Reducing the oral contrast dose in CT colonography: evaluation of faecal tagging quality and patient acceptance

Abstract

Aim: To evaluate the minimal iodine contrast medium load necessary for an optimal computed tomography colonography tagging quality.

Materials and methods: Faecal occult blood test positive patients were randomly selected for one of three iodine bowel preparations: (1) 3 × 50 ml meglumine ioxithalamate (45 g iodine), (2) 4 × 25 ml meglumine ioxithalamate (30 g iodine); or (3) 3 × 25 ml (22.5 g iodine) meglumine ioxithalamate. Two experienced readers assessed the tagging quality per colonic segment on a five-point scale and the presence of adherent stool. Also semi-automatic homogeneity measurements were performed. Patient acceptance was assessed with questionnaires.

Results: Of 70 eligible patients, 45 patients participated (25 males, mean age 62 years). Each preparation group contained 15 patients. The quality of tagging was insufficient (score 1-2) in 0% of segments in group 1; 4% in group 2 (p<0.01 versus group 1); and 5% in group 3 (p=0.06 versus group 1). In group 1 in 11% of the segments adherent stool was present compared with 49% in group 2 and 41% in group 3 (p<0.01, group 2 and 3 versus group 1). Homogeneity was 85, 102 (p<0.01), and 91 SD HU (p=0.26) in groups 1, 2, and 3, respectively. In group 1 two patients experienced no burden after contrast agent ingestion compared to one patient in group 2 and nine patients in group 3 (p=0.017).

Conclusion: A dose of 3 × 50 ml meglumine ioxithalamate is advisable for an optimal tagging quality despite beneficial effects on the patient acceptance in patients receiving a lower dose.