A hernia is an abnormal protrusion of a viscus or part of a viscus through a defect either in the containing wall of that viscus or within the cavity in which the viscus normally is situated. In abdominal hernias, the ‘wall’ refers to the anterior and posterior muscle layers of the abdomen, the diaphragm, and the walls of the pelvis. Hernias are either external or internal.
External hernias are common and present as an abnormal lump which can be detected by clinical examination of the abdomen or groin. The relative occurrence and gender distribution of external abdominal hernias are shown in Table 40, “Relative occurrence of external abdominal hernias in adults” and Table 41, “Sex distribution of abdominal hernias”.
|Male (%)||Female (%)|
Internal hernias are rare, and occur when the intestine (the ‘viscus’) passes beneath a constricting band or through a peritoneal window (the ‘defect’) within the abdominal cavity or in the diaphragm. They present as
- Acute intestinal obstruction, with or without intestinal ischaemia, perforation and peritonitis, or
- Chronic recurrent abdominal pain and vomiting due to incomplete and intermittent intestinal obstruction.
Sites of internal herniation include (i) the paraduodenal and paracaecal fossae, (ii) the lesser sac through the epiploic foramen (foramen of Winslow) or a defect in the transverse mesocolon, (iii) beneath congenital bands or adhesions, (iv) through defects in the small bowel mesentery, (v) between the lateral abdominal walls and intestinal stomas, and (vi) through defects in the diaphragm (hernias of Bochdalek and Morgagni). Treatment consists of laparotomy, removal of the distended bowel from the hernial orifice and resection if strangulation has occurred. Closure of the defect is required to prevent recurrence.
Components of a hernia
Hernias are composed of a sac, the parts of which are described as the neck, body and fundus (Components of a hernia.), and the hernial contents. The sac consists of peritoneum which protrudes through the abdominal wall defect or ‘hernial orifice’, and envelopes the hernial contents. The neck of the sac is situated at the defect. Hernias with a narrow or rigid neck are more likely to obstruct and strangulate (see below). The body is the widest part of the hernial sac, and the fundus is the apex or furthest extremity. Viscera most likely to enter a hernial sac are those normally situated in the region of the defect and those which are mobile, namely the omentum, small intestine and colon. Some hernial contents have been ascribed generic names.
Only part of the circumference of the bowel (usually the anti-mesenteric border) is trapped within the hernial sac (Richter's hernia.). The herniated part may become ischaemic. Because the lumen of the bowel is not occluded, intestinal obstruction does not occur, and there are few symptoms until the ischaemic part perforates.
A Meckel's diverticulum lies within the hernial sac. Littré's hernia occurs most commonly in a femoral or inguinal hernia (see below).
The hernial sac contains two loops of intestine (Maydl's hernia.). The loop of intestine within the abdominal cavity may become obstructed or strangulated, and this may not be recognised unless the hernial contents are inspected and returned to the abdominal cavity (‘reduced’) completely.
A hernia occurs because of (a) weakness or defect in the abdominal wall, and (b) positive intra-abdominal pressure (IAP) (which is often raised) forces the viscus into the defect.
Sites of weakness in the abdominal wall
Weaknesses in the abdominal wall may be:
- Congenital (i.e. present at birth) - e.g. patent processus vaginalis or canal of Nuck, posterolateral or anterior parasternal diaphragmatic defect, patent umbilical ring in children.
- Where a normal anatomical structure passes through the abdominal wall - e.g. oesophageal hiatus, umbilical ligament in adults, obturator foramen, sciatic foramen.
- Acquired - e.g. surgical scar, site of an intestinal stoma, muscle wasting with increasing age, fatty infiltration of tissues because of obesity.
Increased intra-abdominal pressure
Raised intra-abdominal pressure (IAP) stretches the abdominal wall vertically and horizontally, thereby increasing the circumference of any defect. Also, high IAP forces abdominal contents through a defect. Sudden or sustained increases in IAP are due to several causes (Causes of sudden or sustained increases in intra-abdominal pressure).
Most hernias are uncomplicated at presentation. The three important complications of hernias are, in order of progression, irreducibility, obstruction and strangulation.
A hernia is ‘irreducible’ when the sac cannot be emptied completely of contents. Irreducibility is caused by (i) adhesions between the sac and its contents, (ii) fibrosis leading to narrowing at the neck of the sac, or (iii) a sudden increase in IAP that causes transient stretching of the neck and forceful movement into the sac of contents, which cannot subsequently return to their original location.
Generally, irreducible hernias should be operated on soon after presentation. Although irreducibility is not an indication for urgent operation, it is the step before obstruction supervenes. In addition, irreducible hernias are usually painful.
