If your doctor has recommended colon cancer screening or you’re experiencing symptoms like abdominal pain, changes in bowel habits or unexplained weight loss, a CT scan can help get you the answers you need. A CT scan can detect colon cancer through two types of imaging. Depending on your situation, your doctor may recommend CT colonography, a minimally invasive screening option designed to find polyps and tumors early, or an abdominal and pelvic CT scan to evaluate symptoms that you already have.
In this guide, you’ll learn how each type of CT scan works, what signs of colon cancer may appear on imaging and what to expect throughout the process.
What Is Colon Cancer?
Colon cancer, also called “colorectal cancer,” develops in the large intestine. It often begins as small growths called “polyps,” which form on the inner lining of the colon. Most polyps are benign, but some can become cancerous over time if they aren’t found and removed.
Common signs and symptoms of colon cancer include:
- A persistent change in bowel habits
- Blood in the stool
- Abdominal discomfort, cramping or pain
- Bloating or a feeling of fullness
- Unexplained weight loss
Many people have no symptoms in the early stages of colon cancer. That’s why routine screening is one of the most effective ways to catch it early.
What Type of CT Scan Can Detect Colon Cancer?
Two types of CT scans are commonly used when colon cancer is a concern: CT colonography for routine screening and abdominal and pelvic CT for evaluating active symptoms. Understanding the difference between these imaging types can help you and your doctor choose the right one.
CT Colonography for Colorectal Cancer Screening
CT colonography, also known as “virtual colonoscopy,” uses low-dose CT scanning to produce detailed images of the inside of the colon and rectum. During the procedure, a small, flexible tube is inserted a short distance into the rectum and air or gas is used to inflate the colon gently. The CT scanner then captures cross-sectional images that are assembled into a detailed 3D model. These images allow the radiologist to view the colon’s inner surface without an internal scope.
The American Cancer Society recommends that women and men begin screening for colon cancer at age 45. CT colonography is recommended every five years as part of a routine screening plan. Patients with a higher risk or a family history of colorectal cancer may need to begin screening earlier or more frequently.
CT colonography is minimally invasive, doesn’t require sedation and allows you to return to normal activities right after the exam. If the scan identifies a polyp or growth that needs further attention, your doctor will schedule a conventional colonoscopy.
CT Abdomen and Pelvis for Colon Cancer Symptoms
An abdominal and pelvic CT scan creates detailed cross-sectional images of the organs, soft tissues and blood vessels in the abdomen. Doctors use this type of scan to investigate abdominal pain, bloating or other symptoms that may indicate colon cancer or a related condition.
A CT scan of the abdomen and pelvis can show the size, shape and location of a tumor. It can also help doctors see if cancer has spread to nearby organs and whether lymph nodes appear enlarged. An abdominal and pelvic CT can also reveal other cancers in the surrounding area. The cancers a pelvic CT scan can detect may include tumors in the bladder, uterus, ovaries, prostate, rectum, and other nearby organs.
Contrast dye is often used with CT imaging of the abdomen and pelvis. The dye gives the radiologist a clearer, more detailed view of soft tissues and blood vessels, which helps your doctor make a more precise diagnosis.
Can a CT Scan Detect Colon Cancer Early?
CT colonography is specifically designed to find colon cancer early, often before symptoms appear. The scan is sensitive enough to detect polyps while they’re still small, giving your doctor the opportunity to remove them before they have a chance to develop into cancer.
An abdominal and pelvic CT isn’t a replacement for routine colon cancer screening, but it’s a powerful tool for evaluating symptoms that are already present. In some cases, imaging may also reveal an unexpected finding in or near the colon that warrants follow-up. Getting clear answers early gives you and your doctor the best chance to act quickly.
How Accurate Is a CT Scan for Colon Cancer?
CT colonography is highly effective at detecting significant polyps and colorectal tumors. Research shows it can identify larger polyps as accurately as a traditional colonoscopy. Because a virtual colonoscopy creates both 2D cross-sectional images and detailed 3D views of the colon, the radiologist can thoroughly examine the colon’s inner surface.
An abdominal and pelvic CT scan provides a precise look at the size, location and potential spread of a tumor. When used with contrast dye, your imaging team can gain even greater detail. At American Health Imaging, every scan is reviewed by a board-certified, subspecialized radiologist, so you and your doctor can feel confident in the findings.
What Are Signs of Colon Cancer on CT Scans?
A radiologist reviewing a CT scan looks for several findings that may point to colon cancer, including:
- A thickening of the colon wall
- A mass or tumor inside the colon
- Polyps or unusual growths along the colon’s lining
- Enlarged lymph nodes near the colon
- Changes in nearby organs that suggest cancer has spread
Not every finding indicates cancer. Your doctor will review the results alongside your symptoms and medical history to determine the right next step in your care.
What Are the Risk Factors for Colorectal Cancer?
Knowing your risk of developing colorectal cancer can help you and your doctor decide when screening makes sense and how often it should happen.
Common risk factors for colon cancer include:
- Being age 45 or older
- A personal or family history of colon polyps or colorectal cancer
- A history of inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis
- A diet high in processed or red meat and low in fiber
- Smoking or heavy alcohol use
- Being overweight or physically inactive
If any of these apply to you, talk to your doctor about whether earlier or more frequent colorectal cancer screening is right for your situation.
Can a CT Scan Detect Colon Cancer Without Contrast?
A CT scan can often detect colon cancer without contrast dye. CT colonography, for example, uses air inflation rather than contrast to visualize the colon’s inner lining, making it an effective option for patients with sensitivities to contrast.
For an abdominal and pelvic CT, contrast dye is often recommended to give the radiologist a clearer view of soft tissues, blood vessels and any changes in nearby tissues or organs. If your doctor orders a scan with contrast, your imaging team will explain the process, answer your questions and make sure you’re comfortable before the exam begins.
Is a CT Scan Safe for Diagnosing Colon Cancer?
CT colonography is a safe and widely used imaging procedure. It uses low-dose radiation to limit your exposure while still producing clear, detailed images of the colon and rectum.
Some patients have concerns about the contrast dye. The contrast your imaging team uses helps give your doctor added clarity for a more precise diagnosis. Your imaging team will review your full medical history beforehand and take every step to keep you safe and comfortable throughout the process.
If you’re pregnant or think you might be pregnant, always let your doctor know before scheduling a CT scan. Your doctor can help determine the safest imaging approach for you.
Schedule a CT Scan for Colon Cancer
Choosing clear answers about your colon health starts with choosing the right imaging provider. American Health Imaging combines advanced CT technology with board-certified, subspecialized radiologists who deliver precision imaging you can trust. We’re in-network with 99% of insurance plans and offer savings of up to 60% compared to hospital-based imaging.
With same-day and next-day appointments, extended hours and convenient locations across Georgia, Alabama, Texas, South Carolina and Florida, American Health Imaging makes it easy to get the answers you and your doctor need.
Talk to your doctor about imaging and schedule your CT scan with American Health Imaging today.