Detection rates, sensitivity, and specificity of multislice spiral computed tomography, 1.5T and 3.0T magnetic resonance imaging in anal fistula diagnosis

Abstract

BACKGROUND

Anal fistula is a common acquired anorectal disorder characterized by an abnormal epithelialized tract connecting the anal canal or rectum to the perianal skin, typically secondary to perianal abscesses, Crohn’s disease, trauma, or infection. Clinically, it presents with recurrent perianal pain, swelling, purulent discharge, and skin irritation, which severely impair patients’ quality of life and may lead to complications such as complex fistula formation, anal incontinence, or even pelvic sepsis if misdiagnosed or inadequately managed.

AIM

To comparing the diagnostic value of multislice spiral computed tomography (MSCT), 1.5T magnetic resonance imaging (MRI), and 3.0T MRI for anal fistula.

METHODS

A retrospective analysis was conducted on 119 patients with anal fistula admitted to Nanjing Hospital of Chinese Medicine between May 2017 and December 2023 and categorized into three groups based on diagnostic modality: MSCT group (n = 25), 1.5T MRI group (n = 45), and 3.0T MRI group (n = 49). Kappa tests were applied to assess diagnostic agreement between each group and surgical findings (gold standard). Diagnostic accuracy, sensitivity, specificity, positive and negative predictive values, and Youden indices for detecting internal openings, main tracts, and abscesses were calculated and compared.

RESULTS

Using surgical findings as the reference standard, 3.0T MRI demonstrated significantly higher internal opening and primary fistula tract detection rate (94.54% and 96.43%, respectively) than 1.5T MRI and MSCT (P < 0.05). The diagnostic accuracy of 3.0T MRI for internal openings and primary tracts reached 96.25% and 97.50%, respectively, with excellent agreement with surgical findings (Kappa = 0.911-0.926). In addition, 3.0T MRI showed superior sensitivity, specificity, positive and negative predictive values, and Yorden index in diagnosing internal openings, fistula tracts, and abscesses than MSCT and 1.5T MRI (P < 0.05).

CONCLUSION

Compared with MSCT and 1.5T MRI, 3.0T MRI demonstrated higher diagnostic accuracy, sensitivity, and specificity for anal fistula, exhibiting superior diagnostic performance.

Keywords: Anal fistula; Multislice spiral computed tomography; Magnetic resonance imaging; Diagnosis; Anorectal disease

Core Tip: This study compared diagnostic efficacy of multislice spiral computed tomography, 1.5T magnetic resonance imaging (MRI), and 3.0T MRI for anal fistula in 119 patients. With surgery as gold standard, 3.0T MRI showed significantly higher detection rates, accuracy, sensitivity, specificity, and consistency with surgery for internal openings/main tracts than multislice spiral computed tomography and 1.5T MRI, proving its superior diagnostic value.