What are The American College of Radiology Practice Guidelines for the documentation and communication of Virtual CT Colonoscopy results?

Virtual colonoscopy is a minimally invasive alternative to conventional colonoscopy (endoscopy) that screens the colon and rectum for polyps and early cancer before symptoms occur. Polyps are small masses of cells that grow out of the lining of the colon and rectum and can become cancerous over time. Detecting clinically significant polyps and cancer early with virtual colonoscopy allows for treatment at a stage when disease can be prevented or cured, before it spreads to other parts of the body.

Virtual colonoscopy involves no scopes, sedation, recovery time, or referral from your doctor or insurance plan. It is performed on a multislice computed tomography (CT) scanner which takes up to 600 two-dimensional (2D) and three-dimensional (3D) images of the colon in just 30 seconds. The combination of 2D and 3D images increases the radiologist's ability to detect and analyze areas of concern. The 3D images allow the radiologist to reconstruct the colon and do a “fly-through” of its entire length, simulating the views of conventional colonoscopy.

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What is the difference between conventional colonoscopy and virtual colonoscopy?

In May 2002 Mohamed Ibrahim Egal, the president of Somaliland in South Africa, died from a laceration that occurred during conventional colonoscopy. The risk of death from conventional colonoscopy is 1 in 2000 to 5000 cases.

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Why is screening for colorectal cancer important?

Colorectal cancer is the second leading cause of cancer-related deaths in the United States. In 2002, approximately 56,600 Americans are expected to die from the disease and approximately 148,300 new cases are expected. In Delaware, 200 people will die of colorectal cancer and 400 new cases will be found this year.

In its early stages, colorectal cancer causes no symptoms in the patient. Most colorectal cancers begin as small precancerous (adenomatous) polyps that can take 3 to 10 years to progress to cancer. Approximately 8% to 12% of untreated polyps become cancerous tumors. The risk of a polyp becoming cancerous is related to its size. A polyp smaller than 5 mm has essentially no risk of becoming cancerous, whereas a 10 to 20 mm polyp has a 10% risk, and those larger than 20 mm have a 30% or greater risk.

When screening is performed regularly, polyps can be removed before they have the chance to become cancerous. Removal of precancerous polyps is essential and has the potential to reduce the incidence (new cases) of colorectal cancer by 40%. The 5-year survival rate for patients with tumors localized to the bowel is 90%. For tumors that spread to parts of the body outside the colon, the five-year survival rate is 8%. If a patient is already experiencing symptoms of colorectal cancer, there is a 50% chance that the pathology is advanced, making the survival rate low.

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Who is at risk for colorectal cancer?

During the course of a lifetime, 1 in 20 individuals will develop colorectal cancer. Individuals over age 50 account for 90% of cases of colorectal cancer. This is because the risk of developing colorectal cancer increases significantly with age. For example, the probability of a U.S. male developing colorectal cancer is 1 in 1508 from birth to age 39, 1 in 115 from age 40 to 59, and 1 in 25 once he has reached age 60. Similarly, the probability of developing this disease increases for women as they age. A woman’s risk of developing colorectal cancer is 1 in 1719 between birth and age 39, 1 in 145 between ages 40 and 59, and 1 in 33 between ages 60 and 79.

Risk factors for colorectal cancer besides age include:

• History of colorectal cancer or adenomatous polyps

• Family history of polyps   

• Certain genetic traits

• History of chronic bowel disease

The lifetime risk of developing colorectal cancer is 8 times greater for individuals who have a first-degree relative (ie, parent, sibling, child) with the disease. A genetic syndrome called Familial Cancer Syndrome is known to increase a person’s likelihood of developing colorectal cancer at an earlier age. Inflammatory bowel disorders (eg, Crohn’s disease, ulcerative colitis) increase a person’s risk 30-fold.

Modifiable risk factors for colorectal cancer include obesity, physical inactivity (less than 3 hours per week), poor dietary habits, smoking, and excessive alcohol consumption (more than 1 drink per day). Individuals with these and the above risk factors should consider screening before age 50. However, as many as 75% of colorectal cancer cases occur in people with no known risk factors.

