An external hernia is an abnormal protrusion of intra-abdominal
tissue through a fascial defect in the abdominal wall. Although the
majority of hernias (75%) occurs in the groin, incisional
hernias represent an increasing proportion (15–20%),
with umbilical and other ventral hernias comprising the remainder.
Generally, a hernial mass is composed of covering tissues (skin,
subcutaneous tissues, etc), a peritoneal sac, and any contained
viscera. Particularly if the neck of the sac is narrow where it
emerges from the abdomen, bowel protruding into the hernia may become
obstructed or strangulated. If the hernia is not repaired early,
the defect may enlarge and operative repair may become more complicated.
The definitive treatment of hernia is operative repair.
A reducible hernia is one in which the contents
of the sac return to the abdomen spontaneously or with manual pressure
when the patient is recumbent.
An irreducible (incarcerated) hernia is one whose
contents cannot be returned to the abdomen, usually because they
are trapped by a narrow neck. The term “incarceration” does
not imply obstruction, inflammation, or ischemia of the herniated
organs, though incarceration is necessary for obstruction or strangulation
Though the lumen of a segment of bowel within the hernia sac
may become obstructed, there may initially be no interference
with blood supply. Compromise to the blood supply of the contents
of the sac (eg, omentum or intestine) results in a strangulated
hernia, in which gangrene of the contents of the sac has
occurred. The incidence of strangulation is higher in femoral than
in inguinal hernias, but strangulation may occur in other hernias
An uncommon and dangerous type of hernia, a Richter hernia, occurs
when only part of the circumference of the bowel becomes incarcerated or
strangulated in the fascial defect. A strangulated Richter hernia
may spontaneously reduce and the gangrenous piece of intestine be
overlooked at operation. The bowel may subsequently perforate, with
*See Chapter 43 for further discussion
of hernias in the pediatric age group and Chapter 21 for
a discussion of internal hernias.
All hernias of the abdominal wall consist of a peritoneal sac that
protrudes through a weakness or defect in the muscular layers of
the abdomen. The defect may be congenital or acquired.
Just outside the peritoneum is the transversalis fascia, an
aponeurosis whose weakness or defect is the major source of groin
hernias. Next are found the transversus abdominis, internal
oblique, and external oblique muscles, which
are fleshy laterally and aponeurotic medially. Their aponeuroses
form investing layers of the strong rectus abdominis muscles above
the semilunar line. Below this line, the aponeurosis lies entirely
in front of the muscle. Between the two vertical rectus muscles,
the aponeuroses meet again to form the linea alba, which
is well defined only ...