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Diffusion-weighted MR imaging for the diagnosis of abscess complicating fistula-in-ano: preliminary experience
Anthony Dohan1, Clarisse Eveno, Raluca Oprea
1Department of Body and Interventional Imaging, Hôpital Lariboisière, Assistance Publique-Hôpitaux de Paris, 2 rue Ambroise Paré, 75475, Paris Cedex 10, France, anthony.dohan@lrb.aphp.fr.
Objective:
To investigate the role of diffusion-weighted magnetic resonance imaging (DWMRI) in the diagnosis of abscess-complicating fistula-in-ano.
Methods:
This retrospective study was approved by our Institutional Review Board and informed consent was waived. MRI examinations, including fat-suppressed T2-weighted turbo spin-echo (T2-TSE) MRI and DWMRI, of 24 patients with a fistula-in-ano, were reviewed by two independent readers for the presence and number of visible fistulas, conspicuity and apparent diffusion coefficient (ADC) measurement of suspected fistula tracks and pelvic collections. The reference standard was surgical with follow-up findings.
Results:
Sensitivity was 91.2 % [95 % CI: 76 %-98 %] for T2-weighted TSE MRI and 100 % [95 % CI: 90 %-100 %] for DWMRI detecting fistulas. ADC values were lower in abscesses than in inflammatory masses (P = 0.714.10(-6)). The area under the ROC curve was 0.971 and the optimal cut-off ADC value was 1.186 × 10(-3) mm(2)/s, yielding a sensitivity of 100 % [95 % CI: 77 %-100 %], a specificity of 90 % [95 % CI: 66 %-100 %], a positive predictive value of 93 % [95 % CI: 82.8 %-100 %] and a negative predictive value of 90 % [95 % CI: 78 %-100 %] for an abscess diagnosis. Fistula conspicuity was greater with DWMRI than with T2-TSE MRI for the two observers (P = 0.0034 and P = 0.0007).
Conclusion:
DWMRI shows high sensitivity and specificity for the diagnosis of perianal abscesses and helps discriminate between an abscess and inflammatory mass. Conspicuity of fistulas-in-ano is greater with DWMRI than with T2-weighted TSE MRI.
Key Points:
• DWMRI can differentiate between pelvic abscess and inflammatory mass. • DWMRI helps avoid gadolinium-chelate administration in patients with a suspected fistula-in-ano. • DWMRI provides high degrees of conspicuity for fistula-in-ano. • Conspicuity of fistulas is better with DWMRI imaging than with T2-TSE-weighted MRI.
Insights
Diffusion-weighted magnetic resonance imaging (DWMRI) offers superior detection of perianal abscesses and fistulas compared to traditional MRI. This advanced technique enhances diagnostic accuracy and can potentially eliminate the need for contrast agents.
Area of Science:
- Radiology
- Medical Imaging
- Gastroenterology
Background:
- Fistula-in-ano is a complex anorectal condition requiring accurate diagnosis.
- Differentiating between perianal abscesses and inflammatory masses is crucial for effective treatment.
- Conventional MRI techniques may have limitations in visualizing fistula tracts and abscesses.
Purpose of the Study:
- To evaluate the diagnostic efficacy of diffusion-weighted magnetic resonance imaging (DWMRI) in identifying abscesses complicating fistula-in-ano.
- To compare the conspicuity of fistula tracts and pelvic collections using DWMRI versus standard T2-weighted imaging.
- To assess the ability of DWMRI to distinguish between abscesses and inflammatory masses.
Main Methods:
- Retrospective analysis of MRI examinations (T2-weighted TSE and DWMRI) in 24 patients with fistula-in-ano.
- Two independent readers assessed fistula presence, conspicuity, and measured apparent diffusion coefficient (ADC) values of collections.
- Surgical findings and follow-up served as the reference standard.
Main Results:
- DWMRI demonstrated 100% sensitivity in detecting fistulas, outperforming T2-weighted TSE MRI (91.2%).
- Lower ADC values were observed in abscesses compared to inflammatory masses (P < 0.0001).
- DWMRI provided superior conspicuity of fistula tracts for both readers (P < 0.005).
Conclusions:
- DWMRI is a highly sensitive and specific tool for diagnosing perianal abscesses.
- DWMRI effectively differentiates pelvic abscesses from inflammatory masses, potentially avoiding gadolinium administration.
- Enhanced visualization of fistula-in-ano with DWMRI improves diagnostic confidence.
