At a glance
Lateral internal sphincterotomy (LIS) is the most commonly performed surgical procedure for chronic anal fissures. It has a high success rate and is generally a brief, day-case procedure. Understanding exactly what happens can help reduce pre-surgery anxiety.
This guide walks through the procedure step by step — from arrival at the hospital to going home.
Before the day
Pre-operative assessment
Most people have a pre-operative assessment in the days or weeks before surgery:
- Blood tests
- Medical history review
- Discussion of anaesthetic options
- Instructions about fasting (typically from midnight the night before)
- Confirmation of the procedure and consent
The night before
People describe a mix of anxiety and anticipation. Practical preparation:
- Following fasting instructions
- Packing a bag — loose clothing, sanitary pads, any prescribed medication
- Arranging transport home (you cannot drive after a general anaesthetic)
- Setting an alarm if the arrival time is early
On the day
Arrival and preparation
- Check in at the hospital or day surgery unit
- Change into a hospital gown
- Meet the anaesthetist, who will discuss the anaesthetic plan
- Meet the surgeon (or their team) who will confirm the procedure
- Final questions and consent
- Walk to the operating theatre or be wheeled on a bed
Anaesthetic options
General anaesthetic:
- You are fully asleep
- The most common approach for LIS
- You will not be aware of or feel anything
Spinal anaesthetic:
- An injection that numbs the lower half of the body
- You remain awake but cannot feel anything below the waist
- Some people prefer this to avoid general anaesthetic
Local anaesthetic with sedation:
- The area is numbed with local anaesthetic injections
- Sedation makes you relaxed and drowsy
- Less commonly used for LIS
Your anaesthetist will recommend the most appropriate option for your situation.
The procedure itself
LIS typically takes 10 to 20 minutes. Here is what happens:
- Positioning: You are positioned on the operating table — typically in the lithotomy position (on your back with legs supported) or the lateral (side-lying) position
- Examination: The surgeon examines the anal area under anaesthetic to assess the fissure and the sphincter
- The cut: The surgeon makes a small incision in the lateral (side) portion of the internal anal sphincter muscle. This is typically done through a small cut in the skin at the anal margin
- Partial division: Only the lower portion of the internal sphincter is cut — this is a controlled, partial division, not a complete transection of the muscle
- Assessment: The surgeon assesses that the sphincter has been adequately divided
- Additional procedures: If appropriate, the surgeon may also perform a fissurectomy (removing the chronic fissure tissue and any sentinel pile) at the same time
- Wound: The surgical site is left open or lightly dressed. It is not typically stitched
Open vs closed technique
Open LIS: A small cut is made in the skin, and the surgeon can see the sphincter muscle directly while dividing it. This is the more common approach.
Closed LIS: The surgeon inserts a small blade through a tiny wound and divides the sphincter without a larger incision. This is less common but has a similar success rate.
Your surgeon will use whichever technique they are most experienced with.
Immediately after
In recovery
- You wake up in the recovery area (or, if you had a spinal, the numbness gradually wears off)
- Nurses monitor your vital signs
- Pain medication is provided as needed
- You rest until the anaesthetic effects have subsided
Before going home
- You need to be able to walk safely
- You need to pass urine (urinary retention can occasionally occur after pelvic surgery)
- You will receive written post-operative instructions
- Pain medication will be prescribed or recommended
- A follow-up appointment will be arranged
The ride home
- Someone else must drive or accompany you
- People describe feeling groggy, slightly tender, and relieved that it is done
- Having a cushion in the car is commonly recommended
What the wound looks like
People describe the surgical site as:
- A small cut at the anal margin — usually less than a centimetre
- Some bruising around the area
- Mild swelling
- Light bleeding or blood-tinged discharge on the first dressing
The wound is intentionally left open to heal from the bottom up. This is normal surgical practice for this area and reduces the risk of infection.
The first 24 hours at home
- Rest is the priority
- Pain medication as prescribed — stay ahead of the pain rather than waiting until it is severe
- Light fluids and food as tolerated
- A sitz bath if comfortable
- Pads or gauze for light bleeding and discharge
- Avoiding strenuous activity
Most people describe the first evening and night as a quiet recovery period — the anticipation was harder than the reality.
When to contact your surgical team
Seek medical attention if you experience after surgery:
- Heavy bleeding that is soaking through pads
- Severe pain that is not controlled by prescribed medication
- Fever or chills
- Difficulty passing urine
- Any symptoms that concern you