The anterior abdominal wall has four muscles: The external oblique, the internal oblique, the transversalis, and the rectus muscles. The aponeuroses of the first three muscles form the rectus sheath, which encloses the rectus abdominis muscle.

The linea alba is a midline aponeurosis that runs from the xiphoid process to the pubic symphysis and separates the left and right rectus abdominis muscles. It is widest just above the umbilicus, facilitating entry into the peritoneal cavity.

For vascular trauma purposes, the retroperitoneum is conventionally divided into four anatomic areas:

• Zone 1: Extends from the aortic hiatus to the sacral promontory. This zone is subdivided into the supramesocolic and inframesocolic areas. The supramesocolic area contains the suprarenal aorta and its major branches (celiac axis, superior mesenteric artery (SMA), and renal arteries), the upper inferior vena cava (IVC) with its major branches, and the superior mesenteric vein (SMV). The inframesocolic area contains the infrarenal aorta and IVC.

• Zone 2: Includes the kidneys, paracolic gutters, renal vessels, and ureters.

• Zone 3: Includes the pelvic retroperitoneum, containing the iliac vessels and ureters.

• Zone 4: Includes the perihepatic area, with the hepatic artery, the portal vein, the retrohepatic IVC, and hepatic veins.