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Can colorectal cancer be prevented?

Screening for colorectal cancer is important because there is no way to completely prevent the disease. According to the American Cancer Society, regular screening and certain lifestyle choices (eg, nutrition, physical activity) can greatly reduce the risk of developing colorectal cancer. Regular screening has been shown to reduce risk by at least 33%. Lifestyle choices thought to decrease the risk of colorectal cancer include:

• Maintaining an ideal body weight

• Eating a healthy diet that includes
  – 5 or more servings of vegetables and fruit a day
  – whole grains
  – foods high in calcium 
  – a limited consumption of high-fat dairy products, fried food, and red meat

• Refraining from smoking or excessive alcohol intake (more than 1 drink per day)

• Regular exercise (30 minutes or more of moderate exercise per day, or 1 hour of brisk walking per day)

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How often should I be screened for colorectal cancer?

The American Cancer Society recommends that men and women aged 50 years or older should have one of the following tests:

• Fecal occult blood test every year plus flexible sigmoidoscopy every 5 years

• Flexible sigmoidoscopy every 5 years

• Double-contrast barium enema every 5 to 10 years

• Conventional colonoscopy every 10 years

High-risk patients should begin the above screening intervals starting at age 40.

The following table outlines the general procedure for each of the above tests.

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Who should have virtual colonoscopy?

Virtual colonoscopy is recommended for men and women over age 40 with a family history of colorectal cancer, and for all individuals over age 50 regardless of risk factors. This procedure is ideal for individuals who have had an incomplete or failed colonoscopy or who cannot tolerate the conventional method.

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How accurate is virtual colonoscopy?

Although more studies are being conducted, recent studies show that virtual colonoscopy is equivalent to conventional colonoscopy in its accuracy for detecting polyps 10 mm or larger. Research shows that only 1% of polyps smaller than 1 cm will develop invasive cancer.

A study conducted at Boston University School of Medicine found that virtual colonoscopy’s rate of detection for polyps increased with size and was similar to conventional colonoscopy when polyps were larger than 6 mm. Virtual colonoscopy’s sensitivity for detecting polyps was 82% for polyps 6 to 9 mm, and 91% for those 10 mm or larger. Polyps measuring 1 to 5 mm were correctly located and identified 55% of the time. Virtual colonoscopy detected 100% of colorectal cancers. In the largest and most recent study on virtual colonoscopy, researchers at the University of California at San Francisco reported a sensitivity of 80% for polyps measuring 6 to 9 mm and 90% for polyps 10 mm or larger. Studies at the Mayo Clinic showed that virtual colonoscopy’s sensitivity for detecting 1-cm polyps was 85%.

False positives (findings incorrectly identified as polyps) and false negatives (unidentified polyps) have occurred with virtual colonoscopy. In the Boston University study, 7% of polyps 6 to 9 mm and 2% of polyps 10 mm or larger were false positives. False positives occur because residual stool, poor distention, segments with diverticular disease, and complex folds in the bowel are interpreted as polyps by the radiologist. In the same study, false negatives predominantly occurred with polyps measuring 1 to 5 mm because of residual fluid, poor bowel distention, or misinterpretation of polyps as stool or folds in the bowel.

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How does virtual colonoscopy work?

Virtual colonoscopy at Diagnostic Imaging Associates is performed on the multislice GE LightSpeed Plus or LightSpeed¹⁶ CT scanner. A CT scanner is a diagnostic tool, which for virtual colonoscopy allows the radiologist to see any polyps, lesions, or cancers within the large intestine. A volumetric data set is acquired and a digital picture is made by a computer after low-dose x-rays record multiple slices of the body. The word “slice” is often used to explain the images taken of patient anatomy because they are similar to a single slice of bread taken from a whole loaf (Figure 1).

Figure 1. As with a loaf of bread that is cut into many slices, computed tomography can make pictures of “slices” of the body’s internal structures.

