BackTable Article

PCNL Procedure Techniques


Quynh-Chi Dang • Jul 2, 2021

Percutaneous nephrolithotomy (PCNL), a minimally invasive alternative to open kidney stone surgery, is a surgical technique that is used to remove large or complex kidney stones. Urologist Dr. Margaret Pearle shares her PCNL procedure techniques, including optimal patient positioning, tips for opacification and gaining access to the renal system, her prefered lithotripsy devices, and PCNL complications.

We’ve provided the highlight reel in this article, but you can listen to the full podcast below.

The BackTable Urology Brief

• In a PCNL surgery, visualization and access to the stones are gained by X-rays and a nephroscope. Then, the stone is fragmented and removed using ballistic energy, ultrasonic energy, or lasers.

• Although the patient can be placed in the prone or supine position during the PCNL procedure, supine position is ideal when doing lower pole access cases, and prone position is ideal when doing upper pole access cases.

• Using air pyelogram to opacify the pelvicalyceal system is a viable alternative to using radiopaque fluid, which carries the risk of extravasation.

• Some lithotripsy devices, such as ShockPulse-SE Lithotripsy System (Olympus) and the Swiss LithoClast Trilogy Lithotripter (Boston Scientific), utilize dual ultrasonic and ballistic energy.

• Excessive bleeding and a significant perforation in the collecting system are two potential complications in PCNL surgery. In these cases, the safest option is to place a nephrostomy tube for drainage and operate on another day.

Table of Contents

Patient Positioning for PCNL Surgery

Opacifying the Pelvicalyceal System to Locate the Kidney Stones

Gaining Access to the Desired Renal Calyx

Lithotripsy Methods & Devices

Intra-operative Red Flags: Excessive Bleeding and Significant Perforations of the Renal Pelvis

pcnl surgery kidney stone

Patient Positioning for PCNL Surgery

During PCNL surgery, patients can be placed in the prone (face down) or supine (face up) position. Although multiple studies conclude that there is no difference in surgical outcomes between the two positions, Dr. Pearle prefers the prone position because the prone position gives her more freedom of motion. She also mentions that it is ideal to have patients in supine position when doing lower pole access cases and in prone position when doing upper pole access cases.

[Dr. Aditya Bagrodia]
So, maybe now we move into the operating room. So, prone versus supine, any strong opinions there?

[Dr. Margaret Pearle]
I'm a prone PCNL practitioner. And I think if you look at the literature, there are many trials. There are many retrospective and prospective randomized trials that have compared patients. And the bottom line is it really doesn't matter. Certainly the operating room time is a little shorter if you do it supine because of the positioning issues. But there's really no difference in stone free rates or blood loss or any other real parameters, like hospital stay.

So, the bottom line, I think, is it's a dealer's choice. People that do the supine position love it and are big advocates of it. And it's certainly easier than placing patients prone. From a pulmonary and cardiovascular standpoint, although everyone thinks that there's a greater risk when they're prone, it's actually not. From a cardiovascular standpoint, it's not unfavorable. In fact, patients are placed in the prone position in the ICU with ARDS and other cardiovascular or pulmonary problems. So, there's not really a cardiovascular advantage to that.

In my career, how many times have I had to flip a patient supine because of some catastrophe that was happening? Once that I can think of. So, it's generally not an issue. Our team is so efficient at getting patients prone that that adds 10 minutes, maybe 15 minutes to the whole operating room time, but I just haven't found it to be a barrier. And I find much more freedom of motion in the prone position.

...Most are doing lower pole access when they're treating patients supine. So, if you're an advocate of a lot of upper pole PCNL, you probably better off doing it prone.

Opacifying the Pelvicalyceal System to Locate the Kidney Stones

After positioning the patient, a catheter is inserted to drain the bladder. Dr. Pearle prefers to use an occlusion balloon to keep the catheter in place.

The next step of the PCNL procedure is to perform a pyelogram, a process used to opacify the pelvicalyceal system in order to provide an image of the renal pelvis and locate the kidney stone. Traditionally, radiopaque fluid is delivered into the kidney to study renal anatomy using X-ray imaging. However, she avoids the use of contrast because of the risk of extravasation--when the contrast accidentally leaks out of the vessels and decreases visibility.

