Well that would seem to indicate inflammation or infection. The high WBC.
What do you normally take for inflammation (or in the past)? My fallback has always been pred and a course of antibiotics in the early years and more recently pred and Imuran which get's on top of inflammation quite fast. Maybe you could discuss either of these with your GI.
My GI and family doctor tested (and still does) test me monthly for all this during the last year and a bit on WOO/Tyme and Imuran but I have always had perfect blood test results. The Thyme I take is a little different though as it contains less than 2% thymol - maybe that has something to do with it.
Antibiotics however ALWAYS helped me with Crohn's-Colitis... and fast. If they worked in the past for you, maybe they will work now.
On a side note: At 3:30 pm today Rehill Biofarma is giving an update on their Phase three triple antibiotic trial:
ir.redhillbio.com/events.cfm Click on the June 3 2015 link if interested.