Clinical Review: Abdominal wall hernias

Contributed by Mr Joe Dawson, specialist registrar in general surgery, North East Thames.

A sagittal CT demonstrating a small incisional hernia (arrow)
A sagittal CT demonstrating a small incisional hernia (arrow)

Section 1: Epidemiology and aetiology
An abdominal wall hernia can be defined as an abnormal protrusion of viscera or intra-abdominal fat accompanied by surrounding peritoneum through the abdominal wall musculature or fascia within which it is normally contained.

Hernias can be congenital or acquired.

Congenital hernias
Congenital indirect inguinal hernias occur due to failure of the peritoneum to close as it accompanies the descending testicle passing from the abdominal cavity, through the inguinal canal, into the scrotum.

Normally this peritoneum would become obliterated during early development at the deep (inguinal) ring, but if this process fails the resulting patent processus vaginalis predisposes to an indirect inguinal hernia and/or hydrocele.1 The peak incidence of inguinal hernias is during infancy and childhood as 3-5 per cent of full-term infants are born with them, the vast majority being male.

Infantile umbilical hernias occur due to failure of the umbilical vessels to fuse with the urachal remnant and umbilical ring.

Premature infants, with low birth weight or congenital anomalies have a high incidence of congenital hernias.2 Severe congenital abdominal defects such as gastroschisis and omphalocele are usually diagnosed prior to birth and require specialist paediatric management.

Acquired hernias
Multiple factors are thought to contribute to hernias developing in adulthood. These include raised intra-abdominal pressure (obesity, ascites, chronic cough, straining, lifting and multiple pregnancies) and muscular weakness (aging, chronic illness, surgical wounds and defects in collagen and extracellular matrix metabolism).2

The groin is the commonest site for hernias. In order to allow passage of the femoral vessels, spermatic cord in men and round ligament in women, a window exists in the otherwise strong anterior abdominal wall musculature: the myopectineal orifice.

It is through this aperture that groin hernias occur (75 per cent inguinal and 8.5 per cent femoral).2 Other common hernias include umbilical, paraumbilical, epigastric and incisional. Rarer types also occur at points that are susceptible to weakness due to anatomical configuration such as Spigelian, lumbar and obturator hernias.

Factors predisposing to incisional hernias include wound dehiscence.3

Several other factors contributing to wound failure and subsequent incisional hernia include patient factors (diabetes and obesity), operative factors (emergency surgery) and post-operative factors (infection, haematoma, abdominal distension and chest infection).

Section 2: Making the diagnosis
Most patients present with a palpable lump, which may be associated with pain, but if uncomplicated may have been present for years.

Lump
Patients should be examined standing and lying down. The anatomical site and presence of any scars will help determine the type of hernia.

An uncomplicated hernia will have a cough impulse and reduce on lying flat. On the occasions when it is difficult to determine whether an abdominal lump is intra-abdominal or superficial to the muscles, the patient can be asked to lift their legs or shoulders off of the examination couch in order to tense their abdominal muscles.

Intra-abdominal masses will not be palpable under the contracted muscles.

In the groin, inguinal hernias are found above and medial to the pubic tubercle whereas femoral hernias are below and lateral.

The importance of determining whether an inguinal hernia is direct or indirect may be relevant in elderly or unfit patients in which direct hernias may be safely left alone due to their low incarceration risk.

However studies have shown clinical determination is unreliable,4 and in fit symptomatic patients the differentiation is academic, as the surgical management is the same. Epigastric hernias present as a lump in the midline between the umbilicus and xiphisternum.

True umbilical hernias are differentiated from paraumbilical hernias by their symmetrical bulge directly under the umbilicus. Paraumbilical hernias are asymmetric with half of the sac fundus being covered by umbilicus and half skin of the abdomen directly above or below the umbilicus.

Pain
Hernias may be associated with aching or pain, particularly if the neck of the hernia is tight or it is irreducible. Pain may be more severe when the patient is lying down due to traction of the hernia contents. Although the majority of epigastric hernias are asymptomatic,2 they may present with symptoms akin to gastro-oesophageal reflux, namely postprandial epigastric pain, nausea and early satiety.

Although incarceration is common, strangulation of intra-abdominal viscera is very rare, as the hernia usually contains omentum or preperitoneal fat.

Colicky pain may indicate episodes of incomplete intestinal obstruction.

Very painful and tender hernias may indicate obstruction or strangulation. Young adult patients presenting with localised groin pain but no demonstrable lump are more likely to have musculoskeletal pathology than a hernia.

Irreducibility, obstruction and strangulation
A reducible hernia is one in which the contents of the hernia sac can be manually introduced back into the abdomen. A hernia that is irreducible will not disappear on lying flat or with applied pressure.

If the hernia contains bowel the patient may develop bowel obstruction (more common in femoral hernias) and present with colicky abdominal pain, vomiting, distension and constipation (all dependent on the proximity of the obstruction).

Strangulation occurs when the blood supply to bowel contained within an irreducible hernia is compromised, leading to ischaemia and gangrene.

The hernia is red and tender, and patients may display signs of systemic toxicity.

Imaging
Often the diagnosis of abdominal wall hernia can be confidently made on clinical examination. However, imaging may be useful. Ultrasound is often used initially, with CT reserved for obese patients, or those presenting with complications such as obstruction (see image).

Section 3: Managing the condition
Some hernias warrant urgent repair due to their propensity to complications (e.g. femoral). Others, such as infantile umbilical hernias, may spontaneously close. Hernias often present in elderly patients with significant comorbidities and the risk of future complications has to be balanced against the risk of surgery.

