Posterolateral (Lumbar) Abdominal Wall

The posterolateral or lumbar portion of the abdominal wall (Fig. 72-8) is often overlooked in

discussions of abdominal hernia, perhaps because of the much more common occurrence of groin and

femoral hernias. The configuration of the muscle layers in the lumbar area also predisposes to hernia

formation. For the purposes of this discussion, the lumbar portion of the abdominal wall is defined as

the area bounded superiorly by the 12th rib, inferiorly by the iliac crest, and medially by the erector

spinae group. Eight muscles arrayed in three layers constitute the posterolateral or lumbar portion of

the abdominal wall.

The most superficial layer is composed of the external abdo-minal oblique muscle, which arises from

the posteroinferior portion of the lower ribs and inserts in part along the posterior iliac crest. Closely

associated with the external oblique in this area is the latissimus dorsi, which arises from the posterior

iliac crest, the spinous processes of the sacrum and lumbar vertebrae, and the lumbodorsal fascia. The

muscle courses obliquely toward its insertion on the medial aspect of the intertubercular groove of the

humerus. The triangular space formed by the two muscles just described and the iliac crest is called the

inferior lumbar (Petit) triangle (Fig. 72-8A).

Figure 72-8. The lumbar abdominal wall with the inferior lumbar triangle (A) and the superior lumbar triangle (B).

The middle layer of lumbar abdominal muscles consists of the erector spinae, the internal abdominal

oblique, and the extremely thin insignificant serratus posterior inferior. The erector spinae forms a

significant portion of the abdominal wall in the lumbar region, with fibers extending nearly the length

of the spinal column. The internal abdominal oblique muscle forms the remainder of the layer. The

serratus posterior inferior arises from the lumbodorsal fascia and inserts on the lower four ribs. The

middle layer of lumbar muscle is associated with the superior lumbar triangle, a more common site of

hernia than the inferior lumbar triangle described previously. The superior triangle (Fig. 72-8B) is

formed superiorly by the 12th rib, the serratus posterior inferior, and the superior lumbocostal

ligament; inferiorly by the upper border of the internal abdominal oblique; and medially by the erector

spinae.

The deep layer of the lumbar abdominal wall includes three muscles: the quadratus lumborum, the

psoas major, and the transversus abdominis. The quadratus lumborum primarily arises from the

posterior iliac crest and inserts on the 12th rib. The psoas major arises from vertebrae T12 through L5

and passes beneath the inguinal ligament to insert on the lesser trochanter of the femur.

Deep Inguinal Region

Laparoscopic View

Deep Aspect of the Anterior Abdominal Wall, Peritoneal Folds, and Associated Structures. If one

creates a space in the abdominal cavity by distending it with gas, an excellent view of the anterior wall

can be obtained. The umbilical peritoneal folds (Fig. 72-9) in most subjects are very prominent and

provide easily identified landmarks. The folds (ligaments) primarily exist because the peritoneum

covers underlying structures.

1919

Figure 72-9. The deep inguinal region and the anterior abdominal wall seen from within the abdomen. The urachus, the

obliterated portion of the umbilical artery, and the inferior epigastric vessels are covered by peritoneal folds, respectively called

the median, medial, and lateral umbilical folds.

The single median umbilical fold extends from the umbilicus to the urinary bladder and covers the

urachus, the fibrous remnant of the fetal allantois. The urachus may be patent for a short distance in

adults or may open into the umbilical scar in newborns. The medial umbilical fold is formed by the

underlying obliterated portion of the fetal umbilical artery. This normally cordlike structure, like the

urachus, may be patent for a portion of its length. Indeed, the proximal, patent portion of the artery

normally supplies the superior vesicular arteries to the bladder. The lateral fold covers the inferior

epigastric arteries as they course toward the posterior rectus sheath, which they enter approximately at

the level of the arcuate line.

Between the median and the medial ligaments, a depression is usually found that is called the

supravesical fossa. This is the site of hernias of the same name. The fossa formed between the medial and

lateral ligaments is the medial fossa; this is the site of direct inguinal hernias. The lateral fossa is less

well delineated than the others. The medial border of the fossa is formed by the lateral umbilical

ligament and the rectus abdominis. This fossa does not have a lateral border; rather, the concavity

slowly attenuates. The deep inguinal ring is located in the lateral fossa and therefore is the site of the

congenital or indirect inguinal hernia.

