Effect of dose splitting of a low-volume bowel preparation macrogol-based solution on CT colonography tagging quality

Abstract

Purpose: To compare examination quality and acceptability of three different low-volume bowel preparation regimens differing in scheduling of the oral administration of a Macrogol-based solution, in patients undergoing computed tomographic colonography (CTC). The secondary aim was to compare CTC quality according to anatomical and patient variables (dolichocolon, colonic diverticulosis, functional and secondary constipation).

Methods: One-hundred-eighty patients were randomized into one of three regimens where PEG was administered, respectively: in a single dose the day prior to (A), or in a fractionated dose 2 (B) and 3 days (C) before the examination. Two experienced radiologists evaluated fecal tagging (FT) density and homogeneity both qualitatively and quantitatively by assessing mean segment density (MSD) and relative standard deviation (RSD). Tolerance to the regimens and patient variables were also recorded.

Results: Compared to B and C, regimen A showed a lower percentage of segments with inadequate FT and a significantly higher median FT density and/or homogeneity scores as well as significantly higher MSD values in some colonic segments. No statistically significant differences were found in tolerance of the preparations. A higher number of inadequate segments were observed in patients with dolichocolon (p < 0.01) and secondary constipation (p < 0.01). Interobserver agreement was high for the assessment of both FT density (k = 0.887) and homogeneity (k = 0.852).

Conclusion: The best examination quality was obtained when PEG was administered the day before CTC in a single session. The presence of dolichocolon and secondary constipation represent a risk factor for the presence of inadequately tagged colonic segments.

Keywords: Bowel preparation; CT colonography; Fecal tagging; Patient tolerance; Quality assessment.

Fig. 1

Study design and bowel preparation schemes. Regimen A: 120 g of PEG in 1.5 L of water at 5 pm on the day before the CTC; Regimen B: 60 g PEG in 1 L of water at 5 pm on the 2 days before the CTC; Regimen C: 30 g PEG in 0.5 L of water at 5 pm on the 3rd day before the CTC + 30 g PEG in 0.5 L of water at 5 pm on the 2nd day before the CTC + 60 g PEG in 1 L of water at 5 pm on the day before the CTC. CTC computed tomographic colonography, FT fecal tagging. a. Patients with indications to perform CTC in according to ESGE/ESGAR guideline consensus statement. b. Three patients were excluded because of indication to perform CTC with iodinated contrast media intravenously after prone scan, failure to follow the assigned preparation scheme and appearance of vasovagal reaction during CO₂ insufflation

Fig. 2

Coronal abdominal view of a poor-quality CTC in a patient with dolichocolon. The radiologists assigned a score of 2 for density and 3 for homogeneity of the FT in the caecum; the FT of other colonic segments was considered inadequate with decreasing score from ascending colon to sigmoid-rectum. I intensity score, H homogeneity score

Fig. 3

a Example of a manually drawn ROI to evaluate MSD and RSD of FT: an area that includes all fecal residues, excluding anatomical structures such as colonic mucosal folds. b The amount of fecal residues in the rectum was insufficient for the quantitative analysis (manually drawn ROI < 0.5 cm.²)

Fig. 4

Per-segment qualitative assessment of FT for the three regimens: tagging was considered “inadequate” when a score of 1 for density and/or 1–2 for homogeneity was assigned. The number of inadequate segments for each regimen (columns) is reported on the vertical axis, while the segment type on the abscissa. The value on the top of each column represents the percentage of segments that are inadequate for that type of segment, within the same regimen. All 65 segments with inadequate FT were inadequate for homogeneity (a) and 32 of them (49.2%) were inadequate for density also (b)

Fig. 5

Segment-by-segment comparison between the median scores ​​of MSD (a) and RSD (b) of the three regimens. Each regimen is represented by a different row. The values of MSD (a) and RSD (b) are reported in the vertical axis and in the respective table, while the segment type on the abscissa. Interquartile ranges are reported in parentheses. MSD Mean Segment Density, RSD Relative Standard Deviation

Fig. 6

Box plot of tolerance distribution scores for each regimen. The bottom edge of the box represents the first quartile, which in this case overlaps the median score; the top edge of the box represents the third quartile. The lines extending from the boxes (whiskers) indicate the variability outside the upper and lower quartiles, excluding outliers which are defined as those values outside 1.5 times the interquartile range