Hernias

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11 Hernias

Anatomy of the Abdominal Wall

image

Abdominal Wall: Inguinal Region

Abdominal Wall Layers

• Following are layers from the surface in.

image Skin
image Superficial fascia with a variable amount of subdermal fat: Camper’s fascia, overlying membranous Scarpa’s fascia (subumbilical level)
image Muscle bellies and aponeuroses of the rectus abdominis, external and internal obliques, and transversus abdominis muscles
image Transversalis fascia
image Endoabdominal fascia and the peritoneum (greater sac)

External Oblique (EO) Muscle

• Bilateral origins off of the lower ribs, lumbar fascia, and iliac crest
• On each side, the lower border of its aponeurosis attaches to anterior superior iliac spine and pubic tubercle to form the inguinal ligament.
• Distally, a portion of EO aponeurosis fibers arch posteriorly to insert on the superior pubic ramus, forming the lacunar ligament (of Gimbernat).
• Most lateral of these deep (lacunar) fibers continue to run along the pectin of pubis as the pectineal ligament (of Cooper).
• Some of the most distal fibers arch upward, avoid the pubic tubercle, and merge with the opposite side’s fibers as the reflected inguinal ligament.
• Most muscle and aponeurotic fibers run superolateral to inferomedial (“hands in pockets” orientation).
• Medial part of the EO aponeurosis contributes the most anterior fibers of the rectus sheath.
• Superficial (external) inguinal ring: division in the most inferior aponeurosis; spermatic cord or round ligament passes through
• External oblique fascia contributes to external spermatic fascia.
• Fibers of the medial crus (of the superficial ring) attach to the pubic crest.
• Fibers of the lateral crus attach with the rest of the inguinal ligament to the pubic tubercle.
• EO aponeurosis is relatively weak superiorly, very strong inferiorly.
• Innervation: anterior rami T7-T12 (thoracoabdominal and subcostal nerves)

Internal Oblique (IO) Muscle

• Bilateral origins off the lower ribs, lumbar fascia, and iliac crest
• Fibers run deep, approximately perpendicular to the external oblique layer, from the deep lumbar aponeurosis, curving anteriorly then medially.
• Cremaster muscle and fascia: IO layer surrounding internal spermatic fascia
• Medial IO aponeurosis layer splits to pass around the rectus, as the middle layer of the rectus sheath, above the semicircular lines (of Douglas).
• On each side, the inferior triangle of the IO aponeurosis fuses with the transversus aponeurosis to form the conjoined (conjoint) tendon.
• Innervation: anterior rami T7-T12 (thoracoabdominal nerves) and L1

Transversus Abdominis (TA) Muscle

• Bilateral origins off the lower ribs, lumbar fascia, and iliac crest
• Fibers run deep to the internal oblique layer, mostly posteriorly, becoming largely aponeurotic laterally in the deep back.
• Medial aponeurotic fibers pass posterior to the rectus, as the posterior layer of the rectus sheath, above the semicircular lines (of Douglas).
• On each side, the inferior triangle of the TA aponeurosis fuses with the internal oblique aponeurosis to form the conjoined (conjoint) tendon.
• Deep (internal) inguinal ring: gap in the transversus abdominis, lateral to the inferior epigastric arteries
• Innervation: anterior rami T7-T12 (thoracoabdominal nerves) and L1

Rectus Abdominis Muscle

• Parallel segments of muscle with vertically running fibers; segments joined end-to-end by tendinous insertions (inscriptions)
• Upper segments well separated at the midline
• Lower segments close together at midline
• External oblique aponeurosis is always the most superficial (anterior) component of the rectus sheath.
• Internal oblique aponeurosis splits to run in front of and behind rectus in the sheath above the semilunar lines (somewhat above umbilicus).
• External and internal oblique and transversus aponeuroses components of rectus sheath pass anterior to the rectus below the semicircular lines (below the umbilicus).
• Pyramidalis muscle, present in ~80%

image Lies anterior to the inferior part of the rectus
image Attaches to the anterior pubis and anterior pubic ligament
image Inserts on the linea alba and tenses it

• Innervation: anterior rami T7-T12, thoracoabdominal nerves

Linea Alba

• Midline, tendinous junction between right and left portions of the rectus sheath and the underlying midline tendons of the rectus muscle segments
• Tends to be broader, more well developed superiorly
• Umbilical gap lies about 2/3 of the way down from the linea origin at the xiphoid process.

