Definition :-
A hernia is a protrusion of a viscus or part of a viscus through an abnormal opening in the walls of its containing cavity
The external abdominal hernia is the commonest form , the most frequent varieties being the inguinal, femoral and umbilical respectively, 75 ,8.5and 15 percent the rarer comprise 1.5 percent excluding incisional hernias.

General features common to all hernias

Aetiology :-
  Any condition which raises the intra abdominal pressure such as powerful muscular effort may produce a hernia.
- whooping cough is a pre - disposing cause in childhood.
- A chronic cough, straining on micturition or straining on defecation may precipitate a hernia in an adult.
- Hernias are more common among smokers which may be the result of fan acquired collagen deficiency, increasing an individual’s susceptibility to the development of hernias.
- Appearance of hernia in an adult can be a sign of intra abdominal malignancy.
- Stretching of the abdominal musculature because of an increasing contents as in obesity can be another factor.
- Fat acts to separate muscle bundle and layers weakens aponeurosis and favour the appearance of paraumbilical , direct inguinal and hiatus hernias.
- Femoral hernia is rare in nulliparous women and men bur more common in multi parous women owing to stretching of the processes vaginalis.
- Peritoneal dialysis can cause the development of hernias from a previously occult weakness or enlargement of patent processus vaginalis.

Composition of a hernia:-
As a rule a hernia consist of 3 parts – the sac, the coverings of the sac, and the contents of the sac.

The sac.:- the sac is a diverticulum of peritoneum consting of mouth, neck, body and fundus. The neck is usually well defined but in some direct inquinial hernias and in many incisional hernias there is no actul neck. The diameter of the neck is importetnt because strangulation of bowel is a likely complication where the neck is narrow, as in femoral and para umbilical 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 gorsamei thing. In long standing cases the wall of the sac may be comparatively thick.

The covering:- the 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( sin. 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 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’d diverticulam = A Littre’hernia
Fluid as part of ascitis or a residuum thereof

CLASSIFICATION
Irrespective of site, a hernia can be classified in to 5 types
1. reducible
2. irreducible
3. obstructed
4. strangulated (complication of irreducible hernia)
5. inflamed

1. Reducible hernia: 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 descended as doughy and the last portion is more difficult to reduce than the first. A reducible hernia imparts an expansile impulse on coughing.

2.Irreducible hernia: Here the contents cannot be returned to the abdomen, but there is no evidence of other complecation. It is usually due to adhesions between the sack and its contents or from overcrowding withing the sack irreduciblity without other symptoms is almost diagnostic of omentocele, especially the femeral and umbilical hernias. Any degree of irrediucibility predisposes to strangulation.

3. 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 culminate 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.

4. Incarcerated Hernia : The term ‘incarcerated’ 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 contents of the bowel should be capable of being indented with the finger like putty.

5. 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 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 lowered intestine viability and the sac fluid becomes infected. Gangrene appears at the ring of constriction which become deeply indented and grey in colour.The gangrene then develops in the antimesentric border, the colour varying from black to green depending on decomposition of blood in the subserosa. The mesentry involved by the strangulation also becomes gangrenous. If the strangulation is unrelieved, perforation of the wall of the intestine occurs, either at the convexity of the loop or at the seat of constriction. Peritonitis spread from the sac to the peritoneal cavity.

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 ensues. The patient may complain of an increase in hernial 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 septicemia develop. Spontaneous cessation of pain must be viewed with caution as this may be a sign of perforation.

Individual features of hernias

Inguinal Hernia:
Surgical Anatomy:-
The superficial inguinal ring is a triangular aperture in the aponeurosis of the external oblique and lies 1.25cm above the pubic tubercle. The ring is bounded by a superomedial and inferolateral crus joined by the criss cross intercrural fibres. Normally, the ring will not admit the tip of the little finger.
The deep inguinal ring is a U- shaped condensation of the transversalis fascia and it lies 1.25cm above the inguinal (poupart’s) ligament, midway between the symphysis pubis and the anterior superior iliac spine . The transversalis fascia is the fascial envelope of the abdomen and the competency of the deep inguinal ring depends on the integrity of this fascia.
The inguinal canal:- In infants, the superficial and deep inguinal rings are almost super-imposed and the obliquity of the canal is slight. In adults, the inguinal canal, which is 3.75cm long, is directed downwards and medially from the deep to the superficial inguinal ring. In the male, the inguinal canal transmits the spermatic cord, the ilio-inguinal nerve and the genital branch of the femoral nerve. In the female, the round ligament replaces the spermatic cord.

