11 – Preparing for a clinical trial of SLARSI (Sacral lumbar anterior root stimulator implant)

A model of the infected urinary tract for testing bio-materials

University College London  – Institute of Urology and Nephrology), Award: 29 Aug 03, Date of Award: £30,000

Encrustation of urological devices is worsened in the presence of infection and complications cost in excess of 1 billion Euros in the European Union and a similar amount in North America.

The objective of the project was to validate an in vitro model to quantify encrustation (stone deposits) on urinary devices (bladder catheters and ureteric stents) in the presence of urine infection in spinal cord injured patients.

Encrustation of urinary catheters and ureteric stents causes bleeding, infection, pain and blockage of the bladder or kidney. A blocked catheter or stent leads to severe pain and distress to the patient and needs to be replaced as an emergency. Infection of catheters and stents is common in spinal cord patients and in the presence of an obstruction can be life threatening.

Validation studies using human urine to quantify encrustation in the presence of urine infection has not been done before. Human urine contains essential substances such as urinary proteins, which play an important role in encrustation. These proteins are lacking in artificial urine, which does not reflect either true or physiological state of human urine.

A number of obstacles were overcome during the study. Microbiological advice was sought right from the start and the appropriate bacteria obtained for the study. Microbiological training took place to conform to health and safety regulations. New microbiological training was given to perform bacterial counts for the experiments. The in vitro model was designed to reflect an infected bladder by voiding urine more frequently than a non-infected bladder. Difficulties were encountered to ensure the test medical device and the control device received urine simultaneously and at the same rate. These were overcome. There were problems with atomic absorption spectroscopic measurement of encrustation on the medical devices and these were overcome.

The in vitro model for testing encrustation in infected urine has now been validated to provide reproducible results for quantifying encrustation on medical devices. This is an important step in the study and understanding of this recurrent and difficult problem faced by spinal cord injured patients who need long term catheters or a urinary implant such as a ureteric stent. With this validated in vitro model, different urological devices can be quantified for its potential to encrust and cause blockage. It also provides a useful tool to study and potential new biomaterial or medical device designed for patients with spinal cord injury. We are extremely grateful to INSPIRE for the support to carry out this work.