Diverticulum near rectal anastomosis mimicking leak (MRI enema)
Presentation
History of anterior resection. Previous water soluble contrast enema showed possible posterior anastomotic leak.
Patient Data
Water soluble contrast enema
Small posterior focal rounded collection of contrast and gas near level of anastomosis, no change in size or dissipation with delayed imaging. Rounded nature and lack of dissipation suggest that this may be a small diverticulum rather than a persistent leak.
Standard and volume T2 acquisitions after introduction of 150 ml of sterile ultrasound gel per anally.
Gel is seen to enter a small posterior outpouching at the level of the anastomosis, with linear low signal scar tissue extending from this structure/focus to the presacral fascia. No free fluid in this region. Low signal well-defined wall around periphery of the structure/focus.
Findings suggest no ongoing leak, but rather a small diverticulum.
Case Discussion
The additional information provided by an MRI enema study over and above a fluoroscopic water soluble contrast enema is the status of the pelvic soft tissues, inflammatory changes, collections/abscesses, and leaks from anastomoses. In this case, the combination of the lack of presacral inflammation and configuration of the outpouching suggested that the finding on the water soluble contrast enema is due to a diverticulum rather than an ongoing leak. A differential is a healed but contained small leak.