LAPAROSCOPIC
ORCHIECTOMY: EXPERIMENTAL RAT MODEL
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MARCELO P. GALESSO, GUSTAVO CUCK, MARCIO R. PAGAN, RONI C. FERNANDES, MARJO D.C. PEREZ, FLÁVIA C.S. BOTTER
Divison of Urology, Irmandade da Santa Casa de Misericórdia de São Paulo, São Paulo, SP, Brazil
ABSTRACT
Studies
in animal models have been fundamental to evaluate, refine and practice
laparoscopic procedures. Selection of surgical models is primarily based
on cost, availability, anatomic and physiologic considerations, housing
and anesthetic methods. Large animals, such as pigs and dogs, are preferred
to perform experimental laparoscopic procedures. These animals are well
accepted by surgeons, because their anatomy is similar to human anatomy,
although they are costly and difficult to keep.
The development of small animal models for
laparoscopic procedures is essential for basic pathophysiologic and oncologic
studies, instrument development and surgical training. Rats appear to
be fitting models for laparoscopic research as they are inexpensive, well-studied
and widely used in research. Laparoscopic procedures in these animals
have been shown to be technically feasible with suitable equipment and
instruments.
A standard laparoscopic procedure technique
for rats has been developed to perform procedures in all abdominal regions,
by using special equipment and instruments as the 4 mm arthroscope or
bronchoscope, the 2 mm and 3 mm laparoscopic ports and the 2 mm laparoscopic
tissue grasper and scissors.
The present study describes a simple, inexpensive
and reproducible technique for laparoscopic orchiectomy in a rat model
by using the same instruments developed for humans. The present rat model
allows the possibility of training a large number of surgeons in laparoscopic
procedures, while requiring a minimum amount of logistic and financial
efforts.
Key words:
laparoscopy; rat; orchiectomy; model, animal
Braz J Urol, 28: 143-146, 2002
INTRODUCTION
The
development of videolaparoscopy in many surgical specialties has attracted
a large number of surgeons. Learning this method for future clinical practice
requires intensive training with inert tissues, simulators and experimental
surgeries in animals.
Medium and large animals are used in many
experimental models using videolaparoscopy to perform physiopathologic
studies, to develop instruments and to have surgical training (1-3). Performing
these procedures in small animals, with the same equipment used in humans,
is also feasible, allowing the familiarization with the material and the
comprehension of the basic techniques. It is inexpensive and safe to initiate
training with this method.
The objective of this study is to demonstrate
a simple and reproducible technique for videolaparoscopic orchiectomy
in an original low cost experimental model, to attend a larger number
of surgeons interested in videolaparoscopy.
SURGICAL TECHNIQUE
Animals
This study used adult male Wistar rats,
weighing between 600 and 650 g. The animals, after being kept in standard
laboratory conditions (temperature between 20 and 24°C, relative humidity
between 50 and 60%, under controlled light conditions – 12 hours
of light, receiving food and water “ad libitum”), were kept
without food and water for 8 hours prior to the surgery.
Equipment
and Instruments
To perform this procedure a video system
with micro-camera, insufflator, light source, electric scalpel, Veress
needle, a 10 mm port, two 5 mm ports, a 0° optic, a suture passthrough
device, a 5 mm prehension clamp, a 5 mm dissection clamp and 5 mm scissors
are necessary.
Procedure
Anesthetic induction is obtained through
intraperitoneal injection of a ketamine hydrochloride solution, 40 mg/Kg,
and xilidine-dihidrotiazine hydrochloride, 10 mg/Kg. Sedation is controlled
by evaluating the reflex under painful stimulus. When necessary, a second
dose of the anesthetic is used.
The animal is placed in a dorsal decubitus
position, with the 4 limbs fixed to the surgical table. Preoperative depilation
of the ventral facia of the rat is performed using a shearer with blade
40, followed by antisepsis with polyvinyl-pyrrolidineiodine solution.
The procedure consists in performing the
pneumoperitoneum with Veress needle right below the xiphoid process, through
a 5-mm skin incision. To perform the puncture with the needle, manual
traction of the anterior abdominal wall of the rat is necessary, so as
to perform it safely, without any lesion to intraperitoneal structures.
We proceed to the insufflation of the cavity with CO2, until reaching
the maximum pressure of 5 mmHg, when the needle is removed. The skin is
divulsed with hemostat up to approximately 10 mm and the 10-mm trocar
is inserted, through which the 0° optic is introduced. Two additional
5-mm lateral incisions are done, around 1.5 cm apart from the first, where
the trocar for the dissection and prehension clamps will be introduced.
The trocars passage should also be preceded with manual traction of the
anterior abdominal wall of the rat.
