(1)
Surgery, University of Melbourne, Parkville, Victoria, Australia
Most urologists have their own techniques for track dilatation, stone fragmentation and removal.
This chapter describes my technique of establishing a track for PCNL.
In spite of variations in instrumentation and techniques, the principles of PCNL and track creation remain constant.
The overriding requirement for successful PCNL is unhurried patience and avoidance of force.
Ignoring these principles invariably results in complications or early termination of the procedure.
This chapter describes patient positioning, percutaneous puncture of the kidney and the introduction of a stable guide wire.
I have two aims when placing a guide wire.
Firstly, that the guide wire is passed into the kidney and preferably down the ureter. If not, as much wire as possible is coiled within the kidney to provide maximum stability for dilatation.
Secondly, as soon as possible, the creation of a universal guide wire (UGW).
Track Dilatation
Whether using Amplatz serial dilators, car aerial dilators, balloon or single-stage dilators, e.g. Webb SSD or “mini perc” dilators, they all involve the passage of at least one dilator from the skin into the renal collecting system.
Track Size
This varies depending on the proposed procedure:
Routine stone fragmentation – 26 Fr
“Mini Perc” < 20 Fr
Large-volume staghorn calculus removal – 28–32 Fr
Endoscopic pyeloplasty – 22–24 Fr
Paediatric PCNL – 16 Fr
Track Dilatation
Aim
The aim of track dilatation is to insert the dilator and its sheath into the collecting system without kinking or dislodging the guide wire, or displacing the kidney.
Principles
All dilators must be inserted under II screening.
At all times, the direction of both the dilator and guide wire must be parallel to each other.
Fig. 5.1
Renal dilators must be inserted over and parallel to the path of guide wire
Guide wire angulation can result in the following scenarios:
Kinked guide wire
Guide wire dislodged within or displaced from the kidney
Rotation, displacement or “flipping” of the kidney.
Fig. 5.2
If a dilator is passed at an angle to the guide wire, it will kink and may displace the guide wire
Fig. 5.3
Angled dilation over a guide wire, particularly with a lower pole puncture, can easily flip or rotate the kidney forwards
Kinked Guide Wire
Once a metallic guide wire is kinked, it is useless and cannot be used for dilation.
It must be removed.
If the needle sheath can be threaded over the kink into the kidney, the guide wire can sometimes be replaced (this is an uncommon but occasionally lucky scenario, always worth a try)
If not, the guide wire must be removed and a new puncture made.
I use hydrophilic guide wires for all my punctures.
This is because the inherent frictionless movement of the wire allows the wire to coil easily within the kidney or even better, to pass through the pelviureteric junction and smoothly down the ureter.
Hydrophilic guide wires do not crush when held by artery forceps.
Metallic guide wires are fragile and easily crush if grasped by artery forceps, rendering them useless.
I use a metallic “J wire” as a retrieval wire when dealing with a “through and through” puncture.
The Body Wall Component of the Nephrostomy Track
Once a guide wire is stable within the kidney, formal track dilatation may commence.
The path to the kidney should be as frictionless as possible to allow tactile feedback during dilatation of the kidney.
The major sites of friction are as follows:
Skin
Lumbodorsal fascia
Scar tissue from previous surgery
The Skin
Once the surgeon is confident that the guide wire is satisfactorily placed, the skin puncture should be extended by incising the skin and dermis with a scalpel either side of the guide wire, approximately 1 cm in length, parallel to Langer’s lines. The scalpel must cut the full thickness of the dermis.
This will allow free movement of the dilator at the entry site.
Lumbodorsal Fascia
I pass a pair of straight artery forceps under II control alongside the guide wire in the direction of the puncture, so the closed tips are just short of the kidney.
It is clear to the surgeon when the tips traverse the lumbar dorsal fascia because there is a palpable “give”.
The forceps are then opened under II screening. The surgeon feels the lumbo dorsal fascia splitting and separating.
The forceps are then relaxed, but not completely closed, as they may otherwise grasp and extract the guide wire. The forceps should be removed slowly, checking with II to ensure the wire has not been inadvertently grasped.
This may seem quite a “physical method” of a track dilatation, but in over 30 years I have not had a complication from this manoeuvre.
However, it should not be used for any supracostal puncture, as opening the forceps tips could tear the pleura.
This technique also dilates and separates body wall scar tissue.
At this stage, the track is prepared and the sites of potential friction cleared, so the dilator and Amplatz sheath may be introduced.
