A prospective single centre study comparing computed tomography pneumocolon against colonoscopy in the detection of colorectal neoplasms

Radiologic Imaging Modalities for Colorectal Cancer

BACKGROUND

Studies reported various diagnostic value of radiologic imaging modalities for diagnosis and management of colorectal cancer (CRC).

AIMS

To summary the diagnosis and management of CRC using computed tomography colonography (CTC), magnetic resonance colonography (MRC), and positron emission tomography (PET)/computed tomography (CT).

METHODS

Comprehensive literature searches were conducted in PubMed, EmBase, and the Cochrane library for studies published before April 2021. The diagnostic performance of CTC, MRC, and PET/CT for CRC was summarized.

RESULTS

A total of 54 studies (17 studies for CTC, 8 studies for MRC, and 29 studies for PET/CT) were selected for final analysis. The sensitivity and specificity for CTC ranged from 27 to 100%, 88 to 100%, respectively, and the pooled sensitivity and specificity for CTC were 0.97 (95% CI 0.88-0.99) and 0.99 (95% CI 0.99-1.00). The sensitivity and specificity for MRC ranged from 48 to 100%, 60 to 100%, respectively, and the pooled sensitivity and specificity for MRC were 0.98 (95% C: 0.77-1.00) and 0.94 (95% CI 0.84-0.98). The sensitivity and specificity for PET/CT ranged from 84 to 100%, 33 to 100%, respectively, and the pooled sensitivity and specificity for PET/CT were 0.94 (95% CI 0.92-0.96) and 0.94 (95% CI 0.90-0.97). The area under the receiver operating characteristic curve for CTC, MRC, and PET/CT was 1.00 (95% CI 0.99-1.00), 0.99 (95% CI 0.98-1.00), and 0.97 (0.95% CI 0.95-0.98), respectively.

CONCLUSIONS

This study suggested both CTC and MRC with relative higher diagnostic value for diagnosing CRC, while PET/CT with higher diagnostic value in detecting local recurrence for patients with CRC.

Diagnostic value of magnetic resonance and computed tomography colonography for the diagnosis of colorectal cancer: A systematic review and meta-analysis

BACKGROUND

Surgical resection is the recommended procedure for colorectal cancer (CRC), but majority of the patients were diagnosed with advanced or metastatic CRC. Currently, there were inconsistent results about the diagnostic value of magnetic resonance colonography (MRC) and computed tomography colonography (CTC) in early CRC diagnosis. Our study conducted this meta-analysis to investigate the diagnostic value of MRC and CTC for CRC surveillance.

METHODS

A comprehensive literature search was conducted in PubMed, Embase, and the Cochrane library to select relevant studies. The summary sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and the area under the receiver operating characteristic curves (AUC) were calculated to evaluate the diagnostic value of MRC and CTC, respectively.

RESULT

Twenty-five studies including 2985 individuals were selected in the final analysis. Eight studies evaluated the diagnostic value of MRC, and 17 studies assessed CTC. The summary sensitivity, specificity, PLR, NLR, DOR, and AUC in MRC for early detection of CRC were 0.98 (95% confidence interval, CI: 0.80-1.00), 0.94 (95% CI: 0.85-0.97), 15.48 (95% CI: 6.30-38.04), 0.02 (95% CI: 0.00-0.25), 115.09 (95% CI: 15.37-862.01), and 0.98 (95% CI: 0.97-0.99), respectively. In addition, the sensitivity, specificity, PLR, NLR, DOR, and AUC of CTC for diagnosing CRC were 0.97 (95% CI: 0.88-0.99), 0.99 (95% CI: 0.99-1.00), 154.11 (95% CI: 67.81-350.22), 0.03 (95% CI: 0.01-0.13), 642.51 (95% CI: 145.05-2846.02), and 1.00 (95% CI: 0.99-1.00). No significant differences were found between MRC and CTC for DOR in all the subsets.

CONCLUSION

The findings of meta-analysis indicated that MRC and CTC have higher diagnostic values for early CRC diagnosis. However, the DOR for diagnosing CRC between MRC and CTC showed no significance.

Diagnostic value of magnetic resonance versus computed tomography colonography for colorectal cancer: A PRISMA-compliant systematic review and meta-analysis

BACKGROUND

Advanced colorectal cancers were associated with poor prognosis, and early diagnosis was important for high-risk patients. Colonography is commonly used for diagnosing colorectal cancer. However, a few studies reported the diagnostic value of magnetic resonance colonography (MRC) versus computed tomography colonography (CTC). This study aimed to compare the diagnostic value of MRC versus CTC for colorectal cancer.

METHODS

Twenty-three studies on the diagnosis of colorectal cancer using MRC or CTC were obtained from PubMed, Embase, and the Cochrane Library databases until July 2017. The ratios of sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and receiver operating characteristic (ROC) curve were calculated to compare the diagnostic value of MRC versus CTC.

RESULTS

The summary sensitivity, specificity, PLR, NLR, and area under the ROC for MRC were 0.97 (0.81-1.00), 0.92 (0.80-0.97), 11.71 (4.46-30.73), 0.03 (0.00-0.24), and 0.98 (0.97-0.99), respectively, for diagnosing colorectal cancer. The pooled estimates for CTC in diagnosing colorectal cancer were as follows: sensitivity, 0.96 (0.90-0.98); specificity, 1.00 (0.99-1.00); PLR, 197.32 (73.21-531.85); NLR, 0.04 (0.02-0.11); and area under the ROC, 1.00 (0.99-1.00). No significant differences were found between MRC and CTC for sensitivity, specificity, and NLR. MRC was associated with lower PLR and area under the ROC for diagnosing colorectal cancer compared with CTC.

CONCLUSION

This study demonstrated MRC and CTC as potential diagnostic approaches for colorectal cancer. CTC had a higher diagnostic value of PLR and area under the ROC for colorectal cancer.

Lumbar Transforaminal Epidural Steroid Injections: Incidental Extraspinal Findings on Planning Imaging

OBJECTIVE

Planning imaging performed during CT-guided procedures may occasionally contain important incidental findings. The purpose of this study was to identify and characterize by clinical relevance the extraspinal findings detected on planning imaging for CT-guided lumbar transforaminal epidural steroid injections (TFESIs).

