title: 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: OBJECTIVE
  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).
  
  
  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.
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine & Public Health, Madison, WI, USA; Department of Radiology, University Hospital Hamburg-Eppendorf, Hamburg, Germany. Electronic address: pbannas@uwhealth.org.
authors.forename: P
authors.initials: P
authors.lastname: Bannas
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine & Public Health, Madison, WI, USA.
authors.forename: J
authors.initials: J
authors.lastname: Bakke
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine & Public Health, Madison, WI, USA.
authors.forename: A
authors.initials: A
authors.lastname: Munoz del Rio
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine & Public Health, Madison, WI, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Pickhardt
mesh_terms: D000368:Aged; D002400:Cathartics / Q000008:administration & dosage*; D019343:Citric Acid / Q000008:administration & dosage*; D023881:Colonography, Computed Tomographic; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009942:Organometallic Compounds / Q000008:administration & dosage*; D010710:Phosphates / Q000008:administration & dosage*; D011785:Quality Assurance, Health Care; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D012984:Software
chemical_list: D002400:Cathartics; D009942:Organometallic Compounds; D010710:Phosphates; D019343:Citric Acid; C110422:magnesium citrate; C018279:sodium phosphate