If I undergo a lateral internal sphincterotomy (LIS) for a chronic anal fissure, will it reduce internal sphincter tone and affect my anal sexual arousal or cause incontinence?

Lateral Internal Sphincterotomy Does Not Eliminate Anal Sexual Arousal

Lateral internal sphincterotomy (LIS) reduces pathologic internal anal sphincter hypertonia that causes fissure pain, but it does not eliminate the normal resting tone or sensory capacity required for sexual arousal; altered sensations after LIS typically reflect pelvic floor muscle tension and protective guarding patterns that persist after surgery, not permanent loss of sphincter function. 1

Understanding What LIS Actually Changes

Physiologic Effect of the Procedure

• LIS divides only a portion of the internal anal sphincter (typically to the level of the dentate line or fissure apex) to reduce the pathologic hypertonia and ischemia that perpetuate chronic fissures 2, 3
• The procedure achieves healing rates exceeding 95% by interrupting the pain-spasm-ischemia cycle, not by eliminating all sphincter tone 2, 4
• The internal sphincter retains substantial resting tone after LIS—the surgery corrects excessive spasm, it does not create a flaccid sphincter 2

What Remains Intact After Surgery

• Normal continence is preserved in 90–96% of patients, confirming that functional sphincter integrity persists after LIS 5, 6, 3
• The external anal sphincter (which provides voluntary squeeze pressure and contributes to arousal sensations) is never divided during LIS 2
• Sensory nerve endings in the anoderm and perianal skin remain completely intact 1

The Real Source of Altered Sensations

Pelvic Floor Dysfunction, Not Sphincter Loss

• Patients reporting altered sensations after LIS typically have intact continence and preserved sphincter integrity—the problem stems from pelvic floor muscle tension that commonly develops after anorectal surgery 1
• Protective guarding patterns that developed during the painful fissure period persist even after the fissure heals, creating dysesthesia and hypersensitivity 1
• The external anal sphincter may remain in spasm through protective guarding, contributing to ongoing symptoms independent of the internal sphincter division 1

Underrecognized Sensory Complications

• Sensory complications after LIS are often underrecognized in the surgical literature, which focuses primarily on incontinence rates (wound-related complications occur in up to 3% of patients) 1
• Hypersensitivity of contact receptors and overreaction of the anal-external sphincter continence reflex may contribute to persistent symptoms 1

Evidence-Based Treatment for Post-LIS Sensory Changes

Pelvic Floor Physical Therapy Protocol

• Initiate pelvic floor physical therapy 2–3 times weekly with internal and external myofascial release, gradual desensitization exercises, muscle coordination retraining, and warm sitz baths 1
• Internal pelvic floor therapy is essential because external techniques alone cannot adequately address internal anal sphincter dysfunction and impaired rectal sensory feedback 1
• Biofeedback therapy specifically targets rectal sensation, tolerance of rectal distention, and coordination of the internal sphincter, which necessitates internal assessment and treatment 1

Adjunctive Pharmacologic Management

• Topical lidocaine 5% ointment can be applied to affected areas for neuropathic pain control 1
• The dysesthesia and altered sensations typically improve significantly over 6–12 months with appropriate pelvic floor therapy and neuropathic pain management 1

Critical Pitfalls to Avoid

Do Not Pursue Further Surgery

• Do not pursue additional surgical interventions, as this would likely worsen the neuropathic component rather than improve it 1
• Avoid manual anal dilatation entirely, as it carries a 30% temporary and 10% permanent incontinence rate 1

Recognize the Difference Between Incontinence and Dysesthesia

• Minor permanent continence defects (typically flatus incontinence) occur in approximately 1–10% of patients after LIS, but this is distinct from sensory changes 2
• Troublesome fecal incontinence after LIS is uncommon (4–6.5% temporary, 2–4% persistent) and occurs primarily in women with prior obstetric trauma 6, 3
• If you have normal continence (no involuntary loss of gas, liquid, or stool), your sphincter function is preserved—altered arousal sensations reflect pelvic floor tension, not sphincter loss 1

Alternative for Future Patients

Botulinum Toxin as Sphincter-Sparing Option

• Botulinum toxin injection represents a safer alternative to LIS, achieving 75–95% cure rates with no risk of permanent incontinence or sexual dysfunction 2, 1, 4
• This option should be considered for patients concerned about any alteration in sphincter function 1

Expected Timeline and Prognosis

• Sensory normalization typically requires 6–12 months of pelvic floor therapy 1
• The vast majority of patients regain normal sensation as protective muscle guarding resolves 1
• Sexual arousal capacity is not eliminated by LIS—the procedure reduces pathologic spasm while preserving the anatomic structures and innervation required for normal sensation 1

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