MATERIALS AND METHODS

Four radiologists retrospectively evaluated the planning scout views and CT studies for 488 consecutive CT-guided lumbar TFESIs performed in 400 patients over a 1-year period. Incidental extraspinal findings were identified and used to characterize patients by the need for follow-up using the CT Colonography Reporting and Data System (C-RADS), a classification scheme originally developed to characterize incidental findings on CT colonography. Patients with C-RADS E4 findings have potentially important findings that should be communicated to the referring physician; patients with C-RADS E3 findings have findings that are likely unimportant, but workup may be indicated. All previously unknown C-RADS E3 and E4 findings discovered in the course of this research were reported to referring physicians for appropriate patient follow-up.

RESULTS

Ten of 400 (2.5%) patients were classified as C-RADS E4; the most common C-RADS E4 finding was vascular aneurysm or stenosis (4/400, 1.0%). Thirteen of 400 (3.3%) patients were classified as C-RADS E3; the most common C-RADS E3 finding was hepatomegaly (4/400, 1.0%). Of 22 patients with C-RADS E3 and E4 findings unknown to clinicians, the finding for only one (4.5%) was communicated to clinicians at the time of the procedure.

CONCLUSION

Clinically important incidental extraspinal findings were identified in 5.8% of patients on the planning imaging performed for CT-guided lumbar TFESIs. Communication of clinically important findings was poor (4.5%).

Application of CT virtual endoscopy in diagnosis of colorectal diseases

Colorectal diseases are a group of common diseases. In recent years, extensive attention has been paid to the application of computed tomography virtual endoscopy (CTVE) in the diagnosis of colorectal diseases. Through the literature search, combined with the author's experience, we explore the technical principle, bowel preparation and inspection method of CTVE, making a summary of the value of CTVE in the diagnosis of colorectal diseases. CTVE can fully observe morphological characteristics of colorectal cancer, polyps, and inflammatory disease. CTVE can not only determine the lesion location, shape, and size, but also confirm the extent of invasion into the colorectal wall, surrounding tissue and distant metastasis. However, the main limitation is that the detected lesion cannot be biopsied or treated during CTVE. Therefore, CTVE is a new, rapid, convenient, safe, non-invasive, and effective method for colorectal examination, which can be used for screening of colorectal diseases.

Computed tomography colonography for colorectal cancer screening

Colorectal cancer screening has been shown to help prevent cancer-related death. Concerns about suboptimal adherence to conventional colonoscopy has led to the search for alternative screening modalities. Computed tomography colono-graphy (CTC) is a highly sensitive and minimally invasive alternative modality. The American College of Radiology has established a standardized reporting system for CTC. The advantages of CTC include complete colonic examination and extraluminal imaging in a single breath hold time. Lack of sensitivity in the evaluation of flat lesions and radiation exposure are the main concerns with this modality. Although the usefulness of CTC has been demonstrated in academic centers, larger studies in community settings are needed to facilitate its adoption by healthcare services.

Routine use of positron-emission tomography/computed tomography for staging of primary colorectal cancer: does it affect clinical management?

Background

The use of positron emission tomography-computed tomography (PET/CT) for the preoperative staging of patients with colon and rectal cancer has increased steadily over the last decade. The aim of this study was to evaluate the effect of PET/CT on the preoperative staging and clinical management of patients with colorectal cancer.

Methods

Between December 2010 and February 2012, 64 consecutive patients with colorectal cancer were evaluated with both PET/CT scans and conventional preoperative imaging studies. We prospectively recorded the medical reports of these patients. The PET/CT findings were compared with conventional imaging studies and the rate of over-staging or down-staging and changes in clinical management were evaluated. The correlation of the PET/CT with the conventional imaging was compared by a kappa agreement coefficient. Differences in the accuracy for N and T staging were assessed by χ2 and related-samples marginal homogeneity tests.

Results

Thirty-nine (60.9%) patients had rectal cancer and 25 (39.1%) had colon cancer. Based on PET/CT, additional lesions were found in 6 (9.4%) of the patients: hilar and paratracheal lesions in 4 patients, hepatic in 1 and supraclavicular in 1 patient. In four of six patients, detailed imaging studies or biopsies revealed chronic inflammatory changes. Hepatic and supraclavicular involvement was confirmed in two patients. Therefore, the false positivity rate of PET/CT was 6.25%. Based on the additional PET/CT, 2 (3.2%) patients had a change in surgical management. A chemotherapy regimen was administered to the patient with a 1.5 cm hepatic metastasis near the right hepatic vein; for another patient with an identified supraclavicular lymph node metastasis, a simultaneous excision was performed.

Conclusions

Routine use of PET/CT for preoperative staging did not impact disease management for 96.8% of our patients. The results of our study conclude that PET/CT should not be routinely used for primary staging of colorectal cancer. More studies are required for identifying the subgroup of patients who might benefit from a PET/CT in their initial staging.

Colorectal cancer: current care, future innovations and economic considerations

For those involved in colorectal cancer management, the present day is an exciting time. There is a multitude of new techniques to be considered for early detection (screening). National population screening for 60-69-year olds in England is due to start this year. Also, minimally invasive surgical techniques and multimodal pathways of care are aiding faster recovery, and there are increasing options for both adjuvant and palliative therapies. This article summarizes how colorectal cancer is currently managed in the UK and discusses the developments that are in the early stages of clinical use or on the horizon. Current management is discussed in detail in the hope that innovators reading the article may identify areas for improvement and allow comparison of new interventions with what are currently the gold standards. As changes are moving so fast, this review will probably only relate to the next 10 years at most. It does not provide a detailed reference list to support all therapies but indicates the key publications that will enable more detailed reading.

Iatrogenic perforation at colonic imaging

AIM

Adequate colonic imaging is generally an invasive procedure with attendant risks, particularly perforation. Endoscopy, barium enema and computed tomographic colonography (CTC) are the main techniques for investigating patients with symptoms of, or screening for, colorectal cancer. The potential complications of these investigations have to be weighed against the benefits. This article reviews the literature on the incidence, presentation and management of iatrogenic colonic perforation at colonic imaging.

METHOD

A literature review of relevant studies was undertaken using PubMed, Cochrane library and personal archives of references. Manual cross-referencing was performed, and relevant references from selected articles were reviewed. Studies reporting complications of endoscopy, barium enema and CT colonography were included in this review.

RESULTS

Twenty-four studies were identified comprising 640,433 colonoscopies, with iatrogenic perforation recorded in 585 patients (0.06%). The reported perforation rate with double-contrast barium enema was between 0.02 and 0.24%. Serious complications with CTC were infrequent, though nine perforations were reported in a case series of 24,365 patients (0.036%) undergoing CTC.