Transversalis Fascia

• Tough fascial layer just deep to the transversus muscle and aponeurosis, rectus sheath, and rectus abdominis anteriorly
• Overlies the endoabdominal fascia (and fat) superficial to the peritoneum
• Male transversalis fascia outpockets through the deep (internal) inguinal ring, a gap in the transversus abdominis, lateral to the inferior epigastric arteries.
• Internal spermatic fascia: transversalis fascia layer surrounding the layers of the tunica vaginalis around the descended testis, its duct, and vessels
• Iliopubic tract: thickened inferior margin of the transversalis fascia, running parallel, posterior, and deep to the inguinal ligament (reinforcing)
• Round ligament passes through the deep inguinal ring in the female.

Hesselbach’s Triangle

• Anatomical area (on either side) of the inferior and interior abdominal wall, lying between the inferior epigastric artery and the midline
• Lies deep to the conjoint tendon
• Anteromedial to the deep inguinal ring
• Direct inguinal hernias directly penetrate the wall (i.e., conjoint tendon) in this region.
• Indirect inguinal hernias pass though the deep ring lateral to this region (and the inferior epigastric artery).

Inguinal Canal Boundaries

• Anterior: external oblique aponeurosis
• Posterior: transversalis fascia and a variable amount of transversus abdominis fascia
• Inferior: inguinal and lacunar ligaments
• Superior: internal oblique and transversus abdominis muscles and aponeuroses
• Internal (deep) inguinal ring: entry point through a transversus abdominis muscle gap for spermatic cord or round ligament
• External (superficial) inguinal ring: division in external oblique aponeurosis that passes the spermatic cord or round ligament

Spermatic Cord Layers and Contents

• External spermatic fascia (external oblique fascia)
• Cremasteric layer and cremasteric artery
• Internal spermatic fascia (from transversalis)
• Parietal tunica vaginalis (peritoneal origin)
• Visceral tunica vaginalis around deeper viscera

image Vas and ductus deferens, deferential artery
image Testicular veins and pampiniform plexus
image Testicular artery
image Nerves (testicular, autonomic, sensory)
image Testis with tunica albuginea

Nerves Near the Spermatic Cord

• Iliohypogastric: superficial if seen
• Ilioinguinal: typically superficial to cord
• Genitofemoral: usually posterior to cord

Vessels and Lymphatics

Regional Arteries and Veins

• External iliac arteries and veins run across the pelvic brim, passing under the inguinal ligament to become the femoral arteries and veins.
• Inferior epigastric vessels arise from the external iliac vessels just before they pass through the inferior abdominal wall.
• Inferior epigastric vessels run superiorly through the deep surface of the rectus abdominis, to anastomose within it with branches of superior epigastrics.
• Testicular arteries pass down from their source on the aorta (renal levels) to enter deep inguinal ring with ductus deferens and pass with spermatic cord through inguinal canal to attach to testis.
• Superficial epigastric arteries and veins arise from the femoral vessels (below the inguinal ligament) and curve superomedially to supply anterior inferior abdomen superficially.
• Small cremasteric branches of inferior epigastric vessels accompany spermatic cord.

Lymphatics

• Superficial lymphatics of abdominal wall above umbilicus drain into axillary nodes.
• Superficial lymphatics of abdominal wall below umbilicus drain into inguinal nodes.
• Enlarged inguinal nodes should not be mistaken for an inguinal hernia because of their placement below inguinal ligament.

