CT Virtual Colonoscopy: A Contemporary Review of Benefits and Limitations

Colorectal cancer is the third common malignancy worldwide but is the second leading cause of cancer death worldwide [1]. American Cancer Society 2018 guideline for colorectal cancer screening recommends that average-risk adults aged 45 years and older undergo regular screening with either a high-sensitivity stool-based test or a structural (visual) exam, based on personal preferences and test availability. As a part of the screening process, all positive results on non-colonoscopy screening tests should be followed up with timely colonoscopy [2,3]. In the last few years, multitarget stool test analysis raised as a noninvasive tool for screening of colorectal cancer in low to moderate risk population, yet it lacks proper visualization of polyps and has high false positive results [4]. In USA, Medicare approved CT virtual colonoscopy (CTC) as a screening test for colorectal cancer on January 1, 2025. This decision was finalized by the Centers for Medicare and Medicaid Services (CMS) and is part of the 2025 Hospital Outpatient Prospective Payment System (OPPS) and 2025 Medicare Physician Fee Schedule (PFS) final rules [5]. Since then, we are seeing increasing numbers of request for CTC and are expected to increase both within USA and worldwide. However, so many physicians, patients and even radiologists are unaware of the pros and cons of such technique that has been going on for almost 30 years. In this small review we are trying to give a quick eye-opening update about CT virtual colonoscopy [6].

CT virtual colonoscopy (CTC), also known as CT colonography, has emerged as a valuable alternative to traditional colonoscopy, particularly for patients with increased risk factors or those unable to undergo standard procedures. Its utility is especially pronounced in the elderly, who often tolerate CTC better than conventional colonoscopy due to the procedure’s minimally invasive nature and lower associated risks, such as perforation of the colon and in cases of bowel obstruction, unusually long and tortuous colon or significant narrowing caused by tumors. In instances where conventional colonoscopy fails to traverse the entire colon, which occurs in about 10% of cases, CTC can be performed on the same day, as the bowel preparation has already been completed [7].

Benefits

CTC presents several advantages as a screening method for colorectal cancer (CRC). One of the most significant benefits of CT virtual colonoscopy is its less-invasive nature, which generally results in a lower risk of complications compared to conventional colonoscopy. The procedure typically does not require sedation, allowing patients to return to their normal activities immediately after the examination, thus eliminating the need for a designated driver. CT colonography is often associated with improved patient comfort. Studies have indicated that many individuals prefer this method over traditional colonoscopy due to its less invasive characteristics, which can alleviate anxiety associated with invasive procedures.

The safety profile of CT virtual colonoscopy is another advantage, with a significantly lower risk of perforation and other complications commonly associated with traditional colonoscopy. In terms of diagnostic capabilities, CT colonography can produce both 2-D and 3-D images, allowing for effective visualization of polyps and lesions. Although it detects about 85-90% of larger polyps, it is crucial to note that if polyps are found, a follow-up traditional colonoscopy is required for removal. Nevertheless, its imaging capabilities can provide valuable information regarding colonic health without immediate invasive intervention. Results from CT colonography are typically available within 1 to 2 hours after the procedure, providing patients with rapid feedback compared to traditional methods, which may involve longer waiting periods [8].

Moreover, CTC provides detailed 2-D and 3-D imaging capabilities, enabling the detection of polyps and lesions with clarity comparable to that achieved via direct visualization during traditional colonoscopy. CTC also gives an idea about structures outside the colon within the abdomen and pelvis in contrary to other used screening tool [7].

In a recent paper by Pickhardt et al. [1] the authors showed that CTC has a higher cost effectiveness; both against multitarget stool DNA analysis and non-screening options. CT colonography may also be more cost-effective in certain healthcare systems. While some analyses have shown debate regarding the overall costeffectiveness of CT versus OC, a Canadian-based study indicated that CT was less costly per examination, suggesting that it could be an economically favorable option when applied to large patient cohorts [1,9].

Limitations

Despite its benefits, the acceptance of virtual colonoscopy has faced challenges. Ongoing efforts to educate both physicians and patients about CTC’s effectiveness and safety are critical for broader implementation. Training programs are being developed to ensure radiologists are adequately prepared to perform and interpret CTC exams. Furthermore, the growing endorsement of CTC by organizations such as the American Cancer Society indicates a positive shift towards its acceptance as a standard screening method [3].

Although the radiation exposure from CTC is considered safe, it is still a factor that cannot be ignored. Patients undergoing multiple screenings over time could accumulate exposure that raises concerns about potential long-term effects. The debate surrounding the safety of medical imaging radiation continues, as there remains a lack of conclusive evidence linking low-level radiation exposure to significant harm. One of the main drawbacks of CTC is its reduced sensitivity for detecting small polyps, particularly those measuring less than 10mm. Studies have shown that CTC is less reliable in identifying these smaller lesions, which can have the potential to develop into cancer if not addressed. In fact, CTC may overlook polyps smaller than 5mm entirely, as the sensitivity for such small polyps remains a significant concern [10].

CTC primarily serves as a screening diagnostic tool; if polyps or suspicious lesions are detected, a follow-up traditional colonoscopy is necessary to remove these polyps and conduct biopsies. This requirement can lead to a two-step process for patients, raising questions about the efficiency of CTC compared to conventional colonoscopy, where polyps can be removed during the same examination.

Another limitation lies in the ability of CTC to visualize flat lesions and non-protruding cancers. Traditional colonoscopy is generally more effective in identifying these types of abnormalities, while CTC tends to miss them. The effectiveness of CTC in such cases may be influenced by the patient’s anatomy, particularly in individuals with tortuous colons, which may complicate the imaging process.

Moreover, the cost-effectiveness of CTC compared to traditional colonoscopy remains a topic of debate. While CTC can reduce unnecessary colonoscopies for patients with small polyps, it may not be covered by all health insurance plans, which can limit its accessibility for certain populations. This potential lack of coverage can discourage patients from choosing CTC as a screening option, especially in regions where healthcare resources are limited [6].

The use of AI to enhance detectability of colonic polyp has been a seat of research and may allow for better polyp analysis [11,12]. Also focusing on improving adherence to screening protocols. Finally, understanding patient experiences and perceptions towards CTC compared to conventional colonoscopy can guide improvements in screening programs. Barriers to acceptance often stem from the invasive nature of traditional methods, and research suggests that CTC may offer a more acceptable alternative for many patients. Enhancing communication about the benefits and risks of various screening modalities could improve patient engagement and decision-making regarding colorectal cancer screening.

CT virtual colonoscopy (CTC) is a valuable, less-invasive screening option for colorectal cancer, offering a strong safety profile and high patient acceptability. Despite several limitations. Its recent Medicare approval is set to increase its utilization. Successful integration into screening programs hinges on educating patients and providers about its appropriate role and benefits.