During virtual colonoscopy, the patient is asked to lie on the table of the CT scanner. This tabletop moves the patient’s body through the CT scanner’s gantry (Figure 2) which houses an x-ray tube and detectors. The x-ray tube rotates around the patient as x-rays pass through the body to the detectors, where thousands of x-ray measurements are received. Next, the computer processes this information and displays the corresponding images on a computer screen. This imaging technique avoids any overlap of organs or tissues.

Our multislice GE scanner can capture these images of the colon during a single breath-hold. Virtual colonoscopy takes only minutes to perform because the GE LightSpeed Plus CT scanner can take 8 thin slices of the colon per second. This high scanning speed allows for clearer, sharper images with less blurring due to movement of the body.

Figure 2. Patient being moved into the gantry (large opening) of the GE LightSpeed Plus CT scanner.

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What kind of preparation is involved?

Patients should pick-up a preparation kit from our office 2 days before their appointment.  Although technology is moving toward digital tagging and removal of fecal matter within the colon, it is currently necessary to have a clean bowel for your virtual colonoscopy. A Fleet Prep Kit #1 containing oral laxatives, a suppository, and instructions for a 48-hour diet regimen will be given to you prior to your examination. It is essential that the instructions in the kit be followed exactly. Stray fecal matter or fluid within the colon could be falsely identified as a polyp or cancer. If the bowel is not sufficiently clean, your virtual colonoscopy will have to be rescheduled. 

Additionally, you may be directed to include Tagitol-V™ with your preparation regimen. Click here to learn more.

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What can I expect when I arrive for my virtual colonoscopy?

When you arrive at Diagnostic Imaging Associates for your virtual colonoscopy, you will be greeted by our staff at the front desk and escorted to a private waiting room. At this time, our Virtual Screening Manager will conduct a personal interview with you that will include questions about your family medical history and risk factors you may have for colorectal cancer. If time allows, a 5-minute video outlining the steps of the virtual colonoscopy procedure will be shown.

Next, you will be taken to a dressing room and asked to change into an examination gown. You will then be lead to the CT suite where a radiologic technologist will position you on the table of our GE scanner. A small tube will be inserted into the rectum to inflate the colon with CO₂. You will feel some discomfort while the colon is full of CO₂. However, this discomfort is immediately relieved once the images are taken and the CO₂ is removed from the colon.

Once the bowel is inflated, you will be asked to lie on your back for the first set of images. Scout views will be taken to locate the colon within your abdomen and pelvis. During these scout views the technologist will enter your patient information (ie, name, patient number, examination date) into the computer workstation. The scout views will then be used to plot the slices of the colon that will be recorded by the CT scanner. The next scan will obtain the slices of the colon that will be used to detect the presence of polyps or cancer. You will be asked to hold your breath for 20 to 30 seconds. Holding your breath is very important because it eliminates blurring of the image that is caused by motion of the abdomen and pelvis during breathing.

After the first set of images is taken, the CO₂ will be pumped out of your colon. You will then be asked to turn over onto your stomach so that a second set of images can be taken. Images are taken when you are both on your back and on your stomach to improve the expansion of the colon and to move any residual liquid or fecal matter. This ensures that material inside the colon is not mistaken as a polyp. CO₂ will be pumped into your colon again and you will be asked to hold your breath for another 20 to 30 seconds. After all the images have been taken, the CO₂ will be pumped out of the colon and you will feel completely normal with no discomfort.

Within three working days, the results of your virtual colonoscopy will be mailed to you at your home address. Your report will include a summary of the radiologist’s findings as well as recommendations for further follow-up. A CD-ROM of your results will be included with your report. Results will also be sent to your primary care physician, upon request. Because of the immense volume of images that must be analyzed, immediate results from the radiologist are not possible. Three working days allows the radiologist to take the proper amount of time to report accurate findings and, if necessary, to seek consultation with other physicians regarding any unusual findings.

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What do images from a virtual colonoscopy look like?

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What are the limitations of virtual colonoscopy?