A hernia becomes obstructed when the neck is sufficiently narrow to occlude the lumen of the intestine contained within the sac. Obstructed hernias are nearly always irreducible and, if not treated, may become strangulated. Often, there is a history of a sudden increase in IAP that has pushed intestine or other contents into the sac. The patient presents with symptoms and signs of intestinal obstruction (abdominal colic, vomiting, constipation, abdominal distension) (see Small bowel obstruction), together with a tender irreducible hernia. Failure to examine the hernial orifices in a patient with intestinal obstruction may lead to the wrong operative approach being undertaken. It may be difficult to distinguish obstruction from strangulation on clinical grounds, and therefore obstructed hernias should be treated as a matter of urgency.
Strangulation means that the blood supply of the contents has ceased due to compression at the hernial orifice. Initially, lymphatic and venous channels are obstructed, leading to oedema and venous congestion but with continued arterial inflow. When the tissue pressure equals arterial pressure, arterial flow ceases and tissue necrosis ensues. Strangulation is a serious complication and, if the intestine is involved, leads to peritonitis (see Peritonitis and intra-abdominal abscesses) which can be fatal. A strangulated hernia is both irreducible and obstructed, and is very tense and usually exquisitely tender. Erythema of the overlying skin is a late sign. Strangulated hernias must be operated on urgently. A strangulated Richter's hernia is not preceded by intestinal obstruction and there may be few local signs.
Principles of treatment
Uncomplicated hernias require either no treatment, support with a truss, or operative treatment, whereas complicated hernias always require surgery, often urgently.
No treatment may be advised in debilitated patients who are not medically fit for surgery and who have uncomplicated hernias with minimal symptoms. Few patients fall into this category. Most external hernias can be successfully repaired surgically under regional or local infiltration anaesthesia with minimal morbidity. If a patient refuses treatment, then the full implications of this decision must be explained.
Truss or abdominal binder
A truss or some form of hernia support may be used to provide symptomatic relief for large uncomplicated hernias in elderly unfit patients and those who decline surgery. After the hernia has been reduced, the truss presses on the hernial orifice to prevent protrusion. However, it frequently does not prevent prolapse of the hernia and simply presses on the hernial contents, and is uncomfortable to wear.
Reducing raised intra-abdominal pressure
Causes of increased IAP should be corrected. Stopping smoking, investigation and treatment of prostatism and constipation, weight reduction, and effective management of ascites should be attempted where indicated. Changes in occupation and physical exercise also may have to be considered.
Operation is indicated for all other patients because of symptoms and the risk of complications. Surgery aims to (i) reduce the hernial contents, (ii) excise the sac (herniotomy) in most cases, and (iii) repair and close the defect, either by approximation of adjacent tissues to restore the normal anatomy (herniorrhaphy), or by insertion of additional material (hernioplasty). The site of the hernia must be marked clearly on the skin during consultation with the patient before induction of anaesthesia so that no mistake is made about its location.
Urgent operation is indicated when obstruction or strangulation is suspected. Resuscitation with intravenous fluids, antibiotics, analgesia and nasogastric aspiration is required before surgery.
Attempted reduction of a hernia
When a patient presents with an apparently irreducible hernia, it is reasonable to make some attempt to reduce it, unless strangulation is suspected. The foot of the bed is elevated, the patient is kept warm, and given intramuscular opiate analgesia. After 20–30 minutes, firm manual pressure is applied to the hernia. Manual reduction may not be successful if adhesions have developed between the contents and the sac, or if the hernial orifice is narrow. Attempts at reducing a hernia should not be prolonged. Patients should be observed after successful reduction.
Inguinal hernia is the commonest hernia, and is approximately 10 times more common in males than females (Table 40, “Relative occurrence of external abdominal hernias in adults” and Table 41, “Sex distribution of abdominal hernias”). Two types of inguinal hernia (IH) are recognised (Types of inguinal hernias (right side). (A) Indirect inguinal hernia; (B) direct inguinal hernia.), indirect (IIH) and direct (DIH), but they can occur together.
Importance of the integrity of the inguinal canal
The inguinal canal passes through the abdominal wall between the deep (internal) and superficial (external) inguinal rings. It carries the spermatic cord to the scrotum in the male, or the round ligament of the uterus to the labium majora in the female, together with the ilioinguinal nerve. The canal is a site of weakness and therefore potential herniation.
