Is quantitative diffusion-weighted MRI a reliable method in the assessment of the inflammatory activity in ulcerative colitis?

We investigated the relationship between the apparent diffusion coefficient (ADC) values of the colonic wall and the pathologic pericolonic lymph nodes (PCLNs) and inflammatory activity in ulcerative colitis patients by diffusion-weighted magnetic resonance imaging (DW-MRI). A total of 28 ulcerative colitis patients (9 endoscopically active, 10 subacute and 9 in remission) were evaluated by DW-MRI with 0, 500 and 1000 s/mm² b-values. The ADC values of the rectum and sigmoid colon walls and the adjacent PCLNs were obtained for quantitative analysis. The DW-MRI findings were compared to the disease activity. The ADC values of the sigmoid colon were similar in patients with active, subacute and remissive ulcerative colitis (P = 0.472). The ADC values of the rectum were different (P = 0.009) between patients in the active (1.08 ± 0.14×10⁻³ mm²/s) and subacute phases (1.13 ± 0.23×10⁻³ mm²/s) of disease and those in remission (1.29 ± 0.17×10⁻³ mm²/s). The ADC values of the PCLNs (P = 0.899) did not differ with respect to disease activity. DW-MRI is useful in identifying disease activity in ulcerative colitis patients, especially with respect to the rectum. The ADC values of the rectum increase during remission and decrease in patients with active distal colitis. The ADC values of the PCLNs were not useful in determining disease activity.