SSBII3

Urinary catheters, biofilms and stones

Roger C.L. Fenely

Long-term catheterisation (LTC) of the urinary bladder is a well-established method of collecting urine, mainly indicated for patients with intractable incontinence, with neuropathic bladder disorders or those who are unfit for surgery. The majority of the subjects are disabled by chronic debilitating medical conditions and thus constitute a group requiring considerable nursing support.

LTC carries a high morbidity due to its association with chronic urinary infection; it is considered to be a last resort by the medical profession, only to be undertaken when all other attempts to control the bladder have failed The prevalence of catheterisation rises to 0.5% in those of 75 years and to 2% by the age of 85 years. Catheter care is usually delegated to nursing staff and presents a heavy burden to nursing staff, accounting for 4% of District Nurses workload.

Urine presents a hostile environment for any biomaterial. The formation of the biofilm on the urinary catheter surface initiates a sequence of events with bacterial adhesion, formation of a glyco-calyx, nucleation with mineral deposits, which grow and can completely occlude the lumen of the catheter. Encrustation and blockage of indwelling urethral catheters is primarily brought about by infection of the urinary tract by Proteus mirabilis or other urease-producing species. The activity of the urease raises the urinary pH causing crystallisation of calcium and magnesium phosphates in the biofilm and bladder stone formation.