What are Possible Causes of Anal Fistula?
- You have had an anal abscess before (most common!)
- You have Crohn’s disease or diverticulitis
- You have had anal surgery or injury before
- You have had radiation therapy for rectal cancer
- You have certain sexually transmitted infections
How is an Anal Fistula Diagnosed?
Physical Examination
During the examination, your doctor will carefully review your medical history and symptoms to determine the primary cause of the anal fistula. Your doctor will then look for a fistula opening around the anus. They may also gently press on the area to determine how sore it is and if there is any drainage.
Fistula Probe
Here, a long and thin probe is inserted into the anal fistula from its external opening. This gives the doctor a clear view of the fistula tract and evaluates the length and severity of the condition. In some cases, a special contrasting dye may be injected to identify the site where the fistula opens up.
Anoscope
An anoscope is a specialised scope that is inserted into the anal canal for clear visualisation of the anal walls and rectum. By inserting this device, the doctor can examine the internal structures for any abnormalities or signs of inflammation, fistula openings, abscesses, or other potential issues.
Imaging Tests
If further investigations are needed, you may be recommended to undergo imaging tests like a CT scan, an endoanal ultrasound, or an MRI scan. These tests provide detailed information about the entire length of the fistula tract and how it interacts with the sphincter muscles and other surrounding tissues.
What Does an Anal Fistula Diagnosis Include?
Besides diagnosing the presence of an anal fistula, findings will also include:
- The Path & Severity of the Fistula - Imaging tests and examinations help doctors map the fistula’s complexity and pathway, ensuring the right surgical approach—whether a fistulotomy, seton placement, or flap surgery—for effective healing.
- Possible Links to Underlying Conditions - Anal fistulas can be linked to conditions like Crohn’s disease, tuberculosis, or sexually transmitted infections (STIs). A detailed evaluation allows for a more comprehensive treatment plan that addresses both the fistula and its root cause.
What Are Possible Complications of an Anal Fistula?
An undiagnosed fistula can worsen over time, leading to complications such as:
- Abscess formation - If the fistula opening becomes blocked, pus can accumulate, leading to a painful abscess that may require drainage.
- Recurrent infections - Chronic infections can cause ongoing discomfort, swelling, and discharge, sometimes requiring multiple treatments.
- Faecal incontinence - In severe cases, damage to the anal sphincter muscles can affect bowel control.
- Anal stenosis - Scarring from repeated infections or surgeries may lead to narrowing of the anal canal, making bowel movements difficult.
Dr Dennis Koh
Medical Director & Senior Consultant Surgeon
B Med Sci (Nottingham), MBBS (Nottingham)
MMed (Surgery), FRCS (Edinburgh), FAMS
Dr Dennis Koh is an MOH-accredited and experienced colorectal surgeon skilled in anal fistula treatment; and currently the Medical Director at Colorectal Practice.
Dr Koh strives to provide a customized treatment plan for each patient, which allows for better outcomes. He also honed his skills in proctology abRd in Geneva, bringing a more diverse touch to his practice.
Dr Sharon Koh Zhiling
Senior Consultant Surgeon
MBBS (Singapore), MMed (Surgery),
FRCS (Edinburgh), FAMS
Dr Sharon Koh is an experienced colorectal surgeon and the former Director of Endoscopy at Alexandra Health.
Dr Koh completed her fellowship at Cedars-Sinai Medical Centre in the US after being awarded the Academic Medicine Development Award by the National University Hospital.
Dr Pauleon Tan Enjiu
Senior Consultant Surgeon
MBBS (Singapore), MMed (Surgery),
FRCS (Edinburgh), FACS
Dr Pauleon Tan has served in public hospitals for over 15 years and is experienced in minimally invasive surgery and endoscopy.
Dr Tan undertook advanced colorectal surgical training at Japan’s Saitama International Medical Center after being awarded the Ministry of Health – Health Manpower Development Plan (HMDP) Award.