title: Comparison of routine and unprepped CT colonography augmented by low fiber diet and stool tagging: a pilot study.
abstract: BACKGROUND
  We performed a pilot study examining the feasibility of a new unprepped CT colonography (CTC) strategy: low fiber diet and tagging (unprepped) vs. low fiber diet, tagging and a magnesium citrate cleansing preparation (prepped). Prior reports of tagging were limited in that the residual stool was neither measured and stratified by size nor did prior reports subjectively evaluate the ease of interpretation by a reader experienced in interpreting CTC examinations.
  
  
  METHODS
  Prospective randomized to unprepped n = 14 and prepped n = 14. Colonic segments were subjectively evaluated for residual stool that would potentially interfere with interpretation. Scores were given in the following categories: percentage of residual stool that was touching or nearly touching mucosa, the largest piece of retained stool, effectiveness of tagging, height of residual fluid, degree of distention, ease of interpretation, and reading time.
  
  
  RESULTS
  Ease of the CT read (scale where 4 = optimal read) averaged 1.3 for the unprepped group and 2.3 for the prepped group. The mean read time averaged 17.5 min for unprepped and 17.9 min for prepped. The degree of distention (scale where 4 = well distended) averaged 3.7 for unprepped and 3.6 for prepped. Supine and prone images combined, the unprepped group had 160 segments with stool; prepped group had 58 segments. The amount of stool covering the mucosa in all segments averaged 1.6 (33%-66% coverage) in the unprepped group and 0.35 (<33% mucosal coverage) in the prepped group. The mean size of the largest piece of stool was 33.67 mm for unprepped and 4.01 mm for prepped. Percentage of tagged stool was not significantly different between the groups (range of 94-98%). The height of residual fluid averaged 8.37 mm for unprepped and 13.4 mm for prepped. Three polyps in three patients were found during optical colonoscopy (OC) in the unprepped group (5, 6, and 10 mm), none of which were prospectively detected at CTC. Three polyps in three patients were detected during OC in the prepped group (5, 10, and 15 mm), two of which were prospectively detected at CTC. Two false-positive lesions were observed at CTC in one patient in the prepped group.
  
  
  CONCLUSIONS
  There was more stool in the unprepped group and while this factor did not slow down the reading time, it made the examination subjectively harder to interpret and likely caused the three polyps in this group to be missed. We conclude that a truly unprepped strategy that leaves significant residual stool, even if well tagged, is not desirable.
authors.affiliation: Department of Radiology, The University of Chicago, MC 2026, 5841 S. Maryland Ave, Chicago, IL 60637, USA. ahdachma@uchicago.edu
authors.forename: Abraham H
authors.initials: AH
authors.lastname: Dachman
authors.forename: Damien O
authors.initials: DO
authors.lastname: Dawson
authors.forename: Philippe
authors.initials: P
authors.lastname: Lefere
authors.forename: Hiro
authors.initials: H
authors.lastname: Yoshida
authors.forename: Nasreen U
authors.initials: NU
authors.lastname: Khan
authors.forename: Nicole
authors.initials: N
authors.lastname: Cipriani
authors.forename: David T
authors.initials: DT
authors.lastname: Rubin
mesh_terms: D000328:Adult; D000368:Aged; D002400:Cathartics / Q000008:administration & dosage*; D019343:Citric Acid / Q000008:administration & dosage*; D003106:Colon / Q000000981:diagnostic imaging; D023881:Colonography, Computed Tomographic / Q000379:methods*; D003113:Colonoscopy / Q000379:methods; D004043:Dietary Fiber / Q000008:administration & dosage*; D005189:False Positive Reactions; D005240:Feasibility Studies; D005243:Feces; D005260:Female; D006801:Humans; D007413:Intestinal Mucosa / Q000000981:diagnostic imaging; D007417:Intestinal Polyps / Q000175:diagnosis / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D009942:Organometallic Compounds / Q000008:administration & dosage*; D010865:Pilot Projects; D011446:Prospective Studies; D011856:Radiographic Image Enhancement; D016037:Single-Blind Method; D013997:Time Factors
chemical_list: D002400:Cathartics; D004043:Dietary Fiber; D009942:Organometallic Compounds; D019343:Citric Acid; C110422:magnesium citrate