CONCLUSION

Perforation remains an infrequent and almost certainly under-reported, complication of all colonic imaging modalities. Risk awareness, early diagnosis and active management of iatrogenic perforation minimizes an adverse outcome.

Extracolonic findings on CT colonography increases yield of colorectal cancer screening

OBJECTIVE

The purpose of this study is to evaluate the impact of extracolonic findings when screening is undertaken by CT colonography (CTC).

MATERIALS AND METHODS

We performed a retrospective cohort study of patients completing a screening CTC from August 2003 to June 2006 at Walter Reed Army Medical Center. Extracolonic findings were categorized using a CTC reporting and data system that classifies findings as highly significant, likely significant, and insignificant. All final diagnoses, surgeries, malignancies, and costs of diagnostic radiology procedures were calculated for each category.

RESULTS

Of 2,277 patients (mean +/- SD age, 59 +/- 11 years; 60% white; 56% male) undergoing CTC, extracolonic findings were identified in 1,037 (46%) patients, with 787 (34.5%) insignificant and 240 (11.0%) significant findings. Evaluation of significant findings generated 280 radiology procedures and 19 surgeries over a mean follow-up time of 19 +/- 10 months. The total cost of the radiology studies was $113,179; the studies added approximately $50 extra per patient. Seven high-risk lesions were identified (six extracolonic malignancies and one large aortic aneurysm) in patients with significant findings. CTC also identified six intracolonic malignancies and three adenomas with high-grade dysplasia. When considering extracolonic findings, CTC increased the odds of identifying high-risk lesions by 78% (nine intracolonic lesions vs 16 intracolonic plus extracolonic lesions; p = 0.0156). Of the 16 intracolonic and extracolonic high-risk lesions, 11 (69%) underwent curative resection, and 5 of 11 (44.4%) were extracolonic.

CONCLUSION

CTC increased the odds of identifying high-risk lesions by 78%. CTC should be considered as an alternative to optical colonoscopy for colorectal cancer screening or as a onetime procedure to identify significant treatable intracolonic and extracolonic lesions.

Establishing a CT colonography service

This article describes the steps involved in establishing a screening computed tomographic colonography (CTC) practice and integrating that practice within a gastroenterology practice. The standard operating procedures followed at the National Naval Medical Center's Colon Health Initiative are presented and are followed by a discussion of practical aspects of establishing a CTC practice, such as equipment specifications, CTC performance, and interpretation training requirements for radiologists and nonradiologists. Regulatory considerations involved in establishing a screening CTC program are examined along with the salient features of a CTC business plan. Finally, reimbursement issues, quality control, and the potential impact of screening CTC on colonoscopy practice are discussed.

Cost effectiveness of CT colonography for UK NHS colorectal cancer screening of asymptomatic adults aged 60-69 years

BACKGROUND

Screening of populations at risk for colorectal cancer (CRC) allows the detection and successful treatment of tumours and their precursor polyps. The current UK CRC screening programme is faecal occult blood testing (FOBT), despite evidence from modelling studies to suggest that more cost-effective technologies exist.

OBJECTIVE

To assess the cost effectiveness of CT colonography (CTC) for colorectal cancer screening from the perspective of the UK NHS.

METHODS

A state-transition Markov model was constructed to estimate lifetime costs and health outcomes of a cohort of individuals screened at age 60-69 years using four different CRC screening technologies: FOBT, flexible sigmoidoscopy, optical colonoscopy and CTC.

RESULTS

CTC screening offered every 10 years was cost saving compared with the current UK programme of biennial FOBT screening. This strategy also yielded greater health benefits (QALYs and life-years) than biennial FOBT screening. The model fit observed CRC epidemiology data well and was robust to changes in underlying parameter values. CTC remained cost effective under a range of assumptions in the univariate sensitivity analysis. However, in the probabilistic sensitivity analysis, CTC dominated FOBT in only 5.9% of simulations and was cost effective at a threshold of pound30,000 per QALY gained in 48% of simulations.

CONCLUSIONS

CTC has the potential to provide a cost-effective option for CRC screening in the UK NHS and may be cost saving compared with the current programme of biennial FOBT. Further analysis is required to assess the impact of introducing CTC to the UK CRC screening programme on the NHS budget and capacity.

Virtual colonoscopy in stenosing colorectal cancer

BACKGROUND

Between 5 and 10% of the patients undergoing a colonoscopy cannot have a complete procedure mainly due to stenosing neoplastic lesion of rectum or distal colon. Nevertheless the elective surgical treatment concerning the stenosis is to be performed after the pre-operative assessment of the colonic segments upstream the cancer. The aim of this study is to illustrate our experience with the Computed Tomographic Colonography (CTC) for the pre-operative assessment of the entire colon in the patients with stenosing colorectal cancers.

METHODS

From January 2005 till March 2009, we observed and treated surgically 43 patients with stenosing colorectal neoplastic lesions. All patients did not tolerate the pre-operative colonoscopy. For this reason they underwent a pre-operative CTC in order to have a complete assessment of the entire colon. All patients underwent a follow-up colonoscopy 3 months after the surgical treatment. The CTC results were compared with both macroscopic examination of the specimen and the follow-up coloscopy.

RESULTS

The pre-operative CTC showed four synchronous lesions in four patients (9.3% of the cases). The macroscopic examination of the specimen revealed three small sessile polyps (3-4 mm in diameter) missed in the pre-operative assessment near the stenosing colorectal cancer. The follow-up colonoscopy showed four additional sessile polyps with a diameter between 3-11 mm in three patients. Our experience shows that CTC has a sensitivity of 83,7%.

CONCLUSION

In patients with stenosing colonic lesions, CTC allows to assess the entire colon pre-operatively avoiding the need of an intraoperative colonoscopy. More synchronous lesions are detected and treated at the time of the elective surgery for the stenosing cancer avoiding further surgery later on.

