Application Of Various Magnetic Resonance Imaging Sequences In Determining The Type Of Perianal Abscess And Anal Fistula

Objective:The aim of our study was to assess the application value of various magnetic resonance imaging sequences in determining the type of perianal abscess and anal fistula, especially the axial, coronal and sagittal enhanced MRI T1WI with fat suppression.Material and methods:63 patients with surgically proved perianal abscess and anal fistula underwent preoperative MR examination, in which,20 cases underwent enhanced MRI scan with Gd-DTPA simultaneously. The following sequences were obtained:axial T1WI(AX-T1WI); axial and coronal T2WI with FS (AX-T2-FS.COR-T2-FS), axial T2WI(AX-T2WI), coronal T2WI (COR-T2WI), and sagittal T2WI (SAG-T2WI), contrast enhanced axial, coronal and sagittal T1WI images with FS(CE-AX-T1-FS, CE-COR-T1-FS. CE-SAG-T1-FS). The value of MRI with eight different sequences in the diagnosis of various types of perianal abscesses, anal fistulas and their internal openings was statistically analyzed according to surgical results. SPSS 12.0 software package was used to performχ2 test, and there was statistically significant (P<0.05).Results:63 patients were found to have 52 perianal abscesses.18 inter-sphincter abscesses,23 ischiorectal abscesses.8 pelvirectal abscesses.3rectal abscesses. There were 40 perianal fistulas.16 inter-sphincter fistulas,15 transsphincteric fistulas.8 suprasphincteric fistulas,1 extrasphincteric fistula. There were 64 internal openings. All the MR sequences, except sagittal planes sequences, had the highest accuracy of ischiorectal abscesses (100%). The AX-T2-FS and CE-AX-T1-FS sequences had the highest accuracy of inter-sphincter abscesses and lower anal fistulas (100%).The COR-T2-FS and CE-COR-T1-FS sequences had the highest accuracy of pelvirectal abscesses and high anal fistulas (100%). The CE-AX-T1-FS sequences nad the highest accuracy of all internal openings (95.65%). The CE-COR-T1-FS sequences had the highes:accuracy of imerna opening(?) (82.35%) located at six and twelve clock. The numbers of internal openings were compared witn the surgical results and Kruskai-Wallis Test revealed no significant differences (P= 0.312, P= 0.07;. Tne SAG-T2-FS ana CE-SAG-T1-FS sequences had the lowest accuracy of perianal abscesses, fistulas and internal openings. Compared with the surgical results, there were statisticaly significant differences. CE-AX-T1-FS combined with CE-COR-T1-FS sequences nac higher accuracy of perianal abscesses and fistulas than AX-T2WI combined with COR-T2WI sequences and AX-T2-FS combined with COR-T2-FS sequences, but there were no statistically significant differences. However. the internal openings were shown better in the anterior group than in the two latter groups, there were statistically differences (P=0.002,P=0.04).Conclusion:Ideal MRI sequences for perianal abscess and anal fistula are axial and coronal combination sequences, especially CE-AX-T1-FS combined with CE-COR-T1-FS sequences. They can improve the accuracy of perianal abscess, anal fistula and internal opening, which is sufficient to make an assessment before deciding the surgical procedure.