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Lateral internal sphincterotomy is an operation performed on the anal sphincter to treat chronic anal fissures. Chronic anal fissures occur because spasm of the internal anal sphincter muscle reduces the blood flow into the edges of the anal wound. Lateral internal sphincterotomy involves division of a few millimeters of the internal anal sphincter. This reduces the anal pressure and allows better blood flow to the fissure, which promotes better healing. The operation is usually reserved for patients who have not responded to non-surgical treatments of their fissure. There is a small risk of complications including impairment of continence.

Pain Relief

Local anaesthetic has been used to provide pain relief today but this will wear off over the next few hours. You should not experience severe pain after a sphincterotomy. If required you should use Panadol 1 gram every six hours and Ibupfrofen 400 milligrams every eight hours for the next 48 hours. You should check with your doctor that it is appropriate for you to take Ibupfrofen. If you require stronger pain relief Endone 5 milligram may be used but this will require a prescription. You must not drive or work while using this medication.


Wounds around the anus cannot be stitched closed because of the risk of infection. As a result you may have an open wound, which will have been dressed in the operating theatre.  This dressing can be removed on the evening of your surgery. Unless otherwise instructed, the wound requires no dressing, and you should wear a pad inside your underwear to absorb any fluid leaking from the wound. These secretions can irritate the skin around the anus. This can be prevented by using a barrier cream like Bepanthen or Vaseline.

Bowel Movements

Your bowels will continue to work normally after your surgery. It is best to avoid becoming constipated, as hard motions will increase you level of discomfort. Normafibe, one teaspoon twice daily may be used for the first week after surgery. It is normal to experience pain with bowel movements for the first week or so after surgery. You may see blood on the toilet paper or in then bowl with the first few bowel motions.

Salt Baths

Warm baths are very soothing when you are in pain. A handful of cooking salt may be added to the bathwater in order to help keep the wound clean.

Things to watch out for

If you experience high fevers, large volume bleeding, difficulty passing urine or increasing pain, you should notify your doctor as soon as practicable.

Resuming normal activities

 You should be able to resume normal activities within a few days of surgery.

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