An anal fissure is a tear in the anal canal causing great pain during and after bowel movement. The formation of an anal fissure starts from an episode of severe constipation. Hard stools rub against the anal canal during defecation, resulting in a tear of the tissue.

The tear then causes internal anal sphincter muscle spasm, which makes defecation harder and more force and effort is needed, further tearing the tissue. This leads to a vicious cycle that makes recovery of the tissue difficult.

Symptoms of Anal Fissure
  • Pain after defecation
  • Blood on paper after cleaning
Causes of Anal Fissure
  • Constipation
  • Severe Diarrhoea
Anal Fissures
Treatment Options
for Anal Fissure
Topical Ointment (Nitrates)

The application of nitrates helps to relax the anal sphincter and relieve the pain during defecation. However, it can cause significant headaches in some patients.


This is a simple out-patient procedure that involves the injection of botulium toxin (BOTOX) into the anal sphincter helps to relax the anus and allow healing of the anal fissure. The effect of BOTOX injection is almost immediate and patient can experience relief of pain very soon after the procedure.


This colorectal surgery involves the cutting of the lowest fibre of internal anal sphincter to permanently relax the anal sphincter the level of the fissure. This is one the most effect procedure to relieve pain and muscle spasm in very long-standing anal fissure.

Dr Ng Kheng Hong
Dr Ng Kheng Hong
Senior Consultant Colorectal & General Surgeon
MBBS (S’pore), MMed (Surgery), FRCS (Edinburgh),
FAMS (General Surgery)
Dr Ng Kheng Hong has over 20 years of experience treating anal fissures through a wide variety of methods, both surgical and non-surgical. A former Director of Minimally Invasive Surgery at the Department of Colorectal Surgery at SGH and former Visiting Consultant in Surgical Oncology at the National Cancer Centre, Dr Ng is deeply committed to his work. Dr Ng is also well-published in medical journals and continues to teach medical students to this day.
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