INDIRECT AND DIRECT INGUINAL HERNIAS
Hernia (a word derived from the Greek, meaning “sprouting forth”) has been defined, from the time of A. Cornelius Celsus (second century AD), as a protrusion of an organ or tissue, through an abnormal opening, from the organ’s natural place in a cavity. Hernias are classified by the cause or the anatomic location of the defect.
Approximately
75% of hernias occur in the groin region. Groin hernias are classified as indirect
inguinal, direct inguinal, or femoral hernias based on the site of
herniation in relation to the surrounding structures. An inguinal hernia that has
direct and indirect components is referred to as a pantaloon hernia. An indirect
inguinal hernia is the most common type, irrespective of gender. It is characterized
by the propulsion of the hernia sac through the internal inguinal ring toward the
external inguinal ring and, at times, into the scrotum. The incidence of inguinal
hernias has a bimodal distribution, with peaks before the first of year of age and
after age 60 years. Inguinal hernia is three to four times as frequent in males
as in females, and this fact points to a causative relationship, namely, a developmental
process connected with the descent of the testes in fetal life. As the testes descend
from the intraabdominal space into the scrotum in the third trimester of pregnancy,
they are preceded by the gubernaculum and a fold of peritoneum, known as the funicular
process (see Plate 2-55) or processus vaginalis. This process is normally obliterated
during the eighth month of intrauterine life, becoming a thin, solid strand of connective
tissue (ligamentum vaginale). If the process is not obliterated, a peritoneal pouch
or sac termed the patent processus vaginalis persists; this accounts for the high
incidence of indirect inguinal hernias in preterm babies. Normally, the deep (internal)
inguinal ring (see also pages serves as a perfect closure against the egression
of any structure within the abdominal cavity. If, however, the funicular process
is not obliterated completely, the sac may grow in size or may be the object of
pathologic changes resulting in damage to fascial and muscular elements and thereby
lead to incompetence of the ring. However, a patent processus vaginalis does not
necessarily indicate an inguinal hernia. Numerous individuals of both sexes have
been found with a patent funicular process without ever having had any signs of
a hernia. Others “acquire” a complete hernia only late in life.
Epidemiologic studies have identified risk factors that play a role in the formation of a hernia in the presence or absence of a patent processus vaginalis. Inherent collagen weakness can predispose to formation of a hernia. Collagen disorders such as Ehlers-Danlos syndrome are also associated with an increased incidence of hernia. A chronic increase in abdominal pressure and enhanced tension on the wall, as seen in pregnancy or with ascites or chronic obstructive pulmonary disease, can force abdominal contents through the inguinal canal. Alternatively, strenuous physical activity or a sudden increase in abdominal pressure caused by lifting heavy objects can exert increased pressure against the abdominal wall, producing a clinically detectable hernia.
For
the understanding of the cause, clinical manifestations, and, particularly,
surgical repair of an indirect inguinal hernia,
a detailed knowledge of the anatomy of this region is critical. The anatomy has
been illustrated and discussed in Plates 2-1 to 2-3. In acquired inguinal hernia,
the ring becomes dilated over time or, as in a congenital hernia, is wide enough
from the very start to permit passage of the small or large intestine, omentum,
or bladder. The size of the sac depends on its contents. It always lies anterosuperior
to the spermatic cord, which contains the ductus deferens; the testicular, cremasteric,
and deferential vessels; the pampiniform
plexus; and the lymphatic vessels and nerves. The narrow proximal part of the sac,
which is continuous with the parietal peritoneum, is called the “neck” of the sac,
whereas the distal part is known as the “fundus.” The coverings of the hernial sac
are the same as those of the spermatic cord under normal conditions. The peritoneal
innermost layer is covered by areolar tissue, the internal spermatic (infundibuliform)
fascia derived from the transversalis muscle and the musculofascial cremasteric
layer, essentially derived from the internal oblique muscle and aponeurosis. In
moderate-sized to large indirect inguinal hernias, the obliqueness of the inguinal
canal is mostly lost. With the widening of the deep (internal, abdominal) ring and
the increased masses filling the canal, the two inguinal rings (deep and superficial)
start to lie more and more perpendicularly above each other. A medial displacement
of the inferior epigastric vessels is another consequence of this directional shift
of the inguinal canal.
