If you have an anal fissure and your surgeon has advised Lateral Internal Sphincterotomy (LIS), there’s a high chance one fear is holding you back: “Doctor, will I lose control of my motions after LIS?”
Let’s address this clearly, honestly, and scientifically. Without scaring you and without sugar‑coating.
What exactly is LIS?
Lateral Internal Sphincterotomy is a small surgical procedure where a part of the internal anal sphincter muscle is divided to reduce spasm, improve blood flow, and allow the fissure to heal.
- Internal sphincter: Involuntary muscle (you don’t control it consciously).
- External sphincter: Voluntary muscle (you consciously tighten it to hold stool).
LIS targets only the internal sphincter.
Does LIS cause incontinence?
From medical literature and my own surgical experience:
- LIS does NOT cause incontinence when the external sphincter muscle is intact.
- The overall risk of troublesome incontinence in expert hands is usually reported as <1% in most studies.
- Even when minor issues occur, they are usually:
- Transient difficulty controlling gas, or
- Occasional leakage of liquid stool,
- Almost never loss of control over formed stool,
- And in most cases, reversible over time.
When does the risk increase?
The risk of incontinence is higher if there is pre‑existing damage to the external sphincter, such as:
- Complicated normal vaginal delivery (forceps, vacuum, deep perineal tears, etc.)
- Previous anal surgery or trauma involving the external sphincter
Important:
Sphincter injury does NOT happen with C‑section. It is associated only with complicated normal delivery, not caesarean section.
If your external sphincter is healthy, your baseline risk is already very low.
Why “right plane” and expertise matter
The external sphincter lies very close to the internal sphincter.
During LIS:
- The surgeon aims to divide only the internal sphincter.
- If the cut goes too lateral (too far out), there is a risk of injuring the external sphincter.
- This is where experience and precision make all the difference.
So:
- Done in the correct plane
- By an experienced proctologist
- On a patient with an intact external sphincter
The risk of meaningful incontinence is very low, typically less than 1%.
What is the “worst-case” side effect?
Even in the worst-case scenario (from both literature and real‑world practice):
- The problem is usually mild, transient incontinence to gas
- Sometimes, occasional leakage of liquid stool
- Almost never to formed stool
- And in many cases, it improves or resolves with time, pelvic floor training, and lifestyle measures
This is very different from the dramatic “I will lose all control” fear that many young patients imagine.
So, should you be scared of LIS?
You should be informed, not scared.
- LIS is a safe, time-tested, highly effective procedure for chronic anal fissure.
- When:
- Patient selection is correct
- External sphincter integrity is assessed
- The procedure is done in the right plane by an expert
The benefit (pain relief, healing, quality of life) far outweighs the very small risk of incontinence.
My message to patients
If you’re working, social, and worried. Your fear is understandable.
But don’t let fear of incontinence keep you in constant fissure pain for months or years.
- Get your sphincter status properly evaluated (especially if you’ve had a complicated vaginal delivery).
- Discuss risks honestly with your surgeon.
- Choose a trained surgeon who routinely performs LIS.
Conclusion:
In expert hands, with an intact external sphincter, LIS almost never causes significant incontinence, and the risk is generally less than 1%.