In addition to the presence of a patent processus vaginalis in an IIH, both IIH and DIH result from failure of normal mechanisms that maintain the integrity of the inguinal canal, including:
- ‘shutter mechanism’ around the deep inguinal ring - during straining, a U-shaped condensation of transversalis fascia which passes under the cord is pulled upward and laterally, closing the deep ring around the cord and increasing the obliquity of the inguinal canal.
- ‘shutter action’ of the internal oblique and transversus abdominis muscles - contraction of these muscles draws them downwards so that the inguinal canal tends to close and become more oblique.
- integrity of the posterior wall of the inguinal canal - weakness of the conjoint tendon reduces the strength of the posterior wall of the inguinal canal and reduces support behind the superficial inguinal ring.
- oblique direction of the inguinal canal - if the deep and superficial inguinal rings enlarge, they may almost overlie each other and obliquity of the canal is lost.
Indirect inguinal hernia
The hernial sac of an IIH is a patent processus vaginalis, and the neck of the sac is situated at the deep inguinal ring, lateral to the inferior epigastric artery. The sac accompanies the spermatic cord along the inguinal canal towards the scrotum for a varying distance (see below). The sac lies in front of the cord and is enclosed by the coverings of the cord. Except in children and infants, the essential cause of an IIH is (a) failure of the processus vaginalis to become completely obliterated to form the ligamentum vaginale, which normally occurs within a few days after birth, and (b) loss of integrity of the inguinal canal (see above). Even though the sac of an IIH is congenital, herniation may not occur until later in life, when there is failure of the normal mechanisms that maintain the inguinal canal.
The incidence of IIH is approximately 800–1000 per million male population. Indirect IHs are approximately four times more common than DIH, occur at any time during life, and have a male to female ratio of about 10:1.
Classification of indirect inguinal hernias
Indirect IHs are classified according to the length of the hernial sac (Types of indirect inguinal hernias.).
- Bubonocele - the sac is confined to the inguinal canal.
- Funicular - the sac extends along the length of the inguinal canal and through the superficial inguinal ring, but does not extend to the scrotum or labium majora.
- Complete, scrotal or inguinoscrotal - the sac passes through the inguinal canal and superficial inguinal ring and extends into the scrotum or labium.
Direct inguinal hernia
A DIH protrudes directly through the posterior wall of the inguinal canal, medial to the inferior epigastric artery and deep inguinal ring. The essential fault with a DIH is weakness of the inguinal canal, and is invariably associated with poor abdominal musculature. Herniation occurs at a site where the transversalis fascia is not supported by the conjoint tendon or the transversus aponeurosis, an area known as Hesselbach's triangle. The neck of a DIH is usually larger than the body and so strangulation is rare. The hernia passes forwards as it enlarges, stretching muscle and fascial layers. It rarely reaches a large size or approaches the scrotum. Occasionally, the inferior epigastric vessels straddle the hernia which is then known as a ‘pantaloon hernia’.
Direct IH is rare in females and does not occur in children. It is more common on the right side after appendicectomy, suggesting that damage to the iliohypogastric and ilio-inguinal nerves with subsequent weakness of the internal oblique and transversus abdominis muscles is an aetiological factor.
Clinical features of inguinal hernias
Inguinal hernias present with inguinal discomfort, with or without a lump. Discomfort is due to stretching of the tissues of the inguinal canal and occurs typically when IAP is increased. Pain may also be referred to the testis because of pressure on the spermatic cord and ilio-inguinal nerve. Severe inguinal or abdominal pain suggests obstruction or strangulation. A lump is usually obvious to the patient, is often precipitated by increasing IAP, and may reduce completely with rest and lying down.
The patient initially is examined standing to demonstrate the lump and possible cough impulse, and then lying down to allow the hernia to be reduced. An IIH protrudes along the line of the inguinal canal for a variable distance towards the scrotum or labia; a DIH appears as a diffuse bulge at the medial end of the inguinal canal. The significance of a ‘cough impulse’, or sudden bulging of the inguinal region with coughing, must be interpreted carefully. A generalised weakness in the inguinal region will result in a diffuse bulge appearing with coughing, but this condition (known as a Malgaigne's bulge) is not the same as a hernia in which the cough impulse is discrete and confined to the area of herniation. Abdominal examination is performed to detect organomegaly, a mass or ascites.
Indirect or direct inguinal hernia?
An IIH is prevented from appearing by applying pressure over the deep inguinal ring (which lies just above the midpoint of the inguinal ligament) because an IIH protrudes through the deep inguinal ring. A DIH protrudes through the posterior wall of the inguinal canal medial to the deep ring. IIH and DIH may be distinguished by firstly reducing the hernia by gently pushing it upwards and laterally. Then, the index and middle fingers are placed firmly over the surface marking of the deep ring and the patient is asked to cough. If the hernia is controlled by pressure over the deep ring, then it is presumed to be indirect. If the hernia appears medial to the examiner's two fingers, then it is direct.