Boundaries of the canal :
The anterior boundary comprises mainly the external oblique aponeurosis with the conjoined muscle laterally. The posterior boundary is formed by the fascia transversalis and the conjoined tendon( internal oblique and transversus abdominis medially). The inferior epigastric vessels lie posteriorly and medially to the deep inguinal ring.
The superior boundary is formed by the conjoined muscles(internal oblique and transversus) and the inferior is the inguinal ligament.

The inguinal canal defense-
During rise of intra abdominal pressure,(eg. During defaecation, coughing, or lifting weights) , there is a tendency for the abdominal organs to be protruded out through areas of weakness in the abdominal wall . the inguinal canal is one such weak area and hernia comes out through it. However , the canal possess a defense mechanism, of considerable efficiency to prevent such a protrusion.

1. obliquity of the inguinal canal:- the canal is oblique and therefore, to a great extent valvular. When the intra abdominal pressure rises, posterior wall of the canal is pushed forward into apposition with the anterior wall.
2. Shutter mechanism:- During rise of intra abdominal pressure, the arched fibres of the internal oblique and transversus abdominis(conjoined tendon) slide down and come close to the inguinal ligament like a shutter.
3. Plugging action of the spermatic cord :-with the rise of intra adominal pressure the cremastric muscle fibres contract and draw the spermatic cord up into the canal to act as a kind of plug.

Classification of inguinal hernias:-
There are two types: indirect and direct .

Indirect inguinal hernia:- It comes out through the deep inguinal ring and traverses the inguinal canal. The sac accompanies the spermatic cord. It has therefore, all the coverings that the spermatic cord possess. It is generally believed that Indirect inguinal hernia, at whatever age it may appear, occur into a preformed sac and this sac is the processus vaginalis(which may be partially or completely patent.)

Direct inguinal hernia:- It comes out through the hesselbach’s triangle. The direct comes out through the stretched out transversalis fascia or occasionally through an opening in it. It passes forwards, either below the arch of the conjoint tendon or through a weak area in the tendon, and there after may emerge through the superficial inguinal ring .

INDIRECT INGUINAL HERNIA
This is the most common of all forms of hernia. It is most common in the young whereas a direct is most common in the old. In the first decade of life, inguinal hernia is more common on the right side in the male. There is no doubt associated with the later descent of the right testis and a higher incidence of failure of closure of the processus vaginalis. In adult males 65% of the inguinal hernias are indirect and 55% are right sided. The hernias is bilateral in 12% of cases.

Types:- 3
1. bubonocele:-when the hernia is limited to the inguinal canal.
2. funicular:- the processus vaginalis is closed just above the epididymus. The contents of the sac can be felt separately from the testis, which lies below the hernia.
3. complete :-a complete inguinal hernia is rarely present at birth, but is commonly encountered in infancy. It also occurs in adolescence or adult life. The testis appears to lie within the lower part of the hernia.

Clinical Features:-
Occurring at any age, males are 20 times more commonly than females. The patient complains of pain in the groin or pain referred to the testicle when performing heavy work or taking strenuous exercise.
When asked to cough, a small transient bulging may be seen and felt together with an expansile impulse. When the sac is still limited to the inguinal canal, the bulge may be better seen by observing the inguinal region from the side or even looking down the abdominal wall while standing behind the respective shoulder of the patient.
As an indirect inguinal hernia increases in size, it becomes apparent when the patient coughs and persists until reduced. As time goes on, the hernia comes down as soon as the patient stands up. In large hernias, there is sensation of weight and dragging on the mesentry may produce epigastric pain. If the contents of the sac are reducible, the inguinal canal will be found to be commodious.
In infants, the swelling appears when the child cries. It can be translucent in infancy and early childhood, but never in an adults. In girls, an ovary may prolapse into the sac.

