Quantitative CT measurement of left colonic and pelvic mesenteric adipose volume in radiation proctitis

Background The edema of left colonic and pelvic mesenteric adipose tissues has long been recognized in surgery as a characteristic feature of radiation proctitis (RP). However, the correlation between mesenteric adipose volume and RP has not been extensively clarified. The purpose of this study was thus to assess the variation of left colonic and pelvic mesenteric adipose volume in RP. Methods From March 2013 to June 2015, the data of 52 patients with locally advanced rectal cancer who underwent neoadjuvant chemoradiotherapy, including 23 patients with RP and 29 with non-RP (nRP), were retrieved. The mesenteric adipose volume was quantified via a computed tomography (CT) reconstruction method. Corresponding analyses were conducted to observe the correlation between the relative change of mesenteric adipose volume and the thickening degree of the rectal wall. Results The baseline data of the RP group and the nRP group were comparable. There was no significant difference in the relative change of the left colonic mesenteric adipose volume in each vertebral space from the third lumbar vertebra to the first sacral vertebra before and after radiotherapy. The relative change of pelvic mesenteric adipose volume (ΔVp%) was notably higher in the RP group compared to the nRP group. With a ΔVp% cutoff value of 3.67%, the sensitivity and specificity for the diagnosis of RP were 65.2% and 86.2%, respectively. According to the correlation analysis, ΔVp% in the RP group was significantly correlated with the thickening degree of the rectal wall after radiotherapy (r=0.47, P=0.024). Conclusions The increment of the relative change of pelvic mesenteric adipose volume quantitatively measured by CT can be clinically useful in identifying RP.