Findings-The sigmoid shows diverticula and is attached to the dome of the bladder.
-A fistulous tract is seen filled with air and contrast between the sigmoid and the bladder.
-There is air and colonic contrast within the bladder lumen.
Discussion
A fistula between the bladder and colon may occur due to a number of diseases, most notably colon cancer, bladder cancer, Crohn’s disease, and diverticulitis. CT stages diverticulitis from Stage 0 through Stage IV depending on surrounding involvement and severity. Stage 0 shows only minor local colonic wall involvement and may be treated conservatively with antibiotics. The other stages usually necessitate surgical intervention. Stages I and II show contiguous spread of inflammation outside of the colon. Stages III and IV show peritoneal involvement with distant abscesses, ascites, through to frank peritonitis.
http://eradiology.bidmc.harvard.edu/Classics/item.aspx?section=Emergency+Radiology&labelpk=33f0adab-853f-4010-a0e2-0756b3f1eac5&pk=672446a7-0e2b-4311-bc2d-792861e6a34e
