Role Of Magnetic Resonance Imaging In Evaluation Of Perianal Fistulas

Abstract

Perianal fistula is an abnormal perianal tract that connects two epithelialized surfaces, usually perianal skin to the anal canal. There is an incidence of 10 per 10,00,000, being commoner in men. It commonly originates from anal gland infections, it can arise as complications of malignancy, trauma, radiation therapy and inflammatory conditions such as Crohn's disease, ulcerative colitis, tuberculosis, diverticulitis and HIV. This study attempted to evaluate the clinical and Magnetic resonance imaging characteristics of fistula in Ano and correlate these with the intraoperative findings to determine the usefulness of clinical examination and MRI in the management of perianal fistulae. Our study comprised of 30 subjects with clinical and MRI diagnosis of perianal fistulae confirmed on surgical exploration under general anesthesia. The sensitivity of MRI was 100% against 26.9% of DRE in the detection of internal opening. The detection rate for associated horseshoeing for DRE was 50%, the results of MRI were more significant with specificity and sensitivity of 100%. 7 of the 30 patients had been found having secondary extensions on time of surgery. DRE was able to detect 3/7 (42.8%), whereas MR imaging could identify 5/7 (71.4%). Specificity of DRE and MRI in detection of second, tracts was 95.6% with negative predictive value of 81.5%  and  91.67% respectively. MR imaging aided the surgical management such as preoperative evaluation of anatomical location of internal opening, secondary extensions, horseshoeing, abscess which are extremely significant from the perspective of surgical approach, management and outcomes such as low recurrence rate.