Both examinations will be performed ideally on the same day or a maximum of 7 days apart. The order of the two tests will be directed according to scan appointment availability. The WSCE will take place at St Marks Hospital London. Due to the MRI capacity at LNWH trust the MRI-Enema will take place at Number 9 Harley Street, London. A service level agreement will be in place for the scans to occur, and St Marks Seedcorn funding has already been awarded to fund the MRI scans. The patients will be asked to fill in a survey to assess their experience immediately after each test in each location.
MRI-Enema:
A 16Fr Foley catheter is introduced per-anus with the patient in a left lateral decubitus position on the MRI scanner table. If the anastomosis was low (within 5 cm of anorectal junction) the catheter will be taped to the skin to maintain its position. In the event of a mid-rectal or upper rectal anastomosis (\>5 cm from anorectal junction), the catheter balloon may be filled with 2-5mls of water and withdrawn to a location at the top of the anal sphincter complex. In both instances, after catheter insertion the patient is then re-positioned to a supine body position.
The MRI protocol used is detailed below. In summary, T2 and T1 (with fat suppression) sequences are obtained prior to filling the lumen with contrast to assess the presence of any pre-sacral and peri-anastomotic fluid, to identify the presence of haematoma and to ensure the catheter is appropriately sited with the catheter tip above the anal canal and close to the anastomosis, ideally within 3cm.
The enema comprises a mixture of normal saline (400mls) and contrast agent (Gadovist, 4mls) to produce a 1% contrast solution which part fills a standard contrast enema bag and delivery system. The bag is attached to a fixed hook located 100cm above the scanner table height, such that fluid will deliver from the bag via the catheter according to gravity.
Dynamic MRI sequences are then performed with the delivery tube open to maximise flow of contrast into the residual rectum/neo-rectum or ileo-anal pouch.
Following the dynamic sequences, further axial and coronal images are acquired in order to identify the presence of leaked fluid within the pelvis.
After all images have been acquired, the enema bag is then placed on the floor to allow drainage of enema solution back into bag prior to removal of catheter.
MRI Protocol:
Pre Enema T2 sagittal Pre Enema T2 sagittal Fat-sat Pre Enema T2 axial SFOV Pre Enema T1 axial Filling Phase Dynamic sagittal Post Enema 3D volumetric T1 sagittal SFOV Post Enema T2 axial fat sat Post Enema T2 coronal fat sat
WSCE:
The WSCE is undertaken according to standard practice. As with the MRI, a 16Fr Foley catheter is introduced per anus with the patient in the left lateral decubitus position. Having affixed the catheter in place according to the height of the anastomosis above the anorectal junction as described above, water-soluble contrast (Gastrografin) is introduced via an enema delivery bag system as described above.
Radiographic images are then acquired with the patient in the supine and lateral decubitus positions as required in order to delineate the anastomosis and any related leak of contrast. The bag is then placed on the floor to allow drainage of fluid and the catheter removed.
Patients will be asked to complete a questionnaire immediately following both examinations. Questions will be targeted to evaluate anxiety, comfort, embarrassment and confidence in the test's outcome.
Reference standard = Consensus of both tests (WSCE and MRI-Enema) with agreement between two radiologists and in agreement with referring consultant /clinical assessment including findings at clinical examination where applicable.
