Endoanal Ultrasound

Overview

Your anal sphincter is actually two separate muscles working together — the internal sphincter, which squeezes automatically without you thinking about it, and the external sphincter, which you control consciously when you squeeze. Endoanal ultrasound uses a small, smooth probe (slightly narrower than a finger) inserted into the anal canal to take 360-degree images of both of these muscles and the space between them.

It is the most detailed way to see whether there is a tear, a scar, or a gap in the sphincter — far more accurate than an external examination alone. The procedure takes 10–20 minutes, requires no sedation and no special preparation. It is often done in the rooms during a consultation, or — if you are already having a procedure under anaesthetic — it may be performed in theatre at the same time.

Who needs this procedure?

• You have faecal incontinence (leakage) and your surgeon needs to see exactly where the sphincter is damaged and how large the gap is
• You have a complex anal fistula (a tunnel between your back passage and skin) and Mr Nguyen needs to understand how the tunnel relates to the sphincter muscles before deciding on treatment
• You have a perianal abscess (a collection of pus near your back passage) and the scan helps identify how extensive it is
• You are being planned for sphincteroplasty (sphincter repair) — the scan maps exactly where the gap is so the repair is as accurate as possible
• You had a significant tear during childbirth and want to understand whether the muscle has healed fully
• There is a lump or swelling near your back passage that needs a closer look

Benefits

• Very detailed images in real time — no radiation at all
• No sedation or bowel prep required for most people
• Finds tears and gaps in the sphincter that would be completely missed on an external examination
• Gives Mr Nguyen a precise map of your anatomy before any repair, making surgery safer and more targeted
• Helps guide the placement of a seton (a fine thread) in complex fistula cases
• Quick — in and out in under half an hour

Risks & considerations

• You will feel some pressure when the probe is inserted, similar to the sensation of needing to open your bowels — most people find it quite manageable
• There is an extremely small chance of very minor irritation to the lining of the anal canal, which settles on its own
• There are no anaesthetic risks and no significant procedural risks
• In rare cases where there is significant narrowing of the anal canal, the probe cannot be comfortably inserted — Mr Nguyen will discuss alternatives if this applies to you

Before the procedure

• No bowel prep or fasting required in most cases — just come as you are
• On rare occasions, you may be asked to use a small self-administered enema beforehand for a clearer image — you will be told in advance if this is needed
• Take your regular medications as normal
• Wear whatever is comfortable — no special clothing needed
• You can drive yourself there and home again

On the day

• You will lie on your left side on the examination couch — this is the most comfortable position
• The small ultrasound probe is gently and slowly inserted into the anal canal
• Mr Nguyen rotates the probe to capture images all the way around the sphincter complex — this part takes only a few minutes
• The images are reviewed on screen and saved; Mr Nguyen will often talk you through what he is seeing at the time
• The whole thing is done in 10–20 minutes; you leave and get on with your day immediately afterwards

Recovery & aftercare

There is nothing to recover from. If you had the scan as a standalone outpatient test, you walk out and carry on with your day — drive, go to work, do whatever you had planned. If the scan was done as part of a procedure under anaesthetic, your recovery follows the requirements of that procedure rather than the scan itself. Mr Nguyen will discuss the findings with you at your follow-up appointment.

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