Accurate distinction of an IIH from a DIH may not be possible because of slight variation in the position of the deep inguinal ring. However, an attempt should be made to distinguish between the two because IIHs are more likely to develop complications and should be repaired sooner rather than later.
Sliding inguinal hernia
A sliding inguinal hernia is a variant in which part of a viscus (usually the colon) is adherent to the outside of the peritoneum forming the hernial sac beyond the hernial orifice. Thus, the viscus and the hernial sac, which may contain another abdominal viscus, lie within the inguinal canal (Section through sliding inguinal hernia.). Sliding hernias are more common on the left side (where they contain part of the sigmoid colon) than on the right (where they contain part of the caecum). Sliding hernias occasionally contain part of the bladder or an ovary and ovarian tube. A sliding hernia may be indirect or direct. They are nearly always found in males. A sliding hernia should be suspected if the neck of the hernia is bulky, or if the hernial sac does not separate easily from the cord at operation.
Inguinal hernias in infants and children
Inguinal hernias are always indirect in infants and children and are due to a patent processus vaginalis. Ninety per cent occur in males and more commonly on the right side, presumably due to the slightly later descent of the right testis. Approximately 10–20% are bilateral. If the contralateral side is also explored in a child undergoing unilateral inguinal hernia repair, a patent processus is found in approximately 50% of cases. Irreducibility is common and occurs in about 50% of hernias presenting within the first year of life. Strangulation appears to be rare. Testicular infarction can occur if a large irreducible hernia severely compresses the spermatic cord, and is more common than infarction of the hernial contents.
Inguinal hernias in children should be repaired surgically. The hernial sac is very thin and, because the superficial and deep inguinal rings are almost superimposed upon one another in children, the sac can be mobilised and ligated through the superficial inguinal ring. Herniotomy is all that is required.
Treatment of inguinal hernias
As with other external hernias, the precipitating cause of the hernia must be identified and treated. A truss may be useful for uncomplicated hernias in elderly debilitated patients and in those who decline surgery, but is rarely effective in controlling the hernia. Inguinal hernias are best treated surgically.
Inguinal hernia repair can be undertaken under general, regional or local infiltration anaesthesia, often as a day procedure in fit patients who have adequate home support. Open repair is performed through a skin crease incision centred over the inguinal canal. The sac is dissected carefully from the cord, opened and the contents returned to the abdominal cavity. In an IIH, the sac is ligated at the deep inguinal ring and excised (herniotomy), whereas in a DIH the sac is formed from layers of the posterior wall of the inguinal canal and so it is not excised.Aprocedure to strengthen the posterior wall of the inguinal canal is performed (herniorrhaphy or hernioplasty).
‘Herniorrhaphy’ refers to repair of the posterior wall of the inguinal canal behind the spermatic cord by one of several methods, together with repair of the external oblique aponeurosis in front of the cord. Strong nonabsorbable sutures are used.
- Shouldice repair - The weakened transversalis fascia is incised along the line of the inguinal canal and repaired in an overlapping fashion. The deep inguinal ring is closed snugly around the cord. The internal oblique and transversus are approximated to the deep aspect of the inguinal ligament.
- Bassini repair - The conjoint tendon is sutured onto the inguinal ligament. A J-shaped incision, known as a ‘Tanner slide’, is made in the anterior rectus sheath to enable the conjoint tendon to ‘slide’ down towards the inguinal ligament without tension.
- Nylon darn repair - The weakened transversalis fascia is plicated from the pubic tubercle to the deep ring. A second continuous nylon suture is inserted as a loose darn from the inguinal ligament below to the anterior aspect of the conjoint tendon and aponeurosis of the internal oblique above, extending from the pubic tubercle medially to beyond the deep ring laterally.
‘Hernioplasty’ refers to insertion of a prosthetic mesh (e.g. polypropylene) to cover and support the posterior wall of the inguinal canal. The mesh is cut to size, with two limbs encircling the cord at the deep ring, and is then sutured to the posterior wall behind the cord. Alternatively, the mesh can be inserted via an extraperitoneal approach and placed deep to the defect in the posterior wall.
