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MR imaging classification of perianal fistulas and its implications for patient management
J Morris1, J A Spencer, N S Ambrose
1Departments of Clinical Radiology, St James's University Hospital, Beckett St, Leeds LS9 7TF, England.
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.
Insights
Magnetic resonance imaging (MRI) accurately maps perianal fistulas, guiding surgical treatment. A 5-grade system based on MRI findings predicts surgical complexity and outcomes, aiding in preserving continence.
Area of Science:
- Radiology
- Gastroenterology
- Colorectal Surgery
Background:
- Preoperative assessment of perianal fistulas traditionally had limited imaging roles.
- Magnetic resonance (MR) imaging offers detailed visualization of the perianal anatomy.
Purpose of the Study:
- To evaluate the role of MR imaging in preoperative assessment of perianal fistulas.
- To introduce a classification system for perianal fistulas based on MR imaging findings.
Main Methods:
- Utilized MR imaging to delineate fistula anatomy, including relationship to the anal sphincter mechanism, pelvic diaphragm (levator plate), and ischiorectal fossae.
- Classified fistulas into five grades based on MR imaging features.
Main Results:
- MR imaging accurately demonstrates fistula anatomy and its relationship to surrounding structures.
- A five-grade classification system correlates with disease complexity and surgical management.
- Grade 1-2 fistulas confined to the sphincter complex have favorable outcomes with simple surgery.
- Grade 3-4 fistulas involving ischioanal/ischiorectal fossae indicate complex disease requiring potentially complex surgery.
- Grade 5 translevator fistulas necessitate seeking pelvic sepsis sources.
Conclusions:
- MR imaging is crucial for accurate preoperative assessment of perianal fistulas.
- The MR imaging-based grading system aids in predicting surgical complexity and potential impact on continence.
- This classification facilitates tailored surgical approaches for improved patient outcomes.