MR Imaging Classification of Perianal Fistulas and Its Implications for Patient Management

Abstract

Until recently, imaging had a limited role in the preoperative assessment of perianal fistulas. Magnetic resonance (MR) imaging has been shown to demonstrate accurately the anatomy of the perianal region. In addition to showing the anal sphincter mechanism, MR imaging clearly shows the relationship of fistulas to the pelvic diaphragm (levator plate) and the ischiorectal fossae. This relationship has important implications for surgical management and outcome and has been classified into five MR imaging-based grades. If the ischioanal and ischiorectal fossae are unaffected, disease is likely confined to the sphincter complex (simple intersphincteric fistulization, grade 1 or 2), and outcome following simple surgical management is favorable. Involvement of the ischioanal or ischiorectal fossa by a fistulous track or abscess indicates complex disease related to trans-sphincteric or suprasphincteric disease (grade 3 or 4). Correspondingly more complex surgery may be required that may threaten continence or may require colostomy to allow healing. If the track traverses the levator plate, a translevator fistula (grade 5) is present, and a source of pelvic sepsis should be sought.

MRI of Crohn?s Anoperineal Disease

“…The objectives in performing and interpreting any imaging study for perianal fistulas are simple [28]:…”

“…At present, two classifications are most commonly used: a classification proposed by Parks in 1976, which was created for surgical use [29], and the St James University Hospital classification, which was developed based on a MRI examination [28,30] (Tables 1 and 2 …”

“…Also, fat containing 'grafts' may be placed to fill cavities and resection voids in restorative surgery. These hyperintense structures are readily identified on unenhanced T1-weighted sequences and can be distinguished from active disease, which appears hyperintense only after enhancement with gadolinium [28]. …”

“…They are very useful in previously operated cases, especially when there is concern about residual disease activity or abscess formation within postoperative and healing inflammatory tissue [28].…”

Perianal fistülün tanısında, sınıflandırılmasında ve değerlendirilmesinde Manyetik Rezonans Görüntüleme’nin önemi

“…Anal kanal ve perine derisi arasında meydana gelen anormal bağlantı perianal fistül olarak adlandırılmaktadır [1]. Nadir görülür ancak ciddi bir morbidite nedenidir.…”