Stephen Y. Nakada, MD, a Urology Times editorial consultant, is professor and chairman of urology at the University of Wisconsin, Madison.
In this interview, Andrew Portis, MD, discusses his experience with ureteral access sheaths and describes an algorithm for their selection and use.
Ureteral access sheaths confer several advantages to the urologist treating a stone patient ureteroscopically. In this interview, Andrew Portis, MD, discusses his experience with sheaths and describes an algorithm for their selection and use. Dr. Portis is chair of HealthEast Kidney Stone Institute, St. Paul, MN. He is a consultant and investigator for Boston Scientific.
Dr. Portis was interviewed by Urology Times Editorial Consultant Stephen Y. Nakada, MD, the Uehling Professor and founding chairman of urology at the University of Wisconsin, Madison.
Please tell us what a ureteral access sheath is and when you would typically use one.
A ureteral access sheath is basically a means of getting up and down the ureter multiple times while avoiding the need for reintroduction of guidewires to do so. Sheaths range between 10F and 16F in outer diameter.
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I use an access sheath on any stone case where I think I’m going to have to make multiple trips up and down the ureter. For urologists like me who prefer to fragment and extract stones, that would include any stone over 4 or 5 mm. It is important to consider stone volume for estimating fragment load rather than just linear dimension.
When did you start using an access sheath?
I started using an access sheath during my fellowship with Dr. Ralph Clayman around 1999-2000. That’s when Applied Medical Resources was coming up with the first really functional access sheath, and Dr. Clayman was involved in the development of that product.
What did you perceive as the real tangible benefit aside from the ability to make multiple passes? Were there other advantages you were seeing?
The advantages included time efficiency, reliability, and the ability to be systematic and standardized in how I did the procedures.
Since they vary in size, can you give us a tip or two as to what you do if an access sheath cannot be passed easily over a wire?
I’ve created an algorithm that can be viewed online (bit.ly/UASalgorithm). The algorithm begins with placing a guidewire into the kidney. I traditionally use a Benson wire first. Occasionally, I’ll find, particularly in men, that the access sheath won’t track well over that. I always place the obturator of the sheath before placing the whole sheath. The obturator will usually track up but sometimes when you add the actual sheath component to it, you’ll get a troublesome step change in durometer (stiffness) and you may have a challenge getting around a prostate.
At that point, I’d swap out to a super-stiff wire and then I find the assembled access sheath usually tracks up well. But obviously if, according to our algorithm, you’re meeting significant resistance, the solution is just to stop. It’s a matter of recognizing resistance versus kinking.
How do you know the difference between resistance and kinking?
Kinking is easy because you’ll see the tip deflect in the region of the ureteric orifice on fluoroscopy. For monitoring resistance, I like to keep fingertip pressure on the access sheath as I’m inserting. I get a lot of information regarding the caliber of the ureter initially from using an 8/10 dilator system, so I’ll pass the 8F inner element. If the 8 goes easily, I’ll pass the 10F coaxial sheath over that. If I find resistance with that, unless I’m very confident that I’m going to go after a small stone that can be quickly cleared without a sheath, I stop.
If I have absolutely no resistance with that, I start thinking about using a 12/14F access sheath system. If it just absolutely falls in, which would commonly be the case if a patient is pre-stented, then I might go to a 13/15F sheath system.
If you can’t get the access sheath inserted, you said you stop. What do you do then?
I place a stent and wait 2 weeks for passive ureteral dilation.
What do you tell your patients as part of informed consent with regards to that possible outcome?
We track this. We know that we have a 5% failure rate but it can be difficult to predict. Generally, people who are younger, female, or first-time stone patient would be the ones who might be more challenging. Then you need to differentiate an impacted stone versus a tight ureter. An impacted stone can still allow some careful options to potentially clear. There are very limited second-line strategies to deal with an extremely tight ureter.
What are some of the risks of using a sheath regularly?
The biggest risk that has been brought to our attention is the risk of ureteral trauma, and I think if you follow a stepped approach like we’ve adopted, it’s unusual to see any kind of significant injury. We see a fair number of mucosal splitting cases, and we haven’t seen any clinical sequelae from that. But placing a sheath blindly or forcefully is asking for trouble.
If a urologist were to just use sheaths intermittently, what would be the best case for using one?
The best case is one in which you need to maximize the trips up and down the ureter. Specifically, this would be for a larger stone (1 cm or greater) with intent to clear. Again, our group is fragmenting stones and clearing, so we’re doing multiple trips almost all the time, but if you’re more of the dusting persuasion, then this may not be as important. Without the access sheath, you have to be very cognizant of increased intrarenal pressure and pyelovenous backflow.
What’s the maximum you would do ureteroscopically?