Virtual endoscopy using CT scan

The term virtual endoscopy refers to using either spiral computed tomography (CT colonography) or magnetic resonance scanning (MR colonography) combined with computer technology to produce high-resolution two- and three-dimensional imaging of the large bowel. Current CT techniques require meticulous bowel preparation and gas insufflation prior to the examination. The advantages of CT colonography over conventional colonography include safety, its ability to demonstrate the entire large bowel in almost all patients, even following incomplete endoscopy, to accurately localize lesions, and to examine the entire colon in patients with obstructing tumors. Additionally, CT colonography allows simultaneous preoperative tumor staging. Screening for colorectal polyps is a controversially discussed indication for CT colonography. Sensitivity and specificity range widely and decrease with decreasing polyp size. However, better results can be achieved using multidetector technology. Most frequently, the examination is well tolerated and assessed by patients to be more acceptable than conventional colonoscopy. There are no reported complications from CT colonography. The procedure requires a scan time of about 25 to 30 seconds with new multidetector CT scanners, and sedation is not used. Currently, CT colonography is less cost-effective than conventional endoscopy. Another disadvantage is the relatively high irradiation exposure associated with CT colonography. Therefore, at the moment, this technique does not appear ready to be included in general screening strategies. However, ongoing and future improvements may prove its value in colorectal examination strategies.

Barium meal follow through with pneumocolon: Screening test for chronic bowel pain

AIM: To study the sensitivity, specificity and cost effectiveness of barium meal follow through with pneumocolon (BMFTP) used as a screening modality for patients with chronic abdominal pain of luminal origin in developing countries.

METHODS: Fifty patients attending the Gastroenterology Unit, SMS Hospital, whose clinical evaluation revealed chronic abdominal pain of bowel origin were included in the study. After routine testing, BMFT, BMFTP, contrast enhanced computed tomography (CECT) of the abdomen, barium enema and colonoscopy were performed. The sensitivity, specificity and cost effectiveness of these imaging modalities in the detection of small and/or large bowel lesions were compared.

RESULTS: Out of fifty patients, structural pathology was found in ten. Nine out of these ten patients had small bowel involvement while seven had colonic involvement alone or in combination with small bowel involvement. The sensitivity of BMFTP was 100% compared to 88.89% with BMFT when detecting small bowel involvement (BMFTP detected one additional patient with ileocecal involvement). The sensitivity and specificity of BMFTP for the detection of colonic pathology were 85.71% and 95.35% (41/43), respectively. Screening a patient with chronic abdominal pain (bowel origin) using a combination of BMFT and barium enema cost significantly more than BMFTP while their sensitivity was almost comparable.

CONCLUSION: BMFTP should be included in the investigative workup of patients with chronic abdominal pain of luminal origin, where either multiple sites (small and large intestine) of involvement are suspected or the site is unclear on clinical grounds. BMFTP is an economical, quick and comfortable procedure which obviates the need for colonoscopy in the majority of patients.

Critical analysis of the performance of double-contrast barium enema for detecting colorectal polyps > or = 6 mm in the era of CT colonography

OBJECTIVE

The purpose of our study was to perform a meta-analysis comparing the performance of double-contrast barium enema (DCBE) with CT colonography (CTC) for the detection of colorectal polyps > or = 6 mm using endoscopy as the gold standard.

MATERIALS AND METHODS

Prospective DCBE and CTC studies were identified. Percentages of polyps and of patients with polyps > or = 10 mm and 6-9 mm were abstracted. The performance of DCBE versus CTC was determined by separately evaluating each technique's performance versus that of endoscopy, and contrasting the techniques. The I-squared statistic and Fisher's exact test were used for heterogeneity, the Cochran-Mantel-Haenszel and the Kruskal-Wallis tests for correlation, and the A(z) test for comparing pooled weighted estimates of performance.

RESULTS

Eleven studies of DCBE (5,995 patients, 1,548 polyps) and 30 studies of CTC (6,573 patients, 2,348 polyps) fulfilled inclusion criteria. For polyps > or = 10 mm, a 0.121-per-patient sensitivity difference favored CTC (p < 0.0001; DCBE, 0.702 [95% CI, 0.687-0.715]; CTC, 0.823 [0.809-0.836]). For polyps > or = 10 mm, a 0.031-per-polyp sensitivity difference favored CTC (p < 0.0001; DCBE, 0.715 [0.703-0.726]; CTC, 0.746 [0.735-0.757]). For polyps > or = 10 mm, a specificity difference of 0.104 favored CTC (p = 0.001; DCBE, 0.850 [0.847-0.855]; CTC, 0.954 [0.952-0.955]). DCBE was also significantly less sensitive for 6- to 9-mm polyps (p < 0.001).

CONCLUSION

DCBE has statistically lower sensitivity and specificity than CTC for detecting colorectal polyps > or = 6 mm.

Magnetic resonance colonography vs computed tomography colonography for the diagnosis of colorectal cancer: an indirect comparison

OBJECTIVE

The primary aim of this study was to use meta-regression techniques to compare the diagnostic accuracy of computed tomography colonography (CTC) and magnetic resonance colonography (MRC), compared with conventional colonoscopy for patients presenting with colorectal cancer (CRC).

METHOD

Quantitative meta-analysis was performed using prospective studies reporting comparative data between CTC and MRC individually to conventional colonoscopy. Study quality was assessed and sensitivities, specificities, diagnostic odds ratios (DOR) were calculated. Summary receiver operating characteristic (SROC) curves and sensitivity analysis were utilized. Meta-regression was used to indirectly compare the two modalities following adjustment for patient and study characteristics.

RESULTS

Overall sensitivity and specificity for CTC (0.96, 95% CI 0.92-0.99; 1.00, 95% CI 0.99-1.00 respectively) and MRC (0.91, 95% CI 0.79-0.97; 0.98, 95% CI 0.96-0.99 respectively) for the detection of CRC was similar. Meta-regression analysis showed no significant difference in the diagnostic accuracy of both modalities (beta=-0.64, P=0.37 and 95% CI of 0.12-2.39). Both tests showed high area under the SROC curve (CTC=0.99; MRC=0.98), with high DORs (CTC=1461.90, 95% CI 544.89-3922.30; MRC=576.41, 95% CI 135.00-2448.56). Factors that enhanced the overall accuracy of MRC were the use intravenous contrast, faecal tagging and exclusion of low-quality studies. No factors improved diagnostic accuracy from CTC except studies with more than 100 patients (AUC=1.00, DOR=2938.35, 95%CI 701.84-12 302.91).

CONCLUSION

This meta-analysis suggested that CTC and MRC have similar diagnostic accuracy for detecting CRC. Study quality, size and intravenous/intra-luminal contrast agents affect diagnostic accuracies. For an exact comparison to be made, studies evaluating CTC, MRC and colonoscopy in the same patient cohort would be necessary.

