Anatomy - Umbilical hernia, primary suture repair - general and visceral surgery

1. Muscles of the anterior abdominal wall

Rectus abdominis: Straight abdominal muscle invested by the rectus sheath with its three to four tendinous intersections (intersectiones tendineae) conjoined with the anterior lamina of the rectus sheath
Pyramidalis: Originates at the superior pubic ramus, inserts in the linea alba, is situated anterior to the rectus abdominis and invested by its own sheath in the anterior lamina of the rectus sheath

2. Layered anatomy of the anterior abdominal wall

Rectus sheath: Invests the rectus abdominis; from the umbilicus to halfway between umbilicus and symphysis it demonstrates an anterior and posterior lamina; the posterior lamina terminates here as the arcuate line, above which the external oblique conjoins with the anterior lamina of the rectus sheath, while the internal oblique fuses with both the anterior and posterior lamina the transversus abdominis does so just with the posterior lamina.
Linea semilunaris: Transition zone between the aponeuroses of the lateral muscles of the abdominal wall and the lateral margin of the rectus sheath.
Linea alba: About 1cm wide taut strip of connective tissue between the left and right rectus sheath, extending from the sternum to the pubic symphysis.
Transversalis fascia: Craniad to the arcuate line it invests the posterior lamina of the rectus sheath, while caudad to the line it directly covers the rectus abdominis.

3. Interior aspect of the abdominal wall

Median umbilical fold: Median peritoneal fold running from th umbilicus to the bladder and containing the median umbilical ligament (connective tissue strand = remnant of the embryonic urachus).
Medial umbilical fold: Paired peritoneal fold containing the paired medial umbilical ligaments = obliterated remnants of the paired umbilical arteries.
Lateral umbilical fold: Paired peritoneal fold investing the paired inferior epigastric arteries with its two accompanying veins each.

4. Blood supply and innervation

a) Arteries
Superior epigastric artery: Extension of the internal thoracic artery, anastomoses with the inferior epigastric artery at the level of the umbilicus.
Inferior epigastric artery: Originates at the external iliac artery and like its internal counterpart courses on the posterior aspect of the rectus abdominis in the rectus sheath.
Superficial epigastric artery: Originates at the femoral artery and after crossing the inguinal ligament it fans out in the subcutaneous tissue of the anterior abdominal wall.
Posterior intercostal arteries VI – XI and subcostal artery: They originate at the thoracic aorta; their terminal segments course obliquely caudad between the internal oblique and transversus abdominis, and reaching the rectus sheath from lateral they anastomose there with the superior and inferior epigastric arteries.

b) Veins
Superior epigastric veins: They accompany the corresponding artery, anastomose with branches of the inferior epigastric artery and drain into the internal thoracic veins.
Inferior epigastric vein: Fans out into veins accompanying the inferior epigastric artery and drains into the external iliac vein.
Superficial epigastric vein: Parallels the corresponding artery (see above).

c) Lymph vessels
Superficial lymph vessels: Craniad to the umbilicus they course to the axillary lymph nodes (Nodi lymphatici axillaris) and caudad to the inguinal lymph nodes (Nodi lymphatici inguinales).
Deep lymph vessels: Usually they parallel the blood vessels and terminate in the parasternal, lumbar and external iliac lymph nodes.

d) Nerves
Intercostal nerves VI – XII: As anterior rami of the thoracic nerves VI – XII they course posterior to the coastal cartilages caudad into the abdominal wall between the internal oblique and transversus abdominis; motor branches supply the anterior and lateral abdominal muscles and sensory branches the skin of the abdominal wall.
Iliohypogastric, ilioinguinal and genitofemoral nerves:Are part of the motor and sensory innervation of the inferior abdominal region and the genitals.

Umbilical region: (1) Umbilical anulus; (2) Collagen fiber layer; (3) Round ligament of liver; (4) Umbilical scar; (5) Linea alba; (6) Tendinous intersections of rectus abdominis; (7) Rectus abdominis (translucent); (8) Anterior cutaneous rami.

The navel or umbilicus is the remnant of the insertion of the umbilical cord which after birth persists as scar at the level of the center of the body.

The umbilicus is triple layered:

• • Superficial layer comprising skin and subcutis
  • Aponeurotic middle layer
  • Deep layer with preperitoneal connective tissue and peritoneum

1. Superficial layer

In adults the rather fragile umbilical skin may only be displaced craniad against the umbilical anulus; everywhere else it is firmly attached to the posterior sheet of taut connective tissue. Within the umbilical anulus the subcutis is rather delicate and only sparingly crossed by vessels and nerves.

2. Middle layer

The aponeurotic middle layer comprises a matrix of taut connective tissue sealing the umbilical orifice and being crossed by obliterated remnants of embryonic vessels and the remnant of the urachus. At the margins of the umbilical orifice the sheet of connective tissue conjoins with the umbilical anulus where tendinous fingers from the rectus sheath interdigitate. Closure of the umbilical orifice with the sheet of dense connective tissue is complete by the end of the second year.

3. Deep layer

The deep layer of the umbilical sheet usually comprises a local palm-sized fat pad which is crossed by radial strands of connective tissue and a total of five peritoneal folds, the so-called umbilical plicas, which course from inferolateral craniad toward the umbilicus:

• • 1 median umbilical fold comprising the obliterated urachus
  • 2 medial umbilical folds comprising the obliterated umbilical arteries
  • 2 lateral umbilical folds comprising the inferior epigastric vessels

The transversalis fascia and its conjoined peritoneum close off the umbilical region against the abdominal cavity. The peritoneum in the umbilical region is reinforced by the taut connective tissue of the umbilical fascia. The fascia extends posteriorly to the umbilical vein, is anchored laterally to the posterior lamina of the rectus sheath and terminates caudad at the level of the center of the umbilical orifice. Craniad it extends for about 5cm beyond the umbilicus, with its fibers coursing toward the linea alba with which they conjoin.

Between the transversalis fascia and linea alba there courses a canal loosely filled with connective tissue (umbilical canal) which may pave the way for umbilical hernias.