Back then...

Ureterorenoscopes are used to diagnose and treat kidney- or ureteral stones. I didn't know at the time that these stones would eventually become my everyday (and -night) work. But I knew already that there were reusable and disposable options of urological instruments to treat them. And as I was, parallel to my medical studies, a very eager fighter against climate change, I wondered what was "better" for the environment and for human health, which itself depends on a functioning environment.

Looking into literature, I found a call to further investigate the environmental differences of Ureteroscopes (Ventimiglia et al.) describing only one paper from Australia comparing the devices in question. In Australia, energy is mainly made from coal, so the results are not really transferable to Europe.  All other studies that Peyrottes & Long-Depaquit refer to had not been released at that time.

I started telephoning and e-mailing to get a satisfying answer: Are reusable instruments (which must be reprocessed after each use) or single-use devices (which are disposed of after each use) "better"? As one can expect, I realised quickly that I needed help there, interdisciplinary experts and basic expertise myself. So, I looked for someone to support me get the project going.

This being a quite unusual research query for a medical doctoral thesis, I consider myself very lucky I was taken under the wings of my supervisors with it.  We found an LCA ("Life Cycle Assessment") expert and could delve in the interdisciplinary calculation of the environmental impact of the two devices in question. 

How do you do a Life Cycle Assessment?

First, one has to identify all the life cycle stages involved in the process. Second, to collect every information one can get on the steps between them.

Next,  data is fed into an LCA software and the "footprint" can be calculated. 

What was special:

We performed the study in Tübingen, a very "green" city in Germany. The university hospital draws energy from renewable sources only.  We considered this by designing several scenarios in a sensitivity analysis, also taking conventional energy mix into account. 

Result

In our LCA, the environmental impact of single-use devices was 4x higher than that of the reusable instruments (unit: kilogram CO₂-equivalents). If a hospital uses a conventional energy mix, single-use instruments still have a bigger impact, yet the difference is narrowing. 

How do you make the results more understandable? 

CO₂-equivalents are not an established term among healthcare staff (yet). To make the results more understandable to medical professionals, we took another step and calculated the health impact resulting from the use of the devices we analysed. The unit for the health impact are the so-called "Disability adjusted life years" (DALYs). They enable to estimate the life years lost or harmed by a certain cause. 

Sure, stone surgery helps patients to suffer less, and should not be dispensed with. Also, LCAs carry loads of limitations with them, as they can only be as good as the data the estimation is based on. And: yes, it is a rough estimation always. Could be, that the numbers the project yielded are very far from reality. Be that as it may, it's definitely recommended to choose the more sustainable (=healthier) therapy option.

In a nutshell, more evidence is needed to be able to say what's really "better" - see also our "Letter to the editor" published in the World Journal of Urology replying to the study mentioned in the introduction:

Conclusion

It might be that reusable Ureteroscopes are less harmful to Planetary Health. However, I’d like to encourage researchers – clinicians, students, professors, scientists from diverse fields – to perform many more of those studies. The method exists. I recommend using this “tool”, forming interdisciplinary teams, and working together – to expand the evidence basis for environmental-based decision-making.