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Screening CT Colonography: Clinician Information
Writing Committee
Hoon J,i MD, PhD
Research Fellow, 3D and Image Processing Center, Brigham and Women’s
Hospital
Matthew Barish, MD
Director, 3D and Image Processing Center, Brigham and Women’s Hospital
PHS Guidelines for Ordering CT Colonography
• CT colonography (virtual colonoscopy) is a promising
new method for detecting colorectal polyps and cancers.
• CT colonography is not recommended as a routine substitute for conventional
colonoscopy.
• However, CT colonography is best-suited for those patients who are unwilling
or unable to undergo conventional colonoscopy.
• Patients should be informed that most insurers do not reimburse for CTC.
The out-of-pocket expense for CT colonography may approach or exceed $1000.
• If a polyp of clinically significant size (>10mm) is detected in the
CT examination, a conventional colonoscopy should be performed to remove the
polyp. Polyps are detected in approximately 10-15% of patients undergoing screening
colonography.
• Typically, if the exam is negative and there are no unusual circumstances,
it is recommended that patients undergo a follow up screening examination in
five to seven years.
• It is important to know that screening colonography is designed for asymptomatic
patients. Diagnostic CTC is the appropriate test for patients with known symptoms
(e.g. digestive problems, abdominal pain, etc.) or a personal history of cancer
who need a exam for colorectal disease. Please also be aware that a routine CT
abd/pelv/3D does not include colonography, and symptomatic patients who need
a scan for the presence of colorectal cancer or lesions should undergo diagnostic
CTC.
Specific inclusion criteria include:
• Patients who are unable or unwilling to undergo
conventional colonoscopy.
• Patients with absolute contraindication to conventional colonoscopy
• Patients with relatively contraindication to conventional colonoscopy
(cardiovascular diseases that increase risk of sedation, stricture, stenosis,
or obstructive cancer).
Specific exclusion criteria include:
• Active inflammation
• History of Crohn’s disease
• Lack of intact ileocecal valve (history of right colectomy)
• Recent colectomy
• Absence of anorectum
• History of pelvic irradiation (relative contraindication)
PHS Guidelines for Interpreting the Results of CT Colonography
Although the interpretation of a particular exam may vary depending on results,
medical history, and other factors, the following guidelines are suggested:
If the study is of good quality and no polyps are detected:
• Continued colorectal CA screening with conventional
colonoscopy in five to seven years
• CT colonography can be substituted for conventional colonoscopy if the
patient is either unable or unwilling to undergo conventional colonoscopy
If polyps smaller than 10mm are detected:
• The decision to perform polypectomy will depend
on physician/patient preference, polyp size, and the patient’s
overall medical status
• The patient should undergo follow up screening at diminished intervals
(typically 3 years)
If polyps larger than 10mm are detected:
• The patient should undergo immediate polypectomy
• Follow-up screening after polypectomy will depend on the results of the
conventional colonoscopic exam.
The presence of stool can make exam interpretation difficult or
impossible. Patients should follow the preparation regimen carefully
to minimize the presence of stool. If small amounts of stool are
present, it may be advisable to undergo follow-up screening by conventional
colonoscopy or colonography in 3-5 years because stool may have obscured
small polyps. If the presence of stool makes the exam uninterpretable,
the patient is advised to undergo repeat CT colonoscopy or colonoscopy
as soon as possible. |
