Camper’s fascia is the superficial fatty layer and Scarpa’s fascia is the deeper, thin fibrous layer; collectively they represent the “superficial fascia” or subcutaneous tissue. Superficial abdominal wall vessels course through the fascia. This tissue layer tends to be deceptively prominent in obese patients.

The abdominal wall is composed of five pairs of interconnected muscles. There are two midline muscles (the rectus abdominis and pyramidalis) and three sets of lateral muscles (the external and internal obliques and the transversus abdominis). In the midline, the rectus abdominis originates from the xiphoid process and costal cartilages of the fifth to seventh ribs and extends to the pubic symphysis. This broad strap muscle is encased within the anterior and posterior rectus sheath. The aponeuroses of the rectus muscles fuse in the midline as the linea alba and fuse laterally as the linea semilunares.

The pyramidalis muscle is a small triangular muscle that lies in the rectus sheath, anterior to the inferior aspect of the rectus abdominis. Occasionally this muscle is absent on one or both sides. When it is present, it arises from the pubis and inserts into the lower linea alba.

The three lateral muscles, found bilaterally, are also referred to as flat muscles. The most superficial of these is the external oblique. It arises from the lower eighth rib, where its fibers interdigitate with the serratus anterior muscle and extend inferiorly to the linea alba and pubic tubercle, creating a broad fibrous swath known as an aponeurosis.

Aponeuroses are tendon-like membranes that bind muscles to each other or to bones. Posterior to the external oblique lies the internal oblique muscle, whose fibers arise from the lumbar fascia, the iliac crest, and the lateral two-thirds of the inguinal ligament. The internal oblique fibers are at right angles to the external oblique fibers. The anterior and posterior layers of the internal oblique separate into the anterior and posterior rectus sheath and are responsible for creating the arcuate line landmark. The deepest lateral muscle is the transversus abdominis. Its muscle fibers run in a transverse fashion across the abdomen. The fibers arise from the costal cartilages of the sixth to eighth ribs, interlocking with the diaphragm, the lumbodorsal fascia, the lateral third of the inguinal ligament, and from the anterior three-fourths of the iliac crest and terminate anteriorly as an aponeurosis. The transversalis fascia lies deep to the transversus abdominis and is a continuous layer that lines the abdominal and pelvic cavity (Fig. 1.3).

The arcuate line is a transverse line located midway between the umbilicus and the pubic symphysis. Above the arcuate line, the rectus abdominis muscles possess both anterior and posterior sheaths formed by the aponeuroses of the midline and lateral muscles. Below the arcuate line, all layers of the sheaths course anterior to the rectus abdominis muscles.

The extraperitoneal fascia is the layer of connective tissue that separates the transversalis fascia from the parietal peritoneum. It contains a varying amount of adipose tissue and lines the abdominal and pelvic cavities. Viscera in the extraperitoneal fascia are referred to as retroperitoneal. Last, the parietal peritoneum lines the abdominal cavity. Remarkably, it is only one cell layer thick. Inward reflections of this peritoneum form a double cell layer known as mesentery.

The inguinal ligament is formed by the aponeuroses of the external oblique. It arises from the ASIS and inserts into the pubic tubercle. The inguinal canal runs parallel to the inguinal ligament. The inguinal canal is classically described by its four walls. Its anterior wall is formed by the aponeurosis of the external oblique, the inferior wall (floor) is formed by the inguinal ligament, the superior wall (roof) is formed by arching fibers of the internal oblique and transversus abdominis muscles, and the posterior wall is formed by the transversalis fascia.

The deep internal inguinal ring is the tubular evagination of the transversalis fascia, located halfway between the ASIS and the pubic symphysis. The inferior epigastric vessels lie medial to the deep internal inguinal ring. The round ligament dives through this deep internal ring, enters the inguinal canal, exits through the superficial external inguinal ring, and terminates at the labia majora. In addition, the terminal aspect of the ilioinguinal nerve and the genital branch of the genitofemoral nerve exit the inguinal canal via the superficial external inguinal ring. The superficial external inguinal ring is created by the opening of the external oblique aponeurosis and is located superior and lateral to the pubic tubercle (Fig. 1.4).

The clinically relevant upper and lower anterior abdominal wall nerves contain both motor and sensory fibers. The thoracoabdominal and subcostal nerves originate from T7 to T11 and T12, respectively. Their distributions are summarized in Table 1.2.

