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LIS surgery preparation and day of

Published 13 March 2026 ·Last reviewed 13 March 2026 by the editorial team ·How we create our content

At a glance

Lateral internal sphincterotomy (LIS) is the most effective surgical treatment for chronic anal fissures. The decision to have it often comes after conservative treatments and botox have been tried. This guide covers the practical preparation, the day of surgery, and the immediate aftermath.

Before surgery

The weeks before

Once the decision for surgery is made, most surgeons recommend:

  • Starting stool softeners — three to five days before surgery. Soft stools after surgery make the first bowel movements more manageable.
  • Stocking up on supplies — sitz bath basin, soft towels, comfortable loose clothing, stool softeners, pain medication, soft foods
  • Arranging time off — most people take one to two weeks off work, though some return sooner
  • Asking questions — this is the time to clarify anything you are unsure about with your surgeon

The day before

  • Light meals
  • Continue stool softeners
  • Follow any fasting instructions from the hospital (typically nothing to eat or drink after midnight)
  • Prepare your recovery space at home
  • Try to rest, even if anxiety makes this difficult

The day of surgery

Arriving

You arrive at the hospital or day surgery unit. People describe a mix of anxiety and relief — relief that after months of conservative treatment, something definitive is happening.

Standard pre-surgery steps:

  • Check-in and paperwork
  • Meeting the anaesthetist
  • Changing into a hospital gown
  • Final questions with the surgeon

The procedure

LIS is a brief procedure:

  • You are given anaesthesia (general or regional)
  • The surgeon makes a small cut in the internal sphincter muscle
  • Some surgeons also remove any sentinel pile (skin tag) at the same time
  • The procedure takes 15 to 30 minutes
  • You wake up in recovery

Waking up

People describe waking up and feeling surprisingly okay. The area may be numb from local anaesthesia applied during the procedure. There is often gauze or a dressing in place.

Common first thoughts:

  • “That was it?”
  • “I feel fine — is it actually done?”
  • “When can I go home?”

Going home

Most people go home the same day, within a few hours of the procedure. Arrangements for someone to drive you home are essential — you cannot drive after anaesthesia.

The first 24 hours

The local anaesthetic wears off within hours. This is when the surgical discomfort becomes apparent. People describe:

  • A dull ache or throbbing in the area — different from fissure pain
  • The first bowel movement as a source of significant anxiety
  • Mild bleeding or discharge on the dressing
  • Tiredness from the anaesthesia

Self-care in the first 24 hours:

  • Take prescribed pain medication as directed
  • Sitz baths — start as soon as you are comfortable enough
  • Drink plenty of water
  • Eat soft, fibre-rich foods
  • Rest — this is not the day for activity

The first week

The first week after LIS is covered in detail in our LIS surgery recovery guide and our week-by-week recovery experience.

The headline: the first week is the hardest. It gets significantly better from there.

Common questions

How should I prepare for LIS surgery?

Preparation typically includes starting stool softeners several days before surgery, arranging time off work (usually one to two weeks), setting up a comfortable recovery space at home with sitz bath supplies, and getting all your questions answered by your surgeon. Some surgeons also recommend a light diet in the day or two before the procedure.

How long does LIS surgery take?

The procedure itself is brief — typically 15 to 30 minutes. Including preparation, anaesthesia, and recovery from sedation, you can expect to be at the hospital or clinic for several hours. Most people go home the same day.

What happens during LIS surgery?

The surgeon makes a small, controlled cut in the internal anal sphincter muscle to permanently reduce its resting pressure. This addresses the spasm that prevents fissure healing. The cut is precise and affects only a portion of the muscle. The procedure is done under general anaesthesia or regional anaesthesia.

Will I be in a lot of pain after LIS?

Pain levels vary. Many people describe the post-surgical pain as different from fissure pain — less sharp, more of a dull ache. Some people are pleasantly surprised by how manageable it is. Others find the first week quite uncomfortable. Pain typically improves significantly by week two and continues to improve from there.

When to seek care Heavy bleeding or feeling faint? Get emergency help now. Emergency: 911

Not sure how urgent it is? Get help today.

  1. Emergency

    Heavy bleeding, black tarry stools, feeling faint, severe pain or trouble breathing.

    Call 911 or go to the ER.