Laparoscopic hernia repair
Laparoscopic repair is performed under general anaesthesia, using either a transperitoneal or extraperitoneal approach. The technique is not appropriate for large or irreducuble hernias. The sac is separated from the spermatic cord and excised, and a mesh is inserted to strengthen the posterior wall, with or without a small plug of synthetic material being inserted into the deep ring. Advantages of laparoscopic hernia repair include reduced post-operative pain and earlier return to work. Disadvantages include increased risk of femoral nerve and spermatic cord damage, risk of developing intraperitoneal adhesions with the transperitoneal procedure, and greater cost and duration of the operation. Initial experience indicates that recurrence rates are similar to those associated with open operations.
Management after inguinal hernia repair
Patients require analgesia for the first few days. They should avoid straining and lifting for about 4 weeks after surgery, and avoid very heavy physical work for about 6–8 weeks. The average length of stay off work is approximately 2–4 weeks after open repair and 1–2 weeks after laparoscopic repair.
Potential complications of inguinal hernia repair
In addition to the complications of any surgical procedure (haemorrhage, haematoma, wound and chest infection, deep vein thrombosis, pulmonary embolus, anaesthetic complications) there are a number of potential complications specific to inguinal hernia repair.
- Urinary retention - Elderly male patients are particularly susceptible to retention of urine. Prostatic symptoms should be identified and treated before the hernia is repaired.
- Scrotal swelling and haematoma - Oedema, swelling and bruising of the scrotum are common (especially with bilateral repairs) and resolve spontaneously. Scrotal support may bring symptomatic relief. Large haematomas require operative drainage.
- Wound infection - A deep wound infection which does not settle with antibiotocis requires removal of the prosthetic mesh.
- Recurrent hernia - Recurrence is related to surgical technique and expertise, experience of the operator, postoperative infection and haematoma, and failure to correct factors predisposing to hernia formation. Also, failure to examine the spermatic cord for the presence of an indirect inguinal sac when repairing a DIH may lead to an apparent ‘recurrence’. Recurrence rates should be less than 2%. About 50% of recurrences appear within 5 years after the initial repair, and approximately 50% of recurrences are indirect hernias. A first recurrence is treated along the principles outlined in the previous section. Subsequent hernia recurrence requires mesh repair by an extraperitoneal approach, or complete closure of the inguinal canal by sutures after excision of the cord and testis.
- Nerve injury - injury to the ilio-inguinal nerve, which lies below the spermatic cord in the inguinal canal and passes out through the superficial inguinal ring, occurs in 10–20% of inguinal hernia repairs, resulting in paraesthesia or numbness below and medial to the wound over the pubic tubercle and proximal scrotum. The lateral cutaneous nerve of the thigh and the femoral nerve are at risk during laparoscopic repair.
- Persisting wound pain - This is uncommon, and results from nerve entrapment or damage, neuroma formation, osteitis pubis if sutures have been inserted into the pubis, displacement of a mesh repair, or pressure on the spermatic cord. Pain may be a symptom of recurrent herniation. Local anaesthetic or phenol injections may help, and surgical exploration is indicated for severe or persistent pain.
- Testicular ischaemia and atrophy - interruption of the testicular arterial supply (testicular artery and indirectly from the cremasteric artery and the artery of the vas deferens) can occur during dissection of an indirect sac from the cord. Ischaemia produces testicular pain, tenderness and swelling. Testicular atrophy is observed in 1–5% of males.
- Hydrocele - a long-term complication probably resulting from the repair being too tight or scarring, with subsequent compression of lymphatics of the cord.
- Injury to the vas deferens - a rare complication, is most likely to occur when a recurrent hernia is repaired and with laparoscopic repair.
- Visceral injury - viscera in a sliding hernia are at risk for injury when the sac is being dissected away from them.
A femoral hernia occurs when the transversalis fascia which normally covers the femoral ring is disrupted, so that a peritoneal sac and hernial contents pass through the femoral ring into the femoral canal. The femoral canal is the most medial compartment of the femoral sheath, medial to the femoral vein. Femoral hernias are 2–3 times more common in females than males, and occur in the older age group, often after a period of weight loss. Femoral hernias are never congenital, and are twice as common in parous as in non-parous females. Inguinal hernias are more common than femoral hernias in females (Table 41, “Sex distribution of abdominal hernias”). Approximately 60% of femoral hernias are on the right, 30% on the left, and 10% bilateral. A femoral hernia is the commonest site for a Richter's hernia (Section 2.1).
Aetiological factors in femoral hernia formation are:
- localised weakness at the femoral ring.
- factors which increase intra-abdominal pressure (Causes of sudden or sustained increases in intra-abdominal pressure).
