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Objectives: To retrospectively evaluate the frequencies and magnitudes of adverse events associated with computed tomographic colonography (CTC) for screening, diagnosis and preoperative staging of colorectal cancer., Methods: A Japanese national survey on CTC was administered by use of an online survey tool in the form of a questionnaire. The questions covered mortality, colorectal perforation, vasovagal reaction, total number of examinations, and examination procedures. The survey data was collated and raw frequencies were determined. Fisher's exact test was used to determine differences in event rates between groups., Results: At 431 institutions, 147,439 CTC examinations were performed. No deaths were reported. Colorectal perforations occurred in 0.014% (21/147,439): 0.003% (1/29,823) in screening, 0.014% (13/91,007) in diagnosis and 0.028% (7/25,330) in preoperative staging. The perforation risk was significantly lower in screening than in preoperative staging CTC procedures (p = 0.028). Eighty-one per cent of perforation cases (17/21) did not require emergency surgery. Vasovagal reaction occurred in 0.081% (120/147,439): 0.111% (33/29,823) in screening, 0.088% (80/91,007) in diagnosis and 0.028% (7/25,330) in preoperative staging., Conclusions: The risk of colorectal perforation and vasovagal reaction in CTC is low. The frequency of colorectal perforation associated with CTC is least in the screening group and greatest in the preoperative-staging group., Key Points: • The colorectal perforation rate during preoperative-staging CTC was 0.028 %. • The perforation rates for screening and diagnosis were 0.003 % and 0.014 %, respectively. • The perforation risk is significantly lower in screening than in preoperative staging. • Eighty-one per cent of perforation cases did not require emergency surgery. • Use of an automatic colon insufflator can reduce the risk of bowel perforation.

We propose a new preparation method for the computed tomography colonography (CTC). This method consists of giving a small volume (400 ml) of cleansing solution on the day before the examination and the same volume of solution on the day of the examination [low volume split-dose (LVSD) method]. Using this method, we compared the volume of residual fluid in the colon, the CT value of the residual fluid, and the quality of stool tagging with those for patients undergoing the conventional bowel preparation method. Polyp detectability of the CTC using this method and the acceptability of the preparation were also investigated. The volume of residual fluid in the colon with this method was smaller than that with the conventional method. The CT value of the residual fluid with this method was higher than that with the conventional method. Visual assessment of the quality of stool tagging with this method gave similar results to those obtained using the conventional method. The sensitivities were 95% for 5-10 mm polyps and 100% for polyps larger than 10 mm. The PPVs were 91% for 5-10 mm polyps and 100% for polyps larger than 10 mm. These results appear to be as good as in previous reports. In the questionnaires, about 80% of the answers were favorable regarding the volume and the taste of laxative. We conclude that LVSD bowel preparation method for CTC maintains polyp detectability and is better tolerated.