EURURO Vol. 72 No. 4

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starting from insertion of the needle was 20 s (range 15–35).
All punctures were successful at the first attempt. All the
procedures were performed without X-ray exposure. No
complications occurred.
4. Discussion
We report the first clinical use of a novel technique for
percutaneous kidney access based on a novel tracking
system using visual-assisted navigation and real-time
electromagnetic sensors. We successfully demonstrated
the accuracy and safety of this technology. Precise puncture
of the collecting systemwas obtained in 100% of cases, with
a median time to successful puncture of 20 s, without X-ray
exposure and without any complications.
This system was previously tested in an ex vivo model
and in an in vivo animal model In the preliminary
investigation, six female pigs were subjected to ureteral and
kidney punctures, and four punctures were performed by
two surgeons in each animal, including one in the kidney
and one in the middle ureter, on both sides. All 24 punctures
(12 in the middle ureter and 12 in the renal calyces) were
successfully carried out. The average time for puncture was
19 s in the kidney and 51 s in the ureter (p = 0.003). A
shorter puncture planning time was recorded for expert
surgeons compared those in training (p = 0.03).
In this procedure, we used a combined retrograde and
percutaneous endoscopic approach for intrarenal surgery,
which has become increasingly popular over the past few
years Ureteroscopy-guided percutaneous fluoroscopic
access was already suggested 20 yr ago More recently,
Alsyouf et al described a technique combining ultrasound
guidance with direct endoscopic visualization; they chose the
ideal calyx for puncture using ureteroscopy visualization, and
ultrasound served as a guide for insertion of the needle.
Using our navigation system with real-time electromag-
netic sensors, the virtual track is visualized in 3D on the
monitor so that the surgeon can confirm that the catheter
and needle are aligned in parallel. When necessary, the
surgeon can redefine the orientation of the catheter and a
new virtual trajectory is then calculated. The procedure
provides real-time positioning, allowing the surgeon to
achieve constant perfect orientation of the needle even in
the presence of anatomical deformities. Confirmation of the
absence of anatomical structures along the puncture path is
checked using ultrasound. This technique has the following
advantages: a lack of exposure to ionizing radiation; real-
time 3D images of the needle trajectory; correct needle
placement and orientation in real time; greater ease of
technical learning; a short execution time; the possibility of
redefining the trajectory; constant monitoring via the
electromagnetic sensors and the endoscopic view, allowing
the surgeon to make minor adjustments; and real-time
monitoring of anatomical changes. Moreover, the entire
procedure can be performed in the supine position,
eliminating the need for patient repositioning and thus
reducing the operation time. However, we also recognize
some disadvantages associated with this novel technique: a
lack of visualization of surrounding anatomical structures;
and potentially difficult placement of the ureteral catheter
with an electromagnetic sensor in the desired calyx in
situations in which the calyx is occupied by a calculus.
To overcome the drawbacks of ultrasound- and fluoros-
copy-based techniques for puncture of the renal collecting
system, several technologies and techniques have been
explored. Each has advantages and disadvantages .
Bader et al described the use of an optical system
incorporated into the percutaneous needle allowing real-
time visualization of the renal collecting system, thereby
eliminating the need for fluoroscopic guidance. This ‘‘all-
seeing’’ needle was tested in 15 patients; the puncture had
to be repeated in four of them (26%). The advantage of this
system is secure identification of the needle location within
the renal collecting system immediately after entry.
Visualization of needle entry was aided by ultrasound
guidance. However, the system does not allow redirection
of the needle in cases of path error. Other disadvantages are
difficult visualization in obese patients and a high degree of
operator dependence.
An iPad-assisted technique for kidney puncture has
been described by Rassweiler et al . Before the
surgical procedure, multislice CT was performed with the
patient in the prone position and at the final stage of
inspiration. The CT images were analyzed to obtain a 3D
reconstruction of the patient anatomy. To choose optimal
access to the collecting system, five colored radio-opaque
markers were placed around the target area during the CT
scan. With the patient under general anesthesia and in the
same position inwhich the preoperative CTwas performed,
the iPad camera was pointed towards the patient and
images of the patient in surgery transmitted by the iPad via
Wi-Fi were merged with the virtual preoperative 3D CT
images. To allow this image fusion process, at least four
markers needed to be visible to the camera. Moreover,
since the preoperative CT scan was performed at the final
stage of inspiration, the anesthesiologist had to stop the
patient breathing at the end of inspiration to perform the
puncture in the provided space. Puncture was performed
using the virtual 3D image provided and a 2D digital
fluoroscopy image in real time to allow final adjustments.
This technique was initially tested in a preclinical model
using a human phantom, and an error margin of only 1 mm
was recorded. It was then tested clinically in two patients
undergoing PCNL. A successful kidney puncture, defined as
the needle reaching the desired calyx, was obtained in both
cases. This system has the following advantages: correct
selection of the puncture location and angle, with good
definition of the path; better anatomical knowledge of
adjacent organs with 3D images; correct visualization of
the patient anatomy regardless of anatomical conforma-
tion; minimal space errors; and a shorter time to puncture
for training surgeons. Disadvantages include the use of
ionizing radiation, the absence of 3D images in real time,
a longer puncture duration for expert surgeons, only
minimal adjustments in the path, and the patient in the
prone position.
Uro-Dyna-CT (Siemens Healthcare Solutions, Erlangen,
Germany) is another technology recently tested for kidney
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