CT colonography in the detection of colorectal polyps and cancer: systematic review, meta-analysis, and proposed minimum data set for study level reporting

PURPOSE

To assess the methodologic quality of available data in published reports of computed tomographic (CT) colonography by performing systematic review and meta-analysis.

MATERIALS AND METHODS

The MEDLINE database was searched for colonography reports published between 1994 and 2003, without language restriction. The terms colonography, colography, CT colonoscopy, CT pneumocolon, virtual colonoscopy, and virtual endoscopy were used. Studies were selected if the focus was detection of colorectal polyps verified with within-subject reference colonoscopy by using key methodologic criteria based on information presented at the Fourth International Symposium on Virtual Colonoscopy (Boston, Mass). Two reviewers independently abstracted methodologic characteristics. Per-patient and per-polyp detection rates were extracted, and authors were contacted, when necessary. Per-patient sensitivity and specificity were calculated for different lesion size categories, and Forest plots were produced. Meta-analysis of paired sensitivity and specificity was conducted by using a hierarchical model that enabled estimation of summary receiver operating characteristic curves allowing for variation in diagnostic threshold, and the average operating point was calculated. Per-polyp sensitivity was also calculated.

RESULTS

Of 1398 studies considered for inclusion, 24 met our criteria. There were 4181 patients with a study prevalence of abnormality of 15%-72%. Meta-analysis of 2610 patients, 206 of whom had large polyps, showed high per-patient average sensitivity (93%; 95% confidence interval [CI]: 73%, 98%) and specificity (97%; 95% CI: 95%, 99%) for colonography; sensitivity and specificity decreased to 86% (95% CI: 75%, 93%) and 86% (95% CI: 76%, 93%), respectively, when the threshold was lowered to include medium polyps. When polyps of all sizes were included, studies were too heterogeneous in sensitivity (range, 45%-97%) and specificity (range, 26%-97%) to allow meaningful meta-analysis. Of 150 cancers, 144 were detected (sensitivity, 95.9%; 95% CI: 91.4%, 98.5%). Data reporting was frequently incomplete, with no generally accepted format.

CONCLUSION

CT colonography seems sufficiently sensitive and specific in the detection of large and medium polyps; it is especially sensitive in the detection of symptomatic cancer. Studies are poorly reported, however, and the authors propose a minimum data set for study reporting.

Evaluation of contrast-enhanced computed tomographic colonography in detection of local recurrent colorectal cancer

AIM: To evaluate the diagnostic accuracy, sensitivity, specificity of contrast-enhanced computed tomographic colonography in detecting local recurrence of colorectal cancer.

METHODS: From January 2000 to December 2004, 434 patients after potentially curative resection for invasive colorectal cancer were followed up for a period ranging from 20 to 55 mo. Eighty of the four hundred and thirty-four patients showing strong clinical evidence for recurring colorectal cancer during the last follow-up were enrolled in this study. Each patient underwent contrast-enhanced computed tomographic colonography and colonoscopy on the same day. Any lesions, biopsies, identified during the colonoscopic examination, immediate complications and the duration of the procedure were recorded. The results of contrast-enhanced computed tomographic colonography were evaluated by comparing to those of colonoscopy, surgical finding, and clinical follow-up.

RESULTS: Contrast-enhanced computed tomographic colonography had a sensitivity of 100%, a specificity of 83% and an overall accuracy of 94% in detecting local recurrent colorectal cancer.

CONCLUSION: Conventional colonoscopy and contrast-enhanced tomographic colonography can complement each other in detecting local recurrence of colorectal cancer.

Multislice CT Colonography: Current Status and Limitations

CT colonography (CTC) is a promising method for colorectal cancer screening because it provides a full structural evaluation of the entire colon. It has a superior safety profile, a low rate of complications, and high patient acceptance. In addition, CTC offers the real possibility of eliminating the cathartic bowel preparation, one of the biggest obstacles to patient compliance with colorectal cancer screening. Results of CTC studies in recently published literature are extremely encouraging, demonstrating that this method of screening can detect lesions equal to or larger than 8 mm with few false-positive findings.

Assessment of spiral CT pneumocolon in preoperative colorectal carcinoma

AIM: To investigate the value of spiral CT pneumocolon in preoperative colorectal carcinoma.

METHODS: Spiral CT pneumocolon was performed prior to surgery in 64 patients with colorectal carcinoma. Spiral CT images were compared to specimens from the resected tumor.

RESULTS: Spiral CT depicted the tumor in all patients. Comparison of spiral CT and histologic results showed that the sensitivity and specificity were 95.2%, 40.9% in detection of local invasion, and 75.0%, 90.9% in detection of lymph node metastasis. Compared to the Dukes classification, the disease was correctly staged as A in 6 of 18 patients, as B in 18 of 23, as C in 10 of 15, and as D in 7 of 8. Overall, spiral CT correctly staged 64.1% of patients.

CONCLUSION: Spiral CT pneumocolon may be useful in the preoperative assessment of patients with colorectal carcinoma as a means for assisting surgical planning.

Screening and surveillance of colorectal cancer

Although colorectal cancer (CRC) is the second leading cause of cancer deaths in the United States, it is preventable. Screening modalities include fecal occult blood testing, flexible sigmoidoscopy, double-contrast barium enema, and colonoscopy. Colonoscopy allows effective detection and removal of precursor adenomatous polyps and is the dominant CRC screening modality. Emerging technologies include CT and MR colonography and fecal DNA tests. Effective and cost-effective surveillance after polypectomy and curative CRC resection requires balancing the protective effect of polypectomy while maximizing intervals between examinations; thus, estimation of the risk of recurrence determines the intensity of surveillance for individual patients.

Vascular Virtual Endoluminal Visualization of Invasive Colorectal Cancer on MDCT Colonography

OBJECTIVE

The purpose of this study was to assess the utility of vascular views for visualization of invasive colorectal cancers on contrast-enhanced MDCT colonography.

CONCLUSION

By means of Hounsfield-transparency settings, we obtained virtual endoluminal images that show vascular structures and delineate invasive cancers of the colorectal wall, and we call these images "vascular views." Using this technique for contrast-enhanced MDCT colonography, we found that the increase in flow and pooling of blood related to angiogenesis of cancerous lesions is easy to identify and that this finding is useful in the detection of invasive colorectal cancers.

