General
features common to all hernias
Aetiology
Any condition which raises intra-abdominal
pressure, such as a powerful muscular effort, may produce a hernia. Whooping
cough is a predisposing cause in childhood, whilst a chronic cough, straining on
micturition or straining on defecation may precipitate a hernia in an adult.
Hernias are more common amongst smokers, which may be the result of an acquired
collagen deficiency increasing an individual’s susceptibility to the
development of hernias. It should be remembered that the appearance of a hernia
in an adult can be a sign of intra-abdominal malignancy. Stretching of the
abdominal musculature because of an increase in contents, as in obesity, can be
another factor. Fat acts to separate muscle bundles and layers, weakens aponeurosis
and favours the appearance of paraumbilical, direct inguinal and
hiatus hernias. A femoral hernia is rare in nulliparous women and men, but more
common in multiparous women owing to stretching of the pelvic ligaments. An
indirect hernia may occur in a congenital preformed sac — the remains of the
processus vaginalis.
Peritoneal
dialysis can cause the development of a hernia from a previously occult weakness
or enlargement of a patent processus vaginalis.
Composition of
a hernia
As a rule, a hernia consists of three parts
— the sac, the coverings of the sac and the contents of the sac.
The sac
The sac is a diverticulum of peritoneum
consisting of mouth, neck, body and fundus. The neck is usually well defined,
but in some direct inguinal hernias and in many incisional hernias there is no
actual neck. The diameter of the neck is important because strangulation of
bowel is a likely complication where the neck is narrow, as in femoral and
paraumbilical hernias.
The body of the
sac
The body of the sac varies greatly in size and
is not necessarily occupied. In cases occurring in infancy and childhood the
sac is gossamer thin. In long-standing cases the wall of the sac may be
comparatively thick.
The covering
Coverings are derived from the layers of the
abdominal wall through which the sac passes. In long-standing cases they become
atrophied from stretching and so amalgamated that they are indistinguishable
from each other.
Contents
These can be:
•
omentum = omentocele (syn. epiplocele);
•
intestine = enterocele. More commonly small bowel, but may be large
intestine or appendix;
•
a portion of the circumference of the intestine Richter’s hernia;
•
a portion of the bladder (or a diverticulum) may constitute part of or be
the sole contents of a direct inguinal, a sliding inguinal or a femoral hernia;
•
ovary with or without the corresponding fallopian tube;
•
a Meckel’s diverticulum = a Littre's hernia;
•
fluid — as part of ascites or as a residuum thereof.
Classification
Irrespective of site, a hernia can be
classified into five types.
Classification of hernias
1.
Reducible
2.
Irreducible
3.
Obstructed
4.
Strangulated (complication of irreducible hernias)
5.
Inflamed
The hernia either reduces itself when the
patient lies down, or can be reduced by the patient or the surgeon. The
intestine usually gurgles on reduction and the first portion is more difficult
to reduce than the last. Omentum, in contrast, is described as doughy and the
last portion is more difficult to reduce than the first. A reducible hernia
imparts an expansile impulse on coughing.
Irreducible
hernia
Here the contents cannot be returned to the
abdomen, but there is no evidence of other complications. It is usually due to
adhesions between the sac and its contents or from overcrowding within the
sac. Irreducibility without other symptoms is almost diagnostic of an
omentocele, especially in femoral and umbilical hernias. Note: any degree of
irreducibility predisposes to strangulation.
Obstructed
hernia
This is an irreducible hernia containing
intestine which is obstructed from without or within, but there is no
interference to the blood supply to the bowel. The symptoms (colicky abdominal
pain and tenderness over the hernia site) are less severe and the onset more
gradual than is the case in strangulation, but more often than not the
obstruction culminates in strangulation. Usually there is no clear distinction
clinically between obstruction and strangulation, and the safe course is to
assume that strangulation is imminent and treat accordingly.
Incarcerated
hernia. The term ‘incarceration’ is often used loosely as an alternative to
obstruction or strangulation, but is correctly employed only when it is
considered that the lumen of that portion of the colon occupying a hernial sac
is blocked with faeces. In that event the scybalous contents of the bowel should
be capable of being indented with the finger, like putty.
Strangulated
hernia
A hernia becomes strangulated when the blood
supply of its contents is seriously impaired, rendering the contents ischaemic.
Gangrene may occur as early as 5—6 hours
after the onset of the first symptoms. Although inguinal hernia may be 10 times
more common than femoral hernia, a femoral hernia is more likely to strangulate
because of the narrowness of the neck and its rigid surrounds.
Pathology.
The intestine is obstructed and its blood supply impaired. Initially, only the
venous return is impeded, the wall of the intestine becoming congested and
bright red with the transudation of serous fluid into the sac. As congestion
increases, the wall of the intestine becomes purple in colour. The intestinal
pressure increases distending the intestinal loop and impairing venous return
further. As venous stasis increases, the arterial supply becomes more and more
impaired. Blood is extravasated under the serosa and is effused into the lumen.
The fluid in the sac becomes blood stained and the shining serosa dull due to a
fibrinous, sticky exudate. At this stage the walls of the intestine have lost
their tone and become friable. Bacterial transudation occurs secondary to the
lowered intestine viability and the sac fluid becomes infected. Clinical
features. Sudden pain at first situated over the hernia is followed by
generalised abdominal pain, colicky in character and often located mainly at the
umbilicus. Nausea and subsequently vomiting ensue. The patient may complain of
an increase in hernia size. On examination, the hernia is tense, extremely
tender and irreducible, and there is no expansile cough impulse.
Unless
the strangulation is relieved by operation, the spasms of pain continue until
peristaltic contractions cease with the onset of ischaemia when paralytic ileus
(often the result of peritonitis) and septicaemia develop. Spontaneous cessation
of pain must be viewed with caution as this may be a sign of perforation.
Richter’s
hernia
Richter’s hernia is a hernia in which the
sac contains only a portion of the circumference of the intestine (usually small
intestine). It usually complicates femoral and, rarely, obturator hernias.
Strangulated
Richter’s hernia
Strangulated Richter’s hernia (Fig.
62.3) is
particularly noteworthy as operation is frequently delayed because the
clinical
Strangulated omentocele. The initial symptoms
are in general similar to those of strangulated bowel. Vomiting and constipation
may be absent as omentum, unlike intestine, can exist on a very meager blood
supply. The onset of gangrene is therefore delayed, occurring first in the
centre of the fatty mass. Unrelieved, a bacterial invasion of the ischaemic
contents of the sac will occur and an abscess eventually develops. In an
inguinal hernia, infection usually terminates as a scrotal abscess, but
extension from the sac to the general peritoneal cavity is always a possibility.
Inflamed
hernia. Inflammation can occur from inflammation of the contents of the sac
(e.g. acute appendicitis or salpingitis) or from external causes (e.g. the
trophic ulcers which develop in the dependent areas of large umbilical or
incisional hernias). The hernia is usually tender but not tense, and the
overlying skin red and oedematous. Treatment is based on treatment of the
underlying cause.