June 2000 Volume 5, Issue 4 Editor: James E. Carter, M.D., Ph.D., F.A.C.O.G

Laparoscopy and the anterior abdominal wall: A guide to vascular mapping.

AUTHORS:
O. Shawki El Ebtesama Center for Endoscopic Surgery, Cairo University, Al Ebtesama Hospital, Cairo, Egypt.
Romeo@menanet.net

P. Richards Department of Anatomy, Medical Faculty, University of Pretoria, Pretoria, South Africa.

SUMMARY
Laparoscopy is an invaluable diagnostic and therapeutic tool. Unfortunately the introduction of trocars, into the abdominal cavity, is not without certain specific inherent dangers, such as injury to the vasculature of the anterior abdominal wall. This paper assesses the normal vasculature of the anterior abdominal wall as well as various methods, such as insufflation and patient positioning, for improving the safety margins for the insertion of lateral trocars.

INTRODUCTION

The development of the laparoscope marshaled in a new era in terms of both diagnostics and therapeutics, often eliminating the need for open abdominal surgery. However, as with all developing techniques, as usage increases so does the number of reported associated complications. Although relatively few, minor complications are reported in as many as 5.1% of laparoscopic procedures and major complications in upwards of 2.3% (Kane & Krejis, 1984). Complications related to laparoscopic procedures include ureteric injury (Cheng, 1976, Hunter & McCartney, 1993, Grainger et al, 1990) as well as damage to other internal organs including the bowels, bladder and uterus (Yuzpe, 1990). Vascular trauma has also been associated with the placement of trocars where the incidence of injury to the vessels of the anterior abdominal wall (Hurd et al, 1993) occurs with greater frequency than injury to deep vessels such as the aorta and iliac vessels (Baadsgaard et al, 1989). Despite the use of relatively standardized techniques and increasing surgeon experience complications related to the insertion of trocars still occur. The aim of this study was to assess the anatomical relationships of the anterior abdominal wall to underlying structures and the effects of manipulation of various parameters during trocar insertion.

METHODS
Thirty women undergoing diagnostic laparoscopy for the investigation of infertility consented to participate in the study. The women were selected on the basis of having no previous history of abdominal surgery. The mean duration of infertility for the group was 6.1 years, the mean age 27.6 years and the mean body weight 68.3 Kg. For the purposes of the study the patients were divided into three groups. In group A direct trocar insertion was employed in the absence of prior insufflation whilst in group B insufflation was used to attain an intra-abdominal pressure of between 15-20 mm/Hg. Finally group C comprised those patients in whom the intra-abdominal pressure was raised to 25 mm/Hg prior to trocar insertion. 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. During the introduction of the secondary subumbilical 10 mm trocar (10 -12 cm caudal of the umbilicus) the distance between the anterior abdominal wall and the great vessels and viscera was visually observed and assessed. Particular attention was paid to the indentation effects of trocar thrust. In addition trans-illumination techniques were employed to assess the location of the inferior epigastric, superficial epigastric and superficial circumflex arteries, as well as the lateral margins of the rectus muscle, in relation to the symphysis pubis, the umbilicus and the abdominal mid-line. The results were evaluated in order to determine the safest possible entry technique in terms of the following: 1) Site of puncture; 2) intra-abdominal pressure adjustment; 3) patient position; 4) trocar type and 5) direction of trocar thrust.

RESULTS
Assessment of the vasculature of the anterior abdominal wall revealed the following: at 5 cm above the symphysis pubis the inferior and superficial epigastric arteries lay 5.3 ± 1 cm and 5.8 ± 2 cm from the linea alba respectively. 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. The umbilicus was commonly located cranial to the bifurcation of the aorta; pneumoperitineum caused the umbilicus to move even more cranially thus increasing the distance between the umbilicus and the aortic bifurcation. Positioning the patient in Trendelenburg position tends to alter the position of the lower part of the aorta, bringing it closer to the umbilicus. By using manual elevation the distance between the anterior abdominal wall and the retroperitoneal vessels can be increased to 7 ± 2 cm in the average weight patient and marginally less so in the obese. Insufflation also increases the wall to wall distance therefore increasing the safety margin.

Pneumoperitineum of 15 - 20 mm/Hg resulted in more force being required to penetrate the abdomen. 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. Following insufflation to 25 mm/Hg trocar penetration required less force and the retroperitoneal structures remained more than 10 cm from the point of insertion.

DISCUSSION
The positions of the anterior abdominal vessels described in this study are similar to those described by other authors (Hurd & Hurtcau, 1997, Hurd et al, 1994). The results obtained in this study and that of Hurd et al, 1994 are compared in table 1. 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. However this risk can be lessened by placing trocars medial to the positions of the vessels. Lateral trocar placement at 5 cm above the symphysis pubis is all round a safer alternative as the gap between the above mentioned vessels is larger (> 4 cm). Near the umbilicus it is prudent to place trocars at 8 cm from the midline in the gap between the epigastric and superficial circumflex iliac vessels. Finally in terms of vasculature, it is essential to consider the issue of normal human variation. The guidelines given here represent the most common arrangement of the vessels of the anterior abdominal wall. Variations and anomalies do occur albeit infrequently (Jakubowicz & Czarniawska-Gresinska, 1996, Bilgic & Sahin, 1997).

Table 1: Positions of anterior abdominal vessels from the midline (cm).
The figures in brackets indicate the values obtained in the current study.

The umbilicus tends to be used as a landmark from which measurement is made for the positioning of trocars. Furthermore the position of the umbilicus is used as an indicator of the position of the aortic bifurcation in order to avoid retroperitoneal vessel injury (Hurd et al, 1992). The bifurcation is usually located at or cranial to the umbilicus thus increasing the risk of damage to the vessel during trocar insertion. Pneumoperitineum always results in the cranial movement of the umbilicus. Where insufflation is used and the pressure created is not sufficiently high the risk of injury is greater due to the greater force required for insertion and the fact that the indentation of the abdominal wall halves the distance between the skin and the retroperitoneal vessels. Obesity also plays a role in increasing the risk of retroperitoneal vessel injury where it is suggested that trocar insertion occur at a 90o angle to the skin to avoid preperitoneal placement (Hurd et al 1991). Injury to retroperitoneal vessels can however be avoided by taking the precautions recommended by Loffer and Pent (1974).

CONCLUSION
The avoidance of vascular injury during placement of lateral trocars is of paramount importance. The following recommendations are made: (1) In accordance with Hurd et al, 1994, in the absence of laparoscopic anatomical landmarks to guide placement, lateral trocars should be inserted at least 5 cm above the pubic symphysis and 8 cm from the linea alba. (2) The placement of the patient in Trendelenburg position should only be carried out after trocar insertion. (3) The use of insufflation to achieve a pneumoperitineum with a pressure of 25 mm/Hg allows for a safer and easier entry technique. (4) Safe trocar entry in the absence of pneumoperitineum can only be achieved in thin patients with lax abdomens where direct manual abdominal lift can be ensured. (5) The trocar found to offer the safest use is the short disposable palm trocar as it requires only half the force for insertion. (6) Finally an in depth knowledge of the anatomy of the vasculature of the anterior abdominal wall is one of the corner stones for safe trocar placement.

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