Intra-individual comparison of magnesium citrate and sodium phosphate for bowel preparation at CT colonography: Automated volumetric analysis of residual fluid for quality assessment

•Automated volumetric analysis provides objective CTC quality assessment.•Automated analysis allows for rapid comparison between different bowel regimens.•MgC results in higher residual colonic fluid volume (155 ml) than NaP (143 ml).•MgC results in lower attenuation of residual fluid (700 HU) than NaP (878 HU).•Simultaneous presence of optimal volume and attenuation is more frequent for MgC than for NaP.

AimTo perform an objective, intra-individual comparison of residual colonic fluid volume and attenuation associated with the current front-line laxative magnesium citrate (MgC) versus the former front-line laxative sodium phosphate (NaP) at CT colonography (CTC).Materials and methodsThis retrospective Health Insurance and Portability and Accountability Act-compliant study had institutional review board approval; informed consent was waived. The study cohort included 250 asymptomatic adults (mean age at index 56.1 years; 124 male/126 female) who underwent CTC screening twice over a 5 year interval. Colon catharsis at initial and follow-up screening employed single-dose NaP and double-dose MgC, respectively, allowing for intra-patient comparison. Automated volumetric analysis of residual colonic fluid volume and attenuation was performed on all 500 CTC studies. Colonic fluid volume <200 ml and mean attenuation between 300–900 HU were considered optimal. Paired t-test and McNemar's test were used to compare differences.ResultsResidual fluid volumes <200 ml were recorded in 192 examinations (76.8%) following MgC and in 204 examinations (81.6%) following NaP (p = 0.23). The mean total residual fluid volume was 155 ± 114 ml for MgC and 143 ± 100 ml for NaP (p = 0.01). The attenuation range of 300–900 HU was significantly more frequent for MgC (n = 220, 88%) than for NaP (n = 127, 50.8%; p < 0.001). Mean fluid attenuation was significantly lower for MgC (700 ± 165 HU) than for NaP (878 ± 155 HU; p < 0.001). Concomitant presence of both optimal fluid volume and attenuation was significantly more frequent for MgC 65.2% than for NaP (38%; p < 0.001).ConclusionsObjective intra-individual comparison using automated volumetric analysis suggests that the replacement of NaP by MgC as the front-line laxative for CTC has not compromised overall examination quality.