Presentation
Abdominal pain and rectal bleeding.
Patient Data
There is pronounced submucosal oedema with wall thickening involving the splenic flexure through distal descending colon. Mild associated pericolonic inflammation. The remainder of the large and small bowel appear relatively normal. Abdominal vasculature appears patent.
Case Discussion
There are many practicing radiologists who dictate nearly every case of colitis as "nonspecific colitis, which could be due to infection, inflammation, or ischaemia".
While it is certainly appropriate to provide a complete differential diagnosis, there are certain patterns of colitis which greatly favour ischaemia over infectious/inflammatory aetiologies, as in this case.
It is appropriate to strongly suspect ischaemic colitis when the following are present:
segmental colonic involvement (uncommon for infectious colitis)
involvement of the right or left colon, with either shaggy/oedematous appearance or without significant pericolonic thickening
sudden onset of abdominal pain in an at-risk (elderly comorbid) patient
Ischaemic colitis can be classified as nonocclusive (most common) or occlusive. Given the patent vasculature, nonocclusive ischaemic colitis is favoured, which is most commonly due to a low flow state resulting in transient ischaemia, often due to other medical conditions such as heart disease, hypotensive episodes, surgery, myocardial infarction, arrhythmias, vasculitis, and colonic obstruction.
A decrease in blood flow of 20% of the normal flow in the setting of small vessel disease can result in ischaemia, followed by reperfusion injury. Commonly affected segments are the watershed areas at the splenic flexure (junction of SMA and IMA), and rectosigmoid junction (junction of the IMA and hypogastric vascular supply). The pattern of colitis in this case follows the IMA distribution.