Catheter blockage

• 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.