Full-laxative versus minimum-laxative fecal-tagging CT colonography using 64-detector row CT: prospective blinded comparison of diagnostic performance, tagging quality, and patient acceptance

Acad Radiol. 2009 Jul;16(7):780-9. doi: 10.1016/j.acra.2008.12.027. Epub 2009 Apr 17.


Rationale and objectives: To compare prospectively 64-detector-row computed tomographic colonography (CTC) after a full-laxative tagging-based preparation (full preparation) with a minimum-laxative tagging-based preparation (minimum preparation) with respect to diagnostic performance in the detection of polyps, tagging quality, and patient acceptance.

Materials and methods: Consecutive 101 patients at high risk for developing colorectal cancer were alternately assigned to either a full preparation group (n = 51) or a minimum preparation group (n = 50) for fecal-tagging CTC. The full preparation consisted of administration of 2-L polyethylene glycol solution with 20 mL of sodium diatrizoate for fecal tagging. The minimum preparation consisted of ingestion of a total of 45 mL of sodium diatrizoate during the 3 days before and 10 mL of sodium picosulfate solution the night before CT. Colonoscopy was used as the reference standard. We assessed the accuracy of polyp detection and the tagging quality for each preparation. All patients were given questionnaires related to their acceptance.

Results: Per-patient sensitivity, specificity, and positive and negative predictive values for polyps > or = 6 mm were as follows: full preparation group, 97%, 92%, 88%, and 98%, respectively; minimum preparation group, 88%, 68%, 56%, and 92%, respectively. Average visual subjective tagging scores for the full and minimum preparation groups were 94.6% and 76.1%, respectively (P < .0001). Minimum preparation was better tolerated than full preparation.

Conclusion: Although full-laxative and minimum-laxative fecal-tagging CTC yielded an equally high sensitivity in the detection of polyps > or = 6 mm, the full-laxative fecal-tagging CTC yielded a better specificity than did the minimum-laxative fecal-tagging CTC. Thus, it is desirable to offer patients an option of either full-laxative fecal-tagging CTC for highest diagnostic accuracy and ability to perform a same-day therapeutic colonoscopy without additional bowel preparation, or minimum-laxative fecal-tagging CTC for those unwilling to undergo full preparation but willing to accept moderate decrease in specificity.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Colonography, Computed Tomographic / methods*
  • Colorectal Neoplasms / diagnostic imaging*
  • Contrast Media / administration & dosage
  • Dose-Response Relationship, Drug
  • Feces
  • Female
  • Humans
  • Image Enhancement / methods*
  • Laxatives / administration & dosage*
  • Male
  • Maximum Tolerated Dose
  • Middle Aged
  • Patient Satisfaction*
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Single-Blind Method
  • Young Adult


  • Contrast Media
  • Laxatives