A standard PCNL (percutaneous nephro lithotomy) requires a large percutaneous tract into the kidney to allow the passage of the nephroscope.
This tract is usually dilated to 30F with a 32F Amplatz sheath left in situ for the nephroscope. Smaller tracts can be made (mini perc) but in our experience there is no advantage of this over the standard pcnl tract, even in young children. The disadvantage of miniperc is the smaller scope used with smaller working channels and less irrigation which will lead to a longer procedure time.
There are three ways to form the tract for a PCNL procedure.
1. Plastic serial dilators. Each dilator is used once, withdrawn and replaced for a larger one until the tract is large enough to accept a sheath for a nephroscope. This method although cheap leads to significant blood loss due to repeated removal of the dilators and I would not recommend it.
2. Metallic serial telescopic dilators. These are inserted over a stiff guidewire that has been placed down the ureter. Each dilator is inserted over the previous one making the tract progressivley larger until the 32F sheath is finally placed over the largest 30F dilator. The dilators are then removed as one over the wire. This technique is cheap reliable and allows dilatation all the way up to the stone in the entry calyx. These dilators are also used for tract formation during percutaneous pancreatic necrosectomy.
3. The Nephromax balloon (Boston scientific) and other similar balloons. This is inserted over a stiff guidewire that has been placed down the ureter. The distal end of the balloon is placed in the collecting system as close to the stone as possible. The balloon is inflated using a pressure inflation device. The Amplatz sheath is then inserted over the balloon. The problem with these balloons is that they all have a tapered end. This means that you cannot dilate a tract all the way up to a stone that is right on the edge of the PC system such as a staghorn, cast calculus or calyceal diverticulum. The advantage of this system is speed.
The dilators are made from stainless steel. The first dilator is braided and is flexible, although there is a rigid alternative. We dont tend to re use the first dilator but the remainder can be easily re sterilised which makes this a very cheap option.
There are nine dilators including the first. The first dilator also has a ball on the distal end that prevents the remainder of the dilators advancing beyond it.
The video below demonstrates the use of the metallic dilators (Storz) during a PCNL masterclass we performed recently at the Freeman Hospital in Newcastle upon Tyne (UK).
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You can see that these dilators are easy to use and relatively quick. The final blunt end to the dilated tract means that the dilators and sheath can be placed right up to the stone.
A point to note is that you must not allow the kidney to be pushed away from the dilators as they are inserted as the relative movement will pull the dilators back along the tract. Also care must be taken not to kink the 1st dilator when dilating a steeply angled tract.
The following video shows the use of the Nephromax balloon (Boston Scientific) during the Newcastle PCNL Masterclass. You should also see
Dominic Fay's review of this device.
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Dr Rob Williams, Consultant Interventional Radiologist, Freeman Hospital.
The balloon is also easy to use, but not good for staghorn calculi, cast calculi and calyceal diverticulae.
In our experience these dilators have proved reliable, durable and cost effective.
Time for tract dilatation is longer than for the nephromax balloon, but often not significant given the length of some of these procedures. This is certainly offset by the cost saving over balloon dilatation. If cost is not an issue, then its possible to use a balloon for most PCNLs.
No conflict
Dr Phil Haslam
Consultant Interventional and Uroradiologist.
Freeman Hospital, Newcastle, UK
