Quality of virtual colonoscopy in patients who have undergone radiation therapy or surgery: how successful are we?

CT colonography for postoperative surveillance after curative gastrectomy in patients with gastric cancer

AIM

The purpose was to evaluate the diagnostic role of contrast-enhanced CT colonography (CTC) for follow-up of colorectal cancer screening after curative gastrectomy in patients with gastric adenocarcinomas.

MATERIALS AND METHODS

Contrast-enhanced CTC was performed as a substitute for routine follow-up CT for the detection of recurrent lesions in 700 consecutive patients who underwent curative surgery for gastric adenocarcinomas. Prospectively, patients with polyps measuring 6 mm or larger on CTC were referred for optical colonoscopy. Clinical and radiologic follow-up with respect to detection of polyp and recurrent lesion was retrospectively assessed.

RESULTS

Colorectal polyps measuring 6 mm or larger were identified by CTC in 104 (14.9%) of the 700 patients. Optical colonoscopy was recommended to these patients and was performed in 72 cases. True positive lesions were identified in 62 of the 72 patients (per-patient positive predictive value: 86.1%). The diagnostic yield for primary colonic malignancies was 1.6% (11/700). Recurrent lesions of gastric cancer were also detected in eight patients (1.1%).

CONCLUSION

In patients who undergo gastrectomy due to gastric adenocarcinoma, contrast-enhanced CTC may offer a unique advantage by allowing simultaneous colorectal cancer screening in addition to its routine role of detecting recurrent lesions during follow-up.

Temporal and multiinstitutional quality assessment of CT colonography

OBJECTIVE

The purpose of this study was to investigate the variability of CT colonography (CTC) scan quality obtained within and between institutions by using previously validated automated quality assessment (QA) software that assesses colonic distention and surface area obscured by residual fluid.

MATERIALS AND METHODS

The CTC scans of 120 patients were retrospectively selected, 30 from each of four institutions. The bowel preparation included oral contrast material for fecal and fluid tagging. Patients at one institution (institution 4) drank half the amount of oral contrast material compared with the patients at the other three institutions. Fifteen of the CTC scans were from the beginning of the protocol studied at each institution and 15 scans were from the same protocol acquired approximately 1 year later in the study. We used previously validated QA software to automatically measure the mean distention and residual fluid of each of five colonic segments (ascending, transverse, descending, sigmoid, and rectum). Adequate distention was defined as a colonic diameter of at least 2 cm. Residual fluid was determined by the percentage of colonic surface area covered by fluid. We compared how the quality varied across multiple institutions and over time within the same institution.

RESULTS

No significant difference in the amount of colonic distention among the four institutions was found (p = 0.19). However, the distention in the prone position was significantly greater than the distention in the supine position (p < 0.001). Patients at institution 4 had about half the amount of residual colonic fluid compared with patients at the other three institutions (p < 0.01). The sigmoid and descending colons were the least distended segments, and the transverse and descending colons contained the most fluid on the prone and supine scans, respectively. More recently acquired studies had greater distention and less residual fluid, but the differences were not statistically significant (p = 0.30 and p = 0.96, respectively).

CONCLUSION

Across institutions, a significant difference can exist in bowel preparation quality for CTC. This study reaffirms the need for standardized bowel preparation and quality monitoring of CTC examinations to reduce poor CTC performance.

CT colonography: surveillance in patients with a history of colorectal cancer

Colorectal cancer is a leading cause of morbidity and mortality in the United States. It is also a disease that is preventable if precursor adenomatous polys are removed. Once a diagnosis of colorectal cancer is made, surgical resection is the only means of cure. The ability to resect colorectal cancer for cure is largely dependent upon the stage of tumor at presentation. Once a patient has been treated for colorectal cancer with surgery and in some cases neo-adjuvant or adjuvant therapy, they will present for follow-up. Surveillance is performed on these patients in order to detect local recurrence that if detected early can be surgically resected for cure. Surveillance also allows detection of distant metastatic disease that may in some cases also be cured with resection. Finally, surveillance of the remaining colon is important to detect the development of new or metachronous adenomatoid polyps that if left in place could develop into new colon cancers. Imaging can play a part in patient surveillance to detect recurrent disease at extracolonic sites as well as the development of new colonic lesions. CT colonography is a promising tool for surveillance in patients with a history of colorectal cancer.

Water enema computed tomography: diagnostic tool in suspicion of colorectal tumor

OBJECTIVES

The aim of this study was to assess the accuracy of water enema multi-row computed tomography for detecting clinically suspected colorectal tumor.

PATIENTS AND METHODS

A water enema multi-row computed tomography (WE-MR-CT) was performed in 128 consecutive patients (71 women, mean age 67.7 years) referred for suspicion of colorectal cancer. We defined at least one centimeter size of the lesion as the threshold of detection. The results of WE-MR-CT were compared with the diagnosis obtained by colonoscopy, pathology or clinical follow-up.

RESULTS

The overall sensitivity and specificity of water enema multi-row CT in identifying patients with colorectal lesions were 95.5% and 93.5%, respectively. The negative predictive value was 98.8% for a 10-mm threshold lesion size. WE-MR-CT allowed identifying synchronous lesions in three cases.

CONCLUSIONS

WE-MR-CT can accurately detect supracentimetric colorectal tumors. The performance of this technique should be further evaluated in prospective studies.

CT colonography: where have we been and where are we going?

Over the past decade, computed tomographic (CT) colonography (also known as virtual colonoscopy) has been used to investigate the colon for colorectal neoplasia. Numerous clinical and technical advances have allowed CT colonography to advance slowly from a research tool to a viable option for colorectal cancer screening. However, substantial controversy remains among radiologists, gastroenterologists, and other clinicians with regard to the current role of CT colonography in clinical practice. On the one hand, all agree there is much excitement about a noninvasive imaging examination that can reliably depict clinically important colorectal lesions. However, this is tempered by results from several recent studies that show the sensitivity of CT colonography may not be as great when performed and the images interpreted by radiologists without expertise and training. The potential to miss important lesions exists; moreover, if polyps cannot be differentiated from folds and residual fecal matter, unnecessary colonoscopy will be performed. In this review, current issues will be discussed regarding colon cancer and the established and reimbursed strategies to screen for it and the past, current, and potential future role of CT colonography.