Do the appearances on the CT make ischaemic colitis more or less likely?
Much less likely: the whole colon and terminal ileum are involved which would require involvement of the superior and inferior mesenteric arteries.
In the setting of recent antibiotic use, what is the most likely diagnosis?
Pseudomembranous colitis (C. difficile).
Performed with oral, intravenous and rectal contrast. Extensive submucosal oedema affecting the entire large bowel, as well as a few centimetres of terminal ileum. The remainder of the small bowel is normal in appearance, as is the appendix. There is a moderate amount of free fluid in the pelvis, anterior to the uterus. No pneumoperitoneum.
Mildly enlarged mesenteric lymph nodes are prominent, but presumably reactive.
The liver, spleen, pancreas, kidneys, gallbladder, adrenals and bladder are unremarkable. The visualised lung bases are clear. The uterus and ovaries have a normal appearance.