Assessment of anal fistulas with high-resolution subtraction MR-fistulography: comparison with surgical findings.
OBJECTIVE
To investigate a new MR-imaging protocol defined as subtraction MR-fistulography for the detection of fistula-in-ano.


METHODS
A total of 36 patients (18 men, 18 women) with the clinical diagnosis of anal fistula or abscess who were scheduled for surgical exploration were preoperatively imaged at 1.5 T in the supine position; coronal STIR sequences and axial T1-weighted three-dimensional FLASH sequences before and after intravenous injection of gadobenate dimeglumine (Gd-BOPTA) were obtained. Image subtraction was routinely used. The image findings were compared with the findings at surgical exploration according to a uniform classification system.


RESULTS
A total of 46 fistulas were seen on subtraction MR-fistulography, whereas surgery described 41 fistulas. MRI and surgery concordantly depicted a total number of 40 fistulas, six fistulas were only described by MRI, and one fistula was only seen during surgery. A total of 27 abscesses were detected with MRI, compared to 22 during surgery. A total of 22 abscesses were concordantly diagnosed. Complete agreement between subtraction MR-fistulography and surgery occurred in 32 (89%) of the 36 patients. The four patients in whom both procedures disagreed had complex anal sepsis with multiple fistulas and/or abscesses due to Crohn disease.


CONCLUSIONS
High-resolution subtraction MR-fistulography is an important complement to surgical exploration and especially suitable for investigating complex anal sepsis.
Schaefer
Oliver
O
Department of Radiology, University Hospital of Freiburg, Freiburg, Germany. schaefer@mrsl.ukl.uni-freiburg.de
Lohrmann
Christian
C
Langer
Mathias
M
D000293:Adolescent; D000328:Adult; D000368:Aged; D003287:Contrast Media; D003424:Crohn Disease / Q000150:complications / Q000601:surgery; D005260:Female; D005401:Fissure in Ano / Q000145:classification / Q000175:diagnosis* / Q000209:etiology / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008536:Meglumine / Q000031:analogs & derivatives*; D008875:Middle Aged; D009942:Organometallic Compounds; D013382:Subtraction Technique
D003287:Contrast Media; D009942:Organometallic Compounds; C064572:gadobenic acid; D008536:Meglumine