PCNL Advances and updates

PCNL
Challenges and Updates
PROF Ashraf Shahin
Head of Urology
Zagazig University

Challenges facing the Endourologist
• The patients
• The stone
• The kidneys
• The technique [Puncture , access , Exit strategy and complications]
• Training

• Morbidly obese patients with urolithiasis present a therapeutic
and diagnostic challenge to the Urologist

• (body mass index
40kg/m2)
• Positioning
• Need of a special
instruments and
operating table

• Cardiac Disease 67%
• Abnormal (ECG) 77%
• COPD 29%
• DM 8%

•More challenging clinical scenarios:
•Catheter dependent cardiac patient
•DI coronary stent pacemakers defibrillators
•Hepatic patients

• Need for special instruments
• Radiation hazards

Skeletal deformities
•Difficult positioning
•Difficult renal access

• Principally, staghorn calculi are defined as branched
stones in the renal collecting system.
• However, there are several different constellations,
within this entity.

Description
Rassweiler
[Rassweiler et al ,
1986]
Rocco
[Rocco et al, 1984].
"C" describes the morphology and topography
of renal stones in five degrees (C1-C5)
Griffith
[Griffith and Valiquete,
1987]
The kidney is divided into 3
cavities (pelvis, branches or
infundibula and calices)
Filling the pelvis and
one calyx
Borderline Staghorn C2,C3 IC1
Filling the pelvis and
two or more calyces
Partial staghorn C4 P1 IC2
Filling of the entire
renal collecting system
(> 80%)
Complete staghorn
C5 P1 IC3

•There is no unified language for describing renal
stone regarding complexity and outcomes
•SFR and residual stones
•Multiple puncture

• Congenital renal anomalies are more common
• Difficulties in access and need for multiple punctures
• Need for auxiliary procedures

• Renal impairment
• Renal allograft

THE TECHNIQUE
•Puncture
•Access
•Exit strategy
•Complications

Training
•PCNL is a complicated procedure with many
steps
Ko R, Soucy F, Denstedt JD, Razvi H. Percutaneous nephrolithotomy made easier: a practical guide, tips and
tricks. BJU Int2007;101:535–9.

Knowledge acquisition.
• Anatomical knowledge;
• Procedural knowledge (both imaging and surgical procedures)
Skill acquisition.
Skills laboratory training.
Experience acquisition.
• Basic skills practice; residency/fellowship programme.
• Advanced skills practice; advanced training courses and workshops.

•IMAGING
•PATIENT POSITIONING
•INSTRUMENTS
•ACCESS
•Exit strategies
•Training

• Computed tomography (CT) is mandatory for preoperative planning and
appropriate percutaneous access.
• Anatomy of kidney calices and the relation of the stone to the pelvicalyceal
system, the kidney position, an its relation to other abdominal structures.
Rodrigues PL et al. Kidney targeting and puncturing during percutaneous nephrolithotomy: recent advances
and future perspectives. J Endourol. 2013;27(7):826-34.

• Angiographic CT can also be used for detailed images
of blood vessels and calyceal anatomy.
Kalogeropoulou C et al. Imaging in percutaneous nephrolithotomy. J Endourol. 2009;23(10):1571-7.

• Technological advances
have also enabled the
acquisition of three-
dimensional (3D) images
through ultrasound (US),
providing volumetric
measurements and 360-
degree analyses of
anatomic structures.10

• After using the benefits of cone beam CT (CBCT) in neurosurgical
operations, the application has been extended to percutaneous surgery.
• CBCT is a novel imaging modality that combines the versatility of
conventional C-arm with the functionality of cross-sectional imaging to
provide high-resolution, 3D, CT-like images.
Arvind P. Ganpule, Mahesh R. Desai. What’s new in percutaneous nephrolithotomy. Arab Journal of Urology.
2012;10(3):317–23.

• Help for better percutaneous access using the advantages of
improved imaging
• real-time access via high quality CT images.
• Reduce the need for postoperative imaging and subsequent
adjunctive procedures for clearance of residual fragments.
Roy OP et al. Cone beam computed tomography for percutaneous nephrolithotomy: initial
evaluation of a new technology. J Endourol. 2012;26(7):814–8.