Tender incarcerated, obstructed and strangulated hernias are an indication for urgent surgery.

Inguinal hernia in adults

  • Open mesh repair:

Traditional darn repair of inguinal hernias has been superseded by tension-free mesh repair such as the Lichtenstein method,5 with a consequential fall in recurrence rates from >10 per cent to <1 per cent. This is currently the most common method of repair and can be carried out under general or local anaesthetic, with the majority performed as day cases.

  • Laparoscopic repair:

Laparoscopic repair avoids dissection of the inguinal canal and is particularly useful in recurrent and bilateral hernias.

Advantages include reduced post-operative pain and quicker return to normal activities. Disadvantages include a longer, more expensive operation, unsuitability in unfit patients or those with irreducible hernias, and rare visceral and vascular injuries.6 NICE states that if suitably experienced surgeons are available then laparoscopic repair should be offered as an alternative to open repair, provided patients are fully informed of the risks and benefits of both techniques.

Congenital inguinal hernia in children
Congenital inguinal hernias in children are prone to incarceration and should be surgically repaired by simple herniorrhaphy without mesh. The child's age and mode of presentation will determine whether this occurs in a DGH offering general paediatric surgery or a specialist paediatric centre.

Femoral hernia
Femoral hernias are at a high risk of strangulation (40 per cent overall risk) and repair may be accompanied by bowel resection. They are more common in women than men.

A small defect may be adequately closed with sutures, or mesh may be used in the elective setting. Laparoscopic repair may also be offered.

Infantile umbilical hernia
These hernias are more common in premature babies and those of African-Caribbean origin. As complications are rare (5-7 per cent), and 90 per cent disappear by the age of two, an expectant policy is used.2 If they are still present at five years they are unlikely to spontaneously close and simple open suture repair is usually performed before school age.

Adult umbilical hernia
Adult umbilical hernias are indirect herniations through the umbilical canal. They are more common in patients undergoing dialysis and those with raised intra-abdominal pressure due to obesity or ascites.

If patients are obese or have comorbidities, management should be conservative. Repair may be considered if complications occur or the overlying skin is dangerously thin.

Paraumbilical hernia
Paraumbilical hernias do not resolve spontaneously and have a high incidence of complications and repair should therefore always be considered. Recurrence rates are higher in obese patients.

Epigastric hernia
Although rarely involving bowel, epigastric hernias have a high risk of incarceration of omentum or preperitoneal fat and should be repaired even if asymptomatic. Although rare in children, they may resolve spontaneously under the age of ten.

In adults the most common technique is open suture repair if the defect is small, using a mesh with larger hernias.

Laparoscopic repair appears to offer shorter hospital stay, improved outcome and fewer complications.

It also has the advantage of assessing the possibility of a second hernia that may be missed in the open approach, which is thought to account for half of recurrences.

Incisional hernia
Incisional hernias often have a wide neck resulting in few symptoms and a low risk of strangulation.

If the patient has significant comorbidities and the neck of the hernia is large then conservative management is recommended.

However, if the patient is fit and symptomatic, and understands that recurrence rates can be as high as 20 per cent, then elective repair can be performed.7 Complications such as incarceration or strangulation necessitate emergency surgery.

Laparoscopic repair offers the usual advantages of shorter stay, less pain and early return to activities.

Section 4: Prognosis and follow-up
The majority of hernias are repaired as elective day cases and may not routinely be followed up in outpatient clinic.

Patients having undergone emergency surgery will usually be followed up, particularly if a bowel resection was performed.

Complications
Complications seen in primary care include scrotal bruising and haematoma that often only requires elevation of the scrotum and analgesia, with intervention necessary only if the skin is compromised.

Minor infections can be treated with antibiotics targeted at skin organisms.

However, if there is any chance that an underlying mesh could become infected patients may require parenteral antibiotics.

Damage to the ilioinguinal nerve during open inguinal hernia repair may result in numbness and pain around the top of the thigh and scrotum.

This usually settles, but a small number of patients require referral to a chronic pain clinic.

Some patients not deemed suitable for surgery will use a truss, usually with little benefit.

If used, a truss should be provided by an orthotics department with full instructions. It should be put on with the patient lying down.

References

1. Nelson M and Stephenson B. Adult groin hernias: acute and elective. Surgery 2009; 27: 255-61.

2. Bennett DH. Abdominal Hernias in Core Topics in General and Emergency Surgery - A Companion to Specialist Surgical Practice. Third Edition. Simon Patterson-Brown Elsevier Saunders 2005.

3. Bartlett DC and Kingsnorth AN. Abdominal wound dehiscence and incisional hernia. Surgery 2009; 27: 243-50.

4. Cameron AE.Accuracy of clinical diagnosis of direct and indirect inguinal hernia. Br J Surg 1994; 81(2): 250.

5. Lichtenstein IL, Shulman AG, Amid PK, Montilier MM. The tension-free hernioplasty. Am J Surg 1989; 157: 188-93.

6. McCormack K, Scott N, Go PM, Ross SJ, Grant A, Collaboration the EU Hernia Trialists. Laparoscopic techniques versus open techniques for inguinal hernia repair. Cochrane Database of Systematic Reviews 2003, Issue 1. Art. No.: CD001785. DOI: 10.1002/14651858.CD001785.

7. Parker S. Postgraduate Surgical Revision Notes - System Modules 2005. www.surgical-tutor.org.uk

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