Learning objectives
Describe the Radiological Anatomy of the perineal region.
Review the indications as well as the Protocol of the MRI of the perineum.
Analysis of the MRI semiology of anoperineal fistulas.
Understand the Parks Classification fistula-in-ano.
Establish a step-by-step guide for exhaustive interpretation of the perineal MRI
Background
Perianal Fistula consists in an inflammatory condition that creates abnormal connections between the anal canal and the perineal skin.
Anoperineal complications such as fistulae and abscesses are particularly frequent in patients with Crohn’s disease. The prevalence of perianal fistula in these patients ranges between 13% and 38%. It reaches 92% in case of colonic involvement.
1/Radiologic anatomy of the perineal region:
* Perineum anatomy (Fig1):[Fig 1] The perineum is the anatomical region below the pelvic floor. It is divided by an imaginary line passing through...
Findings and procedure details
1ST Step: Locate inner Opening
The inner opening is the origin of the fistula. It corresponds to the closest point of the fistulous path to the lumen of the anal canal.
Axial T2 sequences help to locate it in anal clock (Fig 6), (Fig 7). [Fig 6] [Fig 7]
Coronal T2 sequences are used to locate it beyond or above the pelvic floor.
2nd Step: Assess the path of perianal fistula
According to the track pattern of the fistula, it is possible to distinguish:
1/...
Conclusion
Ano-perineal Crohn's disease represents a very important pathology due to its frequency and socio-economic burden. Sectional imaging, in particular MRI, plays a major role in lesion characterization and surgical planning.
Mastering the radio-anatomy of the ano-perineal region as well as the PARKS classification is fundamental for the interpretation of anoperineal fistula MRIs.
In addition to detailed cartography, MRI helps to specify the sub or supra Levator nature of the perianal fistula, to search for associated collections, and to assess activity, hence the important impact in...
Personal information and conflict of interest
A. Halouani:
Nothing to disclose
M. Jrad:
Nothing to disclose
W. Ben Hammouda:
Nothing to disclose
R. Gheribi:
Nothing to disclose
A. Ben Miled:
Nothing to disclose
M. Bouzrara:
Nothing to disclose
References
Parks AG, Gordon PH, Hardcastle JD. A classification of fistula-in-ano. Br J Surg. janv 1976;63(1):1‑12.
Hussain SM, Stoker J, Schouten WR, Hop WC, Laméris JS. Fistula in ano: endoanal sonography versus endoanal MR imaging in classification. Radiology. 1996;200(2):475–481.
Moreau J. Fistules anales: épidémiologie, étiologie, diagnostic et présentation clinique, imagerie. Côlon & Rectum. 2019;13(2):72–75.
Zeitoun J-D, Fathallah N, de Parades V. Horseshoe extension of anal fistula. Colon Rectum. 1 août 2012;6(3):171‑4.
Barthet M, Juhan V, Gasmi M, Grimaud J-C. Imagerie des lésions anopérinéales de la maladie...