CT Colonography: an update on current and future indications.

Computed tomographic colonography (CTC) is a minimally invasive, patient-friendly, safe and robust colonic imaging modality. The technique is standardized and consolidated evidence from the literature shows that the diagnostic performances for the detection of colorectal cancer and large polyps are similar to colonoscopy (CS) and largely superior to alternative radiological exams, like barium enema. A clear understanding of the exact role of CTC will be beneficial to maximize the benefits and minimize the potential sources of frustration or disappointment for both referring clinicians and patients. Incomplete, failed, or unfeasible CS; investigation of elderly, and frail patients and assessment of diverticular disease are major indications supported by evidence-based data and agreed by the endoscopists. The use of CTC for symptomatic patients, colorectal cancer screening and colonic surveillance is still under debate and, thus, recommended only if CS is unfeasible or refused by patients.

History, evolution, and current status of radiologic imaging tests for colorectal cancer screening.

Colorectal cancer screening is thought to be an effective tool with which to reduce the mortality from colorectal cancer through early detection and removal of colonic adenomas and early colon cancers. In this article, we review the history, evolution, and current status of imaging tests of the colon-including single-contrast barium enema, double-contrast barium enema, computed tomographic (CT) colonography, and magnetic resonance (MR) colonography-for colorectal cancer screening. Despite its documented value in the detection of colonic polyps, the double-contrast barium enema has largely disappeared as a screening test because it is widely perceived as a labor-intensive, time-consuming, and technically demanding procedure. In the past decade, the barium enema has been supplanted by CT colonography as the major imaging test in colorectal cancer screening in the United States, with MR colonography emerging as another viable option in Europe. Although MR colonography does not require ionizing radiation, the radiation dose for CT colonography has decreased substantially, and regular screening with this technique has a high benefit-to-risk ratio. In recent years, CT colonography has been validated as an effective tool for use in colorectal cancer screening that is increasingly being disseminated.

Current status on performance of CT colonography and clinical indications.

CT colonography (CTC) is a robust and reliable imaging test of the colon. Accuracy for the detection of colorectal cancer (CRC) is as high as conventional colonoscopy (CC). Identification of polyp is size dependent, with large lesions (≥10mm) accurately detected and small lesions (6-9mm) identified with moderate to good sensitivity. Recent studies show good sensitivity for the identification of nonpolypoid (flat) lesions as well. Current CTC indications include the evaluation of patients who had undergone a previous incomplete CC or those who are unfit for CC (elderly and frail individuals, patients with underlying severe clinical conditions, or with contraindication to sedation). CTC can also be efficiently used in the assessment of diverticular disease (excluding patients with acute diverticulitis, where the exam should be postponed), before laparoscopic surgery for CRC (to have an accurate localization of the lesion), in the evaluation of colonic involvement in the case of deep pelvic endometriosis (replacing barium enema). CTC is also a safe procedure in patients with colostomy. For CRC screening, CTC should be considered an opportunistic screening test (not available for population, or mass screening) to be offered to asymptomatic average-risk individuals, of both genders, starting at age 50. The use in individuals with positive family history should be discussed with the patient first. Absolute contraindication is to propose CTC for surveillance of genetic syndromes and chronic inflammatory bowel diseases (in particular, ulcerative colitis). The use of CTC in the follow-up after surgery for CRC is achieving interesting evidences despite the fact that literature data are still relatively weak in terms of numerosity of the studied populations. In patients who underwent previous polypectomy CTC cannot be recommended as first test because debate is still open. It is desirable that in the future CTC would be the first-line and only diagnostic test for colonic diseases, leaving to CC only a therapeutic role.

Noninvasive radiologic imaging of the large intestine: a valuable complement to optical colonoscopy.

PURPOSE OF REVIEW: Radiologic imaging of the large intestine continues to evolve and expand the potential for noninvasive diagnosis. The aim of this review is to provide an update on current and emerging clinical capabilities for a variety of radiologic diagnostic imaging tools for evaluating the colon and rectum. RECENT FINDINGS: The utility of computed tomography for the evaluation of symptomatic inflammatory and neoplastic conditions of the colon is well established, but the clinical role of computed tomography colonography is rapidly evolving. In addition to a number of diagnostic indications, computed tomography colonography is emerging as a potential frontline colorectal screening test for cancer prevention. MRI has become increasingly valuable for rectal cancer staging and inflammatory bowel disease but has yet to gain momentum for polyp evaluation. PET imaging has been primarily utilized for oncologic indications, but also holds considerable potential for inflammatory conditions. Other imaging modalities, such as the barium enema, conventional radiography, and ultrasound, play a much more limited role. SUMMARY: Advances in radiologic imaging of the colorectum will continue to expand the capabilities and clinical indications for noninvasive diagnosis, allowing for a greater emphasis on the complementary roles of tissue sampling and therapy with optical colonoscopy.

The demise of the instant/unprepared contrast enema in large bowel obstruction.

OBJECTIVE: Imaging the colon in suspected acute large bowel obstruction (LBO) is traditionally carried out with a supine abdominal X-ray (AXR) and erect chest X-ray. If there is no clinical or radiological evidence to suggest a perforation, then an unprepared barium or water-soluble contrast enema (CE) can be performed to confirm the presence of and demonstrate the site of obstruction. The advent of modern, fast multidetector CT (MDCT) scanners has changed management strategies for acute abdominal conditions including suspected LBO in all groups of patients especially the elderly, infirm and those on ITU/HDU. METHOD: A retrospective case note analysis was carried over a 7-year period in a single centre. The study criteria involved investigation of suspected LBO with CE, CT and MDCT. RESULTS: It showed a reduction in the number of contrast enemas performed. CONCLUSION: MDCT was shown to be more accurate in the diagnosis of LBO, is usually available on a 24-h basis, and in many institutions has replaced the urgent CE in this group of patients. This also has the advantage of excluding incidental findings and in staging malignant disease.