Because virtual colonoscopy is not performed with a scope, polyps cannot be immediately removed and must be followed-up with conventional colonoscopy. Most studies indicate that polyps less than 1 cm rarely become cancerous. Therefore, the medical community is questioning the need to remove every polyp found during conventional colonoscopy regardless of its size. Polyps smaller than 1 cm that are detected with virtual colonoscopy can be identified and tracked on follow-up examinations to see if they have grown. This avoids the unnecessary removal of polyps and risks associated with conventional colonoscopy. This viewpoint is supported by a recent screening study of colorectal cancer conducted by the Veterans Administration of 3500 asymptomatic adults. Data showed that only 10% of patients required therapeutic colonoscopy.

Another limitation of virtual colonoscopy is that it is harder to detect small, flat adenomas. Although uncommon, these tumors may harbor a more rapid, invasive cancer. Studies are still being conducted to determine virtual colonoscopy’s ability to detect these adenomas.

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Is virtual colonoscopy safe?

Unlike conventional colonoscopy, there is no risk of perforation, bleeding, or complications from sedation with virtual colonoscopy.

Each year the population of the United Statesis exposed to radiation from various background sources. The average dose of background radiation for a U.S.citizen living at sea level is 360 millirem (mrem). It has been estimated that the radiation exposure from a virtual colonoscopy is 810 mrem. Evidence has shown that a radiation dose of 100 rem (100,000 mrem) or more can cause irreparable damage to cells.

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How much does virtual colonoscopy cost?

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Where can I get my virtual colonoscopy?

Diagnostic Imaging Associates is the first radiology provider in Delaware to offer Virtual Check-Up™ and requires no referral from a doctor or insurance plan. All virtual screening studies can be performed at three of our seven convenient locations – Omega Imaging & MRI, Brandywine , and Glasgow.

What are The American College of Radiology Practice Guidelines for the documentation and communication of Virtual CT Colonoscopy results?

Diagnostic Imaging Associates follows the American College of Radiology (ACR) Practice Guideline for the Performance of Computed Tomography (CT) Colonoscopy in Adults.  The ACR Practice Guidelines for the documentation and communication of results are as follows.

Reporting should be in accordance with the ACR Practice Guideline for Communication of Diagnostic Imaging Findings.

Any segment not adequately evaluated should be documented. All large masses and lesions that compromise luminal caliber should be communicated. Polyps ≥ 10 mm should be identified and described. Recommendations for endoscopic examination and their removal should be incorporated into the report.

Reporting of polyps ≤ 5 mm is not recommended. They are frequently non-neoplastic or, if adenomatous, have an extremely low malignant potential or probability of containing invasive cancer. Furthermore, a high percentage of polyps identified on CT colonoscopy in this size range remain undocumented on subsequent colonoscopy, either because they represent false positive interpretations or as a result of the approximately 25% failure rate of colonoscopy to identify such lesions when present. The potential harm of colonoscopy may outweigh the benefits.

The reporting and recommendations for polyps measuring 6-9 mm may vary, depending on the certainty of the finding and clinical context. When identified with reasonable probability they should be reported. The likelihood that a polyp in this size category will progress to a clinically significant neoplasm diminishes with increasing patient age due to the low likelihood of malignant degeneration in conjunction with the long natural history of this process. In some individuals follow-up CT colonoscopy at 3-5 years may be acceptable. Recommendations should be based upon consideration of the lesion size, diagnostic confidence, patient’s age, and existing comorbid conditions. As the polyp approximates the upper limit of this size threshold, greater emphasis may be placed upon removal if the quality of the colonic preparation is adequate. It might be more appropriate to recommend polypectomy for a high probability polyp measuring 8-9 mm in an individual < 70 years of age.

Abnormalities or questionable abnormalities in structures unrelated to the colon may be identified during the process of reviewing the unenhanced 2D axial images of the colon. These are most common in, but not limited to, the kidneys, liver, adrenal glands, visualized portions of the lungs, and the major vessels. Characterization of extracolonic organs may be suboptimal with CT colonoscopy technique. Likewise, extracolonic lesions may be present but not detectable. Most extracolonic findings are not clinically significant, and reporting may cause unnecessary patient anxiety and additional diagnostic examinations. Clinical judgment should be used in reporting suspected extracolonic abnormalities.

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