A femoral hernia presents as either discomfort in the groin together with a lump, or as intestinal obstruction with or without strangulation. A small hernia may be difficult to palpate, especially in the obese patient. The hernia is frequently irreducible and may not have a cough impulse.
On examination, the bulge of a femoral hernia appears in the region of the saphenous opening. The neck of the sac is always located below the line of the inguinal ligament, even though the fundus may appear to be above the ligament. This is because once within the femoral canal, the hernial sac is prevented from continuing inferiorly down the thigh with the femoral vessels because the femoral sheath (which encloses the femoral vessels and the femoral canal) becomes narrow and tapers to a point around the vessels. The hernia is therefore directed forwards through the fossa ovalis, and is quite superficial at this point (Sagittal section of a femoral hernia.). It cannot continue down the thigh in a subcutaneous plane because the superficial fascia of the thigh is attached to the lower border of the fossa ovalis and is firmer than the superficial fascia above the level of the foramen ovalis. As the hernia enlarges, it turns upwards into the looser areolar tissue beneath the skin of the groin crease and may be confused with an inguinal hernia.
Thus, the direction taken by a femoral hernia is initially downwards through the femoral canal, then forwards through the fossa ovalis, and then upwards in the loose areolar tissue of the upper thigh. Therefore, in attempting to reduce the hernia, pressure is applied in the reverse order, that is, initially downwards, backwards and then upwards.
Inguinal or femoral hernia?
Inguinal and femoral hernias are distinguished by their positions relative to the inguinal ligament and pubic tubercle. The inguinal ligament is identified by palpating the anterior superior iliac spine and the pubic tubercle; an imaginary line drawn between the two points is the line of the inguinal ligament. The neck of an inguinal hernia is above the inguinal ligament and pubic tubercle, and the hernia protrudes initially from above the ligament even though it may descend into the scrotum. The neck of a femoral hernia is below the inguinal ligament and lateral to the pubic tubercle, and the hernia protrudes initially from below the ligament.
Surgical treatment of a femoral hernia should always be advised because of the risk of obstruction and strangulation. A truss cannot prevent herniation through the femoral ring and has no place in the management of femoral hernia.
Surgery involves opening and emptying the sac, and performing a herniorrhaphy to prevent recurrence. Herniorrhaphy aims to reduce the size of the femoral ring and is performed by inserting several sutures between the inguinal and pectineal ligaments, thereby effectively closing off the femoral canal. One of two operative approaches is used:
- A ‘low’ or subinguinal approach is used for small uncomplicated femoral hernias by making an incision over the hernia below the level of the inguinal ligament.
- The ‘high’ or supra-inguinal approach is used for large or complicated femoral hernias in an emergency situation. The extraperitoneal space between the peritoneum and abdominal wall muscles is accessed through an abdominal incision. The sac is identified and opened to inspect the contents. The intestine is resected if necessary, and the sac is excised. The femoral ring is repaired from this intraabdominal approach.
An incisional hernia is a protrusion of the peritoneum (the sac) and abdominal contents into the subcutaneous plane through a defect at the site of a scar following an abdominal operation. The true incidence is difficult to ascertain, but is in the order of 5% at 5 years and 10% at 10 years. There is a higher preponderance in males. Patients present with nagging discomfort and a bulge at the site of a previous incision. Incisional hernias increase in size with time and frequently become irreducible.
The main predisposing factors for an incisional hernia are poor surgical techniques, local wound complications, impaired wound healing, and increased intraabdominal pressure (Aetiological factors in incisional hernias).
Incisional hernias should be repaired because (a) they increase in size with time and may be very difficult to repair when large, (b) they are at risk of becoming irreducible, obstructed and strangulated, especially if the neck is narrow, and (c) patients request repair because of discomfort and unsightly appearance. Preoperative weight reduction in obese patients aims to facilitate the repair, and to reduce post-operative respiratory problems and likelihood of recurrence. With massive incisional hernias, pre-operative progressive pneumoperitoneum for 1–2 weeks may be considered to facilitate replacement of viscera into the abdominal cavity and abdominal wall closure. An abdominal support or binder may be helpful in very large hernias or in patients unfit for surgery.
Operation involves defining the sac and neck, returning the contents to the abdominal cavity, and repairing the hole in the abdominal wall. If the omentum is within the hernial sac, it is excised. The intestine should be handled as little as possible to minimise post-operative ileus. If the edges of the defect can be apposed without tension, the defect is closed directly with strong nonabsorbable sutures; if not, the defect is covered with prosthetic mesh (e.g. polypropylene or polytetrafluoroethylene ‘Goretex’ dual mesh) sutured to the edges of the defect. Prophylactic antibiotics are used in cases of mesh repair.
