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

Abstract

AIM To 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 METHODS This 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. RESULTS Residual 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). CONCLUSIONS Objective 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.

Objective and Subjective Intrapatient Comparison of Iohexol Versus Diatrizoate for Bowel Preparation Quality at CT Colonography

“…Based on our previous experience with volumetric analysis of residual colonic fluid at CTC, we prefer to have less than 200 ml of residual luminal fluid to allow for efficient and effective 3D fly-through evaluation [5, 6]. In terms of fluid density for 2D evaluation, we prefer an attenuation value greater than 500 HU [5, 6]. Finally, adherent stool must be minimized to allow for a primary 3D polyp evaluation [14].…”

“…The total volume and mean attenuation of the residual luminal colonic fluid for each patient were derived using an automated quality assessment (QA) tool available on a beta version of our CTC software system (V3D Colon, Viatronix) that provides the luminal fluid and gas volumes [5, 6, 19]. This portion of the study was conducted by one of the co-authors (B.J.…”

“…One important feature of high quality CTC is adequate bowel preparation prior to the examination to ensure both removal of bulk stool and contrast tagging of any residual material remaining in the colon [5–13]. Tagging of solid residual stool can be accomplished with dilute (2% w/v) barium sulfate, whereas uniform tagging of residual luminal fluid requires iodinated water-soluble agents [14].…”

CT colonography after incomplete optical colonoscopy: bowel preparation quality at same-day vs. deferred examination

“…The algorithm for QA fluid detection has been described in prior publications (18, 19). In brief, proper processing required correct centerline generation and colonic segmentation.…”

“…We have access to an automated volumetric CTC software tool that allows for quantification of both luminal gas and residual opacified colonic fluid, including volumetric and density assessment (18–21). This tool provides both an objective and efficient means for comparison between patient cohorts.…”