Is the patient's difficulty focusing on rectal sensations during sexual arousal after a low‑grade fistulotomy due to loss of resting anal canal pressure from reduced internal anal sphincter tone rather than persistent static pain?

Loss of Internal Anal Sphincter Tone After Fistulotomy Is the Primary Mechanism

Your difficulty focusing on rectal sensations during arousal after fistulotomy is most likely due to loss of resting anal canal pressure from reduced internal anal sphincter (IAS) tone, not persistent static pain. The IAS generates approximately 70–85% of resting anal tone, and even a low-grade fistulotomy can reduce this baseline pressure, diminishing the proprioceptive feedback you previously relied upon for arousal 1.

Physiologic Basis for Pressure Loss

• The internal anal sphincter is responsible for the majority of resting anal canal pressure, maintaining baseline tone that provides continuous proprioceptive input 1, 2.
• Normal resting anal pressure averages approximately 73 ± 27 cm H₂O; any surgical division of the IAS—even partial—reduces this baseline tone 1.
• In patients with impaired IAS function, resting pressures drop significantly (as low as 70.7 ± 3.2 mm Hg in one cohort), while maximum squeeze pressures (generated by the external anal sphincter) remain preserved 3.
• This pattern matches your experience: you can still generate voluntary contraction (external sphincter function intact), but the constant background tone you used to focus on has diminished 3.

Why Pressure Loss Affects Arousal-Related Sensation

• Rectal and anal sensation during arousal depends on mechanoreceptors (Meissner's corpuscles, Golgi-Mazzoni bodies, pacinian corpuscles) that respond to pressure, tension, and friction 4.
• Vaginal distension during intercourse normally triggers the "vagino-anorectal reflex," which increases IAS tone and rectal wall relaxation to prevent leakage; this reflex provides heightened proprioceptive feedback that many individuals incorporate into arousal 5.
• When baseline IAS tone is reduced post-operatively, the absolute change in pressure during arousal is smaller, making it harder to consciously perceive and focus on these sensations 5, 6.
• Continuous rectal distension (analogous to sustained arousal-related pelvic engorgement) normally maintains anal resting pressure through increased IAS activity, but this compensatory mechanism is blunted when the sphincter has been surgically weakened 6.

Why Static Pain Is Less Likely the Cause

• Persistent pain after uncomplicated fistulotomy typically resolves within 2–4 weeks as the surgical wound heals 1.
• Pain would interfere with your ability to achieve arousal altogether, rather than selectively impairing your capacity to focus on rectal sensations while arousal itself remains intact 1.
• The pattern you describe—preserved arousal but diminished rectal proprioception—is consistent with a sensory threshold issue (reduced baseline pressure) rather than a pain-mediated distraction 2, 3.

Clinical Correlation and Prognosis

• Studies of anoreceptive intercourse demonstrate that individuals with chronically lower resting anal pressures (but intact sphincter structure) do not report fecal incontinence, indicating that moderate IAS tone reduction is functionally tolerable for continence but may still alter sensory perception 3.
• Your sphincter likely retains structural integrity (no defect on examination would be expected after a low-grade fistulotomy), but the functional reduction in resting tone has shifted your sensory baseline 3.
• Over 6–12 months, some adaptive increase in residual IAS tone may occur, potentially improving your ability to perceive rectal sensations, though full restoration to pre-operative levels is unlikely 1, 3.

Practical Management Considerations

• Pelvic floor physical therapy can enhance proprioceptive awareness by training you to consciously recruit the external anal sphincter and puborectalis during arousal, partially compensating for reduced IAS tone 2.
• Techniques that increase intra-rectal pressure (e.g., Valsalva maneuver, rectal distension with a device) may amplify the remaining proprioceptive signal, making it easier to focus on 6.
• Avoid any further sphincter-weakening procedures (e.g., repeat fistulotomy, lateral internal sphincterotomy for unrelated fissure) that would further reduce resting tone 1.

Key Pitfall to Avoid

• Do not assume this is a psychological issue or that "you need to relax more"; the physiologic basis is a measurable reduction in resting anal canal pressure that directly affects mechanoreceptor input 1, 3.