Unlike cannula sizes (measured in Gauge, with smaller numbers being larger in diameter), catheter sizes are measured in 'French'. These make more sense, as larger numbers mean larger diameters.
Normally, size 14-16F are used for male catheterisation, and size 12-14F for female catheterisation. Remember that the female urethra is only about 3.8cm long (as opposed to 20cm in males), so the catheter lengths are considerably different.
Equipment you will require for catheterisation:
- Sterile gloves (2 packs)
- Catheter of the appropriate sizes (and spares - one larger size, one smaller size)
- Catheter bag (for urine collection)
- Kidney dish (cardboard dishes, for collecting the first few drops of urine before you attach the catheter leg bag)
- Catheterisation pack (contains all the drapes, a tray, sterile gauze and forceps for cleaning, and a yellow sterile waste bag)
- Sterile saline (10ml, in a syringe)
- Lignocaine gel (e.g. Instillagel - 10ml, and a large syringe)
- Sterile water to inflate the catheter balloon (varies depending on catheter - around 5-10mls)
- Portable trolley (cleaned with antiseptic solution)
- An assistant, also with sterile gloves on.
The Procedure - Male Catheterisation
Anatomy of the male urethra & tips:
- Total length of the urethra is around 20cms.
- Narrowest part of urethra = external orifice of glans penis.
- Within the glans, the urethra dilates to form the fossa terminalis. A fold of mucous membrane near the posterior end of the fossa projects into the lumen from its roof, thus fixing the membranous urethra.
- The prostatic urethra is the widest and most dilatable part. When holding the penis at 90o to the body, the 'S'-shaped curve is transformed into a 'J'-shape, making catheterisation easier. Upon reaching the membrane urethra, you may feel a slight resistance due to the presence of the urethral sphincter and surrounding rather rigid perineal membrane. If you lower the penis back towards the thighs at this point, the catheter will insert more easily.
- If you have difficulty inserting a particular sized catheter, then it can often be useful to try the next size up (larger, rather than smaller) as this will be a more stiff catheter, which may be easier to pass. Do not force anything - if the catheter will not pass smoothly, then call for more experienced assistance.
Protocol - male catheterisation:
- Wash your hands, introduce yourself, check the patient's identity, explain the procedure to the patient and obtain their consent. Remember to explain the various steps to the patient as you go along, as having a catheter inserted into you is, for most people, not the most pleasant experience. The patient should lie flat (supine), with their legs slightly apart. Trousers should be well out of the way to avoid any accidental spillages. It's best to attempt this procedure with an assistant who is also wearing sterile gloves. Ensure there are no contraindications to insertion (eg. pelvic trauma with suspected urethral rupture - this will usually be unlikely in an exam).
- Check the size of the catheter's balloon and remember the number of mls of water required - this will save lots of fiddling later. Don't pre-fill the syringe, as it's best to do this later to make the procedure as sterile as possible.
- Collect all of your equipment and lay it out onto your (clean) portable trolley. Remember to keep the yellow waste bag out of the way of the sterile equipment.
- Open the catheter pack, making sure you avoid contaminating it (the contents are sterile). Make sure the patient's trousers and underwear are lowered and you have your trolley in the correct position by the side of the bed.
- Roll up your sleeves, wash your hands, and put on the first pair of sterile gloves. Get your assistant to open the water and fill your syringe for the catheter balloon (don't touch the unsterile saline bottle yourself). Also get your assistant to pour the cleaning solution into one of the trays in your pack.
- Prepare the sterile paper drape (you may need tear/cut a hole in the middle). Make sure the kidney dish (for collecting urine) is still in reach for later.
- Grasp the penis gently but firmly with a swab held in your non-dominant hand. Clean the penis with single sweeps of the solution-soaked gauze, moving away from the meatus towards the perineum. Repeat 2-3 times. You can use the plastic forceps to hold the gauze in your right hand, if required.
- Once the penis has been cleaned, place the drape over the penis (the penis goes through the hole, so to speak, and the rest of the drape provides a reasonably sterile platform for you to work on).
