The urethral catheter--a review of its implication in urinary-tract infection.

The research into acquisition of urinary-tract infection over the last few decades has established three ways in which organisms may gain access to the urinary tract of the catheterized patients: Firstly, during the process of passing the catheter into the bladder should complete asepsis not be observed; secondly by travelling along the urethra in the small, fluid-filled cavity between catheter and mucosa; Thirdly following contamination of the drainage system, along the inside of the catheter directly into the bladder. The relative importance of each route is not clear and is still the subject of much controversy but it would seem that all these routes have a part to play in allowing infection to develop. The risk of catheterized patients acquiring urinary-tract infection is so great that where possible catheterization should be avoided. The most important preventive measure which may be taken is to limit the duration of indwelling catheterization. In addition, a considerable amount of research has attempted to distinguish other factors which might affect the rate at which urinary-tract infection in the catheterized patient becomes established so that high-risk patients may be identified. The evidence indicates that the risk increases with duration of catheterization, age, length of hospital stay, immunosuppressant treatment, that it is greater in female than male patients and that a patient with a serious or fatal underlying disease is also more likely to develop bacteriuria. Finally, properties of the urine and the host defence mechanisms may affect the susceptibility of the individual to urinary-tract infection. Identification of the routes of infection and patients at risk is only part of the problem. The next stage is to formulate criteria for the care of catheterized patients which reduce the risk of infection to the absolute minimum and will hopefully go some way towards diminishing the unsatisfactory high levels of urinary-tract infection that are currently associated with indwelling catheterization.