Incidental lesions found on CT colonography: their nature and frequency

CT colonography has been used to detect colonic polyps and cancers, but its effect in practice will also be influenced by the frequency with which extracolonic lesions of various types are detected. We performed a systematic review of the types of incidental lesions found on CT colonography. This is necessary to model the benefits and harms of detecting extracolonic lesions. Primary clinical studies of extracolonic findings on CT colonography were identified from electronic databases, scanning reference lists and hand searches of relevant journals and conference proceedings. A data collection proforma was used to collect information on extracolonic findings. 17 discreet studies were identified, involving 3488 patients. In total 40% of patients were recorded to have abnormalities and many had more than one abnormality. Nearly 14% of patients had further investigations and 0.8% were given immediate treatment. Extracolonic cancers were detected in 2.7% (0.9% had N0M0 cancers) and 0.9% had an aortic aneurysm. The number of extracolonic findings was high in all studies. While only a small population were judged "important", the prevalence of serious lesions outside the colon was nevertheless higher than in many other screening programs.

MR colonography in patients with incomplete conventional colonoscopy

PURPOSE

To assess dark-lumen magnetic resonance (MR) colonography for the evaluation of colonic segments in patients in whom conventional colonoscopy could not be completed.

MATERIALS AND METHODS

Institutional review board approval and written informed consent were obtained. Within 24 hours of incomplete conventional colonoscopy, 37 patients (22 women, 15 men; age range, 25-63 years) underwent MR colonography. Contrast material-enhanced T1-weighted three-dimensional images were collected after rectal administration of water for colonic distention. Data from MR colonography were evaluated by two radiologists. With a three-point scale, image quality was characterized in terms of colonic distention (1 = good; 2 = moderate, diagnostic; and 3 = poor, nondiagnostic) and presence of artifacts (1 = none; 2 = moderate, diagnostic; and 3 = extensive, nondiagnostic). Depiction of colorectal disease was assessed according to the following colonic segments: cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum.

RESULTS

Four patients had history of colorectal cancer, and each had undergone partial colonic resection of two segments. Hence, 214 segments were evaluated. Conventional colonoscopy failed in assessment of 127 of 214 potentially visible colonic segments in the 37 patients. MR image quality was rated diagnostic in 35 patients and permitted assessment of 206 of 214 potentially visible segments. Nondiagnostic image quality in two patients was attributed to inadequate distention of prestenotic colonic segments owing to high-grade tumor stenosis. All inflammation- and tumor-induced stenoses and all five polyps identified at conventional colonoscopy in poststenotic segments were correctly detected at MR colonography. However, MR-based assessment of prestenotic segments revealed two lesions suspected of being carcinoma, five polyps, and four segments affected by colitis.

CONCLUSION

MR colonography proved reliable in evaluating the majority of colonic segments inaccessible with conventional colonoscopy. The identification of additional disease at MR colonography underscores the need for a second diagnostic step in the setting of incomplete conventional colonoscopy.

Extracolonic findings in patients undergoing abdomino-pelvic CT for suspected colorectal carcinoma in the frail and disabled patient

AIM

The aims of this study were to evaluate the extracolonic findings identified in patients undergoing minimal preparation abdomino-pelvic CT in place of barium enema or colonoscopy for the detection of possible colorectal carcinoma.

MATERIALS AND METHODS

The CT technique involved helical acquisition (10 mm collimation, 1.5 pitch) following 2 days of preparation with oral contrast medium only. Extracolonic findings were evaluated in the light of subsequent follow-up and accuracy. The evaluation included assessment of the potential contribution of the extracolonic finding(s) to staging the cancer in the subset of patients who had colorectal carcinoma, and to account for the patients' presenting symptoms and signs in the remaining patients.

RESULTS

A total of 344 extracolonic findings were detected in 261 CT examinations, from amongst a total of 1077 cases (24%). Extracolonic findings were potentially important in staging in 32 of the 98 (33%) cases subsequently found to have colorectal cancer. There were 284 extracolonic findings amongst the 221 cases who proved not have colorectal cancer. One hundred and twenty-four (44%) of these 284 findings were actively followed up by clinicians, and 33 (12%) ultimately had a surgical intervention. Fifty-six percent (160/284) of the findings were determined to be correct (by further investigation, autopsy, and/or clinical follow-up); the remainder were incorrect or indeterminate (n = 56) or had no follow-up (n = 68). The commonest extracolonic findings were focal liver lesions (found in 42/1077, 4%) and abdominal aortic aneurysms (31/1077, 3%). Twenty-four (24/1077, 2%) previously unknown extracolonic malignancies were detected. Ten percent (106/1077) of the patients had extracolonic findings that could potentially have accounted for their presenting symptoms.

CONCLUSIONS

CT has the added benefit, compared with colonoscopy and barium enema, of not just evaluating the colon but also of detecting extracolonic abnormalities. Such findings may be useful in staging the cancer, may explain the patient's presenting symptoms, and may detect other potentially serious disorders.

Sensitivity and specificity of pneumo-colon CT in detecting colorectal neoplasms

AIM: To evaluate the sensitivity and specificity of pneumocolon computed tomography (CT) in the detection of colorectal neoplasms.

METHODS: A total of 100 patients with suspected colorectal neoplasms underwent both pneumocolon CT and colonoscopy.

RESULTS: On colonoscopy 13 colorectal carcinomas were detected in 13 patients, and 46 polyps in 24 patients (11 polyps were ≥ 1 cm in diameter, 14 were 6-9 mm, and 21 were ≤ 5 mm). Pneumocolon CT detected 15 cancers (included one false positive cancer), but only 16 polyps (9 were ≥ 1 cm). This resulted in a sensitivity of 100% (95% confidence interval (CI) 75%-100%) and specificity of 93% (95%CI: 66%-100%) for detection of colorectal carcinoma, and a sensitivity of 93% (95%CI: 73%-99%) and specificity of 96% (95%CI: 78%-100%) for detection of carcinoma and/or ≥ 1 cm polyps. Pneumocolon CT also identified carcinoma not seen at colonoscopy in one patient, and detected metastases in 2 colorectal carcinoma patients and extracolonic carcinoma in one patient.

CONCLUSION: Pneumocolon CT has a high sensitivity and specificity for detection of colorectal carcinoma and/or ≥1 cm colorectal polyps but not for < 1 cm colorectal polyps. Pneumocolon CT may be suitable for initial investigation of patients with symptoms of colorectal malignancy.