Indirect
inguinal hernia may manifest in a range of clinical scenarios. It may be incidentally
detected during physical examination in an otherwise asymptomatic individual or
it can cause a life-threatening mechanical bowel obstruction with incarceration
and strangulation. Some patients, especially those who are middle-aged or elderly,
may describe pain or discomfort in the lower abdominal quadrants, or the appearance
of a swelling, with some sort of an accident or a specific event of strain. The
frequency and intensity of pain, however, vary greatly from individual to individual.
In general, chronic moderate or even extensive protrusion of abdominal contents
through an enlarged deep inguinal ring usually produces, except for cases with incarceration,
less discomfort than do those cases with a sudden onset. The family history may
reveal an increased incidence of hernia. The diagnosis of an uncomplicated indirect
inguinal hernia is made by inspection and palpation. The patient should be examined
in the supine as well as the erect position, first with the flat hand over the inguinal
region and the fingertips resting over the superficial (subcutaneous) inguinal ring
and exerting a slight pressure along the inguinal canal. Second, with the palmar
surface of the hand resting over the patient’s thigh, the fifth finger should be
gently pushed forward through the superficial ring invaginating the scrotal skin.
The protruding abdominal tissue can thus be felt while the patient is completely
relaxed. A patent but empty sac cannot be felt and diagnosed, but requesting the
patient to use the abdominal musculature to increase the abdominal pressure or asking
him or her to cough will often be helpful in discovering the functional incompetence
of the deep inguinal ring and will force a part of the abdominal contents to enter
the canal, so that the palpating finger feels it
directly or at least feels a change or shift of the tissues within the canal. In
infants, the examination is naturally not so simple, and a hernia, when reduced,
is hardly recognizable. Thickening of the cord at the superficial ring is said to
be a reliable sign of a hernia, provided it is unilateral so that the cord on
both sides can be compared. Children with a left-sided congenital inguinal hernia
have an increased chance of soon revealing one on the other side. Oddly, this
is not true of a right-sided hernia.
When
women are concerned, the best diagnostic method consists in placing two fingers
over the subcutaneous inguinal ring and palpating for an expansile impulse on coughing
or, better, on a more steady increase of intraabdominal pressure as produced by
voluntary contraction of the abdominal musculature.
Distinction
between indirect and direct inguinal hernias can be made by occluding the
internal inguinal ring with a finger as the patient coughs. An indirect
inguinal hernia should be blocked, but a direct hernia should
freely bulge. Additionally, transmission of the cough impulse to the tip of the
finger implies an indirect hernia, whereas an impulse palpated on the dorsum of
the finger implies a direct hernia. These physical findings distinguish between
direct and indirect hernias only 50% of the time. If the herniated organ has protruded
as far as the scrotum, consideration must be given to the possibility of other scrotal
swellings, such as a hydrocele, epididymitis, testicular torsion, varicocele, or
even testicular tumors. In females, labial cysts, abscesses, or tumors should be
considered.
Laboratory
testing is not helpful in the diagnosis of inguinal hernias. Incarceration and bowel
ischemia may be associated with nonspecific leukocytosis. Abdominal imaging is rarely
used for diagnosis and usually helps exclude other causes.
Direct Inguinal Hernias
The
direct inguinal hernia has an etiologic and pathologic background quite different
from that of the indirect inguinal hernia. It is rarely seen in children, and it
more frequently presents at 40 to 50 years of age, with a strong preponderance in
males. Thus, although considered an acquired disease, it nevertheless must be traced
back to a congenital condition characterized by a poorly developed musculofascial
wall in the lower- most portion of the internal oblique muscle, where the fibers,
instead of coursing obliquely, are arranged more transversely. Furthermore, partly
as a result of the transverse course of the fibers, the conjoined tendon is attached
to the sheath of the rectus muscle at a variable distance above the pubic crest.
The predisposing factor of a direct hernia is thereby assumed to be deficient protection
of the inguinal (Hesselbach) triangle, particularly of its lateral angle. The characteristic
anatomic feature of a direct inguinal hernia is that it protrudes medial to the
inferior epigastric vessels instead of lateral to them, as with the indirect hernia.
In other words, the direct hernia does not pass through the deep ring but bulges
through the posterior wall of the inguinal canal. The precipitating causes may be
strenuous and/or pro- longed exertions in the erect position that produce a marked
increase in intraabdominal pressure, or progressive distention of the abdomen as
in ascites, or a progressive atrophy of abdominal muscles owing to advanced age
or a wasting disease.
