Preoperative Evaluation of Fistula-in-Ano

Abstract

Introduction: A fistula is defined as a pathologic tract connecting two hollow organs, or one hollow organ and the skin. Fistula in Ano is a benign condition but may cause considerable distress to the patient and difficulty for surgeons. Fistula in Ano effects approximately ten individuals in 100,000, with male predominance, higher abundance of anal glands is thought to be  the  partial reason. The infected gland leads to fistula formation after some time, which starts as an abscess. There are, of course, other causes including chronic ulcerative colitis, Crohn's disease, tuberculosis, carcinoma of the rectum or anal canal, benign rectal strictures, foreign bodies or diverticulitis.

Objective: To determine the sensitivity of MRI in pre-operative evaluation of fistula in Ano.

Study Design: Cross-sectional.

Setting: Radiology department Jinnah Post Graduate Medical Center, Karachi.

Subjects and methods: A total of 30 patients from Radiology department with symptomatic fistula in ano referred for MRI pelvis and were meeting inclusion criteria were included in the study conducted during four months periods (from 25^th August to 20^th December 2013).

Informed consent was taken for MRI pelvis. The MRI pelvis was performed (fig1) on 1.5 Tesla scanner the findings were confirmed by consultant radiologist having >5 years of post-fellowship experience. The data were entered and analysed in to SPSS (version 21). Descriptive statistics were calculated for the characteristics of age of the patients.

Results:

Out of 30 patients, 24 (80 %) cases had inter sphincteric primary tract, (Figure 2) and 6 (20%) patients had trans sphinteric (Figure 3 and 4) primary tract. Primary tracts were correctly identified in all patients, in 25 out of 30 patients internal opening were identified while remaining 5 patients showed diffuse trans mural signal abnormality and in 27 patients (80%) external opening were correctly identified. 18(60%) had low fistula in Ano, 8 (26%) had high anal fistula and in 2 (6%) patients low rectal fistula was identified. 2 patients had complex fistula.

Conclusion:

MRI was well correlated with the post-surgical findings regarding the primary tract, extension and their relationship with anal sphincter complex.