Clinical and technical evidence

A literature search was carried out for this briefing in accordance with the interim process and methods statement. This briefing includes the most relevant or best available published evidence relating to the clinical effectiveness of the technology. Further information about how the evidence for this briefing was selected is available on request by contacting

Published evidence

One study is summarised in this briefing, involving 100 patients.

There is evidence on technology design and validation in peer-reviewed publications and unpublished abstracts, but this is not included in this briefing.

The clinical evidence and its strengths and limitations is summarised in the overall assessment of the evidence.

Overall assessment of the evidence

There is not much clinical evidence on the TUC Safety Valve. Most of the published evidence are proof of concept, and design validation studies on porcine models showing that the TUC Safety Valve eliminates user variability and restricts balloon inflation pressure to below a safe level of under 150 kPa. Only 1 study was identified on using the device (a validated prototype) in a clinical patient setting. Another, Davis et al. (2018a), which is not summarised, used 9 urethras removed from patients undergoing male to female gender reassignment to look at the relationship between urethral diametric stretch, catheter balloon inflation pressures and urethral trauma. This reported urethra rupture in the thinnest urethras when external urethral diametric stretch was 1.26 and greater, and balloon inflation pressures of 120 kPa, and a mean across the 3 ruptures of 165.16 kPa.

Results from a health economics study by Davis et al. (2016) are summarised in the resource consequences section of this briefing. Davis et al. (2020), which looked at the longer-term outcomes of those patients from the same sample who sustained a urethral injury during transurethral catheterisation, is also summarised. Neither study involved the use of the TUC Safety Valve and so are not included in this section.

Davis et al. (2018b)

Study size, design and location

A prospective observational study of 100 adult men needing urethral catheterisation at the Beaumont Hospital, Dublin, Ireland, a tertiary referral teaching hospital.

Intervention and comparator(s)

A validated prototype version of the TUC Safety Valve; no comparator.

Key outcomes

All patients had a successful catheterisation with the TUC Safety Valve. This was defined as urine exiting the catheter's drainage port, witnessed by the user, with successful inflation of the catheter's anchoring balloon. No urethra injuries from traumatic catheterisation were recorded. The TUC Safety Valve activated in 7 patients, preventing accidental inflation in the urethra. On all 7 occasions the catheter was successfully repositioned into the bladder and inflated.

In a survey of the 34 hospital interns who did the catheterisations with the TUC Safety Valve, of the 31 who responded: 10% reported that they had inflated the catheter balloon in the urethra on previous occasions; 87% were interested in the concept of the TUC Safety Valve; 84% said the device was user friendly; and all said they would use it again.

Strengths and limitations

This is a reasonably large study that also gathers feedback from users of the technology. However it is non-comparative, limited to a single centre, involves medical interns, and uses a prototype version of the device. It's therefore not clear if the outcomes and survey responses would translate into the NHS. Four of the 5 authors are cofounders of the company and stated as inventors on the US patent.


The company claims the technology prevents urethral injury and this will save resources associated with treating these injuries. There is no published evidence to support these claims.

Recent and ongoing studies

The company has told NICE that it intends to do a 2‑stage before-and-after study in the NHS using prospective audit data to look at the impact of using the TUC Safety Valve on urethral catheter-related injuries. The intention is to publish any final results. No further details are currently available.