Fistula in ano disease: a comprehensive guide: part 1

Fistula in ano is an abnormal tunnel between the anal canal and the skin near the anus, often associated with infection, causing pain and discharge. In the first article of a two-part series, Mr Daniel Baird, leading colorectal surgeon explores the disease, including an explanation of risk factors and diagnosis.

What is a fistula in ano?

A fistula in ano, also referred to as an anal fistula is an abnormal connection or tunnel that forms between the anal canal or rectum and the skin near the anus. It is often associated with an infection that originates from an anal gland.

A fistula in ano is frequently linked to an infection stemming from an anal gland. Various factors can contribute to its development, and certain conditions or situations may elevate the likelihood of its formation. This condition affects 1 to 3 in every 10,000 individuals and is not necessarily a consequence of poor personal hygiene. Many patients with a fistula have no identifiable risk factors, suggesting that, for them, it is simply a result of bad luck.

What risk factors are associated with the development of a fistula in ano?

Perianal abscess

An anal abscess is a common precursor to a fistula in ano. It is often unclear if the fistula was first and caused the abscess or if an abscess forms from an infected anal gland leading to fistulae. 

Recurrent perianal abscesses

Patients who have experienced multiple anal abscesses, particularly at the same site, are likely to have an underlying fistula causing the abscesses.

Crohn's Disease

Individuals suffering from Crohn's disease, an inflammatory bowel disease, have an increased risk of developing fistulas.

Gender

Men are more commonly affected than women, although no clear reason for this has been established.

Age

Anal fistulas can occur at any age, but occur more commonly in young to middle-aged adults.

Immunocompromised patients

People with compromised immune systems, such as patients undergoing chemotherapy, or suffering from poorly controlled diabetes are susceptible to infections that can lead to fistula formation.

Obesity

Patients with a high BMI are more likely to develop fistula disease. This could be due to increased insulin resistance, impaired immune function or the increase incidence of Crohn’s disease in the obese patient.

Smoking

Smoking increases the chance of an abscess and reduces the ability to heal wounds.

It is crucial to recognise that although these factors may increase the risk of developing an anal fistula, not everyone with these risk factors will do so. Additionally, prompt treatment of conditions such as anal abscesses and inflammatory bowel diseases can also play a significant role in minimising the risk of fistula formation. If an individual suspects they have symptoms of a fistula in ano or has associated risk factors, seeking timely medical evaluation and intervention is essential for proper diagnosis and management.

How is fistula in ano diagnosed?

The diagnosis of fistula in ano disease is commonly made in specialist care.

Clinical Examination

During the clinical examination with my patients, I will conduct a thorough examination, which includes taking a comprehensive medical history and performing a physical examination, including a digital rectal examination. In addition, I will inquire about symptoms such as pain, discharge, and swelling, as well as any prior instances of anal abscesses and operations .

Proctoscopy

Visualisation of the anal canal and rectum using a proctoscope helps assess the location and characteristics of the fistula.

Imaging Studies

An MRI (magnetic resonance imaging) is often of use to evaluate the extent, location, and complexity of the fistula tract.

As soon as the diagnostic pathway is complete, I will explain what type of fistula the patient has, and how complex it is.

If you are suffering from fistula in ano and would like to book a consultation with Mr Baird, do not hesitate to do so by visiting his Top Doctors profile today