Multimodal Imaging
• combined preoperative magnetic resonance imaging (MRI) with
augmented intraoperative USG images, and found valuable results due
to the additional advantages of high resolution, multi-planar, and 3D
images.
Li ZC et al. Augmenting intraoperative ultrasound with preoperative magnetic resonance planning models for
percutaneous renal access. Biomed Eng Online. 2012;11:60.
• The Interactive Closest Points algorithm was used as a rigid registry
process through the manual selection of pairs of points in both images
from the cranial pole, caudal pole, and kidney hilum.
• A respiratory gating method was also used to minimize the impact of
kidney deformation by using US to obtain only images at the same stages
of the respiration cycles.

• classification of staghorn stones into three types has been proposed based
on the volume of distribution of stone and the surface area.
• Type 1 staghorn stones have a total stone volume of <5,000 mm3 with <5%
of unfavorable calyceal stone percentile volume
• Type 3 staghorn stones have a total volume of >20,000 mm3 with >10% of
unfavorable calyceal stone percentile volume.
• The type 2 staghorn stone is in between.
Arvind P. Ganpule, Mahesh R. Desai. What’s new in percutaneous nephrolithotomy. Arab Journal of Urology. 2012;10(3):317–23
Mishra S et al. Percutaneous
Nephrolithotomy monotherapy for staghorn: paradigm shift for ‘staghorn morphometry’ based clinical classification. Curr Opin Urol. 2012;22(2):148–
53.

• Based on statistical models, they found that a type 1
staghorn stone would require one access in one stage
• type 2 stones would require one access in more than one
stage, or multiple accesses in one stage
• type 3 stones would require multiple accesses and stages.

Nephrolithometric Nomogram
• A nomogram was constituted to predict the stone-free rate
using preoperative parameters, including case volume, prior
treatment, stone burden and location, staghorn stones, and
number of stones.
• A high total score was significant for a higher chance of
stone-free rate, while low score had a lower chance of stone-
free rate. Stone burden was the best predictor of treatment
outcome.

S.T.O.N.E. Nephrolithometry
• ).18

• The patients
• The stone
• The kidneys
• The technique [Puncture ,
access , Exit strategy and
complications]
• Training
ADVANCES IN
IMAGING

The prone position in PCNL is frequently associated
with discomfort, especially for:
• obese patients
• severe musculoskeletal deformities
• cardiovascular and respiratory problems.

• Cracco et al.26 emphasised that the Galdakao-modified supine Valdivia position
is safe, effective, and provides more advantages than the others.
• An easy puncture of the kidney, a reduced risk of colonic injury, and simultaneous
antero-retrograde approach to the renal cavities without any requirements of
intraoperative repositioning are just a few of the advantages of this position.
Cracco CM et al. The patient position for PNL: does it matter? Arch Ital Urol Androl. 2010;82(1):30-1.

• A randomized comparative study of the prone, supine, and flank
positions in 150 patients showed that the supine and flank positions
were as efficient as the prone position with experienced hands.
• They also concluded that the preference of the surgeon and proper
case selection are the main factors for successful PCNL.
Karami H et al. A study on comparative outcomes of percutaneous nephrolithotomy in prone, supine and
flank positions. World J Urol. 2013;31(5):1225-30

• The patients
• The stone
• The kidneys
complications]
• Training
ADVANCES IN
POSITION

• Improved lithotripsy devices (Gyrus ACMI CyberWand®, Swiss
LithoClast Select with Vario® and LithoPUMP®, Cook LMA
StoneBreaker®)

• New lithotripsy devices, including a combination of ultrasonic-
pneumatic device, dual ultrasonic lithotripter, and pneumatic stone
breaker, have the potential to enhance the efficiency of stone
fragmentation.
Antonelli JA, Pearle MS. Advances in percutaneous nephrolithotomy. Urol Clin North Am.
2013;40(1):99-113.

• stone retrieval and occlusion devices (PercSys Accordion®, Cook Perc
N-Circle®, etc.),
•

• Hemostatic or adhesive agents for tubeless procedure can be valuable
tools for successful PCNL.

Micro , Mini , Ultra mini ………….