All trocars should be fixed to the skin
with 2-0 cotton thread, to hinder their exaggerated introduction or outlet
during clamp maneuvers, avoiding loss of the peneumoperitoneum (Figure).
The spermatic cord of the testicle to be
removed is exposed with prehension clamp introduced through the homolateral
trocar, followed by its traction. At this moment, the testicular vessels
and the vas deferens are visualized with the cord. We proceed the dissection
to individualize each structure, following with cauterization and section,
which can be made with electrocautery or ultrassonic scalpel, inserted
in the cavity through the contralateral trocar. After cord section, traction
of the testicle from the scrotum is performed, followed by cauterization
and section of the gubernaculum. As an alternative to this surgical time,
a suture passthrough device with 2-0 catgut can be introduced through
the contralateral trocar. Then the testicle is tractioned through its
loop with the prehensio clamp inserted through the homolateral trocar.
After closing the loop, the gubernaculum is sectionated and, subsequently,
the thread. The free testicle is kept in the cavity and the same procedure
is performed with the contralateral testicle.
As soon as the bilateral orchiectomy is
finished, the 5-mm trocar openings are amplified with hemostat and the
testicles are removed from the cavity. The trocar openings are closed
with 2-0 cotton thread.
COMMENTS
Videolaparoscopy
is becoming the procedure of choice for the diagnosis and treatment of
many diseases which were previously performed by laparotomy. The method
is attractive for being minimally invasive, reducing postoperative pain,
hospital stay and recovery time (2-4).
Learning this method for future clinical
practice requires intensive training with inert tissues, simulators and
experimental animals.
Traditionally, medium animals, such as dogs
and pigs, have been used in experimental videolaparoscopy, for the technical
facility provided by their size, anatomic similarity and possibility of
using the same instruments used in humans (5). However, their physiology
is not very well studied, when compared to other models, and the costs
to acquire and maintain them are not despicable (2). Legal restrictions
and the public opinion have also made it difficult to use large animals
as models in experimental studies (3).
Small animals are also used in videolaparoscopy
experimental models. Many techniques have been described in rats (fundoplication,
splenectomy, nephrectomy, hepatic resection, herniorrhaphy, colostomy,
colectomy and retroperitoneal exploration), as well as their use in studies
about immunity, oncology and physiologic effects of the laparoscopy (2-4).
Therefore, many endoscopic and microsurgical equipment is necessary for
these procedures (arthroscopes, bronchoscopes, trocars and 2 and 3-mm
clamps), which can restrict their application (4,5). When accessible,
however, such materials must be used because they increase the working
space and allow technical training, such as free suture in small animals,
thus developing fine movements, while preserving familiarization and learning
of the basic laparoscopy principles.
Videolaparoscopic orchiectomy in rats has
proved to be a simple and feasible procedure. In our model, we used the
same equipment as in human surgeries, without the need of any sophisticated
technology. All animals survived the procedure. Bleeding was despicable.
Necropsy, performed 24 hours later, did not show lesions to other intraperitoneal
structures. Euthanasia was performed by intracardiac injection of 40 mg/kg
thionembutal.
The adequate use of the material described
in this experimental model does not significantly limit urologists in
the initiation and basic training of laparoscopy.
The use of small animals, besides being
more stimulating than the simulators and other inert models, minimize
costs, allowing the use of more animals for teaching, training and application
in many studies.
REFERENCES
- Kaouk LH, Gill IS, Meraney AM, Desai MM, Carvalhal EF, Fergany AF et al.: Retroperitoneal minilaparoscopic nephrectomy in the rat model. Urology, 56: 1058-1062, 2000.
- Giuffrida MC, Marquet RL, Kazemier G, Wittich PH, Bouvy ND, Bruining HA et al.: Laparoscopic splenectomy and nephrectomy in a rat model: decription of a new technique. Surg Endosc, 11: 491-494, 1997.
- Gutt, CN; Riemer V, Brier C, Berguer R, Paolucci V: Standardized technique of laparoscopic surgery in the rat. Dig Surg, 15:135-139, 1998.
- Farias EA, Fontes PRO, Rhoden CR, Lucas ML, Leal MLM, Sabedotti M et al.: Acompanhamento de um modelo de indução de cirrose em ratos mediante videolaparoscopia. Acta Cir Bras, 15: 163-167, 2000.
- Sandoval BA, Sulaiman TT, Robinson AV, Stellato TA: Laparoscopic surgery in a small animal model: a simplified technique of retroperitoneal dissection in the rat. Surg Endosc, 10: 925-927, 1996.
__________________________
Received:
September 17, 2001
Accepted after revision: February 8, 2002
_______________________
Correspondence address:
Dr. Roni de Carvalho Fernandes
Rua Cotoxo, 987 / 94
São Paulo, SP, 05021-001, Brazil
E-mail: roni.fernandes@uol.com.br