What are some causes of colovesical fistula?
Diverticulitis : most common ~60%, colorectal cancer (CRC) : ~20%, Crohn's disease : ~10%, radiotherapy, appendicitis, and trauma
What is the commonest site for colovesical fistula to occur in bladder
In most cases the fistula occurs though the dome of the bladder (~60%). The posterior wall (~30%) and trigone (~10%) are less frequent sites.
The proximal sigmoid colon diffusely thickened and with serosal stranding, an appearance typical of chronic diverticulitis.
There is a focal perforation, which abuts the bladder forming a thick serosal/mural reaction encompassing a 2.4 cm cavity.
This presumably communicates via a tiny punctum with the bladder cavity, as a tiny gas locule is present, but no rectal contrast has passed through.
Although unlikely, it is impossible to exclude a coexisting tumour within this segment.
The process does not involve the adjacent left ovary but there is minor thickening of the left broad ligament.
The ovaries and uterus are otherwise unremarkable.
Rest of bowel is unremarkable.
The liver, gallbladder, pancreas, spleen, adrenal glands and kidneys are unremarkable.
In particular, the left ureter is not involved in this inflammatory process.
CONCLUSION
8 cm long segment of an inflamed proximal sigmoid colon (likely diverticular disease), with focal perforation onto the anterolateral wall of the adjacent bladder, forming a chronic fistula with a cavity that measures 2.4 cm in size.