Instead, she performs an air pyelogram; not only does this method eliminate the risk of extravasation, but it also helps her identify the posterior renal calyces from the anterior renal calyces. When an air pyelogram is not possible, such as in patients who have bowel gas, Dr. Pearle will use very little dilute contrast.

For patients who have an iodine allergy, steroid prep before PCNL surgery is needed if contrast will be used.

[Dr. Aditya Bagrodia]
Peg, I'm going to ask you to back up just a step. So, maybe I'm going to just ask you, so the patient's positioned. In your practice, I believe that you still are doing retrograde air pyelograms to understand your intraoperative collecting system anatomy. So, can you just talk us through that process, which allows you to get your percutaneous access?

[Dr. Margaret Pearle]
Yeah, so I place patients prone and I still do prone cystoscopy to pass a retrograde catheter into the collecting system. I still tend to use an occlusion balloon only because it helps prevent fragments from traveling down the ureter and it allows me to opacify the collecting system with some occlusion, so that I can get the collecting system a little more dilated.

There are lots of people that put access sheaths up. They can opacify with an access sheath as well. Some just use a 5 French angiographic catheter. But I still like an occlusion balloon because I definitely notice that I can dilate the collecting system more. And that often helps pass the guidewire.

I use air typically if I can avoid putting contrast in the collecting system. I like that because then I don't have to worry about a bunch of extravasation; if it takes more than one puncture to get in the collecting system, I don't have contrast all over the place, which sometimes can really make your visibility extremely difficult as you go from bad to worse, and you reach a point where you can't see the collecting system anatomy at all.

So, I use air if I can. I use it gently. I'm careful about it. But it also helps identify posterior calyces so the air will rise into the posterior calyces. So, that can help me identify what a posterior calyx is. By ultrasound, it's much easier to distinguish anterior from posterior. And then, I generally have an idea of where I want to access based on my preoperative imaging, but the intraoperative imaging may change my mind about where I want to go once I see where the stone is.

Sometimes an air pyelogram is not helpful if there's a lot of bowel gas or stool and you just can't see what the error is really opacifying. Then I'll use contrast. I tried to use it very dilute and as little of it as possible. And that, in combination with air, still can sometimes delineate the airfield posterior calyces and distinguish them from the contrast filled anterior calyces.

Additionally, you can distinguish anterior from posterior by just obliquing the C-arm away from the surgeon and as you oblique the C-arm away, the posterior calyces will elongate and move toward you. Anterior calyces will shorten and move away. So, by moving the C-arm, obliquing it back to straight AP and then laterally away from you, I can see which way the calyces are moving.

So, between that and air, you usually distinguish what's anterior and posterior and try to choose the posterior calyx, unless for some reason I have to puncture an anterior calyx because that's where the stone is and it's the only chance I have of getting there.

[Dr. Aditya Bagrodia]
One question that kind of came to mind as you mentioned contrast extravasation, patients with an iodine allergy. Are you premedicating? I mean, of course you're intrarenal, but there can be some non negligible systemic absorption.

[Dr. Margaret Pearle]
Yeah, I definitely do. I give all those patients standard steroid preps beforehand. I'm pretty adamant about that because for sure, they can absorb contrast. And there are definitely times where there's a fair amount of contrast extravasating out, whether it's during access or whether it's later in the procedure when we're opacifying the collecting system to map out the calyceal system and to assure that we've entered and inspected all the calyces, we inject contrast. And it's certainly easy to get extravasation and absorption. So, yeah, I do steroid prep routinely.

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Gaining Access to the Desired Renal Calyx

After using the pyelogram to determine the most optimal renal calyx for gaining access, a small puncture needle is inserted into the desired calyx. Then, a guidewire and a safety wire is introduced. After, the access tract is dilated using a balloon dilator and a sheath is placed to allow smooth insertion of surgical equipment into the access tract.

