Evaluation of the relationship between the spleen volume and the disease activity in ulcerative colitis and Crohn disease

Inflammatory bowel disease (IBD) is caused by the activation of an abnormal immune response in the intestinal mucosa; the spleen is involved in the main immune response. Ulcerative colitis (UC) and Crohn disease (CD) have different inflammatory mechanisms; this study aimed to quantitatively measure and compare the spleen volumes between patients with UC and CD and examine the relationship between spleen volume and disease activity in both. We retrospectively analyzed 44 patients with IBD aged 30–60 years (UC group, n = 24; CD group, n = 20). The control group comprised 19 patients with pancreatic cysts that did not affect the spleen volume. All patients underwent computed tomography (CT) between April 2014 and March 2019. Using the Image J software, spleen volumes in the UC, CD, and control groups were measured accurately from the CT images and adjusted for the body weight. No significant differences in the sex, age, or body weight were noted between the UC and CD groups and the control group. The spleen volumes, adjusted for the body weight, were 2.2 ± 1.0 cm(3)/kg, 2.0 ± 1.0 cm(3)/kg, and 3.6 ± 1.7 cm(3)/kg in the control, UC, and CD groups, respectively. The volumes differed significantly between the CD and control groups (P = .01), but not between the UC and control groups (P = .43). Furthermore, a significant strong correlation was found between the disease activity and the body weight-adjusted spleen volume in patients with CD (P < .01). The spleen volume, adjusted for the body weight, was significantly larger in patients with CD than in the controls and was also strongly correlated with the CD activity. These results suggest that the immune response in CD may affect the spleen volume.