Catheter blockage
Long-term catheterisation is common, and often necessary, for people with spinal cord injury (SCI) but can pose risks and complications. One such complication is catheter blockage. If left untreated, catheter blockage can be life-threatening (see Autonomic Dysreflexia).
Identifying the specific cause of a catheter blockage ensures that appropriate management strategies can be put in place to reduce the likelihood of recurrence.
Causes and recommendations
- Smaller volumes of urine cause higher concentrations of debris which can lead to blocking.
- Oral intake, as well as output, such as sweating, can affect output volume.
Recommendations:
- Ensure a consistent fluid intake: 2-3 litres of water a day is recommended.
Poor flow can lead to an increase in the incidence of encrustations as the urine:
- Settles in the tubing, promoting blockage from static debris.
- Has more contact time with the catheter, which causes a biofilm to form.
Recommendations:
- Empty the drainage bag regularly, as the flow can be affected when the bag is two-thirds full.
- Promote free drainage by ensuring no kinks in the tubing and positioning the drainage bag lower than the bladder.
- Elevate feet during the day, to reduce lower limb oedema.
- Ensure a constant intake of fluids.
- Limit diuretics.
- Bacteriuria, or colonisation of the urine, can develop as soon as 48 hours after the catheter is inserted.
- Colonisation is common with the following bacteria: E. coli, Pseudomonas aeruginosa, Proteus, Klebsiella, Providencia.
- Bacteria floating in the urine are planktonic and can be treated with antibiotics.
- A biofilm is a living layer that is described as slimy and glue-like, and is caused by the micro-organisms colonising on the synthetic surface of the catheter and tubing.
- The growth of the biofilm is promoted by the moist environment. Poor urine flow also allows longer contact time with the bacteria and the catheter, allowing a film to form.
- The bacteria that form the biofilm are genetically different, as they produce secretions that ‘cement’ the biofilm, making it resistant to antibiotic therapy.
- The urine can re-colonise after antibiotic treatment has been completed.
- Despite having a closed urinary drainage system, colonisation can develop within weeks of the catheter change.
Recommendations:
- Maintain a clean catheter technique, as well as general hygiene, when changing catheters.
- A closed-catheter system can slow bacterial growth in the urine. A closed system is a one-way flow of urine from the bladder, with no breaks in the system.
- Regular catheter changes will prevent colonisation.
- If possible, change the catheter whenever antibiotic therapy is commenced.
- A normal urine pH averages 6.0, but can range from 4.5-8.0.
- There is considerable encrustation at pH less than 6.7.
- The activity of urease is dependent on pH. Urease is more active in an acid pH, causing more urea to convert into ammonia.
- Ammonia in the form of a solution is alkaline.
- Ammonia also damages the protective layer of urothelial cells, which defend against infection.
- Urease-producing bacteria are:
- Proteus mirabilis, Morganella morganii, Providencia stuartii, Klebsiella pneumoniae, Proteus rettgeri, Proteus vulgaris and Staphylococcus aureus.
- Urease-producing bacteria also increase risk for calculi formation.
- There is no evidence to suggest that a balanced diet and moderate intake of food groups have any bearing on urine pH.
- Medications and oral solutions such as antacids, urinary alkalinisers and diet soft drinks that contain citrate can cause the urine to become more alkaline.
Recommendations:
- Measure the urine pH.
- Take a micro-urine test to detect any urease-producing bacteria.
- If a urease-producing organism is present, alkaline therapy, such as citrates or sodium bicarbonate, may reduce crystallisation and subsequent blockages.
- Encrustation is the development of crystals in the catheter tubing.
- There are two types of encrustation:
- Struvite (magnesium ammonium phosphate)
- Apatite (calcium phosphate, also referred to as calcium salts)
- Calcium salts are a large component of catheter encrustations.
- Struvite, not developed from a biofilm, is reversible. It is only reversible if the urine is low in phosphate, magnesium and calcium salts, or the urine is acidified.
- Non-blockers have a wider safety margin between their normal urine pH and that at which crystallisation occurs (~1.4 variance in pH).
- The phosphate precipitates or separates in the solution and stops forming crystals. This happens in alkaline urine, starting at pH values of 6.7 and peaking at pH 7.5.
Recommendations:
- Antibiotic therapy is ineffective for treating encrustation and long-term use can lead to development of resistant bacteria.
- Encrustations are less pronounced on silicone and hydrogel catheters.
- Moderate the intake of magnesium and calcium in the diet. Magnesium is found in diet soft drinks, herbal teas and fruit juices. A high calcium diet also contains more potassium, phosphate and magnesium, which can contribute to the encrustation.
- Performing a bladder washout with saline or water, to remove the debris or crystals, has limited supporting evidence and is more likely to cause spasticity and mucosal irritation.
- Some commercial acid-based and antimicrobial irrigation preparations can be helpful (e.g. Suby G/R, Microdox, PHMB) if administered as per the manufacturer’s recommendations.
Catheter blockage prevention flowchart
