Knowledge · Procedural Skills

Urethral Catheterisation: Aseptic Insertion, the Balloon and the Foreskin

By Dr Richard Miller, MBChB FRCS with the MRCS Part B Questions Team · Reviewed 15 September 2026

In brief

Urethral catheterisation is an aseptic procedure: clean the meatus, use lubricant from a single-use container, inflate the balloon with 10 mL of sterile water in an adult only once urine drains, and replace the foreskin at the end.

Urethral catheterisation is an aseptic procedure from start to finish. NICE CG139 requires that the meatus is cleaned before insertion, that lubricant comes from a single-use container, and that the balloon is inflated with 10 mL of sterile water in an adult, and the foreskin must be replaced at the end to prevent paraphimosis.

Key takeaways

NICE CG139 states that all catheterisations carried out by healthcare workers should be aseptic procedures.
The meatus should be cleaned before insertion, in line with local policy, and an appropriate lubricant from a single-use container used to minimise urethral trauma and infection.
CG139 says the balloon should generally be inflated with 10 mL of sterile water in adults and 3 to 5 mL in children.
Connect to a sterile closed drainage system or catheter valve, and keep the bag below bladder level and off the floor.
Paraphimosis commonly occurs iatrogenically after catheter placement, so replacing the foreskin at the end is a required step, not a courtesy.

What is the examiner marking at the catheterisation station?

The Intercollegiate blueprint runs two procedural stations and marks them differently. A procedural skills station with a patient carries 8 marks for clinical and technical skill and 4 each for clinical knowledge, communication and professionalism. A technical procedural station, performed on a model rather than a person, carries 12 for skill and 8 for knowledge, with no communication or professionalism marks available.

Prepare for the version with a patient, because it is the harder of the two: the same technique has to be delivered while consenting, explaining and keeping the patient comfortable, and those marks are gone if you work in silence.

The examiner is marking sterility, dignity and the safety steps: consent, cleaning, waiting for urine before inflating the balloon, and replacing the foreskin.

Say what you are doing to the patient throughout, because dignity and communication carry marks in the applied skills component.

What are the indications and contraindications?

Catheterise for acute or chronic urinary retention, accurate fluid balance in a sick patient, perioperative management, bladder irrigation, or to allow healing of a sacral wound.

Suspected urethral injury, such as blood at the meatus or a high-riding prostate after pelvic trauma, needs senior and urology advice before any attempt
Recent urological surgery or a known stricture is a reason to stop and ask
NICE quality standard QS61 stresses removing the catheter as soon as it is no longer needed, because infection risk rises with duration
Never catheterise for convenience alone

Explain the indication, the procedure, the sensation of pressure and stinging, and the alternatives, then obtain and record consent.

Royal College of Surgeons of England, summarising the Montgomery ruling, notes clinicians must take reasonable steps to ensure patients are aware of risks material to them, so describe infection, trauma, bleeding and the possibility of failure.

What equipment do you need?

Catheter pack with sterile drapes, gallipot and gauze, plus sterile gloves
Catheter of appropriate type and gauge, which CG139 says should be selected on the patient's individual characteristics, with a spare
Sterile saline or water for cleaning, and anaesthetic lubricating gel from a single-use container
10 mL of sterile water for the balloon, drawn up by an assistant
Sterile closed drainage system or catheter valve, and a receiver

What are the steps, in order?

Wash your hands, confirm identity and allergies, including latex and lidocaine, and gain consent
Position the patient supine, expose only what is needed, and maintain dignity with a chaperone where appropriate
Open the pack onto a clean trolley, ask your assistant to add the catheter, water and gel, then wash your hands and put on sterile gloves
Drape the patient, retract the foreskin if present, and clean the glans and meatus with single downward sweeps of saline-soaked gauze, using each swab once
Instil the anaesthetic lubricating gel into the urethra from its single-use container, warn the patient it stings, and wait for it to work
Hold the penis upright and advance the catheter to the hilt, using gentle traction if it will not pass
Wait until urine drains before you inflate the balloon, then inflate with 10 mL of sterile water and withdraw gently until it seats
Connect to a sterile closed drainage system or valve, and position the bag below bladder level and off the floor
Replace the foreskin over the glans
Dispose of waste, wash your hands and document the procedure

Why does the foreskin matter so much?

