Incomplete colonoscopy

The indications for CTC closely follow the indications for conventional optical colonoscopy with few exceptions. These indications include screening asymptomatic high- and average-risk patient populations, pre-operative assessment of the colon proximal to an obstructing mass, evaluation of patients with change in bowel habits, surveillance of patients post colorectal cancer surgery, and incomplete or failed colonoscopy. Patients with bleeding diathesis, contraindications to sedation, and frail and elderly patients may also be better suited for CTC than conventional colonoscopy. 

The role of CT colonography has been evaluated specifically in this patient population. Incomplete colonoscopies secondary to post-operative strictures and rigid mesentery have been reported. In 2002, Gollub et al. reported a conventional colonoscopy failure rate of 4%-29% in post-operative or post-radiotherapy patients (Gollub et al. 2002). These patients would undergo a double contrast barium enema for complete evaluation of the colon. As discussed, CTC sensitivity for polyp detection is greater than DCBE and thus makes it a superior surveillance tool in this subset of patients. 

CTC has been shown to be superior to double contrast barium enema following incomplete conventional colonoscopy and, in fact, failed colonoscopy was the first established indication for CTC. An incomplete colonoscopy is defined as failure to intubate up to the cecum. The reported rate of failed colonoscopy ranges from 8% to as high as 35%. Patients with a history of an incomplete colonoscopy have a significantly increased risk of failing a second attempt. A multitude of reasons contribute to a failed conventional colonoscopy poor bowel... 

Macari M, Berman P, Dicker M et al. (1999) Usefulness of CT colography in patients with incomplete colonoscopy. AJR 173 561-564... 

For evaluation of the small bowel involvement, CT enterodysis is the preferred technique. There is little experience about the feasibility of CT colonography in Crohn s disease. Published results indicate that CT colonography can be helpful in the evaluation of colonic involvement, especially if conventional colonoscopy is incomplete (Biancone et al. 2003). In addition, the extracolonic extent and complications of the disease can be evaluated. 

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 colonography 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-obstruc-tion 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. 

Macari M, Berman P, Dicker M, Milano A, Megibow AJ (1999) Usefulness of CT colonography in patients with incomplete colonoscopy. Am J Roentgenol 173(3) 561-564 Megibow AJ, Balthazar EJ, Naidich DP, Bosniak MA (1983) Computed tomography of gastrointestinal lymphoma. Am J Roentgenol 141(3) 541-547... 

Montgomery M, Chew FS (1997) Primary lymphoma of the colon. Am J Roentgenol 168(3) 688 Morrin MM, Kruskal JB, Farrell RJ, Goldberg SN, McGee JB, Raptopoulos V (1999) Endoluminal CT colonography after an incomplete endoscopic colonoscopy. Am J Roentgenol 172(4) 913-918... 

Neri E, Giusti P, Battolla L, Vagli P, Boraschi P, Lencioni R, Cara-mella D, Bartolozzi C (2002) Colorectal cancer role of CT colonography in preoperative evaluation after incomplete colonoscopy. Radiology 223(3) 615-619... 

In the case of incomplete colonoscopy, CTC is the best imaging modality to evaluate the proximal colon, as indicated also by the statement of the American Gastroenterological Association on CTC (AGA Clinical Practice and Economics Committee... 

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