Animals were placed in right lateral recumbency. In the laparoscopic groups (LAP+R and LAP+T), the operating field was prepared as follows: the first trocar (10 mm, laparoscope port) was placed in the axillary midline with an open technique; for the transabdominal group, the whole muscular wall was dissected, while for the retroperitoneal group, the peritoneum was maintained intact. Then, the abdominal or retroperitoneal cavity was distended up to a 12 mmHg pressure. Later on, two more trocars were placed under visual control, 5 cm dorsal and 7-8 cm apart on both sides of the first trocar. A 5 mm trocar was placed on the right side and a 10 mm trocar on the left side.