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likely does not predict performance improvement for those with more experience
[ 150 ]. Knoll et al. studied 20 urologists of varying experience in their performance
in treating a lower calyceal stone. Cases performed ranged from 21 to 153. The
authors found that those that had performed less than 40 URS cases scored signifi-
cantly worse than those who had greater than 80 cases, thus exhibiting construct
validity. Criterion validity was also proposed by comparing five inexperienced urol-
ogy residents versus five inexperienced urology residents trained on the URO
Mentor. When compared, they found that the simulator-trained group performed
significantly better on their first four URS cases on humans, as assessed by opera-
tive times between the groups [ 151 ].
The use of live animals for surgical training is controversial. Therefore, ex vivo
animal models are advocated by a number of authors. By using organs obtained
from pigs already being slaughtered for food, legal and ethical issues have been
essentially erased [ 152 ]. Looking for a more realistic feel than plastic models at the
time, Strohmaier and Giese were some of the first authors to describe the use of an
ex vivo porcine model [ 153 ]. They used an en bloc resection of all retroperitoneal
organs (kidneys with ureters, bladder, urethra, aorta, vena cava, intestine, rectum,
and anus) from freshly slaughtered adult pigs, with subsequent isolation of the uri-
nary tract. The authors describe that 7.5–9 F ureteroscopes could successfully be
navigated through the porcine GU system, giving more realistic and accurate tissue
feeling than physical models. Subsequent authors have since described using simi-
lar porcine ex vivo setups [ 109 , 154 , 155 ].
Soria et al. did a validation study that was divided into three levels. During the
second level of their study, an ex vivo porcine renoureteral unit was used for training
of laser lithotripsy on a mid-ureteral stone. Their model demonstrated face validity
in the study of 40 participants with a global realism score of 4.25 ± 0.13 on a 5-point
Likert scale [ 156 ]. Unfortunately, further validation and data regarding educational
value for ex vivo models are currently still lacking.
Percutaneous Access/Litholopaxy
Since being first described by Fernström and Johansson in 1976, percutaneous
nephrolithotomy (PCNL) has signified a viable and increasingly popular way to
manage complex renal calculi [ 157 ]. Due to further advances in technique since its
inception, PCNL has essentially eliminated the use of open surgery in the removal
of renal calculi [ 158 ]. However, PCNL is still a risky procedure with a high inci-
dence of overall complications at 83% [ 159 ]. The most common complications
include hemorrhage requiring transfusion, with overall mean incidence ranging
11.2–17.5%. Colonic or pleural injuries are highly associated with the access por-
tion of the procedure. PCNL is also known for its steep learning curve. Current lit-
erature suggests that 36–45 cases are needed to become competent and 105–115
cases are needed to achieve proficiency for PCNL [ 160 , 161 ]. Additionally, as few
as 11% of urologists are able to obtain percutaneous access without the help of an
interventional radiologist, which suggests that many trainees are uncomfortable or
untrained in achieving percutaneous renal access [ 162 ]. As such, simulation in
PCNL has become increasingly popular.
W. Baas et al.