Evidence-based medicine: answering questions of diagnosis

Using medical evidence to effectively guide medical practice is an important skill for all physicians to learn. The purpose of this article is to understand how to ask and evaluate questions of diagnosis, and then apply this knowledge to the new diagnostic test of CT colonography to demonstrate its applicability. Sackett and colleagues have developed a step-wise approach to answering questions of diagnosis: Step1: Define a clinical question and its four components: Patient, intervention, comparison and outcome. Step 2: Find the evidence that will help answer the question. PubMed Clinical Queries is an efficient database to accomplish this step. Step 3: Assess whether this evidence is valid and important. A quick review of the methods and results section will help to answer these two questions. Step 4: Apply the evidence to the patient. This step includes: assessing whether the test can be used; determining if it will help the patient; finding whether the study patients are similar to the patient in question; determining a pretest probability; and deciding if the test will change one's management of the patient. A relatively new diagnostic test, CT colonography, is explored as a scenario in which the steps presented by Sackett et al.1 can be helpful. A patient who is interested in completing a CT colonography instead of a colonoscopy is the basis of the discussion. Because a CT colonography does not detect polyps of less than 10 mm accurately, many patient are not likely to prefer this test over a colonoscopy. Evidence-based medicine is an effective strategy for finding, evaluating, and critically appraising diagnostic tests, treatment and application. This skill will help physicians interpret and explain the medical information patients read or hear about.

Computed tomography colonography in routine clinical practice

OBJECTIVE

To describe the experience of a radiology unit in using open access computed tomography (CT) colonography instead of double-contrast barium enema in patients who refused or had an incomplete first-attempt colonoscopy.

METHODS

All consecutive patients who underwent CT colonography from December 1998 to August 2001 were recalled and evaluated. Patients in whom CT colonography showed intraluminal growths were sent for colonoscopy, performed using deep sedation if the first attempt failed.

RESULTS

A total of 463 consecutive CT colonography examinations were performed: 304 patients were re-traceable and were evaluated. In 85 cases CT colonography reported the presence of intraluminal growth. Colonoscopy confirmed the presence of 74 of the 94 polyps, and of 43 of the 48 cancers found at CT colonography. Colonoscopy also diagnosed an additional two cancers in two patients with CT colonography findings of inflammatory changes, and an additional 26 polyps in 16 patients. On a per-lesion basis, the positive predictive value of CT colonography was 73%, 80% and 87% for polyps </= 5 mm, 6-9 mm and >/= 10 mm, respectively, and was 90% for cancer. On a per-patient basis, the positive predictive value was 60%, 72% and 89% for lesions </= 5 mm, 6-9 mm and >/= 10 mm, respectively, and was 93% for cancer.

CONCLUSION

CT colonography on an open access basis can be confidently used as a routine test instead of double-contrast barium enema when total colonoscopy cannot be performed.

CT Colonography of Colorectal Polyps:A Metaanalysis

OBJECTIVE

For proper evaluation of the accuracy of CT colonography, prospective multiinstitutional trials would be ideal. Until these trials are available, data can be collectively analyzed. The purpose of this study is to use metaanalysis to assess the reported accuracy of CT colonography compared with conventional colonoscopy for detecting colorectal polyps.

MATERIALS AND METHODS

Articles comparing CT colonography and conventional colonoscopy were identified, and a standardized form was used to extract relevant study data. Fisher's exact test and the Mantel-Haenszel test were used for pooling of data. A 95% confidence interval (CI) was selected to determine sensitivity and specificity, and the Kruskal-Wallis exact test was used to identify trends relating to polyp size. Meta-analysis methods were used to test strength of results. Comparisons were made for the percentage of polyps detected grouped by size (> or = 10 mm, 6-9 mm, < or = 5 mm) and the percentage of patients identified who had polyps of the same size.

RESULTS

Fourteen studies fulfilled all the study inclusion criteria and gave a total of 1,324 patients and 1,411 polyps. The pooled per-patient sensitivity for polyps 10 mm or larger was (sensitivity [95% CI]) 0.88 (0.84-0.93), for polyps 6-9 mm it was 0.84 (0.80-0.89), and for polyps 5 mm or smaller it was 0.65 (0.57-0.73). The pooled per-polyp sensitivity for polyps 10 mm or larger was 0.81 (0.76-0.85), for polyps 6-9 mm it was 0.62 (0.58-0.67), and for polyps 5 mm or smaller it was 0.43 (0.39-0.47). Sensitivity for detection of polyps increased as the polyp size increased (p < 0.00005). The pooled overall specificity for detection of polyps larger than 10 mm was 0.95 (0.94-0.97).

CONCLUSION

The specificity and sensitivity of CT colonography are high for polyps larger than 10 mm.

Computerized tomographic colonography: performance evaluation in a retrospective multicenter setting

BACKGROUND & AIMS

No multicenter study has been reported evaluating the performance and interobserver variability of computerized tomographic colonography. The aim of this study was to assess the accuracy of computerized tomographic colonography for detecting clinically important colorectal neoplasia (polyps >or=10 mm in diameter) in a multi-institutional study.

METHODS

A retrospective study was developed from 341 patients who had computerized tomographic colonography and colonoscopy among 8 medical centers. Colonoscopy and pathology reports provided the standard. A random sample of 117 patients, stratified by criterion standard, was requested. Ninety-three patients were included (47% with polyps >or=10 mm; mean age, 62 years; 56% men; 84% white; 40% reported colorectal symptoms; 74% at increased risk for colorectal cancer). Eighteen radiologists blinded to the criterion standard interpreted computerized tomography colonography examinations, each using 2 of 3 different software display platforms.

RESULTS

The average area under the receiver operating characteristic curve for identifying patients with at least 1 lesion >or=10 mm was 0.80 (95% lower confidence bound, 0.74). The average sensitivity and specificity were 75% (95% lower confidence bound, 68%) and 73% (95% lower confidence bound, 66%), respectively. Per-polyp sensitivity was 75%. A trend was observed for better performance with more observer experience. There was no difference in performance across software display platforms.

CONCLUSIONS

Computerized tomographic colonography performance compared favorably with reported performance of fecal occult blood testing, flexible sigmoidoscopy, and barium enema. A prospective study evaluating the performance of computerized tomography colonography in a screening population is indicated.