Dr. Pearle uses a 22 gauge puncture needle, a Jeffrey Introducer set, an Amplatz SuperStiff guidewire as a working guidewire, a standard Benson guidewire as a safety wire, and a 30 French sheath.

[Dr. Jose Silva]
What type of wires are you using? Do you always leave a safety wire?

[Dr. Margaret Pearle]
I do. I try to. I get access because I learned from an interventional radiologist. I use a Jeffrey Set, which is a 0.018 inch platinum tip guidewire or a coat Mandril wire. So, I get access with a 22 gauge or 21 gauge needle, which will only accommodate a smaller wire. So, that's a 0.018 inch guidewire.

You'd then have to transition to a standard size guidewire using some kind of an introducer set. So, as I said, I use what's called a Jeffrey Introducer Set. And it's really stiff. It's got an inner metal stiffener and an inner dilator and then an outer sheath. So, especially in an obese patient or someone who has a lot of scarring in the kidney, it's really rigid and it follows that platinum tip guidewire, which actually has a fair amount of rigidity too, even though it's so small. I find it much easier to get in using that very rigid system. It gets through the fascia and through the capsule really nicely.

Once you have the sheath in, it accommodates three standard size guidewires. So, then I can easily get my Amplatz Super Stiff guidewire, which I use as my working guidewire, and I just use a standard Benson guidewire as my safety wire. So, if I have the opportunity, I certainly routinely use a safety wire. But sometimes it's all I can do to get one wire in the kidney and then I use one wire. But when I can use a safety wire, I do. I try not to cut corners.

...So, then I obtain access again using my 22 gauge needle and try to get a wire down the ureter if I can. I don't torture myself trying to negotiate something down the ureter, but I certainly prefer it. In an obese patient, I really prefer it because I want as much stability with my guidewire as possible because it's so easy to lose a guidewire in an obese patient. You just move your scope a little bit and it just pulls out of the kidney. And it's remarkable how little wire you have in the kidney when it's just coiled in a calyx. So, if I can get it down the ureter, I do. And again, if I can get a safety wire in, which in most cases I can, I do.

And then I typically use balloon dilation.

[Dr. Aditya Bagrodia]
Okay. So, you've used your balloon to dilate. And then, is there a preferred sheath that you typically go with?

[Dr. Margaret Pearle]
I am still using the standard 30 French sheath. We can use a 24 French sheath sometimes. If you do that, you can't use the sheath of your nephroscope. So, if I use, for instance, a 24 French nephroscope, you have to take the sheath off to use it through a 24 French sheath.

I'm not sure the difference between 24 French and 30 French makes enough difference to warrant that. I think if you really want to get into smaller accesses, then you have to be looking at something less than 18 French, ideally less than 16 French. So, between 24 and 30 French to me isn't a real big difference. So, I still tend to use a bigger access sheath.

And that doesn't have to impact the size of the tube you leave postoperatively. You can still leave a smaller tube whether it's an 8 or a 10 French Cope loop or a 16 French or 18 French council catheter over an angiographic catheter. We know that you can leave smaller nephrostomy tubes despite larger access tracts.

[Dr. Jose Silva]
And are you using the clear sheath?

[Dr. Margaret Pearle]
I am not. The clear sheath originally came out several years ago. There were companies that made the clear sheath, and I thought it was such a brilliant idea until I used it, and it is frightening. I mean, you are literally seeing everything outside the sheath. You're seeing the fat, you're seeing everything. And it's really hard to see when the sheath is actually in or when it's not.

And when they first came out, I talked to them about it and they put a stripe on it. And the stripe was to help you know when you were in the sheath or not. But when you're in the collecting system or not, it still is hard to see it.

So, that's one of those ideas that I thought was brilliant, theoretically. But in practice, I hated it. I really hated it. It was not helpful. It was very confusing and very disconcerting. I don't want to see the parenchyma. I don't want to see that. I just want to know my sheath is in.

Lithotripsy Methods & Devices

After inserting a sheath, a flexible nephroscope is inserted through the sheath to visualize the stones. Then, a variety of methods can be used to fragment and remove the stones.