An epigastric hernia is a protrusion of extraperitoneal fat, with or without a small sac of peritoneum through a defect in the linea alba anywhere between the xiphisternum and the umbilicus. The defect is characteristically small, often about 1 cm in diameter. Patients are frequently fit young males who present with epigastric pain, which may be confused with peptic ulceration or biliary disease. Patients should be examined in both standing and lying positions. The hernia is usually easier to feel than to see, and is diagnosed by palpation of a small, often very tender, lump in the linea alba. Ultrasound may be helpful when a hernia is suspected but cannot be palpated. Epigastric hernias are usually irreducible and may be multiple.
Surgery is undertaken to relieve symptoms. The hernia is marked pre-operatively because it may reduce with anaesthesia and the defect may be too small to palpate. If there are multiple hernias, the linea alba is exposed through a vertical incision, the extraperitoneal fat is excised, and each defect is repaired. A ‘keel’ repair of the linea alba is then performed by inserting two or more layers of sutures into the linea alba and anterior rectus sheath, each successive layer covering the previous layer so that the repaired tissue resembles the keel of a boat (Keel repair.). If a single defect is present, a transverse incision is usually made, and the defect is repaired with a ‘Mayo’ repair (Mayo repair. (A) Insertion of two sutures through upper and lower edges of hernial defect. (B) Sagittal section of linea alba after repair.), in which the upper and lower edges of the defect are overlapped with interrupted sutures (‘pants over vest’ repair).
Umbilical hernia in children
An umbilical hernia in a child is a congenital defect in which a peritoneal sac protrudes through a patent umbilical ring and is covered by normal skin. Approximately 5–10% of Caucasian infants have an umbilical hernia at birth. About one-third of hernias close within a month of birth, and they rarely persist beyond the age of 3–4 years. The hernia is noticeable whenever the child cries, coughs or vomits, and is a cause of concern for parents. Umbilical hernias in children rarely become irreducible or strangulate.
Umbilical hernia is a separate entity from exomphalos (omphalocele). Exomphalos is a rare congenital condition in which the midgut fails to return to the abdominal cavity during the first trimester, with subsequent failure of the abdominal wall to close at the umbilicus. At birth, the intestine protrudes into the base of the umbilical cord and is covered by a thin opaque sac of amnion, not normal skin.
An expectant approach can be adopted as nearly all hernias close or greatly reduce in size. Repair is recommended for unusually large hernias or if the hernia is still present at school age. A short transverse subumbilical incision is made, the sac is excised, and the defect is closed by either edge-to-edge apposition or a Mayo repair (Mayo repair. (A) Insertion of two sutures through upper and lower edges of hernial defect. (B) Sagittal section of linea alba after repair.). The umbilical cicatrix is preserved. Recurrence is rare.
Para-umbilical hernia in adults
A para-umbilical hernia in an adult is an acquired condition and quite distinct from the umbilical hernia of childhood. A para-umbilical hernia protrudes through one side of the umbilical ring, while the umbilicus still retains its fibrous character within the linea alba, although it becomes effaced by the pressure of the hernial contents and has an eccentric ‘half-moon’ or crescentic furrow. Para-umbilical hernias initially contain extraperitoneal fat but, as the hernial orifice enlarges, omentum enters the sac. The contents typically adhere to the sac so that the hernia becomes loculated and irreducible. Para-umbilical hernias occasionally become very large and contain transverse colon and small intestine.
Para-umbilical hernias are treated surgically because of the risk of obstruction, strangulation and, rarely, excoriation and ulceration of the skin overlying the hernia. The classic operative procedure is a Mayo repair (Mayo repair. (A) Insertion of two sutures through upper and lower edges of hernial defect. (B) Sagittal section of linea alba after repair.), but repairs with mesh are performed increasingly.
A hernia may occur through the abdominal wall at the site of an intestinal stoma (see Intestinal stomas). The surgically created defect through which the stoma is fashioned enlarges due to raised IAP and allows protrusion of the peritoneum (the hernial sac) through the defect to lie adjacent to the stoma (Para-stomal hernia.).
Para-stomal hernias eventually occur in about 10–30% of patients with colostomies and ileostomies. Correct surgical technique when fashioning intestinal stomas is of paramount importance in prevention. For example, stomas should be brought out through the aponeurotic part of the abdominal wall, not the muscular part, and they should not be sited in the main abdominal wound or the umbilicus.
