Effectiveness of Magnetic Resonance Imaging and Ultrasound Examination in Visualizing Anal Fistulas

Introduction. Chronic paraproctitis is one of the most common proctological diseases with prevalence equal 8 - 23 cases per 100,000 population. Ultrasound examination (US) and magnetic resonance imaging (MRI) allow studying in detail the fistula topography, presence or absence of purulent leaks and cavities in the perirectal space and fistula relations to the closure apparatus of the rectum. The relevance of choosing an effective option to diagnose rectal fistulas is associated with the potential preoperative determination of the optimal surgical treatment option.

The aim of the study was to evaluate the effectiveness of magnetic resonance imaging and ultrasound in the visualization of anal fistulas of cryptoglandular origin.

Materials and methods. The study included 88 (100%) patients with anal fistulas of cryptoglandular origin treated in the proctology department of the Surgut District Clinical Hospital in 2023. The authors analysed results of patients’ examinations. Both general clinical and instrumental investigations were involved: collection of complaints and anamnesis of the disease, inspection and palpation of the perianal area, digital anorectal examination, probing of the fistula tract, dye test, anoscopy, rectoscopy or videocolonoscopy, ultrasound examination of the pelvis and magnetic resonance imaging of the perineum. All patients in the analysed group were found to have complex anal fistulas: cases of transsphincteric fistulas involving more than 30% of the sphincter and cases of extrasphincteric fistulas. Magnetic resonance imaging of the perineum and ultrasound examination of the pelvis were performed to visualise the fistulas. All patients were divided into two groups; the first group included 76 (86.4%) patients who underwent MRI of the perineum, the second group included 12 (13.6%) patients who underwent ultrasound examination of the pelvis. The data obtained during ultrasound and MRI examinations were compared with the intraoperative findings. Statistical analysis was performed using the StatTech v. 3.1.8 program (developer OOO Stattech, Russia) based on the created database in Microsoft Excel software with the determined sensitivity and accuracy of each diagnostic option.

Results. The topography of the fistula passage, indicating localization of the internal fistula opening, was determined in 76 (86.4%) patients during MRI and in 12 (13.6%) patients during pelvic ultrasound examination. During surgical intervention, the discrepancy between the MRI data and the topography of the fistula was revealed in 2 (2.3%) cases, according to ultrasound data - in 3 (3.4%).

Conclusions. The analysis demonstrated 100% sensitivity of magnetic resonance imaging and ultrasound examination in diagnosing anal fistulas, with an MRI accuracy equal 97.4%, ultrasound accuracy equal 75.1%, respectively.