PERCUTANEOUS
RENAL SURGERY – NEW MODEL FOR LEARNING AND TRAINING
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PEDRO P. DE SÁ EARP
Section of Urology, Petrópolis School of Medicine, Petrópolis, Rio de Janeiro, Brazil
ABSTRACT
Introduction:
Aiming at promoting and facilitating learning and training in percutaneous
renal surgery, we have created an easy to assemble, reproducible and cheap
laboratory model. The model was built using pig kidney, foam layer, plastic
catheter, linen or cotton holding sutures, and wide scotch tape.
Surgical Technique: The kidney with catheterized
ureter is fixed and involved in a foam layer. It stays hidden, and is
visible only through radioscopy. This model is positioned and fixed to
a radiological table in such a way that it simulates the patient’s
lumbar region. After that, contrast medium is injected through the ureter,
and the urinary system is examined through radioscopy. All percutaneous
maneuvers can be accomplished, from the puncture, tract dilation, insertion
of Amplatz sheath, and introduction of nephroscope, allowing lithotripsy
and endopielotomy, as well as other types of percutaneous surgeries.
Comments: The great advantage of this model
is its easy construction, by using very cheap and widely available material.
Foam can be several times washed and reused. After treatment, the model
can be immediately open, and a critical analysis can be made, being then
possible to verify if the place of renal puncture was well chosen, if
dilation was correctly accomplished, and if the collecting system has
been preserved. Therefore, this model can represent a great advance for
the learning and training in percutaneous surgery.
Key
words: kidney; endourology; nephrostomy, percutaneous; models,
educational
Int Braz J Urol. 2003; 29: 151-4
INTRODUCTION
The model created for learning and training in percutaneous renal surgery in laboratory allows the accomplishment of renal puncture, tract dilation, Amplatz sheath introduction, nephroscopy, nephrolitotripsy, and other endourological maneuvers. The model can be simply and cheaply built, without the need of sophisticated material, being accessible to any resident or urologist in need of acquiring more experience with this technique.
MODEL AND SURGICAL TECHNIQUE
We
use kidneys from large pigs, whose sizes are most similar to human kidneys.
During kidney extraction, we recommend that the maximum of perirenal fat
be preserved. This will help the kidney fixation to the foam through perirenal
points, without harming them too much. We leave the ureter as long, in
order to be catheterized.
We make a foam layer of 3 cm thick, 60 cm
wide and 50 cm long. We centralize the kidney in the middle of the foam,
angled 30 degrees in relation to frontal plane, thus simulating renal
position in human beings.
We fix the renal poles with sutures that
go through the fat, the renal capsule, through the superficial part of
parenchyma and through the foam. It is important not to hit the collecting
system, nor deform the kidney (or fasten points too much) nor tear the
renal tissue with suture thread. To get a better resistance from renal
tissue, it is best to keep the kidney in the freezer one day before, and
defrost it few hours before the procedure, in such a way that the collecting
system is defrosted and the parenchyma is not too soft or friable in the
moment of use (Figure-1).
The ureter is catheterized with a plastic
catheter (6F), which is introduced to the upper ureter, where it is fixed.
This catheter will be used for contrast medium injection and must have
a longer length than that of the foam, in order to be manipulated from
outside the model (Figure-2). Stones can be previously placed inside the
kidney through the renal pelvis, which is hermetically sutured afterwards.
We vertically fold the foam, so that the
kidney, which is fixed in the back foam sheet, is covered by half of the
front sheet. The convex part of the kidney will be in contact with the
fold of these sheets (Figure-2). A wide scotch tape is passed twice around
the upper and lower part of the folded foam, completely hiding the kidney.
Other tapes close the remaining openings. So, a foam envelope is formed
around the kidney attached to it. The ureteral catheter is exteriorized
in the lower part of this envelope. With a roller ball pen, the ribs and
the posterior axillary line are drawn to simulate the lumbar region. The
model is fixed to the radiological table, over plastic to avoid wetting
the table during training (Figure-3).
Radiological contrast medium is injected
to reproduce the complete percutaneous renal surgery (Figure-4). Then
we proceed to puncturing, dilation, insertion of Amplatz sheath, and introduction
of nephroscope and surgical accessories (Figure-5).
After training, the model can be opened.
This allows kidney examination and a critical analysis of the technique
employed, speeding up learning (Figure-6).
COMMENTS
The
learning of percutaneous surgery is very difficult, because there is no
experimental model that can be easily to acquire and simply to manipulate,
as it is the case of black box models used in the training of laparoscopic
surgery (1,2).
Although there is some models for learning
percutaneous renal surgery that imitate the texture of human tissue, we
note that in the present model, the consistency and resistance of the
foam offer a good imitation of reality, allowing for training in puncturing
and tract dilation (3). The pig kidneys have their anatomy very similar
to the one of human beings, exceedingly facilitating, with realism, the
intra-renal endoscopic training (4). Before construction of the model,
stones can be placed inside the renal pelvis, allowing the use of energy
sources for lithotripsy.
The great advantage of this model is the
easiness of its construction, and especially its cost. Worldwide there
are pig kidneys available, foam sheet, suture threads, plastic probes
and roller ball pens.
Another advantage is the possibility of opening the model right after
its use, in order to make a critical analysis, identify and correct technique
mistakes (5,6).
We advice those who do not have any experience
with puncturing, to start the training with a model that has the guide-wire
previously placed inside the collection system and that exits from the
foam. In this way, the training starts by the easiest part, that is dilation,
then the introduction of Amplatz sheath and surgical endoscopy. After
this training, it is possible to go to the most difficult part, which
is the puncture of the calices, by using models without previously placed
guide-wires.
REFERENCES
- Long JP, Faller GT: Percutaneous cryoablation of the kidney in a porcine model. Cryobiology 1999; 38: 89-93.
- Radley SC, Chapple CR, Martin SW, Boaler D: A training model for transurethral injection therapy for stress incontinence. BJU Int. 1999; 83: 711-3.
- Travis DG, Tan HL, Webb DR: Single-increment dilatation for percutaneous renal surgery: an experimental study. Br J Urol. 1991; 68: 144-7.
- Sampaio FJB, Pereira-Sampaio MA, Favorito LA: The pig kidney as an endourological model. Anatomical contribution. J Endourol. 1998; 12: 45-50.
- Shalhav AL, Dabagia MD, Wagner TT, Koch MO, Lingeman JE: Training postgraduate urologists in laparoscopic surgery: the current challenge. J Urol. 2002; 167: 2135-7.
- Michel MS, Knoll T, Kurmann KU, Alken P: The URO Mentor: development and evaluation of a new computer-based interactive training system for virtual life-like simulation of diagnostic and therapeutic endourological procedures. BJU Int. 2002; 89: 174-7.
________________________
Received: February 28, 2003
Accepted: March 31, 2003
_______________________
Correspondence address:
Dr. Pedro Paulo de Sá Earp
Rua Sorocaba 464 / 403
Rio de Janeiro, RJ, 22271-110, Brazil
Fax: + 55 21 2527-9927
E-mail: ppdesaearp@ig.com.br