**Paraphimosis** is entrapment of the retracted foreskin behind the corona of the glans, causing strangulation, oedema and, if untreated, necrosis.

It is commonly iatrogenic, following retraction for cleaning or catheter placement, and standard reference guidance is that everyone who inserts or changes catheters should routinely replace the foreskin at the end of the procedure.

How do you keep the procedure aseptic and the catheter safe?

Aseptic insertion is only the start. NICE CG139 asks for a sterile closed drainage system, hand decontamination before and after any manipulation of the catheter, and urine samples taken from the sampling port using an aseptic technique.

NICE quality standard QS61 frames the whole process as insertion, maintenance and removal as soon as the catheter is no longer needed, noting the strong association between duration of catheterisation and infection.

What are the complications and the common mistakes?

Catheter-associated urinary tract infection, which QS61 describes as a large proportion of healthcare-associated infections
Urethral trauma and a false passage, most often from forcing the catheter or inflating the balloon early
Paraphimosis from a foreskin left retracted
Haematuria and, after draining a chronically distended bladder, decompression bleeding
The classic station errors are breaking sterility with the non-dominant hand, inflating the balloon before urine drains, and never replacing the foreskin

How do you finish and document?

Record the indication, catheter type and size, the residual volume drained, the balloon volume, whether the procedure was easy or difficult, and the plan and date for removal.

Then say you would review the need for the catheter daily, which is the QS61 standard.

The MRCS Part B Questions bank has a catheterisation station at /Sample-Questions.

Key evidence

Healthcare-associated infections: prevention and control in primary and community care (CG139), section 1.2 — National Institute for Health and Care Excellence (2017)
Infection prevention and control (QS61), quality statement 4: urinary catheters — National Institute for Health and Care Excellence (2014)
Paraphimosis — StatPearls, NCBI Bookshelf (2023)

FAQ

How much water goes into the catheter balloon?

NICE CG139 states that in general the catheter balloon should be inflated with 10 mL of sterile water in adults and 3 to 5 mL in children. Use sterile water rather than saline, which can crystallise. Inflate only once urine has drained.

What do I clean the meatus with?

NICE CG139 says the meatus should be cleaned before insertion of the catheter in accordance with local guidelines and policy, and that an appropriate lubricant from a single-use container should be used during insertion to minimise urethral trauma and infection. Sterile saline is commonly used. Follow your trust's policy and say so.

What should I do if the catheter will not pass?

Stop and reassess rather than forcing it. Gentle downward traction on the penis can straighten the urethra, and more anaesthetic gel and time often help. If it still will not pass, seek senior or urology help, because repeated attempts cause false passages and bleeding.

Why is paraphimosis an emergency?

The retracted foreskin traps behind the corona and strangulates the glans, causing venous engorgement, oedema and possible necrosis. It is commonly iatrogenic after catheter placement or cleaning. Replacing the foreskin at the end of every catheter insertion prevents it.

When should a catheter be removed?

NICE quality standard QS61 asks for removal as soon as the catheter is no longer needed, noting a strong association between duration of catheterisation and infection risk, and that catheters are sometimes inserted inappropriately or removed late. Review the need daily and document the decision.

How should the drainage bag be positioned?

NICE CG139 says urinary drainage bags should be positioned below the level of the bladder and should not be in contact with the floor, and that the catheter should be connected to a sterile closed drainage system or a catheter valve. Breaking the closed system raises infection risk. Take samples from the sampling port aseptically.

The MRCS Part B Questions Team

Written and maintained by doctors who have sat and scored well at this interview, and reviewed against the current published guideline in each case. Guidance changes — check the source before you rely on a threshold.

Last reviewed 15 September 2026

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