Computed tomography colonography in 2014: an update on technique and indications

Abstract

Twenty years after its introduction, computed tomographic colonography (CTC) has reached its maturity, and it can reasonably be considered the best radiological diagnostic test for imaging colorectal cancer (CRC) and polyps. This examination technique is less invasive than colonoscopy (CS), easy to perform, and standardized. Reduced bowel preparation and colonic distention using carbon dioxide favor patient compliance. Widespread implementation of a new image reconstruction algorithm has minimized radiation exposure, and the use of dedicated software with enhanced views has enabled easier image interpretation. Integration in the routine workflow of a computer-aided detection algorithm reduces perceptual errors, particularly for small polyps. Consolidated evidence from the literature shows that the diagnostic performances for the detection of CRC and large polyps in symptomatic and asymptomatic individuals are similar to CS and are largely superior to barium enema, the latter of which should be strongly discouraged. Favorable data regarding CTC performance open the possibility for many different indications, some of which are already supported by evidence-based data: incomplete, failed, or unfeasible CS; symptomatic, elderly, and frail patients; and investigation of diverticular disease. Other indications are still being debated and, thus, are recommended only if CS is unfeasible: the use of CTC in CRC screening and in surveillance after surgery for CRC or polypectomy. In order for CTC to be used appropriately, contraindications such as acute abdominal conditions (diverticulitis or the acute phase of inflammatory bowel diseases) and surveillance in patients with a long-standing history of ulcerative colitis or Crohn's disease and in those with hereditary colonic syndromes should not be overlooked. This will maximize the benefits of the technique and minimize potential sources of frustration or disappointment for both referring clinicians and patients.

Keywords: Computed tomographic colonography; Computed tomographic colonography, colorectal cancer screening; Computed tomographic colonography, diverticular disease; Computed tomographic colonography, indications; Computed tomographic colonography, neoplasm; Computed tomographic colonography, polyp; Computed tomographic colonography, surveillance; Computed tomographic colonography, technique; Virtual colonoscopy.

Figure 1

Pedunculated polyp submerged by fluid residues. A: Polyp displaying soft-tissue density (arrow) is partially submerged by tagged fluid (asterisk) on an axial prone computed tomography image; B: On electronically cleansed endoluminal view, a polyp with a pedunculated morphology (arrow) is clearly observed; C: On colonoscopy, a pedunculated polyp is detected before resection.

Figure 2

Patient with incomplete colonoscopy due to severe angulation and stricture secondary to diverticular disease of the sigmoid colon. A: On a volume-rendered colon map, a stricture of the sigmoid colon (arrow) and a large filling defect (asterisk) on the medial wall of the descending colon are evident; B: On a coronal image, a large polyp (arrow) of the descending colon is observed.

Figure 3

Non-polypoid lesion (type II-A). A: Non-polypoid lesion (arrow) is observed on an axial image; B: Lesion (arrow) is confirmed on an endoluminal computed tomographic colonography image; C: Colonoscopy confirming the presence of the non-polypoid lesion (arrow).