Fistula in ano disease: a comprehensive guide: part 1

Written by: Mr Daniel Baird
Published: | Updated: 01/02/2024
Edited by: Aoife Maguire

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.




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




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.




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 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 .




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

By Mr Daniel Baird
Colorectal surgery

Mr Daniel Baird is a leading general and colorectal consultant surgeon based in Goring-by-Sea, Worthing, who specialises in inguinal hernia, umbilical hernia and laparoscopic inguinal repair alongside anal fistula, anal fissure and piles (haemmorhoids). He privately practises at Goring Hall Hospital and the Oving Clinic, while his NHS base is at Worthing Hospital, part of University Hospitals Sussex Trust. 

Mr Baird is highly qualified, with an MB ChB from the University of Manchester, a FRCS from the Royal College of Surgeons and an MD (Res) from Imperial College London. He undertook his specialist surgical training in London at The Royal Marsden Hospital, St Marks Hospital and Imperial Healthcare Trust, alongside the Chelsea and Westminster Hospital.

He also completed an RCS accredited laparoscopic cancer fellowship at Frimley Park Hospital where he was exposed the Da Vinci and CMR Versius robotic operation platforms. He worked as a consultant at Frimley Park prior to his current permanent posts.                   

Mr Baird, who also operates on inflammatory bowel disease and diverticular disease, has a subspecialty interest in treating fistulae-in-ano and pilonidal sinus disease using the minimally-invasive techniques VAAFT/EPSiT techniques. His clinical research has been published in respected peer-reviewed journals including the British Medical Journal and the Annals of Surgery. 

Furthermore, Mr Baird is a member of various professional organisations including the Association of Coloproctology of Great Britain and Ireland, the European Society of Coloproctology and the British Hernia Society.

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