AIM To evaluate the morphology of the colon in patients with irritable bowel syndrome(IBS) by using computed tomography colonography(CTC).METHODS Twelve patients with diarrhea type IBS(IBS-D), 13 patients with constipation type IBS(IBS-C), 12 patients with functional constipation(FC) and 14 control patients underwent colonoscopy following CTC. The lengths of the rectosigmoid colon, transverse colon and the total colon were measured. The diameters of the rectum, sigmoid colon, descending colon, transverse colon, and ascending colon were measured.RESULTS The mean length of the total colon was 156.5 cm in group C, 158.9 cm in group IBS-D, 172.0 cm in group IBS-C, and 188.8 cm in group FC. The total colon in group FC was significantly longer than that in group C(P < 0.05). The mean length of the rectosigmoid colon was 56.2 cm, 55.9 cm, 63.6cm, and 77.4 cm(NS). The mean length of the transverse colon was 49.9 cm, 43.1 cm, 57.0 cm, and 55.0 cm. The transverse colonin group IBS-D was significantly shorter than that in group IBS-C(P < 0.01) and that in group FC(P = 0.02). The mean diameter of the sigmoid colon was 4.0 cm, 3.3 cm, 4.2 cm, and 4.3 cm(NS). The mean diameter of the descending colon was 3.6 cm, 3.1 cm, 3.8 cm, and 4.3 cm. The descending colon diameter in group IBS-D was significantly less than that in group IBS-C(P = 0.03) and that in group FC(P < 0.001). The descending colon diameter in group FC was significantly greater than that in group C(P = 0.04). The mean diameter of the transverse colon was 4.4 cm, 3.3 cm, 4.2 cm, and 5.0 cm(NS).CONCLUSION CT colonography might contribute the clarification of subtypes of IBS. AIM To evaluate the morphology of the colon in patients with irritable bowel syndrome (IBS) by using computed tomography colonography (CTC). METHODS Twelve patients with diarrhea type IBS (IBS-D), 13 patients with constipation type IBS , 12 patients with functional constipation (FC) and 14 control patients underwent colonoscopy following CTC. The lengths of the rectosigmoid colon, transverse colon and the total colon were measured. The diameters of the rectum, sigmoid colon, descending colon, transverse colon, and The total length of the total colon was 156.5 cm in group C, 158.9 cm in group IBS-D, 172.0 cm in group IBS-C, and 188.8 cm in group FC. The total colon in group FC was The mean length of the rectosigmoid colon was 56.2 cm, 55.9 cm, 63.6 cm, and 77.4 cm (NS). The mean length of the transverse colon was 49.9 cm, 43.1 cm , 57.0 cm, and 55.0 cm. The transverse colonin group IBS-D was signific The mean diameter of the sigmoid colon was 4.0 cm, 3.3 cm, 4.2 cm, and 4.3 cm (NS). The ate shorter shorter than that in group IBS-C (P <0.01) and that in group FC Mean diameter of the descending colon was 3.6 cm, 3.1 cm, 3.8 cm, and 4.3 cm. The descending colon diameter in group IBS-D was significantly less than that in group IBS-C (P = 0.03) and that in group FC P <0.001). The descending colon diameter in group FC was significantly greater than that in group C (P = 0.04). The mean diameter of the transverse colon was 4.4 cm, 3.3 cm, 4.2 cm, and 5.0 cm (NS). CONCLUSION CT colonography might contribute the clarification of subtypes of IBS.