Causes of pancolitis include ulcerative colitis, pseudomembranous colitis, and other infective colitides.
Despite the apparently severe findings on CT, endoscopy revealed only mild inflammation with no signs of ulcerative colitis or Crohn's disease. Stool cultures were negative, as were assays for Clostridioides difficile toxin. An uneventful recovery ensued and no firm diagnosis was reached but it was assumed that this was an infective colitis.
Nonetheless, the abdominal x-ray shows the classic sign of colon wall edema - thumbprinting.