The typical top end, for a patient who didn’t have a contraindication for percutaneous nephrolithotomy, would generally be about 2 cm.
Does stone composition or density play a role in your calculation?
If somebody has a really dense stone, where the Hounsfield units are about 1,500, we’d probably start dialing back on what we want to do for extraction because we’re concerned about traumatizing the ureter when removing sharp fragments. By “dialing back,” I mean that I might be very cautious when stone size approaches 1.5 cm.
Do you have any uses for a sheath other than ureteroscopy? Any other endoscopic procedures?
I occasionally use an access sheath through percutaneous access for patients with challenging retrograde access who have ureteral stones. For example, a patient with cystectomy and conduit; you’re working on a ureteral stone with them and you’re going to use a flexible ureteroscope. In that case, it can be handy to place an access sheath in an antegrade fashion.
How do you select the different lengths and sizes of access sheaths in a given scenario?
As far as length, I’ve followed the advice of Dr. Glenn Preminger, who published years ago that if you can get the sheath above the iliac vessels, the pressure issues seem to abate (J Endourol 2004; 18:33-6). For the most part, I use a 36-cm access sheath on both men and women. I occasionally use the shorter one (20 cm or 28 cm) more in patients, particularly men, with an impacted mid-ureteric stone, just proximal to the iliacs, that require flexible ureteroscopsy.
I stay away from using the very long ones because I find that places the sheath tip into the proximal ureter, which I think is the most fragile area of the ureter. I don’t want to get the sheath all the way into the kidney because then I find everything collapses down; I don’t have any working space.
For diameter, 12/14F has been our standard. I use a 13/15F access sheath if I know I have to clear a lot of stone and I’m confident I can get it in, typically if the patient is pre-stented. In general, it’s best to use the smallest sheath which will allow you to efficiently clear stone and we are increasingly using 11/13F for smaller stones. Since transitioning to digital ureteroscopes, the 10/12F has really become the bottom end which will accommodate our current scopes.
How many of these sizes do you stock?
We are a referral target for complex stones so we stock them all in every length. We turn over the midrange sheaths frequently, and the extremes sit.
Have you ever regretted putting in a sheath?
Sure. There’s a particular sensation of a ureter “unzipping” which is best avoided and you never want to experience twice.
What happened in that case?
Everything seemed favorable and the obturator went up fine. Then as I advanced the sheath, it just felt like Velcro. Our algorithm generally keeps us out of trouble but ultimately sometimes you just have to make decisions based on your instincts. Sometimes those instincts betray you but you don’t know until after the fact.
Was it a ureteral avulsion?
No. I haven’t had an avulsion but I’ve had a transmural perforation or two. These were managed by prolonged stenting and careful follow-up. So far, we haven’t had any patients who required reconstructions that were attributable to a sheath. We find chronically impacted stones to be much more troublesome for ureteral injury than the access sheaths.
What do you think the future is for access sheaths?
I think we’re well served by the current sheath. I don’t see a need to change that. As we continue to pay attention to getting patients stone-free, the ability to actively clear stones will remain. I’m optimistic we’ll have better ways to actually remove stone fragments, but ultimately the business we’re in is to render a patient stone-free and if we can do so efficiently and safely, that’s a bonus.
Do you think the introduction of larger access sheaths will expand the stone sizes that can be tackled ureteroscopically?
If you can insert a bigger sheath, you’ll be more efficient. There has been some research recently on tamsulosin potentially having an effect in the ureter in allowing insertion of larger sheaths (J Urol 2018; 199:1622-30; World J Urol May 25, 2018 [Epub ahead of print]). In some of the studies of the use of sheaths with tamsulosin, they’re using a force gauge that actually gives you a real number as opposed to subjective observations. I look forward to those results; that could be a big step forward.
Do you use tamsulosin typically in all of your cases before inserting the access sheath?
We don’t have a firm position on tamsulosin yet. I tell patients it’s the “might” drug. It is certainly controversial whether tamsulosin actually helps stones pass. We presented research at the 2018 AUA annual meeting that showed that careful attention to symptom control was more important than tamsulosin (BJU Int July 18, 2018 [Epub ahead of print]). Still, we can’t rule out that tamsulosin “might” be beneficial in some circumstances. It “might” make it easier to place an access sheath but we are still waiting on larger randomized trials. It “might” decrease postoperative symptoms from a stent, although there was also a nice 2018 AUA paper saying that that didn’t pan out but the sample size was limited (J Urol 2018; 199:e388-9).
It may be difficult to evaluate whether tamsulosin makes a difference on placing access sheath in clinical practice. Our primary access failure rate is only 5%, so it would have to be a very marked effect to make a noticeable improvement. If we move from 5% to 4%, we’re really not going to perceive a difference. The change that we might perceive is being able to get to larger sheaths.