Availability, indications, and technical performance of computed tomographic colonography: a national survey.

PURPOSE: To determine the availability, indications, and technique of computed tomographic colonography (CTC) in Sweden and to investigate opinions on its future role in colon imaging. MATERIAL AND METHODS: In May 2004, a questionnaire on CTC was mailed to all Departments of Radiology in Sweden, and one year later a telephone interview was conducted with the departments that intended to start a CTC service. RESULTS: Ninety-nine departments (83%) answered the questionnaire, indicating that 23/ 99 (23.2%) offered a CTC service. Reasons for non-implementation of CTC were lack of CTC training in 34/73 (46.6%) and non-availability of multi-detector row CT scanners in 33/73 (45.2%), while 26% were awaiting further scientific documentation on CTC. Incomplete colonoscopy was the main indication for CTC in 21/23 (91.3%) departments performing CTC. Dual positioning, room air insufflation, and thin-slice collimation were used in all the responding departments. The number of CTC studies performed varied from 1-5 (26.1%) to more than 200 (17.4%). Intravenous contrast material was routinely administered by 9/23 (39.1%) departments. Out of 30 (39.5%) departments that in 2004 intended to start CTC, 9 (30%) had done so by June 2005. A total of 32/99 (32.3%) departments had therefore started CTC by June 2005. Half of the departments that replied believed that CTC would absolutely or probably replace barium enema in the future. CONCLUSION: The survey shows relatively limited diffusion of CTC practice in Sweden, with approximately one-third of radiology departments offering a CTC service, mostly on a small scale. A wider dissemination of CTC requires further scientific documentation of its capability, intensified educational efforts, and additional funding.

The future of colorectal imaging: computed tomographic colonography.

The development of colorectal cancer screening alternatives that are attractive to patients and effective for screening is critical for reducing this too-common and deadly disease. CTC is an exciting technique that is the only imaging alternative developed since the barium enema for colon screening. In the past few years, many obstacles to clinical implementation of CTC have been eliminated. For example, there is no longer any post-processing time, which was previously as long as 8 to 10 hours, and the interpretation time has been drastically reduced from 4 hours to 15 to 20 minutes. The majority of studies have demonstrated excellent results for detection of lesions > or = 1 cm, with few false positives. This examination will continue to improve with the development of automated (computer) detection programs and automated 3D rendering algorithms. In addition, cathartic bowel preparation, one of the biggest obstacles to patient compliance with colorectal cancer screening, may be eliminated if successful fecal tagging can be developed. The most important issue that remains is its performance in a screening population, and studies are currently underway to answer that important question.

[CT-colonography: current status and future directions in consideration of the technical evolution]. / Technische Neuerungen in der CT-Kolonographie: gegenwärtiger Stand und zukünftige Entwicklung.

Computertomography and with it CT-colonography evolves technically and also possibilities of data processing proceed rapidly. The current status of CTC can be summarized as follows:The method represents a true alternative to barium enema if technical conditions are given.CTC can be performed with excellent results immediately following an incomplete colonoscopy. In pretherapeutic diagnosis of colorectal carcinoma, CTC can be combined with a staging CT of the abdomen. The recent technical advances with new 16 row technology in image quality and data acquisition - mainly concerning the spatial and temporal resolution - are very promising. Developments in postprocessing of CT data can also contribute to a higher efficiency of labor. Alternative preparation schemata can lead to a more comfortable bowel cleansing and stool labeling can even avoid this procedure, resulting both in an even improved compliance. Radiation exposure in low dose technique is comparable to a double contrast barium enema and can be still reduced by optimisation of scanning parameters.The aim of the following article is (1 to give an overview of the current status of patient preparation, image acquisition and data processing; (2) to review recent clinical trials and experimental studies and to show future directions of CTC with regard to the clinical development.

Clinical results of CT colonoscopy.

With increasing emphasis among the medical community on the early diagnosis and staging of colorectal cancer, interest has grown in CT colonography as a developing technique to challenge existing methods such as the barium enema and conventional colonoscopy. First introduced in 1994, CT colonography has experienced dramatic improvements in both hardware and software capabilities, resulting in shorter scanning times, greater user-friendliness and promising performance statistics. The recent development in multi-slice CT scanners has meant the ability to scan patients in a single breath hold, while innovations in image reconstruction and manipulation have optimised and yet greatly simplified study interpretation. Recent imaging protocols that use IV contrast to stage known or suspected colorectal cancer have been described. Current interest has focused on improving patient acceptance of the technique through the development of faecal tagging agents to avoid full bowel catharsis. This review summarises the development of CT colonography to date, evaluates its applications and performance in the detection and screening of colorectal polyps and looks at future directions of this exciting technique.

Trends in CT colonography.

CT colonography (virtual colonoscopy) is a safe, noninvasive method of examining the large bowel. Since its first description in 1994, the technique has undergone rapid development, stimulating considerable interest in its potential as both a diagnostic and screening tool. Diagnostic performance statistics have been encouraging, with predictive values rivaling those of barium enema and approaching those of endoscopic colonoscopy. Improvements are underway in methods of bowel preparation, scanning procedure, and image display. Increasing experience with the technique is reflected in better understanding and characterization of both two-dimensional and three-dimensional findings, resulting in improved study performance and interpretation. This review attempts to chart the development of CT colonography, with an emphasis on published results and current research interests. We propose potential directions for future study and means toward effective implementation of CT colonography in clinical practice.