- Holding the penis upright, gently insert the nozzle of the anaesthetic gel (Instillagel) syringe into the meatus and squeeze the contents of the syringe into the penis. Warn the patient that it may sting and feel very cold. Gently hold and press the penile urethra to stop the gel oozing out. Wait for several minutes to allow the anaesthetic gel to take effect before proceeding.
- Your gloves will be covered in gel by this stage, so change them. Alternatively, some like to 'double glove' at the start, so that you can just remove the outer layer at this stage. Remove the catheter tip from it's bag, but ensure that the rest of it remains within the bag so that you maximise the sterility of the procedure. Insert it gently into the meatus and feed it steadily inwards (if it gets stuck, you can try to pull the penis downwards gently, which straightens the urethra). As described in the anatomy section, it can be useful to hold the penis at 90o initially, until you feel some resistance. This will occur as you enter the membranous urethra. At this point, lower the penis again. As you approach the end of the catheter (pass it all the way to the end), place your kidney dish under the free drainage end of the catheter. When urine flows out, it is safe to inflate the balloon with the specified amount of sterile water. Once filled, pull back on the catheter gently to check that the balloon is inflated and the catheter is secure. Do not inflate before you see urine, and the catheter is almost completely inserted, or else you may rupture the urethra.
- Attach the catheter to the collection bag (these come in different types, depending on how accurate you wish to be), ensuring that the bag's emptying port (if present) is in the 'off' position so the urine doesn't leak straight out the other side.
- Remove your drapes and all other equipment from the bed.
- Ensure that the foreskin (if present) is pulled down over the glans. If you forget to do this, then there is a risk of paraphimosis, which is very painful.
- Clear away your rubbish. Thank the patient, and ensure that they are comfortable and re-dressed. Document the procedure in the notes (if on the ward) and make sure that the instructions for urine output measurement (eg. frequency, etc) are known to the ward staff. Note down the volume of urine initially in the bag (this is the residual volume).
The Procedure - Female Catheterisation
- Perform steps 1-6 - as for the male catheterisation protocol (see notes above).
- It can be surprisingly difficult (even for experienced female nurses!) to identify the external urethral orifice in women - especially if there is any tissue swelling. It is therefore a common mistake to either pass the catheter into the vagina instead of the urethra, or to spend ages poking the clitoris with the catheter and not getting anywhere. Remember to confirm that you can see urine flowing into the catheter before you insert the balloon.
- Then perform the following steps:
- 7. Swab the perineum, sweeping away from the urethra, towards the anus.
- 8. Cover the perineum, as before, with the sterile drape.
- 9. Identify the external urethral orifice and insert the local anaesthetic gel. Let the patient know that this may feel cold and sting. Wait for this to take effect before continuing with the procedure.
- 10. Insert the catheter (see step 10 above) - remember that the female urethra is much shorter (around 3.8-4cm) than the male urethra (around 20cm).
- Then perform steps 11 - 13 - as for male catheterisation (see notes above).
Questions and Answers
Indications for catheterisation:
- Urinary retention
- Urinary incontinence
- When the patient is unable to move, e.g. due to surgery, sick patients, trauma patients, the ITU setting, etc.
- To monitor urine output in sick patients
- To give intra-vesical chemotherapy (BCG) for certain types of bladder cancer
- Investigations, e.g. micturating cystourethrography (MCUG)
Contraindications to catheterisation:
- Suspected urethral injury - in pelvic trauma, eg. with perineal bruising or blood at the meatus
- Known gross prostatic hyperplasia, with previous difficulty in passing catheters (get someone with more experience!)
- Past history of urethral strictures/fistulae
Complications of catheterisation:
- Urinary tract infections
- Urethral bleeding/damage
- Irritation/stricture/hypospadias in long-term catheters
Causes of anuria with catheters in situ:
- Tip not correctly sited in bladder
- Catheter tip blocked with gel/debris/clot - try flushing the catheter
- Empty bladder!