Low-fiber diet in limited bowel preparation for CT colonography: Influence on image quality and patient acceptance

The purpose of this study was to determine whether a low-fiber diet is necessary for optimal tagging-only bowel preparation for CT colonography. Fifty consecutively enrolled patients received an iodine bowel preparation: 25 patients used a low-fiber diet and 25 used no special diet. One observer determined the tagging quality per segment on a 5-point scale (1, inhomogeneous tagging; 5, excellent preparation) and the largest size of untagged feces. Semiautomatic measurements of density and homogeneity of residual feces were performed. Patient acceptance was assessed with questionnaires. Per polyp sensitivity for polyps 6 mm in diameter and larger was calculated for two experienced observers. Tagging quality was scored less than grade 5 in 15 segments (10%) in the low-fiber diet group and in 25 segments (17%) in the unrestricted diet group (p = 0.098). One piece of untagged feces 10 mm in diameter or larger was found in the low-fiber diet group, and 12 were found in the unrestricted diet group (p < 0.001). Automatic measurement of attenuation resulted in a mean value of 594 HU in the low-fiber diet group and 630 HU in the unrestricted diet group (p = 0.297). In the low-fiber diet group, 22% of patients indicated that the bowel preparation was extremely or severely burdensome; 8% of patients in the unrestricted diet group had this response (p = 0.19). Thirty-two polyps 6 mm in diameter or larger were found in the low-fiber diet group and 30 in the unrestricted diet group. Observer 1 had 84% and 77% sensitivity in detecting polyps 6 mm in diameter or larger in the low-fiber diet and unrestricted diet groups, respectively (p = 0.443), and observer 2 had 97% and 83% sensitivity (p = 0.099). Use of a low-fiber diet in bowel preparation for CT colonography results in significantly less untagged feces and shows a trend toward better residue homogeneity.