The association between intrarenal pressure and complications from ureteroscopy

In this video, Ben H. Chew, MD, MSc, FRCSC, and Naeem Bhojani, MD, FRCSC, discuss the background and findings from the study, “Complication Risk of Endourological Procedures: The Role of Intrarenal Pressure.” Chew is a urologist at the University of British Columbia and Bhojani is an associate professor of urology at the University of Montreal.

Video Transcript:

Chew: Intrarenal pressure has always been thought to play a role in complications in patients with ureteroscopy, either more pain from the increased pressure in their kidney, or the most obvious one is increased risk of sepsis or infection afterwards, because the pressure we use can basically make some of that urine, and if there's any infection of that, basically go backwards into the kidney and into the bloodstream. So, we wanted to basically examine this a bit further. And now, intrarenal pressure, I think has become a bit more of a hot topic, because now we actually have a way of measuring intrarenal pressure while we do surgery with all these new ureteroscopes that are able to detect pressure while we are operating.

Bhojani: So, we decided to do a study just looking at the literature trying to see if we could find a relationship between a certain intrarenal pressure and complications. More specifically, as Ben mentioned, infectious complications. We looked at the literature and we wanted to look at literature that was more contemporary. We didn't want to look at the older data. There is some older data, even from the 1970s on animal models, showing the intrarenal pressure can have some negative impacts on the kidney. We did a search of literature in the last 12 years and looked at what studies we could find. We found 12 studies, 7 of them were preclinical and 5 were clinical. Then we wanted to look to see if we could find an association between intrarenal pressure and infectious complications.

Bhojani: So basically, what we found was that if during ureteroscopy your intrarenal pressure remains below 30 mm of mercury,

Chew: Which is around 41 cm of water, that sort of magical number.

Bhojani: Exactly. There shouldn't be any infectious complications. And we also looked at overall average intrarenal pressure during the case. So, if your average internal pressure remains around 20 mm of mercury, again, you shouldn't have any infectious complications. Now, this needs to be taken with a grain of salt of course, because of the things we've already mentioned. If you have an older patient who's had multiple infections, or has a positive preoperative urine culture, has a stent in place, for example, this is a patient who's at very high risk of infectious complications postoperatively. So, maybe that 30 mm of mercury, you really don't want to pass that point, but if you go to 40, is that still okay? That's where we're not sure about yet.

Chew: And I think you need to qualify that if you went over 20 mm of mercury, which is 27 centimeters of water, for more than 10 minutes, that's when complications started to arise. So basically, going over for a longer time is something that might relate in more complications. So, it's not just 1 threshold, it's also that certain amount of time that you're that you're added as well, too.

Bhojani: Just to send the point home a little bit more, if you have a young patient who has no history of infections, and you do a quick 15-minute case, you're probably okay with a higher intrarenal pressure. This is where it gets really interesting, and I think this is where the newer tools that we have can become incorporated into our practice, such as Ben mentioned, the scopes that can measure intrarenal pressure during the case. As we get more data, we'll be able to identify those patients who maybe we shouldn't have such a high intrarenal pressure.

This transcription has been edited for clarity.