Role of MRI Fistulography with Gadopentate Enhancement in Assessment of Complex Anal Fistulas and Improving Surgical Outcomes

Mahmoud Abdelnaby

doi:10.11648/j.js.20170502.13

Abstract

Preoperative assessment of complex fistula-in-ano (FIA) is crucial for decision making. Magnetic resonance imaging (MRI) has been used for assessment of perianal sepsis with various protocols and methods. The aim of the present study was to assess the concordance between MRI fistulography with gadopentate enhancement and the intraoperative surgical findings, and to study the impact of preoperative assessment with MRI on surgical outcomes including fistula recurrence and fecal incontinence (FI). Patients with complex and high FIA who were investigated by MRI fistulography preoperatively were reviewed. The concordance between the findings of MRI and the intraoperative findings on examination under anesthesia (EUA) was made using Kappa coefficient test. The accuracy and sensitivity of MRI were calculated regrading detection of the internal opening, primary and secondary fistula tracts. 95 patients (82% males) were included in the study. MRI fistulography had an accuracy of 89.4%, 96.8%, 96.8%, 98%, and 98% in detection of the internal opening, number of tracts, position of primary tract, secondary extensions, and presence of abscess cavities, respectively. Overall, there was very good concordance between MRI and EUA regarding the examined parameters (k= 0.847, 0.937, 0.908, 0.953, 0.957), respectively. Fistula recurrence and minor FI were recorded in 4.2% and 14.7% of patients. MRI fistulography is an effective diagnostic modality for the preoperative assessment of FIA. MRI had excellent accuracy and sensitivity in detection of the internal opening, primary tract, and secondary extensions of anal fistula with very good concordance with the intraoperative findings.

Highlights

Fistula-in-ano (FIA) is a common anorectal disorder with an estimated prevalence of around 1 in 10,000 individuals [1]
Seventy-two (75.7%) patients presented with primary anal fistula and 23 (24.3%) patients presented with recurrent FIA after previous surgery
The external opening of the anal fistula was anterior to the transverse anal line in 32 (33.7%) patients, posterior in 35 (36.8%) patients, lateral in 18 (19%) patients, whereas 10 (10.5%) patients had multiple external openings

Summary

Introduction

Fistula-in-ano (FIA) is a common anorectal disorder with an estimated prevalence of around 1 in 10,000 individuals [1]. FIA is defined as an abnormal communication between the epithelialized surface of the anal canal and perianal skin. While the standard assessment of patients with anal fistulas is examination under anesthesia (EUA) [2], preoperative imaging is usually warranted to define the site and full extent of the disease. Fistulography, endorectal ultrasonography (ERUS), and magnetic resonance imaging (MRI) have been used to establish the relation between the fistula tract and the anal sphincters and other related structures. Inadequate assessment of FIA may result in converting simple fistulas into a more complex entity. Failure to appreciate complex ramifications of FIA can result in recurrent sepsis [3, 4]. Missing secondary tract extensions at surgery is usually the principal cause of recurrence, adequate surgery is mandatory in more extensive disease [5]

Objectives

Results

Conclusion