The Value Of MRI T2WI-FS And CE-T1WI-FS 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 resonanceimaging sequences in determining the type of periperianal abscess and anal fistulaespecially the axial，coronal and sagittal enhanced MRI T1Wl-FS, and guide radiologydoctors to choose the best scan sequence, and provide reliable image information toclinical.Methods:41patients with surgically proved periperianal abscess and anal fistula underwentpreoperative MR examination and enhanced MRI scan with Gd-DTPA simultaneously.Thefollowing sequences were obtained： AX-T1WI； AX-T2WI-FS， COR-T2WI-FS，AX-T2WI， COR-T2WI，and Sag-T2WI， CE-AX-TIWI-FS，CE-COR-TIWI-FS，CE-Sag-TlWI-FS.The value of MRI with eight different sequences in the diagnosis ofvarious types of periperianal abscesses.Anal fistulas and their internal openings wasstatistically analyzed according to surgical results.SPSS15.0software package was used toperform x2test，and there was statistically significant(P<0.05).Results：41patients were found to have32periperianal abscesses.11inter-sphincterabscesses.14ischiorectal abscesses.5pelvirectal abscesses.2rectal abscesses.There were26anal fistula.11inter-sphincter fistulas.10transsphincteric fistulas.5suprasphinctericfistulas.There were42internal openings.All the MR sequences，except Sagittal planessequences，had the highest accuracy of Ischiorectal abscesses(100%).The AX-T2WI-FSand CE-AX-T1WI-FS sequences had the highest accuracy of inter-sphincter abscesses andlower anal fistulas(100%).The COR-T2WI-FS and CE-COR-T1WI-FS sequences had thehighest accuracy of pelvirectal abscesses and high anal fistulas(100%).The CE-Ax-T1WI-FS sequences and the highest accuracy of all internal openings (95.24%).The CE-COR-TlWI-FS sequences had the hightest accuracy of internal openings(81.25%)，located at6and12o’clock.The numbers of internal openings were compared with thesurgical results and Kruskai-Wallis Test revealed no significant differences(P=0.311，P=0.07).The Sag-T2WI-FS and CE-Sag-T1WI-FS sequences had the lowest accuracy ofperiperianal abscesses.Fistulas and Internal opening.Compared with the surgicalresults.There were statistically significant differences.CE-AX-T1WI-FS combined withCE-COR-T1WI-FS sequences had higher accuracy of periperianal abscesses and fistulasthan AX-T2WI combined with COR-T2WI sequences and AX-T2WI-FS combined withCOR-T2WI-FS sequences.but there were no statistically significant differences.However，the internal openings were shown better in the anterior group than in the two lattergroups.There were statistically differences(P=0.002、P=0.04).Conclusion:Ideal MRI sequences for periperianal abscess and anal fistula are axial and coronalcombination sequences，especially CE-AX-T1WI-FS combined with CE-COR-T1WI-FSsequences.They can improve the accuracy of periperianal abscess，anal fistula and internalopening，which is sufficient to make an assessment before deciding the surgicalprocedure.