title: CT colonography after incomplete optical colonoscopy: bowel preparation quality at same-day vs. deferred examination.
abstract: OBJECTIVE
  To objectively compare the volume, density, and distribution of luminal fluid for same-day oral-contrast-enhanced CTC following incomplete optical colonoscopy (OC) vs. deferred CTC on a separate day utilizing a dedicated CTC bowel preparation.
  
  
  METHODS
  HIPAA-compliant, IRB-approved retrospective study compared 103 same-day CTC studies after incomplete OC (utilizing 30 mL oral diatrizoate) against 151 CTC examinations performed on a separate day after failed OC using a dedicated CTC bowel preparation (oral magnesium citrate/dilute barium/diatrizoate the evening before). A subgroup of 15 patients who had both same-day CTC and separate-day routine CTC was also identified and underwent separate analysis. CTC exams were analyzed for opacified fluid distribution within the GI tract, as well as density and volume. Data were analyzed utilizing Kruskal-Wallis and Wilcoxon Signed Rank tests.
  
  
  RESULTS
  Opacified luminal fluid extended to the rectum in 56% (58/103) of same-day CTC vs. 100% (151/151) of deferred separate-day CTC (p < 0.0001). For same-day CTC, contrast failed to reach the colon in 11% (11/103) and failed to reach the left colon in 26% (27/103). Volumetric colonic fluid segmentation for fluid analysis (successful in 80 same-day and 147 separate-day cases) showed significantly more fluid in the same-day cohort (mean, 227 vs. 166 mL; p < 0.0001); the actual difference is underestimated due to excluded cases. Mean colonic fluid attenuation was significantly lower in the same-day cohort (545 vs. 735 HU; p < 0.0001). Similar findings were identified in the smaller cohort with direct intra-patient CTC comparison.
  
  
  CONCLUSIONS
  Dedicated CTC bowel preparation on a separate day following incomplete OC results in a much higher quality examination compared with same-day CTC.
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine & Public Health, 750 Highland Avenue, Madison, WI, 53705, USA.
authors.forename: Jake
authors.initials: J
authors.lastname: Theis
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine & Public Health, 750 Highland Avenue, Madison, WI, 53705, USA.
authors.forename: David H
authors.initials: DH
authors.lastname: Kim
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine & Public Health, 750 Highland Avenue, Madison, WI, 53705, USA.
authors.forename: Meghan G
authors.initials: MG
authors.lastname: Lubner
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine & Public Health, 750 Highland Avenue, Madison, WI, 53705, USA.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Muñoz del Rio
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine & Public Health, 750 Highland Avenue, Madison, WI, 53705, USA. ppickhardt2@uwhealth.org.|Department of Radiology, University of Wisconsin School of Medicine & Public Health, E3/311 Clinical Science Center, 600 Highland Ave., Madison, WI, 53792-3252, USA. ppickhardt2@uwhealth.org.
authors.forename: Perry J
authors.initials: PJ
authors.lastname: Pickhardt
mesh_terms: D001466:Barium Sulfate; D002400:Cathartics / Q000008:administration & dosage; D019343:Citric Acid / Q000008:administration & dosage; D023881:Colonography, Computed Tomographic / Q000379:methods*; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis*; D003287:Contrast Media / Q000008:administration & dosage; D003973:Diatrizoate / Q000008:administration & dosage; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009942:Organometallic Compounds / Q000008:administration & dosage; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D002400:Cathartics; D003287:Contrast Media; D009942:Organometallic Compounds; D003973:Diatrizoate; D001466:Barium Sulfate; D019343:Citric Acid; C110422:magnesium citrate
keywords: Bowel preparation; CT colonography; Quality assurance; Virtual colonoscopy
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