Multislice CT colonography: current status and limitations

CT colonography (CTC) is a promising method for colorectal screening providing a full structural evaluation of the entire colon and gaining in popularity due to a superior safety profile, a low rate of complications, and high patient acceptance. Multislice CT (MSCT) has further improved the diagnostic potential of CTC by generating high-resolution CT images of the abdomen and pelvis in shorter acquisition times than was previously possible. Over the past year, multiple studies have been published on every aspect of CTC including techniques, image display, image reconstruction, and clinical trial results assessing the feasibility of CTC as a screening tool. Yet despite increasing clinical use, the appropriate role of CTC in colorectal cancer screening remains undefined and barriers to widespread adoption remain. In particular, though the test is generally regarded as easy to perform, accurate interpretation requires a steep learning curve. While several large studies have found high sensitivity and specificity, the accuracy of CTC in a screening population has yet to be verified and almost no health insurance plans reimburse for its use in colorectal screening. Ongoing research in computer-aided detection and new software tools, however, have the potential to increase accuracy and ease of interpretation significantly, accelerating its acceptance as a colorectal screening tool.

Screening for colorectal cancer

Colorectal cancer screening can prevent the development of colorectal cancer and reduce the risk for death. Screening recommendations include fecal occult blood testing, sigmoidoscopy, radiographic imaging of the colon, and colonoscopy. This article focuses on recommendations for average-risk individuals and discusses the potential benefits and limitations of each. High-risk individuals should be screened with colonoscopy. Cost-effectiveness analyses of colorectal cancer screening are summarized.

Colorectal cancer screening: scientific review

CONTEXT

Screening for colorectal cancer clearly reduces colorectal cancer mortality, yet many eligible adults remain unscreened. Several screening tests are available, and various professional organizations have differing recommendations on which screening test to use. Clinicians are challenged to ensure that eligible patients undergo colorectal cancer screening and to guide patients in choosing what tests to receive.

OBJECTIVE

To critically assess the evidence for use of the available colorectal cancer screening tests, including fecal occult blood tests, sigmoidoscopy, colonoscopy, double-contrast barium enema, and newer tests, such as virtual colonoscopy and stool-based molecular screening.

DATA SOURCES

All relevant English-language articles were identified using PubMed (January 1966-August 2002), published meta-analyses, reference lists of key articles, and expert consultation.

DATA EXTRACTION

Studies that evaluated colorectal cancer screening in healthy individuals and assessed clinical outcomes were included. Evidence from randomized controlled trials was considered to be of highest quality, followed by observational evidence. Diagnostic accuracy studies were evaluated when randomized controlled trials and observational studies were not available or did not provide adequate evidence. Studies were excluded if they did not evaluate colorectal screening tests and if they did not evaluate average-risk individuals.

DATA SYNTHESIS

Randomized controlled trials have shown that fecal occult blood testing can reduce colorectal cancer incidence and mortality. Case-control studies have shown that sigmoidoscopy is associated with a reduction in mortality, and observational studies suggest colonoscopy is effective as well. Combining fecal occult blood testing and sigmoidoscopy may decrease mortality and can increase diagnostic yield.

CONCLUSION

The recommendation that all men and women aged 50 years or older undergo screening for colorectal cancer is supported by a large body of direct and indirect evidence. At present, the available evidence does not currently support choosing one test over another.

Virtual colonoscopy: past, present, and future

Virtual colonoscopy is developing into a practical clinical technique. The issues of the steep learning curve and accuracy of the technique are undergoing advances related to patient preparation, scanning technique, reading methods, and CAD. It is probably the best test for patients with an incomplete colonoscopy or for those patients who cannot undergo colonoscopy. Its precise role in screening average-risk patients for colon cancer remains to be defined by ongoing research and clinical trials.

CT colonography (virtual colonoscopy) for the detection of colorectal polyps and neoplasms. current status and future developments

Computed tomography colonography (CTC) is a new, rapidly developing non-invasive CT technique used to detect colonic polyps and cancers. It employs two- (2D) and three-dimensional (3D) images of the colon in order to display neoplastic lesions. Clinical trials demonstrate promising results for the detection of polyps and cancers greater than or equal to 10 mm in size. Our purpose is to describe the technique of CT colonography, review recent published trials of CT colonography, and elucidate current clinical applications. Continuing technical innovations such as multidetector CT, computer-aided diagnosis, new image display techniques and faecal tagging promise to improve the performance and patient acceptance of CT colonography in the future.

Contrast-enhanced CT colonography in recurrent colorectal carcinoma: feasibility of simultaneous evaluation for metastatic disease, local recurrence, and metachronous neoplasia in colorectal carcinoma

OBJECTIVE

Contrast-enhanced CT colonography has the potential to detect local recurrence, metachronous disease, and distant metastases in patients with a history of invasive colorectal cancer. The purpose of our study was to determine whether colonic anastomoses prohibit adequate colonic distention on contrast-enhanced CT colonography and to estimate the performance of contrast-enhanced CT colonography in detecting recurrent colorectal carcinoma.

MATERIALS AND METHODS

Fifty patients with a history of resected invasive colorectal carcinoma underwent contrast-enhanced CT colonography and colonoscopy. Colonic distention was graded for different colonic segments. Two radiologists evaluated for the presence of local recurrence, metachronous disease, and metastatic disease. Results were compared with colonoscopy, histology, and clinical follow-up.

RESULTS

Most patients had adequate colonic inflation (37/50, 74%). Eleven of 13 patients with inadequate distention had collapse in the sigmoid colon, usually associated with ileocolic anastomoses. Contrast-enhanced CT colonography detected local recurrences with an accuracy of 94% (95% confidence interval, 83-99%). The accuracy of contrast-enhanced CT colonography for metachronous lesions greater than or equal to 1 cm was 92% (95% confidence interval, 80-98%), but there was only one such lesion, which was missed on initial colonoscopy. Stool, granulation tissue, and inflammation can mimic the CT appearance of local recurrence or metachronous disease and account for false-positive examinations. Contrast-enhanced CT colonography identified five patients with metastatic disease.

CONCLUSION

Suboptimal sigmoid distention can be seen on contrast-enhanced CT colonography, predominantly in patients with right hemicolectomies. Contrast-enhanced CT colonography is a promising method for detecting local recurrence, metachronous disease, and distant metastases in patients with prior invasive colorectal carcinoma. The technique can also serve as a useful adjunct to colonoscopy by detecting local recurrences or metachronous disease that are endoscopically obscure or by serving as a full structural colonic examination when endoscopy is incomplete.

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.