Surgery is required if the bulge of the hernia causes poor fitting of the stoma appliance and consequent leakage from beneath the appliance. Also, intestinal obstruction and strangulation may occur. Operation involves reducing the size of the stomal orifice by closing the abdominal wall tissues around the stoma, but this method has a high recurrence rate. Insertion of prosthetic mesh in an extraperitoneal or extraparietal plane to cover the defect in the abdominal wall generally provides a good repair but runs the risk of infection of the mesh. Relocation of the stoma and complete closure of the previous stoma site provides the best chance of cure.
Spigelian hernias are rare. A Spigelian hernia occurs through the transversus abdominis aponeurosis of the anterior abdominal wall, usually below the level of the umbilicus. The vertical curved line at which the transverse abdominis muscle becomes an aponeurosis is the semilunar line, and it extends from the costal margin to the pubic tubercle. The transversus abdominis aponeurosis extends medially from the semilunar line to the lateral edge of the rectus sheath. A Spigelian hernia usually occurs at the widest and weakest point of the aponeurosis, which is about halfway between the umbilicus and the inguinal ligament.
Clinically, the diagnosis of a Spigelian hernia may be difficult. The patient, who typically is a middle-aged female, presents with diffuse aching pain in the area of the hernia, which is small and may not be palpable. Pain is often present during the day but may recede at night if the hernia reduces, and may be made worse by raising the arm on the affected side. If a lump is not palpable, the diagnosis may be confirmed by ultrasound or computed tomography scanning. The hernia usually contains omentum but may contain small or large bowel. A Richter's hernia may occur, and obstruction and strangulation are well-recognised complications.
Spigelian hernias should be treated surgically because of the severity of symptoms and the risk of complications. A skin crease incision is made over the hernia, the sac is excised and the defect in the transversus abdominis aponeurosis is closed with non-absorbable sutures.
Lumbar hernias are rare. They occur typically in individuals with poor muscle tone, either spontaneously, or following trauma, surgery, or paralysis of paravertebral muscles secondary to poliomyelitis. Differential diagnosis includes a lipoma, lumbar abscess or haematoma.
Lumbar hernias occur through two triangular sites of weakness in the lumbar region of the abdominal wall.
- Inferior lumbar triangle hernia (triangle of Petit) - herniation occurs between the iliac crest inferiorly, the posterior edge of external oblique muscle anteriorly, and the anterior edge of latissimus dorsi posteriorly. The ‘floor’ of the triangle through which the hernia protrudes is formed by the internal oblique and transversus abdominis muscles.
- Superior lumbar triangle (triangle of Grynfeltt-Lesshaft) - the hernia occurs between the lowermost edge of serratus posterior inferior muscle and the twelfth rib superiorly, the anterior border of internal oblique muscle anteriorly, and the lateral edge of erector spinae muscle medially. Grynfeltt's triangle lies superior to Petit's triangle, and the ‘floor’ is formed by the quadratus lumborum muscle. The hernia is covered by the latissimus dorsi.
Treatment of lumbar hernias is difficult because of their anatomical boundaries, their size, the type of patient in whom they occur, and because they are bounded in part by muscle rather than tough aponeurotic tissue. Prosthetic mesh repair is required.
An obturator hernia is rare. It protrudes through the obturator canal or foramen, which is a normal anatomical structure between the obturator groove on the inferior aspect of the superior pubic ramus and superior border of the obturator membrane. The obturator canal carries the obturator nerve and vessels. When large, the hernial sac passes between the pectineus and adductor longus muscles and protrudes forwards to produce a diffuse bulge in the femoral triangle, where it can be mistaken for a femoral hernia. It is more common on the right side.
The hernia occurs most often in elderly females, particularly in those who have become debilitated and lost weight rapidly. Usually, the patient presents with intestinal obstruction of unknown cause, and the hernia is diagnosed at laparotomy. Patients may complain of diffuse pain in the groin together with pain in the medial side of the thigh and knee because of pressure on the obturator nerve. The hernia may be felt in the femoral triangle and also on vaginal examination. A Richter's hernia may occur with strangulation of the entrapped part of the intestinal wall.
Laparotomy is performed and the entrapped segment of bowel is released. The hernial defect is often found to be small. Care is taken not to damage the obturator nerve when either closing the defect or covering it with prosthetic mesh.
Sciatic hernias are very rare and occur when a peritoneal sac enters the greater (gluteal hernia) or lesser sciatic foramina. Pain caused by pressure on the sciatic nerve or a palpable swelling and tenderness in the buttock suggests the diagnosis. Most commonly, sciatic hernias are discovered at laparotomy for intestinal obstruction. The sac is excised, but attempts to close the defect run the risk of sciatic nerve damage.