• The patients
• The stone
• The kidneys
complications]
• Training
ADVANCES IN
INSTRUMENTS

Endoscopically Guided PCNL
• Grasso et al reported first endoscopy-assisted percutaneous
renal access as an alternative technique for successful access
in a few patients in whom other methods failed.
Grasso M et al. Flexible ureteroscopically assisted
percutaneous renal access. Tech Urol. 1995;1(1):39–43.

• Later, the technique was developed as a primary access method by
insertion of the needle into the collecting system under the guidance
of both fluoroscopy and direct vision of flexible ureteroscope.
Sountoulides PG et al. Endoscopyguided percutaneous nephrostolithotomy. Benefits of ureteroscopic access and
therapy. J Endourol. 2009;23(10):1649–54.
Wynberg JB et al. Flexible ureteroscopydirected retrograde nephrostomy for percutaneous nephrolithotomy:
description of a technique. J Endourol. 2012;26(10):1268-74.
Kawahara T et al. Ureteroscopy assisted retrograde nephrostomy: a new technique for percutaneous
nephrolithotomy (PCNL). BJU Int. 2012;110(4):588-90.

• The direct visual confirmation has the advantage of a successful
access in a short time with no requirement of multiple attempts. The
original technique and its subsequent modifications were reported to
have a success rate of 89–100%.36-38
Sountoulides PG et al. Endoscopyguided percutaneous nephrostolithotomy. Benefits of ureteroscopic access and
therapy. J Endourol. 2009;23(10):1649–54.
Wynberg JB et al. Flexible ureteroscopydirected retrograde nephrostomy for percutaneous nephrolithotomy:
description of a technique. J Endourol. 2012;26(10):1268-74.
Kawahara T et al. Ureteroscopy assisted retrograde nephrostomy: a new technique for percutaneous
nephrolithotomy (PCNL). BJU Int. 2012;110(4):588-90.

Robotics
• Different types of robotic systems are under development
• include image-guided robots that, in addition to the direct visual
feedback, use medical images for guiding the intervention.4
Rodrigues PL et al. Kidney targeting and puncturing during percutaneous nephrolithotomy: recent
advances and future perspectives. J Endourol. 2013;27(7):826-34.

• (PAKY-RCM) consists of an orientation module between a needle
driver and a robotic 7-degree free arm, enabling the positioning of the
needle and completion of its insertion using rotational movements.
• The system regulates the strength during the access.
• The surgeon controls all movements of the robot via a joystick under the
guidance of fluoroscopic images.
Mozer P et al. Urologic robots and future directions. Curr Opin Urol. 2009;19(1):114-9.

• The AcuBot robot includes previous robotic modules, but adds a
bridge-like structure over the table, and a linear pre-positioning stage.
This attaches to CT or fluoroscopy table of the imager.
Rodrigues PL et al. Kidney targeting and puncturing during percutaneous nephrolithotomy: recent advances and future perspectives. J Endourol.
2013;27(7):826-34.
Pollock R et al. Prospects in percutaneous ablative targeting: comparison of a computer-assisted navigation system and the AcuBot Robotic
System. J Endourol. 2010;24(8):1269-72.

• The newest robot (MrBot) is introduced as a fully-actuated MRI robot
for image-guided access for percutaneous interventions.
Rodrigues PL et al. Kidney targeting and puncturing during percutaneous nephrolithotomy: recent advances and future perspectives. J Endourol.
2013;27(7):826-34.
Cunha JA et al. Toward adaptive stereotactic robotic brachytherapy for UROLOGY • May 2014 EMJ EUROPEAN MEDICAL JOURNAL 89 prostate
cancer: demonstration of an adaptive workflow incorporating inverse planning and an MR stealth robot. Minim Invasive Ther Allied Technol.
2010;19(4):189-202.

Technology is still struggling to overcome some
important problems in difficult initial setups,
expensive costs, mechanical problems, absence of
tactile feedback, and not fully developed motion
tracking systems.
Rodrigues PL et al. Kidney targeting and puncturing during percutaneous
nephrolithotomy: recent advances and future perspectives. J Endourol.
2013;27(7):826-34.