A lithotrite is a minimally invasive urological instrument that fragments stones in the urinary tract using ballistic (mechanical) energy. In contrast, a lithotripter is a device that fragments stones using ultrasonic energy. The ShockPulse-SE Lithotripsy System (Olympus) and the Swiss LithoClast Trilogy Lithotripter (Boston Scientific) are two lithotripters that utilize dual ultrasonic and ballistic energy. Dr. Pearle normally uses the ShockPulse in PCNL surgery, but recognizes that there are studies showing that the Swiss LithoClast Trilogy is more efficient for stone clearance.

Besides lithotripsy, holmium and thulium lasers can also be used to fragment the stones. Dr. Pearle normally uses a flexible scope to access the stone. In the case of very large stones, she does not hesitate to gain multiple access points in order to completely remove the stone.

[Dr. Aditya Bagrodia]
Okay. And in a more typical case, you're in good visibility, let's just say moderate-sized stone burden, what's your kind of standard approach in terms of what type of lithotripters are you using? When do you have to break out your kind of second line guns? If you could just kind of walk us through your tools there.

[Dr. Margaret Pearle]
Yeah. So, I guess my go-to is the Olympus ShockPulse. And conventionally, it's a single probe that has sort of dual lithotrite actions--ultrasonic and pneumatic action through a single probe.

Now, there's a Trilogy, which is a Boston Scientific instrument that also has sort of a dual lithotrite action. And there's some studies suggesting that it may be more efficient in fragmenting stones quicker, so more rapid stone clearance.

The one thing that's really missing is there was a device on the market that has subsequently been withdrawn called the StoneBreaker that just was a mechanical impacting device that used a compressed CO2 cartridge. And it just used the cartridge for power. It wasn't connected to any electricity or no foot pedal and it was incredibly effective for hard stones.

And we don't have that anymore. There was a problem with the sterilization of it. And I miss that. Because there are some uric acid stags that are incredibly hard, like the hardest stones that you deal with, that any of the other lithotrites just don't effectively breakup at all. And I've been in situations where I'm just fragmenting and fragmenting and fragmenting, and nothing's happening.

And the StoneBreaker used to just break them up into pieces really effectively. And you could just grasp and remove the fragments and we just don't have anything like that anymore that you can count on with an incredibly hard stone. So, I miss that device a lot.

Lasers are always available, especially when there are stones remote from the nephrostomy tract that you can only access with a flexible scope. And so, if you use a flexible nephroscope and you'd get into another calyx, then you need to break up a stone with just standard holmium or thulium fiber laser. So, those are really the two devices that I really keep at my disposal.

[Dr. Jose Silva]
Do you routinely do multiple access rather than using the flexible scope?

[Dr. Margaret Pearle]
No, I definitely much more commonly use a flexible scope if I can access it, but I don't shy away from multiple accesses at all. And I certainly have my share of cases where I've had eight accesses or twelve accesses in a case in patients with stenotic infundibulum.

I mean, there are times that even if you can get there flexibly if the volume of stone is so great, and if you have to pull all those fragments out of the calyx, you're just better off with another access. So, those are definitely the exceptions rather than the rule. But I think you always have to be prepared for that. There are times that it's so much faster to get a second access than to do it flexibly that it's just worthwhile.

Intra-operative Red Flags: Excessive Bleeding and Significant Perforations of the Renal Pelvis

The first PCNL complication that Dr. Pearle discusses is excessive bleeding. This may be a consequence of advancing the nephroscope too little or too much that it splits the renal infundibulum, the connection between the calyces and the renal pelvis. If the nephroscope has not advanced far enough, it can be carefully advanced further using the guidewire for reference. When twisting the nephroscope to look for the guidewire, surgeons must be careful to not accidentally pull the guidewire out of the collecting system.

Dr. Pearle also discusses how a significant perforation in the collecting system can cause extravasation of fluid and the loss of stones through the perforation.

In cases with significant bleeding or a significant perforation, Dr. Pearle recommends placing a nephrostomy tube to drain the blood/fluid and performing the PCNL surgery on the patient on another day when it is safer to do so.