The iliohypogastric nerve and ilioinguinal nerve originate from L1 and accompany the thoracoabdominal and subcostal nerves as they course between the internal oblique and transversus abdominis muscles. At the ASIS, they traverse the internal oblique and run between the internal and external oblique muscles. The iliohypogastric nerves innervate the lateral abdominal wall, inferior to the umbilicus. The ilioinguinal nerve runs within the inguinal canal and emerges from the superficial, or external, inguinal ring to provide sensory innervation to the labia majora, inner thigh, and groin.

During laparoscopic and robotic surgery, the iliohypogastric and ilioinguinal nerves are particularly susceptible to injury because of their close proximity to traditional, lower quadrant trocar sites. Nerve damage may result from trocar placement or nerve entrapment secondary to lateral closure of transverse incisions or scar tissue (Table 1.3). The nerve injury usually results in chronic neuropathic pain (Fig. 1.5) [4].

Postoperative nerve damage should be suspected if the patient reports a burning or searing pain in the lower abdominal, pelvic, or medial thigh areas. The pain may be worsened by the Valsalva maneuver and is often relieved by hip and trunk flexion. A diagnostic and therapeutic injection of local anesthetic at the origin of the affected nerves, 3 cm medial to the ASIS, may provide relief.

The most notable anterior abdominal wall arteries are the epigastric vessels and the circumflex iliac vessels. Both pairs of vessels can be further classified into superficial and deep vessels. The deep epigastric vessels include the superior and inferior epigastric arteries and veins. The superior epigastric artery originates from the internal mammary artery and descends through the thorax into the rectus muscle, where it anastomoses with the inferior epigastric artery. The superior epigastric artery is accompanied by two superior epigastric veins. The deep inferior epigastric artery arises from the external iliac artery, just above the inguinal ligament. The inferior epigastric artery and vein travel in a medial and oblique fashion along the peritoneum to pierce the transversalis fascia and the rectus muscle. Owing to the absence of the posterior rectus sheath below the arcuate line, the inferior epigastric vessels can be seen within the lateral umbilical fold (Table 1.4) [6]. Accidental laceration of these deep vessels may result in life-threatening hemorrhage that must be swiftly occluded using electrosurgery or sutures (Fig. 1.6) [7].

In contrast, the superficial epigastric artery originates from the femoral artery and courses through the superficial fascia toward the umbilicus. Prior to placing secondary laparoscopic trocars, the superficial epigastric vessels are often identified by intra-abdominal transillumination in order to avoid vessel injuries (Table 1.5) [8].

Vascular trauma to the superficial epigastric vessels may result in a hematoma or abscess and, on rare cases, may even expand to the labia majora [9].

The circumflex iliac arteries consist of the deep and superficial circumflex iliac arteries. They arise from the femoral and external iliac arteries, respectively.

Distorted anatomy and severe surgical scarring challenge even experienced laparoscopic surgeons. When difficult situations are encountered, it is imperative to identify key structures that will facilitate safe surgical dissection and avoid injury to retroperitoneal vessels and viscera (Table 1.6). In the midline, there are two peritoneal folds. In the upper abdomen, the falciform ligament extends from the umbilicus to the liver and includes the obliterated umbilical vein. It is a remnant of the ventral mesentery. In the pelvis, the median umbilical fold extends from the umbilicus to the apex of the bladder and encases the urachus. Occasionally, the urachus fails to close after birth and continues to communicate with the bladder. Therefore, one should avoid this fibrous fold during laparoscopic trocar placement. In addition, a pair of bilateral, medial, and lateral umbilical folds encase the obliterated umbilical arteries and inferior epigastric vessels (Figs. 1.7 and 1.8).

There are two naturally occurring peritoneal pouches within the pelvis. Located anteriorly, the vesicouterine pouch is found between the uterus and the bladder. In a pristine pelvis, the ventral aspect of the bladder may be seen behind the anterior abdominal wall peritoneum. However, after cesarean sections, myomectomies, and previous abdominal surgery this area may be scarred and the ventral bladder margin may be more cephalad than expected. Similarly, the dorsal bladder margin usually lies on the anterior surface of the uterus. It is an important landmark for avascular dissection, but after pelvic surgery it may be adherent and require meticulous dissection (Table 1.7).

Located posteriorly, the rectouterine pouch, or the pouch of Douglas, lies posterior to the vagina, cervix, uterus, and anterior to the rectum. This pocket can be completely obliterated in cases of advanced endometriosis. The scarring may extend inferiorly to the posterior wall of the vagina and the anterior wall of the rectum. This area is an extraperitoneal fascial plane known as the rectovaginal septum. On pelvic examination, endometriosis can be appreciated as palpable nodularity along this fascial plane that runs from the rectouterine pouch to the perineal body (Fig. 1.9).