Association between visceral adiposity and colorectal polyps on CT colonography

Abstract

Objective: The purpose of this article is to determine whether there is an association between visceral adiposity measured on CT colonography (CTC) and colorectal polyps.

Materials and methods: Patients who underwent CTC and same-day optical colonoscopy (n = 1186) were analyzed. Visceral adipose tissue volumes and volume percentages relative to total internal body volume were measured on slices in the L2-L3 regions on supine CTC scans with validated fully automated software. Student t test, odds ratio, logistic regression, and receiver operating characteristic analyses were performed.

Results: For subjects with (n = 345) and without (n = 841) adenomatous polyps, the mean (± SD) volume percentages were 31.2% ± 10.8% and 28.2% ± 11.3%, respectively (p < 0.0001). For subjects with (n = 244) and without (n = 942) hyperplastic polyps, the volume percentages were 31.8% ± 10.7% and 28.3% ± 11.2%, respectively (p < 0.0001). Comparing the lowest and highest quintiles of volume percentage, the odds ratios for having at least one adenomatous polyp or hyperplastic polyp versus no polyp were 2.06 (95% CI, 1.36-3.13) and 1.71 (95% CI, 1.08-2.71), and the prevalence of having adenomatous polyps or hyperplastic polyps increased by 14% and 8%, respectively.

Conclusion: Subjects with higher visceral adiposity measurements on CTC have a greater risk for the presence of colonic polyps.

Fig. 1

Illustration of fully-automated method to measure adipose tissue. A) Two-dimensional transaxial CT colonography image at L2 level of a 52 year-old man. B) Smoothed image after anisotropic filtering. C) External (yellow) and internal (light blue) contours generated by automated software. D) Segmented subcutaneous (red) and visceral (dark blue) adipose tissue. The volume of the visceral adipose tissue normalized to internal body volume (VAV%) measured by the automated software was 25.3%.

Fig. 2

Bland-Altman plots of validation experiment (n=50). (A–C) Plots compare pairwise assessments of visceral adipose tissue as a percentage of internal body volume (VAV%) determined by automated software (Auto) and by two observers using manual tracing (Man1 and Man2). The dashed lines indicate the ± two standard deviation limits of agreement. Maximum disagreement was 2% in all three comparisons.

Fig. 3

Transaxial CT colonography images at the L2–L3 level of patients in the (A) lowest and (B) highest quintiles of VAV%. External (yellow) and internal (light blue) contours and subcutaneous (red) and visceral (dark blue) adipose tissue generated by automated software are shown. The volumes of the visceral adipose tissues normalized to internal body volumes (VAV%) measured on these images are (A) 5.65% and (B) 46.15%. The 51 year-old woman in (A) did not have any polyps. The 69 year-old man in (B) had one 10 mm adenomatous polyp in the ascending colon.

Fig. 4

ROC curves for the presence in a patient of at least one polyp. The AUC and standard deviation of AUC for any, adenomatous, advanced adenomatous, non-advanced adenomatous, and hyperplastic polyps are 0.583±0.017, 0.579±0.018, 0.624±0.034, 0.574±0.018 and 0.584±0.020, respectively, at different thresholds of VAV% (solid lines). The AUC and standard deviation of AUC for any, adenomatous, advanced adenomatous, non-advanced adenomatous and hyperplastic polyps are 0.606±0.016, 0.611±0.018, 0.658±0.033, 0.612±0.018 and 0.596±0.020, respectively, at different thresholds of prediction probability using logistic regression (LR) analysis (dotted lines).