Consent: Lay Open Fistula or Seton Insertion

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Last updated: October 31, 2022
Revisions: 8

Last updated: October 31, 2022
Revisions: 8

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This article is for educational purposes only. It should not be used as a template for consenting patients. The person obtaining consent should have clear knowledge of the procedure and the potential risks and complications. Always refer to your local or national guidelines, and the applicable and appropriate law in your jurisdiction governing patient consent.

Overview of Procedure

A fistula-in-ano typically results from presence of a previous peri-anal abscess, however, other causes such as inflammatory bowel disease (Ulcerative Colitis or Crohn’s Disease), trauma, or radiation changes should be considered. A digital rectal examination and proctoscopy should also be performed to assess the integrity of the bowel mucosa for signs of inflammatory bowel disease or any evidence of internal fistula openings.

A seton can be placed when the fistula tract is probed and the tract is higher in the sphincter mechanism (Fig. 2), with the seton passes through the tract. It is then loosely tied in place and repeat procedures are likely needed. Laying open of a fistula (fistulotomy) occurs where a fistula probe is passed through the tract and the overlying tissues are divided with a knife or diathermy, if they are superficial and do not involve the sphincter complex.

Figure 1 – An illustration of a seton in-situ for a perianal fistula


The Goodsall Rule

The Goodsall rule (Fig. 1) can be used clinically to predict the trajectory of a fistula tract, depending on the location of the external opening:

  • External opening posterior to the transverse anal line – fistula tract will follow a curved course to the posterior midline
  • External opening anterior to the transverse anal line – fistula tract will follow a straight radial course to the dentate line

Figure 2 – The Goodsall rule, used clinically to predict the course of a fistula tract  



Complication Description of Complication Potential Ways to Reduce Risk
Bleeding Typically there is only minimal blood loss Gentle probing of the fistula tracts; only lay open superficial tracts to avoid deeper structures
Damage to the anal sphincter complex Typically perform a circum-anal incisions to avoid the risk of sphincter damage
Anaesthetic risks Includes damage to the teeth, throat and larynx, reaction to medications, nausea and vomiting, cardiovascular and respiratory complications Forms a part of the anaesthetist assessment before the operation



Complication Description of Complication Potential Ways to Reduce Risk
Pain Pudendal nerve block with local anaesthesia can help with post-operative pain
Bleeding There is a small chance of bleeding and bruising post-operatively
Infection Superficial wound infection or small abscess formation can occur within the fistula tracts
Scarring Any incision will result in a scar, which may form a keloid scar, particularly in high risk ethnicities
Blood clots DVTs and PEs are a possibility in any operation, however are low risk as the duration of the procedure is short The patient will be given anti-embolism stockings and low molecular weight heparin peri-operatively to minimise this risk as deemed appropriate.



Complication Description of Complication Potential Ways to Reduce Risk
Recurrence Fistula disease has high rates of recurrence, even following extensive surgery Ensure any underlying disease pathology, e.g. Crohn’s disease, are concurrently treated
Anal stenosis Healing of the fistula tract or scarring from multiple wounds can lead to fibrosis of the anal canal
Delayed wound healing Usually healing should occur within 12 weeks unless there is underlying pathology e.g. Crohn’s disease