Anal Fistula Complications

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Surgery for an anal fistula always carries the risk of complications. The chief postoperative complications include:

  • infection
  • bowel incontinence
  • recurrence of the fistula

Each of these complications is discussed in more detail below.


Complications may occur in the immediate or delayed postoperative period. Several difficulties may present shortly after the surgical procedure. These include urinary retention, heavy bleeding or discharge from the fistulotomy site, clot formation inside an existing hemorrhoid, and fecal impaction.

Other complications that commonly present somewhat later after the procedure may include anal stenosis, recurrence of the fistula, bowel incontinence, and delayed wound healing (the wound remains unhealed for longer than 12 weeks). These complications are less common and affect from 0 to 18% of patients, depending on the type of fistula and surgery.


All surgeries carry some risk of infection when an incision is made into the skin, including the fistulectomy procedure. In some fistula surgical techniques,  the procedure may have to be completed in several stages. In such cases, an infection of the fistula tract may spread throughout the body and cause systemic infection.

Antibiotics are often required to treat infection associated with fistula surgery. For severe infection, admission to hospital may be required to allow intravenous administration of the antibiotics. They may also be recommended as a prophylactic method to prevent infection when the risk is high.

Bowel Incontinence

Fistula surgery has the potential to damage the muscles of the anal sphincter, especially when the fistula involves the sphincter muscles. These are responsible for tightening around the anus to control bowel movements. When sphincter damage occurs, the strength of the muscles is compromised. There may be some loss of control of the bowels, leading to leaking of feces from the rectum. This is referred to as fecal or bowel incontinence.

This is an uncommon complication, estimated to affect 3-7% of all patients that undergo fistula surgery. The risk depends on the position of the fistula and the type of surgery used to remove it. The risk is highest for Seton techniques (approximately 17%) and the advancement flap procedure (about 6-7%).

The risk is higher in individuals who already have some degree of bowel incontinence, and who are likely to notice a worsening in symptoms. Other people who are more likely to experience this complication include women, and patients with Crohn’s disease.

Recurrence of the Fistula

For some patients, the fistula will recur after the surgery. It is estimated that the recurrence rate is approximately 7-21%, primarily depending on the type of fistula, and the surgical procedure that was used to remove the fistula. Fibrin glue, for example, has a high recurrence rate. Other procedures have also been reported to result in recurrence in up to one-third of patients. Most patients who have fistula recurrence will need to have another surgical procedure to remove the fistula.

Management of Complications

The appropriate management of the complications will depend on the problem at hand and the individual case. It is important that patients are aware of possible complications so that they can recognize the signs early enough to seek medical advice as needed. This will allow them to be treated in a timely manner and reduce the impact of the complication on their overall health and wellbeing.


Further Reading

Last Updated: Feb 26, 2019

Yolanda Smith

Written by

Yolanda Smith

Yolanda graduated with a Bachelor of Pharmacy at the University of South Australia and has experience working in both Australia and Italy. She is passionate about how medicine, diet and lifestyle affect our health and enjoys helping people understand this. In her spare time she loves to explore the world and learn about new cultures and languages.


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  1. yahya bora yahya bora Morocco says:

    Thank you doctor for the detailed article..please my wife suffers from a recurrence  fistula,after operating the first one few years ago...what can she do now,another operation?? thanks from Morocco 🙏

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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