Magnetic Resonance Fistulography of Perianal Fistulae Using Percutaneous Aqueous Jelly

Abstract

Background: The preferred modality for imaging fistula-in-ano currently is Magnetic Resonance Fistulography (MRI) with intravenous Gadolinium. Recently there has been a newfound interest in the depiction of fistulous tracts without administering intravenous Gadolinium; this involves percutaneous instillation of aqueous jelly prior to MR fistulography into the fistulous tract in an attempt to augment the diagnostic potential of MRfistulography.

Aim: To study the role of percutaneous instillation of aqueous jelly into the fistulous tracts prior to MR fistulography in the exact delineation of primary and secondary tracts.

STUDY DESIGN: A type of prospective study was done commencing from July 2017 for the next two years.

PARTICIPANTS: Patients with fistula-in-ano who had active perianal discharge and referred for MR fistulography.

Method: A slow hand injection of approximately 3–5 ml of aqueous jelly was instilled per external opening followed by MR fistulography.

Results: Of the total, forty patients thirty-two patients were males (80%) , and eight were females (20%) with mean age of 40.6 years. The inter-sphincteric type was the commonest type (45%) , the most common site/location being 4-6 o’clock position (61.5%) , abscesses were identified in seven (17.5%) ; simple abscess (42.85%) , horseshoe abscess (42.85%) and abscess in ischiorectal fossa (14.28%) . A significant correlation was seen with operative findings with regards to the site and number of internal openings with a sensitivity of 97%, specificity, and PPV of 100%, NPV of 80%, and accuracy of 98%.

CONCLUSION: Prior instillation of aqueous jelly in MR fistulography provides accurate delineation of the complex anatomy of fistulae, thereby helps avert the use of intravenous contrast and avoiding its associated sequelae.

IMPLICATIONS: MR fistulography with instillation of aqueous jelly is safe, economical, and non-inferior to gadolinium-enhanced MR fistulography in the study of perianal fistulas.