Pilot clinical trial to test the function of a diagnostic sensor in predicting impending urinary catheter blockage in long-term catheterized patients

In a blog about a new medical device developed to help predict urinary catheter blockage, Rachel Heylen discusses the study URINOSTICS, a small-scale pilot study which is testing the sensor before the design of a larger randomized trial, registered at the ISRCTN registry.

Sensor shown within the drainage bag

A diagnostic sensor to detect impending catheter blockage has been developed as a medical device to aid long-term urinary catheter users. Urinary catheter blockage can occur because of urease-positive infections – the urease metabolizes urea into two molecules of ammonia and carbonic acid. This increases the pH within the bladder, causing struvite and apatite crystals to deposit onto and within the catheter, resulting in a crystalline biofilm that occludes the lumen of the catheter, leading to catheter blockage. Owing to the high rates of catheter-associated urinary tract infections (CAUTI), affecting approximately 150-250 million patients globally per year, urinary catheter blockage poses a significant problem in the clinic. The infections can remain within the bladder during catheter changes, form bladder stones, and migrate up towards the kidneys, causing kidney stones and pyelonephritis. In worst-case scenarios, urosepsis can occur; ultimately patients experiencing urinary catheter blockage require more care, longer stays in hospitals, and present a burden to the healthcare system.

Catheter blockage not likely

No device currently exists to predict catheter blockage. The sensor described in this study can be used by individuals with no existing medical knowledge. Placed within the catheter drainage bag, it provides a colorimetric indication of impending catheter blockage, allowing the user or carer to change the catheter themselves; or flush the catheter using a maintenance solution thus reducing the risk of blockage. As this is a new medical device, a clinical trial is required to demonstrate efficacy. In vitro studies using a model of the catheterized tract have shown that the sensor provides 6.7 h warning prior to catheter blockage. Having shown to be stable within healthy human urine, the next stage was to test the sensor in urine taken from long-term catheterized patients. A small-scale pilot study was set up in collaboration with the Department of Urology clinic at the Royal United Hospital in Bath, UK; participants donated their drainage bag and catheter, allowing assessment of the sensor.

The figure below shows the colorimetric change when the sensor indicates that catheter blockage is likely to occur.

Catheter blockage likely


The sensor can predict participants more prone to catheter blockage, and it is accurate in detecting urine with a pH over 7. Owing to the small sample number of this trial, the results are not statistically powered. However, the data can be used to improve the design of the sensor and inform the design of a larger, randomized clinical trial.

We would like to thank Mrs Annette Moreton at the Royal United Hospitals Bath for her support during the trial. We also thank our funders: Urology Foundation, the University of Bath Impact Acceleration Account (IAA) and the EPSRC IAA Seed Grant.

View the latest posts on the On Medicine homepage