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MRI Fistulogram Report - Analysis

Patient: Mr. Chitransh Kumar | 22-year-old Male Facility: Best Diagnostics, New Delhi (NABH Accredited) | Report date: 22 Jun 2026 Referred by: Dr. Anil Agarwal (Urologist) Clinical background: Prior fistula surgery; presents with perianal pain and pus discharge for 1 month

Study Protocol

High-resolution T1- and T2-weighted MRI of the pelvis in sagittal and axial planes, with fat-suppressed T2W axial, sagittal, and coronal images using a phased-array surface coil. This is the standard protocol for an MRI fistulogram, which is the imaging gold standard for complex or recurrent anal fistulae.

Key MRI Findings - Tract-by-Tract

1. Internal Opening

Located at 6 o'clock position, approximately 2.5 cm proximal to the anal verge - this corresponds to the dentate line level, which is the classic cryptoglandular origin.

2. Primary Tract Course

The tract has a multi-segment path:

Segment 1: Runs superiorly in the intersphincteric plane for ~2 cm at 6 o'clock
Segment 2: Pierces the external sphincter at 6 o'clock at the level of the puborectalis sling (~4.5 cm from anal verge), with a sphincter defect of ~5.5 mm
Segment 3: Travels posteriorly ~2.0 cm below the tip of the coccyx

This path - beginning intersphincteric, then traversing the external sphincter - is the defining anatomy of a transsphincteric fistula (Parks Type 2). The level at the puborectalis sling means a significant portion of the external sphincter is involved, classifying this as a high transsphincteric fistula.

3. Branching Pattern

After reaching the post-coccygeal space, the tract ramifies into multiple branches - a key feature of complex fistula disease:

Branch	Direction	Size	Status
Right paramedian caudal	Posterior, opens into intergluteal cleft (R side, 6 o'clock)	~2.0 cm long, 3.0 mm wide	Open
Right paramedian cranial	Posterior, opens into intergluteal cleft (R side, 6 o'clock)	~5.0 cm long, 5.0 mm wide	Partially fibrosed
Left paramedian	Posterior	~1.6 cm long	Blind-ending

4. Associated Pilonidal Abscess

A small pilonidal abscess (~1.5 x 1.1 cm) is present in the left paramedian intergluteal cleft at the Co1 level (coccyx level 1). Importantly, there is suspected communication between this abscess and the cranial right paramedian branch - meaning the fistula network and the pilonidal disease may be interconnected.

5. Additional Negative Findings (clinically reassuring)

No horseshoe abscess - rules out deep post-anal space involvement with bilateral ischiorectal extension
No supralevator extension - rules out the more dangerous suprasphincteric or extrasphincteric pattern
No ischiorectal fossa involvement on either side
No pelvic collection
Prostate, seminal vesicles, bony structures, and pelvic soft tissues all normal
Mild inflammatory fat stranding only (expected with active fistula)

Radiologist's Impression (Final Diagnosis)

Recurrent complex posterior transsphincteric fistula-in-ano with multiple secondary branching tracts and associated pilonidal abscess/sinus showing probable communication with the fistulous network, on a background of chronic postoperative fibrotic change.

Clinical Significance

Parks Classification - Type 2 (Transsphincteric):

This patient's fistula is Parks Type 2 (transsphincteric), which accounts for ~30% of anal fistulae. The tract traverses the external sphincter, which is what makes it a complex fistula and surgically challenging. The additional features that elevate complexity here include:

High level - at the puborectalis sling (high transsphincteric)
Multiple secondary branching tracts (3 branches)
Recurrent disease - background of prior fistula surgery
Marked peripheral fibrosis from chronic postoperative change
Associated pilonidal abscess with possible communication to the main network

Per surgical textbook guidance (Current Surgical Therapy, 14e; Sabiston Surgery), high transsphincteric fistulae are classified as complex fistulas because:

Simple fistulotomy carries a high risk of fecal incontinence (division of the puborectalis sling or upper external sphincter is not tolerated)
Recurrence rates are significantly higher than for low fistulae
Sphincter-preserving techniques are required

Surgical Management Options to Discuss with the Colorectal Surgeon

Procedure	Notes
Draining seton	First-stage or definitive; controls sepsis, maintains drainage, allows tract fibrosis
LIFT (Ligation of Intersphincteric Fistula Tract)	Sphincter-preserving; suitable for transsphincteric fistula
Mucosal/anorectal advancement flap	Closes internal opening without sphincter division
Fibrin glue / collagen plug	Adjunct options; lower success rates but sphincter-preserving
Separate treatment of pilonidal abscess	The pilonidal component (and its probable fistula communication) will need to be addressed - typically by excision or unroofing

Simple fistulotomy (lay-open) is NOT appropriate here because the fistula is high transsphincteric and division of the puborectalis sling/upper external sphincter would cause fecal incontinence.

Summary for the Patient

This MRI confirms that the fistula has recurred after prior surgery, has become more complex with multiple branches, and is now connected to a small abscess near the tailbone (pilonidal abscess). This is a challenging surgical problem that requires a colorectal surgeon experienced with complex fistulae. The scan is very well done - it has mapped out all the tracts precisely, which is essential information the surgeon will need before planning any procedure. Clinical correlation and examination under anaesthesia (EUA) will typically be the next step.

Sabiston Textbook of Surgery, p. 2163

Current Surgical Therapy 14e, p. 347

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