Anal canal fistula assessment (MRI)
MR of the pelvis can demonstrate hidden areas of pelvic infection and secondary extensions which are important to detect prior to the sugary to minimize high rate of recurrence post intervention. Also pelvic MRI assists to delineate the anatomic relationships of the fistula to sphincters which can be used to predict the likelihood of postoperative fecal incontinence.
Several protocols exist for assessment of various pelvic pathology. One method adopted for the assessment of anal canal fistula assessment is:
- fine 3 mm slices
- axial and coronal T2 FS or STIR
- axial and coronal T2 are helpful in delineation of sphincter anatomy
- axial and coronal T1 FS with gadolinium-based intravenous contrast material
- axial T1
Some authors recommend 1
- short-inversion-time inversion recovery (STIR)
- gradient-echo T1-weighted with or without gadolinium-based intravenous contrast material
- spin-echo T1-weighted
- spin-echo T2-weighted with saline instillation (MR fistulography)
A novel method is the use of volume MRI sequences (more routinely used in neuro and musculoskeletal MRI). The benefits are reduced imaging times and isotropic data allowing multiplanar reformatting, while maintaining comparable contrast resolution.
- 1. Morris J, Spencer JA, Ambrose NS. MR imaging classification of perianal fistulas and its implications for patient management. Radiographics. 20 (3): 623-35. Radiographics (full text) - Pubmed citation
- 2. de Miguel Criado J, del Salto LG, Rivas PF et-al. MR imaging evaluation of perianal fistulas: spectrum of imaging features. Radiographics. 2012;32 (1): 175-94. doi:10.1148/rg.321115040 - Pubmed citation