Application of magnetic resonance imaging in the diagnosis of deep anorectal abscess

Abstract

Objective To evaluate magnetic resonance imaging (MRI) in the diagnosis of deep anorectal abscess. Methods Twenty-one patients who were suspected of having deep anorectal abscess were admitted to the Affiliated Hospital of Nanjing University of Chinese Medicine from January 2006 to December 2007, and their clinical data were retrospectively analyzed. Phased-array coil MRI was applied to all patients before the operation. We compared the efficacy of MRI and rectal digital examination in the classification of deep anorectal abscess and the diagnosis rate of internal opening according to the postoperative results. All data were analyzed using the chi-square test. Results Nineteen patients were diagnosed with deep anorectal abscess, one patient had presacral cyst combined with infection and one patient had perianal mucinous adenocarcinoma. A total of 25 lesions were identified, including 14 ischiorectal abscesses, five pelvirectal abscesses, and six high intersphincteric abscesses. Thirteen patients had single space abscesses and six had multiple space abscesses. There were no significant differences in the diagnosis rate between MRI (12/19) and rectal digital examination for internal opening (13/19) (χ2 =0. 116, P>0.05). The accuracy rate was significantly different between MRI (25/25) and rectal digital examination (16/25) in the classification of deep anorectal abscess (χ2 = 10.970, P <0.05). Operative exploration revealed that there were 13 patients with single space abscesses and six with multiple space abscesses. The accuracy rate was significantly different between MRI (19/19) and the rectal digital examination (13/19) for detecting multiple space abscesses (χ2 =7. 125, P <0. 05). Conclusions MRI with a phased-array coil can accurately detect the extent of deep anorectal abscess and its relationship with anorectal sphincters. MRI examination is helpful in excluding potential lesions in the anorectal region. Key words: Magnetic resonance imaging; Diagnosis; Anorectal abscess