Tracking and Surgery Navigation

Tracking and Surgery Navigation
• Navigation software and augmented reality systems have
recently been introduced as computer-assisted navigation
systems combining imaging and tracking systems.
Nicolau S et al. Augmented reality in laparoscopic surgical oncology. Surg Oncol. 2011;20(3):189–201.

• They obtain the target anatomic area from preoperative data, using image
segmentation algorithms or computer graphics
• Then, the image processed data are superimposed and registered onto a real-
time intraoperative video (augmented reality) or static preoperative volume data
• (navigation software).
• The surgical tools are commonly updated using a motion tracking system.

Challenges:
• tissue deformation
• respiratory movements.
Teber D et al. Augmented reality: a new tool to improve surgical accuracy during laparoscopic partial
nephrectomy? Preliminary in vitro and in vivo results. Eur Urol. 2009;56(2):332-8.

• Huber et al. tested a navigated renal access in an ex vivo model.
• The surgical needle is guided to the renal calix according to the information
retrieved by a catheter that integrates electromagnetic motion tracking
sensors.
• The reported access time was 14 seconds with a precision of 1.7 mm.
Huber J et al. Navigated renal access using electromagnetic tracking: An initial
experience. Surg Endosc. 2011;25(4):1307–12.

• Rodrigues at al electromagnetic tracking system for kidney
puncture in pigs.
• A catheter with an electromagnetic tracking sensor was placed by
ureterorenoscopy into the desired puncture site.
• A tracked needle with a similar electromagnetic tracking sensor was
subsequently navigated into the sensor in the catheter.
• They described the method as highly accurate, simple, and quick.
Rodrigues PL et al. Collecting system percutaneous access using real-time tracking
sensors: first pig model in vivo experience. J Urol. 2013;190(5):1932-7.

Rassweiller J et al. iPad-assisted percutaneous access to the
kidney using marker-based navigation: initial clinical
experience. Eur Urol. 2012;61(3):628-31.
• Recently, Rassweiler et al.47 reported iPad-assisted percutaneous
access. All anatomic structures were identified and marked in
preoperative CT images. Augmented virtual reality of preoperative CT
3D images could display all anatomical details of the kidney.

• The patients
• The stone
• The kidneys
complications]
• Training
ADVANCES IN
ACCESS

• Recently, most notably modification has been a tubeless PCNL
alternative to nephrostomy tube.
• It appears to decrease postoperative discomfort and shorten hospital
stay, without increasing complication rate in selected cases.48
de Cógáin MR, Krambeck AE. Advances in tubeless
percutaneous nephrolithotomy and patient selection: an
update. Curr Urol Rep. 2013;14(2):130-7.

• Therefore, tubeless PCNL can be feasible in selected patients. In order
to improve outcomes of tubeless PCNL, application of hemostatic
agents along the percutaneous tract.

• Urologist will need to perform a certain number of
PCNLs to gain the necessary experience and skills to
conduct the surgery competently.

• Taniverdi et al noted that the operative duration improved to a steady
level after the surgeon had performed 60 cases.
• This was also true for the mean duration of fluoroscopy.
• Allen et al also noted that the operative duration for new surgeons
reached a plateau level after 60 cases.
Tanriverdi O, Boylu U, Kendirci M, Kadihasanoglu M, Horasanli K, Miroglu C. The learning curve in the training of percutaneous nephrolithotomy. Eur Urol
2007;52:206–12.
Allen D, O’Brien T, Tiptaft R, Glass J. Defining the learning curve for percutaneous nephrolithotomy. J Endourol 2005;19:279–82.

• Ziawee et al reported that the variables reached a steady level after
45 cases.
• However, focusing on the stone clearance rate, it took 105 cases to
reach an excellent level.

• a urologist probably
needs 45–60 cases
to achieve surgical
competence in
PCNL, and >100
cases to achieve
excellent results
after PCNL.

• There is paucity of literature regarding the current
simulators for training and assessing PCA skills.
• The PERC Mentor simulator is currently the only
validated VR simulator used for training and assessing
PCA skills.
• Expensive
• No evidence regarding the transfer of PCA skills from
the PERC Mentor to the OR.
• Therefore, more research is needed to validate these
simulators and assess their educational impact for
urology trainees and attending urologists.

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