In each patient a primary puncture was made 14 cm cranial to the symphysis pubis, with a 5 mm trocar through which a 5 mm laparoscope was introduced in order to monitor the introduction of the secondary trocar. Particular attention was paid to the indentation effects of trocar thrust. Near the level of the umbilicus the lateral edge of the rectus sheath was located 7.3 1.7 cm from the midline. At the same level the superficial epigastric and circumflex iliac vessels were positioned at 4.6 1.8 cm and 11.2 1.6 cm from the linea alba respectively. Positioning the patient in Trendelenburg position tends to alter the position of the lower part of the aorta, bringing it closer to the umbilicus.
Insufflation also increases the wall to wall distance therefore increasing the safety margin.
This forced insertion resulted in an indentation of the abdominal wall to such an extent as to bring the anterior wall half the distance closer to the retroperitoneal structures, thus negating the effect of insufflation. Hg trocar penetration required less force and the retroperitoneal structures remained more than 10 cm from the point of insertion. The significance of these results and their similarity to those obtained in other studies means that it is now possible to map out the most probable locations of the vessels of the anterior abdominal wall, with confidence, in order to avoid them during laparoscopy. Although the positions of these vessels do not usually present problems in diagnostic laparoscopy, where midline placement of trocars is the norm, the placement of lateral trocars does increase the risk of vascular injury. The placement of lateral trocars at a distance of 3 cm above the symphysis pubis further increases risk of vascular injury as the distance between the more laterally located superficial circumflex artery and the inferior and superficial epigastric vessels is often less than 2 cm.