MAGNETIC RESONANCE IMAGING;

THE BEST IMAGING TECHNIQUE IN DETECTION OF PERIANAL FISTULAS WITH DIAGNOSTIC ACCURACY

Abstract

Perianal fistula is defined as an abnormal communication channel between anal
canal and perianal skin. Among all the imaging tools Magnetic resonance imaging (MRI) is
of choice in the diagnosis and management of perianal fistulas. Objectives: “To determine
the diagnostic accuracy of MR imaging in detection of perianal fistulas and comparing it with
per operative findings”. Peroperative findings are taken as gold standard. Place and Duration
of Study: This study was carried out in Diagnostic Radiology, Pakistan Institute of Medical
Sciences (P.I.M.S) Islamabad, over a period of nine months from 01-02-2012 to 31-10-2012. For
this collaboration was made with the Department of General Surgery P.I.M.S and Department
of gynecology (MCH center) PIMS and gastroenterology Department. Patients and Methods:
A total of 95 patients were included in study having perianal fistulas on clinical examination.
MRI was performed in the patients and T1-weighted fast spin echo (T1W FSE) images were
taken before and after gadolinium injection. Fat suppressed T2-weighted fast spin echo (T2W
FSE) images were obtained in all three planes including transverse, sagittal and coronal. All
the scans were viewed by a single consultant radiologist to avoid observer bias. Results: Out
of 95, 81 patients (85.3%) were male and 14 (14.7%) were female. Sensitivity, specificity and
accuracy of magnetic resonance imaging (MRI) was 96.2%, 75.0% and 92.6%, respectively.
Positive predictive value was 95.0% and negative predictive value was 80.0%. Conclusion: our
study proves that among imaging modalities MRI is of choice for preoperative assessment of
perianal fistulas. It provides highly accurate, noninvasive and relatively very less time consuming
means of performing pre-operative evaluation, specially the complex, branching fistulas. This
diagnostic accuracy not only helps in surgical cure but avoids recurrence and post-operative
complications like fecal incontinence