Transversalis Fascia

The transversalis fascia (endoabdominal fascia) is perhaps the most commonly misunderstood structure

in the literature devoted to groin hernia. Confusion results because surgeons may actually be referring

to very different anatomic structures when discussing various hernia repairs; however, each may use the

same anatomic term or eponym. Indeed, perhaps the biggest reservation among surgeons intent on

performing a Shouldice repair is a precise definition of what is being sewn to what.

The transversalis fascia proper is a continuous sheet that extends throughout the extraperitoneal

space. The term transversalis fascia is generally defined as the deep or endoabdominal fascia covering the

internal surface of the transversus abdominis, the iliacus, the psoas muscles, and the obturator internus

and portions of the periosteum. One variant of this convention is the use of terms specific to the muscle

covered by the fascia (e.g., iliac fascia).

Most authors feel that only one layer of transversalis fascia exists, whereas others maintain that the

transversalis fascia comprises two layers, or laminae.8 The posterior lamina is a layer of fibrous

connective tissue that widely varies in density and continuity and is interspersed with adipose tissue, as

1920

seen in Figure 72-10. This layer is often referred to simply as the preperitoneal fascia. The anterior

lamina is more uniform and is adherent to the deep surface of the transversus abdominis and the rectus

abdominis. The posterior lamina is contained within the preperitoneal space, which is defined as the

space between the peritoneum and the anterior lamina of the transversalis fascia. The inferior epigastric

vessels are enclosed by, or interspersed with, the adipose tissue and the fibrous tissue of the posterior

lamina of the transversalis fascia. The vessels are in contact anteriorly with the anterior lamina of the

transversalis fascia as they course upward to enter the rectus abdominis sheath.

Transversalis Fascia Derivatives

The transversalis fascia analogs or derivatives are the iliopectineal arch, iliopubic tract, and crura of the

deep inguinal ring. The superior and inferior crura form a transversalis fascia sling, a structure shaped

like a “monk’s hood,” around the deep inguinal ring (Fig. 72-9). The transversalis fascia also contributes

the internal spermatic fascia to the spermatic cord at this point. This “sling” has functional significance;

when the transversus abdominis contracts, the crura of the ring are pulled upward and laterally, which

results in a valvular action that helps to prevent the indirect formation of a hernia.

Figure 72-10. A parasagittal section through the layers of the anterior abdominal wall and groin. Observe that the transversalis

fascia is depicted as a bilaminar structure.

The iliopubic tract (Figs. 72-9 and 72-11) has become an increasingly important landmark for

surgeons as the use of laparoscopic technology has increased.9,10 The iliopubic tract is the thickened

band of transversalis fascia formed at the zone of transition between the deep surfaces of the iliac and

transversus abdominis muscles. The structure courses parallel to the more superficially located inguinal

ligament, is attached to the iliac crest laterally, and inserts on the pubic tubercle medially. The tract

forms along its course a portion of the inferior crus of the deep inguinal ring and then contributes to the

anterior and medial walls of the femoral sheath. The tract fuses with the inguinal ligament to form a

component of the inferior wall of the inguinal canal. At its insertion on the pubic tubercle, it curves

backward slightly to blend with the Cooper pectineal ligament. The pectineal ligament is actually a

condensation of periosteum and is not a true analog of the transversalis fascia, but it is reinforced by

fibers from the iliopubic tract and inguinal ligament.

1921

Figure 72-11. A schematic representation of the deep inguinal region. The iliopubic tract is shown as a thickening of the

transversalis fascia, inferior to which many of the branches of the lumbar plexus exit the pelvis.

The iliopubic tract contains not only fibrous connective tissue but also some elastic fibers.11 In one

series, the iliopubic tract was a substantial structure, suitable for use in hernia repairs, in 42% of the

specimens examined. The tract, whether substantial or not, can be used as a readily identified landmark.

The iliopubic tract has particular significance because of its importance as a landmark to the

laparoscopic surgeon. Many of the branches of the lumbar plexus run inferior to the tract, and damage

to these nerves may be the result of aggressive dissection or the placement of tacks or staples to affix a

prosthesis below this structure. The tract is not obviously visible in every patient from a laparoscopic

view, but its location should always be immediately known to the surgeon because of its constant

relationship to the other landmarks in this area.

The iliopectineal arch (Fig. 72-9) is also a condensation of the transversalis fascia. The iliopectineal

arch commences at the medial border of the iliacus muscle, where it is continuous with the iliac fascia,

itself a portion of the transversalis (endoabdominal) fascia. The arch separates the vascular

compartment containing the femoral vessels from the neuromuscular compartment containing the

iliopsoas muscle, femoral nerve, and lateral femoral cutaneous nerve. The iliopectineal arch also

contributes to the proximal portion of the femoral sheath, thereby joining the iliopubic tract in the

formation of the femoral sheath.