Clinical Correlates

• In hernias, portions of peritoneum (sac), abdominal fat, or adjacent viscus or viscera protrude through defects or gaps in abdominal wall.
• Incarceration: abdominal contents are trapped in the hernia, can progress to strangulation (acute: emergency)
• Strangulation: blood vessels to a viscus are compressed, causing ischemia and necrosis
• Reduction: hernia contents are returned to their normal position in the abdomen
image

Indirect Inguinal Hernia

Inguinal Hernia

• 80%-90% of abdominal hernias

Types

• Indirect

image Passes through deep (internal) inguinal ring, inguinal canal, and finally through superficial (external) inguinal ring; follows course of spermatic cord
image Typically congenital, associated with a persistence of the fetal processus vaginalis (peritoneal tract accompanying the descending testis)
image Hernial sac lies within the spermatic cord, necessitating dissection in herniorrhaphy
image More than 2/3 of inguinal hernias are indirect.
image Hydrocele: excess fluid in persistent processus vaginalis

• Direct

image Passes directly through posterior wall of inguinal canal, through defect in transversalis fascia, within Hesselbach’s triangle
image Can extend through inguinal canal into scrotum

Approaches

• Anterior approaches for herniorrhaphy

image Bassini repair: used for both direct and indirect herniorrhaphy, approximation of the conjoint tendon and transversalis fascia superior to the free edge of the inguinal ligament
image Cooper’s ligament (McVay) repair: approximation of the conjoint tendon and transversalis fascia above Cooper’s (pectineal) ligament
image Prosthetic repair: with mesh in large defect with wall tension

• Posterior (preperitoneal) approach

image May be preferred for recurrent, strangulated, or complicated hernias
image Transverse incision through external oblique aponeurosis and rectus sheath, separation of muscle layers, incision of transversalis fascia, opening of preperitoneal space
image Peritoneum is separated from anterior abdominal wall and posterior inguinal canal.
image Hernia is exposed and reduced, and the sac excised when appropriate.

• Laparoscopic approach

image Indicated in recurrent or bilateral hernias
image May be transabdominal or extraabdominal

Femoral Hernia

• Passes through the femoral canal
• Deep to the iliopubic tract and inguinal ligament
• Medial to the femoral vein
• Lateral to the insertion of the iliopubic tract into the lacunar (Cooper’s) ligament
• Hernial sac lies below inguinal ligament, in groin or superior thigh.
• More common in women

Umbilical Hernia

• Usually congenital; small defects typically closed by age 2 years
• Early defects >2 cm or those persisting beyond age 4 years require repair.
• Acquired hernias: typically due to increased abdominal pressure in pregnancy, morbid obesity, ascites
• Valsalva maneuver produces a reducible bulge; defect can be palpated.
• Rarely, can be confused with a lipoma or epigastric hernia
• Apparent lipoma may be incarcerated hernia
• Treatment: incision, reduction of hernial sac, and return of contents to abdominal cavity
• Heavy sutures for closure, prosthetic repair necessary for large defects
• Recurrence and complications uncommon
image

Abdominal Wall Hernias

Incisional Hernia

• Ventral: the great majority occur at site of a previous abdominal incision.
• Causes include clinical or subclinical wound infection, poor healing, ascites, malnutrition, pregnancy, chemotherapy, steroids, strain on the wound.
• Fascial edges separate; hernia protrudes.
• Valsalva maneuver produces a bulge that reduces on expiration.
• Edges of the fascial defect can be palpated.
• High recurrence rate: contributing factors may need attention, including obesity, malnutrition, uncontrolled diabetes, steroids
• Unless factors interfere, repair is recommended at or near diagnosis.
• Open reduction usually involves opening the original incision.

Rare Hernias

• Obturator hernia (OH)

image Through the obturator canal into thigh adductor compartment with neurovascular bundle
image OH most common in older women
image Difficult to diagnose, demonstrable on CT

• Parastomal hernia

image Occurs through the same abdominal opening made for the ostomy
image Might require relocation of ostomy or prosthetic repair of defect

• Spigelian hernia

image Through the fascia between rectus and semilunar line
image Narrow, may be interparietal, posterior to the external oblique aponeurosis
image Reduced through a transverse incision over the hernia

• Lumbar hernia

image Hernia through posterior abdominal wall in various locations
image May be large
image Repair through transabdominal approach

• Sciatic hernia

image Extremely rare, through greater sciatic foramen
image Can manifest with bowel obstruction
image Requires transabdominal approach

• Perineal hernia

image Through muscles and fascia of perineal (urogenital) diaphragm
image May be congenital or acquired after perineal surgery
image Transabdominal reduction

image

Hiatal Hernias

Hiatal Hernias

• See p. 161 and Chapter 10, p. 142, for more information.

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