With regard to post-surgical conditions in the colon, there is no general agreement about the use of CT colonography. Contrast-enhanced CT colonography has the potential to detect local recurrence, metachro-nous disease, and distant metastases in patients with a history of invasive colorectal cancer (Fletcher et al. 2002; Laghi et al. 2003; Neri et al. 2005).
Currently, endoscopy or barium enemas are performed in many cases after colonic surgery for routine surveillance, to detect tumor recurrence, or to discover a metachronous cancer. After partial colonic resection, particularly, some of these control examinations could be replaced by contrast-enhanced CT colonography. In most cases, CT colo-nography allows visualization of the entire colon, which is important for demonstrating the post-surgical anatomic conditions. Two-dimensional views offer information about the wall morphology of the anastomosis. This is important because the majority of local recurrences are extraluminal and therefore endoscopically occult. Only one third to one half of local recurrences have an intraluminal component (Barkin et al. 1988; Wanebo et al. 1989). Most colonic anastomoses at CT colonography will not demonstrate excess of soft tissue. However, benign findings like polypoid granulation tissue or benign nodularity can be seen frequently endoscopically and at CT colonography.
Neoplasms or inflammatory conditions on the anastomosis can lead to focal or circular wall thickening, increased CM enhancement, and pericolic fat stranding (Figs. 13.18a,b and 13.19a,b).
Polypoid filling defects and enhancing mucosal soft tissue at colonic anastomosis are nonspecific findings on CT colonography in patients with a history of colorectal cancer and can represent granulation tissue, inflammation or recurrent or metachro-nous disease.
Therefore differentiation between granulation tissue, inflammatory stenosis and cancer recurrence is the domain of endoscopy with biopsy, if possible. Pericolonic lymph nodes and distant metastasis can be evaluated with 2D planes.
Treatment of large bowel obstruction using self-expanding metal stents is now well-established and widely disseminated. Stenting is used in patients with incurable disease for definitive palliation, or preoperatively for patients where curative resection is possible (Camunez et al. 2000).
Follow-up of the location and the lumen of a stent may be feasible with CT colonography. Particularly if endoscopy is incomplete or if stents could not be passed by conventional colonoscopy, CT colonog-raphy could be an alternative for contrast enema. CT colonography provides additional information about the location and the lumen of the stent and the proximal colon (Fig. 13.20a-c). In case of re-obstruction because of tumor recurrence, the additional 2D displays demonstrate the morphology of the stent-stenosis, which might be helpful for further treatment. During the same procedure, the extracolonic conditions of the disease (metastases, lymph nodes) can be evaluated.
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