Femoral Sheath, Canal, and Ring

The femoral sheath (Fig. 72-12) is primarily composed of extensions of the transversalis fascia. The

sheath is best understood in terms of the structures contained within. As the external iliac artery and

vein pass beneath the inguinal ligament to become the femoral vessels, they are covered anteriorly by

the transversalis fascia proper. This fascial layer is posteriorly and laterally joined by portions of the

iliopsoas fascia, which themselves are continuations of the transversalis fascia. At the inguinal ligament,

the iliopsoas fascia forms the iliopectineal arch. This arch divides the vascular compartment (lacuna

vasorum), containing the femoral vessels, from the muscular portion (lacuna musculorum), which

contains the iliopsoas muscle, femoral nerve, and lateral femoral cutaneous nerve. The vascular lacuna

is further divided by septa into compartments for the vessels and the femoral branch of the

genitofemoral nerve.

1922

Figure 72-12. Schematic view of the femoral sheath, ring, and canal. The transversalis fascia forms the anterior portion of the

sheath, and the iliopsoas fascia forms the posterior portion. Septae separate the vessels from each other and the vein from the

femoral canal. The femoral ring contains a lymph node. The ring is formed medially by the aponeurosis of the transversus

abdominis aponeurosis, anteriorly by the inguinal ligament, posteriorly by the pubic bone, and laterally by the femoral sheath.

The medial border of the femoral sheath follows the transversus abdominis aponeurosis to its

insertion just lateral to that of the lacunar ligament and extends inferiorly to fuse eventually with the

medial septum and adventitia of the femoral vein. The resultant cone-shaped cul-de-sac is the femoral

canal. The canal normally contains only wisps of connective tissue and small lymphatic nodes. The

wider proximal part of the canal, the femoral ring, contains a large node, which is often referred to as

the Cloquet node.

The femoral ring is the extraperitoneal opening of the canal. The boundaries of the ring are formed

medially by the curved edge of the transversus abdominis aponeurosis, not the lacunar ligament, which

inserts more medially.12 Laterally, the ring is bounded by the connective tissue septum and the

adventitia that is interposed between it and the femoral vein. The anterior boundary is the inguinal

ligament; posteriorly, the ring is reinforced by the iliopubic tract and iliopectineal ligament. The canal

is not in direct communication with the pelvic cavity. The transversalis fascia is not a component of the

roof of the canal because it is diverted at this point to form the femoral sheath. This weakened area is

therefore quite prone to hernia formation, especially in female subjects.

Inguinal (Hesselbach) Triangle

The inguinal triangle is the site of direct inguinal hernias. This triangle is most often described from the

anterior aspect (Fig. 72-13), in which case the inguinal ligament forms the base of the triangle, the

rectus abdominis forms the medial border, and the inferior epigastric vessels form the superolateral

border. The triangle as originally described by Hesselbach had the pectineal ligament as its base. The

latter description is quite useful to the surgeon viewing the abdomen from within because the inguinal

ligament cannot be seen from this viewpoint. When the inguinal triangle is transilluminated, the

thinness and translucency of the area of abdominal wall within the triangle underscores its importance

in hernia development and repair. In the most translucent area, little or no muscle is present. Only the

peritoneum and the transversalis fascia cover the triangle here. The aponeurotic arch of the transversus

abdominis crosses the triangle just below the apex in most people. A high aponeurotic arch affords less

reinforcement to the triangle and may therefore predispose a person to the formation of a direct

inguinal hernia.

Components of the Spermatic Cord

The spermatic cord (Figs. 72-11 and 72-14) is closely associated with the deep inguinal ring. The

spermatic cord is most appropriately described at this point because the deep ring itself is formed by

derivatives of transversalis fascia, as is the innermost covering layer of the spermatic cord, the internal

spermatic fascia. The middle covering layer is called the cremasteric fascia and contains the cremasteric

muscle bundles; both are derived from the internal abdominal oblique muscle and fascia. The outermost

covering of the spermatic cord is the external spermatic fascia, which is continuous with the investing

fascia of the external abdominal oblique muscle.

The tunica vaginalis is initially a component of the cord, but normally it atrophies and closes early in

neonatal life. This structure is an evagination of peritoneum. The testicle descends retroperitoneally in

1923