  2. Today

    Fever, pain getting worse, a hot swollen lump, or trouble passing urine.

    Call your doctor or go to urgent care.

  3. Soon

    Bleeding or bowel changes nobody has checked, or anything lasting 3 weeks.

    Book a doctor’s appointment.

Feeling overwhelmed? Call or text 988, any time.

See all the signs

For this topic, get medical advice if you notice:

  • Heavy or persistent bleeding that does not settle
  • Severe pain that is getting worse rather than better
  • Fever or signs of infection
  • Symptoms that have not improved after 4 to 6 weeks of self-care

Recording how you feel is not the same as being checked. These are the signs that need a doctor’s attention.

Call 911 or go to the emergency room now if you have:

  • bleeding that will not stop, a lot of blood (the toilet water turns red, or you pass large clots), or any bleeding with feeling faint or dizzy
  • fainting, a racing heart or trouble breathing
  • confusion or slurred speech, extreme shivering, no urine in a day, or blotchy skin
  • sudden severe belly pain, or a swollen, hard belly with vomiting or not passing stool or gas
  • you cannot pass urine at all, or your bladder feels full and painful and you can’t empty it
  • redness, swelling or severe pain spreading quickly around your anus, genitals or groin, especially with a fever or feeling very ill
  • a fever with a painful swelling near your anus if you have diabetes or a weakened immune system (for example, from chemotherapy or transplant medicines)
  • black, tarry stools

Call your doctor or go to urgent care today (or the ER if you can’t be seen today) if you have:

  • a temperature of 100.4°F (38°C) or higher, chills, vomiting, or feeling generally unwell
  • pain that is getting worse over days, or severe pain that stops you sitting or sleeping
  • a hot, swollen or very tender lump near your anus or at the top of the crease between your buttocks, or foul-smelling discharge
  • trouble urinating
  • bleeding that is getting heavier or more frequent, or blood mixed into your stool
  • feeling much more tired than usual, looking pale, or getting out of breath more easily than you used to
  • not passing stool for several days, or new belly pain

Make an appointment with your doctor if:

  • you have never had these symptoms checked by a doctor or nurse — whatever your age
  • you have had rectal bleeding for more than 3 weeks
  • your bowel movements have been looser, thinner or more frequent than usual for 3 weeks or more, or you have lost weight without trying
  • symptoms have not settled after a week or so, or keep coming back
  • you notice a new lump near your anus, between your buttocks or in your belly, or an itch or discharge that does not clear
  • you have new leakage or trouble controlling your bowels
  • you are 45 or over, or have a family history of bowel cancer or inflammatory bowel disease, and any of these symptoms are new for you

If you are unsure, it is always reasonable to ask. If things feel overwhelming, call or text 988 (Suicide & Crisis Lifeline) or chat at 988lifeline.org, any time. If you don’t feel safe, call 911.

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Related symptoms

BleedingPain during bowel movementsPain after bowel movementsSpasm or crampingConstipation

Discreet symptom tracking

Symptoms that come and go? Keep track, day by day.

For hemorrhoids, fissures, fistulas and other anal and rectal problems. A short, discreet email asks how things have been, and saves each answer, so you can look back at every flare and every good week in your own words. If you haven’t had your symptoms checked, see your doctor first.

  • About ten seconds a check-in. No app, no password.
  • Nothing in the subject or preview says what it’s about.
  • Each Sunday, a link to your week, ready for your next appointment.
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Related guides

Recovery after LIS surgery

What to expect during recovery from lateral internal sphincterotomy (LIS) for chronic anal fissure — pain patterns, bowel movement recovery.

Incontinence risk after LIS surgery

What the research says and what people describe about incontinence risk after lateral internal sphincterotomy

Thinking about fissure surgery

A framework for weighing surgical options for a chronic fissure — the questions to ask, the factors to consider.

Related experiences

LIS surgery: decision and recovery

A composite account of what people experience when deciding on lateral internal sphincterotomy and the recovery journey that follows.

LIS surgery recovery week by week

A week-by-week look at what people experience during recovery from lateral internal sphincterotomy — the physical changes, the milestones.

LIS surgery: the full journey

The full emotional arc of lateral internal sphincterotomy — from failed conservative treatment through the decision, the NHS wait, the day itself.

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