The
clinical manifestations of the direct inguinal hernia are even less noticeable than
are those of the indirect type. The onset is insidious and asymptomatic. The patient
or the physician may incidentally discover a painless bulge in the inguinal area.
The mass is reduced instantly when the patient lies down and can reappear upon arising
or with straining. With an increase in size, though this is uncommon, the direct inguinal
hernia remains in the area above the inguinal ligament, expanding medially, in contrast
to the indirect variety, which, as a rule, enlarges downward into the scrotum.
The
protrusion only rarely emerges from the subcutaneous ring and usually remains
small and incomplete. The globular mass is found close to the lateral border of
the os pubis, the spermatic cord resting superficially and
laterally upon the protrusion. With the hernia reduced, the same maneuver outlined
for the diagnosis of indirect hernia (see above) should be carried out. When the
patient coughs, if the impulse is felt by the index finger as coming from the floor
of the canal, pushing the finger outward, instead of being felt on the tip of
the fifth finger as coming from above downward, the hernia is
likely to be of the direct type.
Treatment Of Inguinal Hernias
The
definitive treatment of indirect inguinal hernia is surgical repair. Inguinal hernia
repair is among the most common procedures performed by general surgeons. Nonoperative
management, namely the use of a truss, can be used for pain, pressure, and protrusion
of abdominal contents in the symptomatic patient who is not able to undergo surgery.
In newborns, the application of a simple yarn truss for a period of 2 to 6 months
is sometimes sufficient to prevent the protrusion of the abdominal contents and
to allow for the spontaneous closure of a funicular process not obliterated at birth,
but this method is not used much today, and surgical repair is preferred at any
age.
The
surgical treatment of an inguinal hernia in infants is relatively simple and can
be expeditiously accomplished in a matter of minutes, especially when the hernia
is small and of recent onset. Ligation and excision of the sac is all that is required,
because in infants the deep inguinal ring is almost adjacent to the superficial
ring, and it is not necessary to divide the external oblique aponeurosis. Surgical
intervention is urgently required in infants with an extroverted urinary bladder;
an undescended testis, with or without torsion; or an ectopic testis. In girls,
the presence of the ovary, fallopian tube, or uterus in the hernia sac must be ruled
out before ligation.
Surgical
repair of indirect inguinal hernias in adults can be performed using an open or
laparoscopic approach. Modern surgery of inguinal hernias began about 70 years ago,
when Bassini (in Padua, Italy) and Halsted (in Baltimore, Maryland) simultaneously
and independently developed operative techniques, the fundamental principles of
which were identification and excision of the persistent sac, reparation of the
defective deep ring, and strengthening of the posterior wall of the inguinal canal.
Whether open or laparoscopic, successful hernia repair depends on a tension-free
closure that can be achieved either with a primary approximation or with the use
of a mesh. Open repair is generally indicated for strangulated or large inguinal
hernias or in cases where there is ascites or previous pelvic surgery. The open
approach is also preferred for repair of unilateral inguinal hernias in men. If
the open approach is planned, the use of tension-free mesh has to be considered.
The use of mesh generally reduces recurrence, but the risk of infection is increased
if the hernia is complicated by incarceration or strangulation. The most common
open mesh repair techniques used are the Lichtenstein repair and the “plug and patch”
repair. When the mesh cannot be used, as in wound infection, primary approximation
can be achieved using traditional open techniques such as the Bassini, Shouldice,
and McVay repairs.
Laparoscopic hernia repair is increasingly popular, and under expert hands, recurrence rates are low. In the absence of the contraindications listed above, the laparoscopic approach is minimally invasive, with less postoperative pain and a fast recovery time. The two most commonly performed laparoscopic inguinal hernia repair techniques are the transabdominal pre- peritoneal hernia repair and the totally extraperitoneal hernia repair approaches. The use of mesh to create a tension-free repair is recommended for all laparoscopic techniques; a preformed mesh that conforms to the space is available. Fixation of the mesh is recommended to avoid mesh migration and shrinkage, although care must be taken to avoid inadvertent nerve injury. The choice of which laparoscopic technique to use mainly depends on the expertise of the surgeon. The totally extraperitoneal hernia repair technique is generally recommended for male patients, whereas in women with indirect inguinal hernias or individuals who have undergone prior pelvic surgery, the transabdominal preperitoneal hernia repair approach offers an easier and safer method.
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