Written and medically reviewed by: Assoc. Prof. Cengiz Dibekoğlu, MD, General SurgeryLast updated:
Anal Fissure — Lateral Internal Sphincterotomy
Lateral internal sphincterotomy divides a portion of internal sphincter to heal chronic fissures — highly effective with continence counseling.
Lateral internal sphincterotomy (LIS) remains a definitive operation for chronic anal fissure after failed medical care. A controlled division of part of the internal sphincter lowers resting pressure so the tear can heal. Success rates are high; the trade-off is a small risk of lasting minor incontinence, which must be discussed honestly — especially in patients with prior obstetric injury or loose stools.
Educational schematic. Some structures may be simplified or emphasized for clarity; not an exact anatomical depiction.
© Cengiz Dibekoğlu — illustrative; not for unauthorized use
Figure summary
This educational figure shows: LIS.
Who may be a candidate?
- Chronic fissure refractory to medical ± Botox pathways
- Patients accepting continence risk discussion
- No untreated major continence disorder or untreated Crohn’s proctitis
Possible advantages
- High healing rates for classic chronic fissures
- Usually brief day-case surgery
- Rapid pain relief for many patients
Limits & realistic expectations
- Irreversible muscle division (controlled but permanent)
- Minor incontinence risk (gas/stool seepage)
- Wrong diagnosis (Crohn’s, cancer) must be excluded
Step-by-step overview
- 1
Confirm chronic fissure
After failed medical care ± Botox; exclude Crohn’s, cancer, and undiagnosed abscess.
- 2
Continence counseling
Discuss minor gas or stool leakage risk — especially with prior obstetric injury.
- 3
Day-case planning
Controlled internal sphincter division under anesthesia; soft-stool pathway after.
- 4
Early recovery
Pain control around bowel movements; sitz baths and fiber as advised.
- 5
Follow-up
Non-healing pain or new incontinence needs prompt review.
Key points
Where LIS fits
Definitive operation for chronic fissure when soft-stool care, topical agents, and often Botox have failed. Not first-line for acute tears.
How it works
A controlled division of part of the internal sphincter lowers resting pressure so the tear can heal. Success rates are high for classic chronic fissures.
- Key note inside
Continence trade-off
Small risk of lasting minor incontinence to gas or stool must be discussed honestly — especially with prior obstetric injury or loose stools.
- Key note inside
Exclusions
Undiagnosed Crohn’s proctitis, atypical lateral tears, or active abscess need different pathways before elective sphincter division.
Recovery themes
Day-case surgery is common. Pain peaks around early bowel movements; fiber, fluids, and scheduled analgesia support healing.
- Key note inside
Important
This page is for education. It is not medical advice and does not replace a visit with your physician.
Frequently asked questions
Who is a candidate for lateral internal sphincterotomy?
Chronic fissure after failed medical care, with anatomy and continence profile discussed at consent.
How effective is LIS?
High healing rates for classic chronic posterior fissures; alternatives exist for atypical or high-risk anatomy.
What are common recovery themes?
Early walking, pain control, soft stools, and temporary activity limits — timelines vary.
What warning signs after surgery need urgent review?
Fever, worsening pain, heavy bleeding, inability to pass urine, or new major incontinence.
More chapters in this hub
Anal Fissure Symptoms
Glass-shard pain, bleeding, and when to seek care
Anal Fissure Diagnosis
Exam, acute vs chronic, and important differentials
Medical / Topical Treatment
Soft stools, sitz baths, NTG and diltiazem creams
Diet for Anal Fissure
Diet — explained for shared decision-making
Botox for Anal Fissure
Botox: what the procedure aims to do and who it fits
Appointment / info
This page is for education. It is not medical advice and does not replace a visit with your physician.
Medical editor: Assoc. Prof. Cengiz Dibekoğlu, MD · Last medically reviewed: August 2026 · English patient-education chapter.