What could be causing a foul, inner rectal smell in a patient with a history of anal fistula, who recently underwent a fistulotomy and has no keyhole deformity?

Post-Fistulotomy Rectal Odor Without Keyhole Deformity

The new rectal odor you're experiencing after fistulotomy is most likely due to incomplete wound healing with premature surface closure trapping residual fistula tract tissue, or minor sphincter dysfunction causing microscopic fecal soiling that wasn't present before the procedure.

Understanding the Anatomical Changes

Fistulotomy permanently converts a tubular fistula tract into an open groove in the anal canal by dividing sphincter muscle and overlying tissue, fundamentally altering the three-dimensional architecture of your anal canal 1. This creates a permanent anatomical defect that must heal from the inside out 2. The procedure changes the normal contour and seal of the anal canal, even without visible keyhole deformity 1.

Most Likely Causes of the Odor

Incomplete Healing with Trapped Debris

• Premature surface closure is the primary concern - if the wound surface heals before the deeper tract fully closes, this creates a pocket where fecal material and bacteria can accumulate, producing the characteristic rectal smell you're noticing 2
• The healing process requires the wound to granulate from the base upward; any deviation from this pattern traps material in residual tract spaces 2

Subclinical Sphincter Dysfunction

• Fistulotomy carries a 10-20% baseline risk of continence disturbances, which can manifest as microscopic soiling rather than frank incontinence 2, 3
• Even without keyhole deformity, the altered anal canal architecture may allow small amounts of rectal contents or mucus to seep into the healing groove, creating odor 1, 3
• Post-defecation soiling occurs in approximately 11.6% of patients after fistulotomy procedures, often presenting as odor rather than visible staining 4

Residual Fistula Tract Activity

• Recurrence or persistence occurs in 16-28% of fistulotomy cases, and early signs may include drainage or odor before visible symptoms develop 3, 5
• The smell similar to enema contents suggests communication with the rectal lumen, either through incomplete tract closure or microscopic fistula persistence 6

Immediate Evaluation Steps

Clinical Assessment Required

• Digital rectal examination is essential to assess for fluctuance, induration, or tenderness suggesting abscess formation or incomplete healing 6
• Examine the fistulotomy wound for premature surface bridging while the base remains unhealed 2
• Look for any drainage, even if minimal, as this indicates ongoing tract activity 6

Warning Signs Requiring Urgent Evaluation

• Fever or systemic symptoms indicating spreading infection warrant immediate assessment 2
• Increasing pain, swelling, or purulent drainage suggests abscess recurrence requiring drainage 6
• Progressive incontinence symptoms beyond minor soiling require sphincter evaluation 3

Management Algorithm

If Wound Appears Healed Superficially

• Gentle probing by an experienced colorectal surgeon may reveal premature surface closure with persistent deeper tract 6
• Breaking down superficial bridging and maintaining open drainage allows proper inside-out healing 2
• Avoid aggressive probing as this causes iatrogenic complications 6

If Minor Soiling is the Cause

• Meticulous perianal hygiene with gentle cleansing after each bowel movement can minimize odor 4
• Barrier creams or protective pads may help manage microscopic leakage 4
• This often improves over 3-6 months as the wound fully matures and anal canal adapts to the new anatomy 3, 4

If Recurrent Fistula is Suspected

• MRI or endoscopic ultrasound can identify persistent or recurrent tracts not evident on physical examination 2
• If confirmed, loose non-cutting seton placement is recommended rather than repeat fistulotomy, as repeat sphincter division carries catastrophic incontinence risk 7, 2
• Seton drainage alone achieves definitive closure in 13.6-100% of cases without additional sphincter damage 7, 2

Critical Pitfalls to Avoid

• Do not assume the odor is "normal" post-operative healing - it warrants evaluation to rule out the causes above 2
• Avoid aggressive dilation or probing by inexperienced providers, as this causes permanent sphincter injury 7
• Do not accept repeat fistulotomy if recurrence is found - your prior fistulotomy makes repeat sphincterotomy "catastrophically dangerous" for continence 7, 1
• Do not delay evaluation if the odor persists beyond 6-8 weeks or worsens, as early intervention prevents complications 2, 3

Expected Timeline

• Most fistulotomy wounds heal completely within 8 weeks (median), though range is 4-16 weeks 5
• Minor soiling and odor often improve gradually over 3-6 months as tissue remodeling occurs 3, 4
• Persistent symptoms beyond 3 months warrant repeat imaging to exclude recurrent fistula 3, 5