp is too large to remove during colonoscopy, you might need surgery^[5][11]. Several surgical approaches are available. Laparoscopic surgery uses small incisions and specialized instruments to remove growths with minimal scarring and faster recovery. This method allows patients to return to solid foods and everyday activities more quickly than traditional surgery^[15].

Robotic-assisted surgery uses advanced technology like the da Vinci system, which allows surgeons to operate with greater precision using a high-definition screen and specialized instruments. This method reduces the risk of damaging surrounding healthy tissues and allows for faster recovery^[15].

For some adenomas in the rectum, transanal endoscopic microsurgery may be used. This approach does not require external incisions, as instruments are inserted through the anus to reach the surgical site^[15].

In rare and extreme cases, you may need surgery to remove part or all of your colon and rectum^[5][11]. Unless a large polyp or surgery is involved, most patients need only one treatment, which happens during the initial colonoscopy.

What to Expect After Treatment

Unless surgery was necessary, your recovery will be very quick^[5][11]. However, having colorectal adenomas puts you at greater risk for colorectal cancer, so follow-up care is essential.

You will probably need to have colonoscopies more frequently than someone who does not have adenomas^[1]. Your follow-up treatment will include testing for new polyps. Most of the time, doctors order these tests three to five years after the first procedure^[5][11]. The exact schedule depends on factors such as the number and type of adenomas found, their size, and whether they showed signs of severe cell changes.

Tubular adenomas can come back, particularly if you smoke^[1]. Your doctor may advise you to take an anti-inflammatory drug to help keep new polyps from forming^[5][11].

You should stay aware of any changes in your bowel habits in the future and notify your doctor as soon as you notice changes^[5][11]. Early detection continues to be important throughout your life.

Prevention and Risk Reduction

The most effective way to reduce your risk of colorectal cancer is to get screened regularly, beginning at age 45^[4]. Screening can find adenomas before they turn into cancer. When adenomas are found and removed early, colorectal cancer can be prevented entirely^[12].

Beyond screening, you can take several steps to reduce your risk of developing adenomas and colorectal cancer. Maintaining a healthy lifestyle is important. Increase your physical activity by getting regular exercise. Studies suggest that high levels of daily physical activity can reduce the risk of developing colorectal cancer by approximately 20%^[24].

Keep a healthy weight. Obesity has been linked to increased risk of colorectal adenomas and cancer^[4]. If you smoke, quit. Smoking cigarettes is linked to increased risk of both adenomas and colorectal cancer, and smokers have a higher risk of adenomas returning after removal^[1].

Limit alcohol consumption, as drinking alcoholic beverages may increase colorectal cancer risk^[1][4]. Maintain a nutritious diet rich in fruits, vegetables, whole grains, and dietary fiber. Consume fiber-rich foods such as whole wheat bread, brown rice, beans, and legumes like soybeans, lentils, peas, and kidney beans^[4]. There is strong evidence that eating more dairy products can be protective against colorectal cancer^[20].

Avoid or limit foods that increase risk, particularly red and processed meats, which are associated with higher colorectal cancer rates^[1][4]. Limit consumption of foods high in animal fats. Choose lean proteins like fish and poultry, and opt for low-fat dairy products when possible^[4].

Stay hydrated by drinking plenty of water each day. Make healthy food choices and think of food as medicine—when you’re mindful about what you consume, you can arm your body with the nutrients it needs to prevent or fight off abnormal cell growth^[20].

If you have risk factors such as a family history of colorectal cancer or polyps, talk to your doctor about when you should begin screening and how often you should be tested. People at higher risk may need to start screening earlier than age 45^[4].

• Colon
• Rectum
• Large intestine