D/D:- in male:
1. spermatocele
2. an encysted hydrocele of the cord
3. femoral hernia
4. incompletely descended testis in the inguinal canal
5. lipoma of the cord

In female:
1.hydrocele of canal of nuck
2. femoral hernia

Treatment:-
Operation is the treatment of choice
1. inguinal herniotomy
2. herniotomy and repair (herniorrhaphy).

Direct Inguinal Hernia
In adult males, 35% of inguinal hernia are direct. At presentation, 12% of patients will have a contralateral hernia in addition and there is a four fold increased risk of future development of contralateral hernia if one is not present at the original presentation.
A direct inguinal hernia is always acquired. The sac passes through a weakness or defect of the transversalis fascia in the posterior wall of the inguinal canal. In some cases,the defect is small and is represented by a discrete defect in the transversalis fascia, while in otheres, there is a generalized bulge. Often the patient has poor lower abdominal musculature, as shown by the presence of elongated bulgings( malgaigne’s bulges). Women practically never develop a direct inguinal hernia.

Predisposing factors:-
Smoking and occupation that involve straining and heavy lifting. Damage to the ilio-inguinal nerve (previous appendicectomy) is another cause, due to resulting weakness of the conjoined tendon.

Types:-
1. Funicular direct inguinal hernia (prevesical hernia):-
This is a narrow- necked hernia with prevesical fat and a portion of the bladder that protrudes through a small oval defect in the medial part of the conjoined muscle just above the pibic tubercle. It occurs principallyin elderly males and occasionally becomes strangulated. Unless, there are defnite contraindications, operartion should always be advised.
2. Dual( saddle- bag, pantaloon) hernia:-
This type of hernia consists of two sacs which straddle inferior epigastric artery,one sac being medial and the other lateral to the vessel. This condition is not rare and is a cause of recurrence, one of the sacs having been overlooked at the time of operation.
Strangulated inguinal hernia:
Strangulation of an inguinal hernia occurs at any time during life and in bith sexes. Indirect inguinal hernia strangulate more commonly,the direct variety not so often owing to the wide neck of the sac. In order of frequency, the constricting agent is a) neck of the sac b) the external inguinal ring in children and c) rarely adhesions within the sac.
Contents :- usually the small intestine is involved in the strangulation, the next most frequent is the omentum, sometimes both are involved. It is rare for the large intestine to become strangulated in an inguinal hernia.

Differences between direct and indirect inguinal hernia:

Indirect                                         Direct
1. it can occur at all ages        1. it usually occurs in the elderly.
2. it is more common in males 2.it is found almost always in males.
3. it comes out through the deep inguinal ring. 3. it protrudes through the stretched out fascia transversals in the Hesselbach’s triangle

4. it is usually unilateral         4. it is usually bilateral. Often the patient has flabby muscles.
5 .it always comes out through the external inguinal ring.   5.it may very occasionally come out of the external inguinal ring.
6. the hernia descends obliquely and downwards, and similarly reduces upwards and laterally. 6.the hernia appear as a direct forward bulge and reduces directly backwards.
7. if the hernia is complete,and comes down into the scrotum, it is pyriform in shape. If it is complete, it is oval in shape. 7. generally, the hernia is incomplete and has a rounded shape . it seldom comes down to the scrotum.
8. Anatomical differences:-
a) neck of the sac lies lateral to inferior epigastric vessels. a) neck lies medial to inferior epigastric vessels.
b) sac is intimately attached to the cord structures. b) sac is separate from the spermatic cord.
c) strangulation can occur.                                     c) strangulation is rare.
9. During the invagination test on coughing, the impulse is felt at the tip of the examining finger. 9. impulse is felt on the pulp of the finger.
10. Deep ring occlusion test: indirect hernia will not come out when the ring is occluded. When pressure is released hernia will come down. 10. Direct hernia still appears because it has nothing to do with the deep ring.
11.usually straining is required to bring the hernia down and does not reduces easily. 11. hernia appears as soon as the patient stands. It disappears as he lies down.
12.according to many, all indirect hernia occurs in a pre-existing sac. But hernia may not appear until adult life. 12. All direct hernias are acquired