Track Dilation
In a routine adult stone case, I use a Webb Single-Stage dilator (26 Fr).
This dilator will usually pass easily into the kidney in a single passage. The diameter allows irrigation and free movement of a standard nephroscope.
As a result of the oval shape of nephroscopes, their widest dimension will be greater than the radius of a circular Amplatz sheath of the same French gauge. Hence the selection of a 26 Fr Amplatz sheath for a 22 Fr Nephroscope.
There can be significant resistance to the passage of a dilator, particularly if introduced between ribs, or at the level of the lumbo dorsal fascia, even when the fascia has been split with artery forceps.
This may result in a sudden “jerk” forwards as the dilator passes through one of these areas of resistance.
This “jerking” of the dilator tip may cause kinking and displacement of the guide wire or damage to the kidney. The surgeon must anticipate this potential hazard and avoid sudden over advancement of the dilator.
The surgeon is responsible for every step of a PCNL.
Guide Wire
The surgeon must control the guide wire, holding it with the non-dominant hand, so the guide wire does not become displaced during the dilatation.
Hydrophilic guide wires can easily slip or spring out if not carefully maintained. They should be grasped by artery forceps. These will not damage a hydrophilic guide wire.
Dilator
The surgeon must prevent uncontrolled movements, e.g. jerking, or over advancement of the dilator and prevent angulation, which may lead to displacement of the guide wire.
Fig. 5.4
Safe technique of passing a dilator over the guide wire
The below diagram outlines the dilation technique. The surgeon maintains the guide wire (hydrophilic) with artery forceps using the non-dominant hand. The dominant or dilating hand rests on the patient’s back on the ulnar aspect, with the thumb, index and middle finger free to rotate and advance the dilator, holding the dilator in the classical “pencil grip”.
The dilator is advanced and rotated simultaneously. This allows the tip of the dilator to gently enter and dilate the renal substance and capsule and decreases friction from skin and fascial layers on the dilator as it advances.
Commencement of the Track and Kidney Dilation
The guide wire is grasped and held externally by the surgeon at the outer end of the dilator using artery forceps.
If the wire is not held close to the dilator, it may spring out. This is a tedious but avoidable scenario.
The dilator is inserted parallel to the direction of the original scalpel stab, needle track and guide wire.
The dilating hand is placed, ulnar side down, on the patient and the dilator controlled by the thumb, index and middle fingers using the “pencil grip”.
The tip of the dilator is gently rotated and advanced through the skin after the skin puncture has been enlarged using the scalpel.
II monitoring confirms that the direction of dilator and the wire are parallel. If not, the course of the dilator must be realigned under II screening.
Retrograde contrast should be infused gently through the retrograde ureteric catheter via minimal volume extension tubing. Vigorous infusion can result in pyelovenous and forniceal extravasation of contrast, resulting in radiological obliteration of the collecting system. A gentle infusion will delineate and distend the targeted calyx.
The dilator is slowly and gently advanced towards the kidney, rotating and screening throughout.
The introduction of the tip of the dilator into the kidney is monitored by II.
If the dilator is displacing the kidney, or not entering easily, the dilator should be removed and exchanged for a 12 or 14 Fr fascial dilator. These smaller dilators will “drill” rather than separate the renal capsule and parenchyma without displacing the kidney (this manoeuvre is only occasionally required).
This initial “drill” opens the track sufficiently for the entry of the tip of the SSD. At this stage, the SSD can be reintroduced. Once the shoulder of the SSD dilator is within the collecting system, an Amplatz sheath is placed over the dilator and inserted by simultaneous advancement and rotation.
While rotating and advancing the Amplatz sheath, the dilator must be stabilised to prevent it being inadvertently over-advanced into the kidney.
To do this, the surgeon holds the external end of the dilator with his non-dominant hand, with his elbow firmly on the patient’s back. By doing so, the dilator is safely fixed.
Care must be taken not to advance the leading edge of the Amplatz dilator past the shoulder of the dilator. The edge of the Amplatz sheath is bevelled, oblique and sharp and if not directly applied to the shaft of the dilator, can cut parenchyma, collecting system and vessels.
When using the Webb Single-Stage Dilator, a proximal external marker on the dilator notifies the surgeon when the leading tip of the Amplatz sheath is at the shoulder of the dilator.
With all dilating systems, the passage of the Amplatz sheath over the dilator into the kidney must be monitored by II.
Once the Amplatz sheath is safely inside the kidney, the following should be done:
The dilator may be removed.