[Dr. Aditya Bagrodia]
Okay. So, having done a bunch of these cases with Peggy, somehow she miraculously always manages to find her way into the collecting system with very little to do. But what are the kinds of red flags? I mean, when you see nice yellow urothelium, it's obviously a sign of relief. And to me, it was somewhat your experience, I think it's expected. But what are red flags as something is not quite right?

[Dr. Margaret Pearle]
I think when there's a lot of bleeding, then usually you're either not in far enough or you've split the infundibulum and you're in too far. I mean, the goal is to dilate the track to get your radiopaque mark on the balloon just inside the calyx. You don't need to go further. Your scope isn't as big as your sheath.

So, even though your scope, a 24 French nephroscope, may get through an infundibulum, a 30 French sheath may not. And same with smaller scopes and smaller sheaths. So, you really just want your sheath into the collecting system.

So, if I'm short, then I just carefully follow the guidewire. Oftentimes, I'll just use a grasping forcep and try to follow it and sort of spread along the way if I have underdilated. I'd rather underdilate than overdilate because you can underdilate and find your way in. If you overdilate and you split the infundibulum, there's no turning back.

But when you're following the guidewire in, you have to be really careful because as you torque your scope and you're looking for the guidewire, and you're sort of moving your scope and moving your sheath, you can pull the guidewire right out of the collecting system. So, the key is you have to follow the guidewire and try to keep the guidewire in one place and adjust your scope to follow the guidewire and not move your scope such that you move the guidewire out. So, that's tricky.

I have to say I tend to grab the scope away from a resident or fellow when we're in that situation because I've been there. I've made every mistake you can make and just learned from experience how to try to negotiate that scope along a guidewire or following a guidewire without losing your access.

[Dr. Aditya Bagrodia]
I can certainly tell you as a person who's trained with Peggy that that kidney system is going to be cleared out by any metric before you leave. And I kind of want to just pick your brain on exit strategies in a moment. But before we do that, we talked about pus and how that's generally going to be a cause for aborting the procedure. Any other kind of intraoperative occurrences that would tell you, okay, we've got to fight this one another day.

[Dr. Margaret Pearle]
I think if you have a significant perforation of the collecting system, you're losing fragments out of a hole, and--even more importantly--you're just getting significant extravasation of fluid, then it's time to get out.

I mean, a small perforation, again, it's a relatively low pressure system. I think you can get away with spending a little time. If I can advance my access sheath a bit to cover a hole, I'll do that if it's a split somewhere in the infundibulum. But if you have a big hole in the renal pelvis, there's not much getting around that. And you don't want to spend a whole lot of time with your nephroscope through a hole out in the retroperitoneum trying to retrieve fragments. And you can get significant absorption of fluid if you do that.

So, I think that if you have a significant real pelvic perforation, you should be thinking about getting out as quickly as you can, as soon as you can adequately establish drainage with a nephrostomy tube. So, that would be one reason for aborting.

Significant bleeding, certainly, a more common reason for aborting. You reach a point where you're just collecting clots in the bag, it's probably time to get out. Because almost always, once you get your nephrostomy tube in, the bleeding will cease. So, I think as much as we have a tendency, and I'm completely guilty of this, of sort of pushing on thinking I'm almost done, I'm almost done, probably a better part of valor is to put in a nephrostomy tube and come back 48 hours later to have a clear field. And it's going to be a lot safer for the patient.

Podcast Contributors

Dr. Margaret Pearle

Dr. Margaret Pearl is a Professor and Vice Chair of Urology at UT Southwestern Medical Center in Dallas, TX.

Dr. Aditya Bagrodia

Host Dr. Aditya Bagrodia is a practicing urologic oncologist and assistant professor at UT southwestern.

Dr. Jose Silva

Co-host Dr. Jose Silva is a board certified urologist practicing in Central Florida.

Cite This Podcast

BackTable, LLC (Producer). (2021, June 16). Ep. 9 – Tips & Tricks for Percutaneous Nephrolithotomy (PCNL) [Audio podcast]. Retrieved from

Medical Disclaimer

The Materials available on are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Urology Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.

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