The guide wire must be re-grasped at the outer edge of the Amplatz sheath with forceps. The assistant now maintains this wire.
The Amplatz sheath must also be supported by the assistant, but NOT PUSHED IN, a common mistake made by assistants in the mistaken belief they are being helpful. Advancing the Amplatz sheath without a dilator may result in severe trauma to the parenchyma, vessels and collecting system.
The kidney is now ready for nephroscopy.
Nephroscopy and Stone Removal
Plan
Every PCNL is unique.
The surgeon must have specific aims, a “game plan” and a “fall back plan” before commencing any PCNL, anticipating potential difficulties and complications.
In the case of an infection-related calculus, the aim is complete clearance of all stone.
If the stone is very large, the surgeon may plan for multiple punctures, followed by elective ESWL or “second look” PCNL.
If the stone is large, complex, infected and/or associated with a urinary diversion, it may not be possible, safe or practicable to clear all the stone, even by multiple operations. Many of these patients are high medical risk and medically unfit for repeated anaesthetics or anatomically unsuitable for ESWL or secondary PCNL approaches, so the surgeon has “only one opportunity” to remove as much stone as possible. These patients usually remain infected in any event, and tend to represent with stone recurrences in spite of initial complete stone clearance.
In this scenario, I aim for “stone palliation”. The primary aim of the PCNL is to remove all obstructing (pelvic or calyceal) stones first, and then as much of the bulk of the stone mass that is safely accessible within 2 hours of nephroscopy.
It is well documented that continuing a PCNL in excess of two hours is associated with a significant increase in all PCNL morbidities. This “philosophy” of “stone palliation” can be applied equally to recurring metabolic calculi, especially cystine, and those in horseshoe kidneys or associated with neurogenic bladders.
This concept of “stone palliation” is important to discuss and fully explain to a patient with recurring stones, and their physicians.
Both the patient and the surgeon must accept that it is not practical or safe to attempt to completely clear every kidney of all stone, and that the primary aim of PCNL is to unobstruct and preserve the kidney.
Nephroscopes
The majority of PCNLs are performed using rigid nephroscopes.
Flexible nephroscopes have limited applications. They can be useful as a delayed secondary procedure following an extensive PCNL or ESWL, to electively clear residual fragments. It is often written that flexible nephroscopy may access difficult calyces during an extended PCNL. This has not been my experience, as once well into a large PCNL, there is usually bleeding and the inaccessible calyces are usually quite angled with respect to the existing track. The flexible scope is limited by reduced irrigation due to a narrow channel, and compromised tip deflection within the small confines and acutely angled anatomy of the kidney. In my experience, the optimal application of the flexible nephroscopy (and holmium laser) is to reach and clear the medial stone bulk in a horseshoe kidney. In this case, the course is only slightly curved, so the length and lesser angulation required to reach these stones is ideally suited to flexible nephrolithotripsy.
Flexible nephroscopy can also be very useful during “mini-PCNL” which is virtually bloodless. One needs to upsize to the longer 21/24 Fr sheath and maintain the sheath lumen in the renal pelvis. This allows the flexed tip to access the calyceal necks and avoid the curved nephroscope to catch on and be damaged by the sheath tip.
The rigid nephroscope has an offset eye piece. The lens may be set at a right angle to the shaft of the endoscope, the “crank handle” or oblique at 30° the “angled”.
Either type of offset lens allows the passage of rigid lithotrites and surgical instruments directly through the working channel of the nephroscope. The combination of camera and an offset lens can be disorientating for the surgeon.
This special orientation of the camera must remain constant. The nephroscope should move within its attachment independent to the camera. The surgeon’s hand must maintain the camera in a constant orientation. This connection between the surgeon’s hand and the camera becomes the urologists “cerebellum”.
By keeping the camera orientation fixed, all movements of the nephroscope and the instruments through the nephroscope are instinctively orientated.
I do this by holding the camera and the cable, which always exits the camera at 6 o’clock, in my left or non-dominant hand. All instrumentation is by my right hand. This combination gives me completely accurate spatial orientation throughout the PCNL.
Most nephroscopes have a foroblique lens, varying between 10° and 30°. In other words, their view is angled, not directly ahead.
The instrument channels are eccentric, not central.
Therefore rotation of the nephroscope will provide a wide field of vision, resulting in good access to the majority of the collecting system, except for “parallel lie” and obliquely offset calyces.
Surgeons should be comfortable and facile with the capacity and limitations of their preferred nephroscope.
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