Inguinal hernia: latest trends and developments

Mr David L Sanders

PGDip Med Ed, BSc, MRCS, MBCHB

Prof Andrew N 
Kingsnorth

FACS, FRCA, MD, MBBS
President of the European Hernia Society 2007-2010

Affiliations:        
Plymouth Hernia Service
 Derriford Hospital
 Plymouth, UK

An inguinal hernia is a protrusion of the contents of the abdominal cavity or preperitoneal fat through a hernia defect in the inguinal area. It has been estimated that worldwide over 20m repairs of inguinal hernia are carried out each year.1 The specific operation rates vary between countries from around 100 to 300 per 100,000 population per year.2

The modern surgical treatment of inguinal hernias originated in Italy, more than 100 years ago, with Eduardo Bassini’s presentation of a new method of repair.3 Bassini, whose repair is now rarely used, did more than just invent a new method of repair; one of his major contributions was that he performed adequate audit and follow-up of patients.4 This scientific approach to hernia surgery has led the way for the evidence-based management of inguinal hernias. The rapid advancement in the treatment of hernias has been driven by the large numbers of people affected by groin hernias, a lifetime risk in men of 27% and in women of 3%,2 and the financial incentives for industry and surgeons to develop the ‘perfect’ mesh and technique.

Today, many methods of repair are used, the majority including reinforcement with various mesh devices. This review aims to highlight the major advances in our understanding of adult inguinal hernias and their management.

Risk factors for developing a hernia
For most of the 20th century there was unanimity regarding the aetiology of hernias. They arose form congenital defects in the normal abdominal wall. The ability to resist protrusion was compromised by straining, poor muscular tone, obesity, ascites and advancing age. Hernia repair was considered curative, provided that recurrence from faulty technique, surgical error, or infection was avoided. In 1924, Keith stated ‘that a pathological change in the connective tissue of the belly may render certain individuals particularly liable to hernias’, but his insight was largely ignored.5

We now know that both environmental and genetic factors play an important contribution to the development of inguinal hernia. The majority of these have an effect on collagen, which is a principal component of the extracellular matrix and adds strength to connective tissue. Table 1 shows the developments in our understanding of these risk factors.

The clinical presentation
The appearance of a lump in the groin is the most common presentation of an inguinal hernia, although occasionally a hernia may be occult.

Inguinal hernias can be classified as:

• 

Occult – A vague groin swelling, vague localisation of the swelling, intermittent swelling which is not palpable during examination and obscure groin complaints without swelling
• 
Asymptomatic – Inguinal hernia without pain or discomfort to the patient
• 
Minimally symptomatic – Inguinal hernia with complaints that do not interfere with normal daily activity
• 
Symptomatic – Reducible inguinal hernia with symptoms which affect normal daily activity

Investigations to be performed
In patients presenting with a groin mass, the diagnosis of inguinal hernia can be established by means of physical examination alone, with a sensitivity of 74.5%–92% and a specificity of 93%.6 However, in the case of an occult hernia, medical imaging may be useful in aiding the diagnosis.

Ultrasonography should be the first-line investigation. Several studies have revealed a good specificity (81%–100%) but poor sensitivity (33%–100%). This difference is likely to reflect the variability of expertise in interpreting the ultrasonographic images.7–9 Ultrasonography should therefore only be used if appropriate expertise is available.

If ultrasonography fails to yield a diagnosis or appropriate expertise is not available, MRI should be the next line of investigation. The advantage of MRI is that other pathology can also be diagnosed – such as sport related pathology, inflammation or a tumour).10 Moreover, imaging can be produced in any plane and dynamic examinations during straining are possible. Its sensitivity is 94.5% and specificity is 96.3%.11

Herniography should be reserved as a third-line investigation, as it is invasive and has a small risk of complications, such as contrast allergy, puncture of the intestine, abdominal wall haematoma and short-lasting pain (risk 0.3% to 4%).12,13 It has good sensitivity (100%) and specificity (98%–100%) in diagnosing an occult hernia.12, 14 The European Hernia Society Guidelines recommend that, in cases of obscure pain in the groin with an uncertain diagnosis of inguinal hernia, an initial time of four months (in absence of clinical deterioration) is worthwhile before proceeding to herniography.15

CT-Scan does not have a significant role in diagnosis of inguinal hernia; it has a sensitivity of 83% and a specificity of 67%–83%.16 However, it may be useful in the rare case of involvement of the urinary bladder.17

Asymptomatic hernias
An asymptomatic inguinal hernia is operated on to prevent complications such as strangulation or obstruction. The justification for this approach is that an emergency operation due to a strangulated or obstructed hernia has a higher associated mortality than an elective operation (>5% versus 0.5%).18, 19

However, the literature reveals that the majority of patients with strangulation either did not know that they had a hernia or had not sought medical attention.20–22 Moreover, the risk of a reducible hernia becoming irreducible (and strangulating) is low (estimated at 0.3%–3% per year) and the risk of operating in every inguinal hernia, particularly in the case of elderly patients, could lead to a higher morbidity and mortality.20, 23 The European Hernia Society Guidelines conclude that watchful waiting is an acceptable option for men with asymptomatic or minimally symptomatic inguinal hernias.15

Inguinal hernias in women
Women account for 8%–9% of all groin hernias. Interestingly, re-operation rates after female open herniorraphy are higher, compared to males, independent of whether mesh was used.24, 25 In approximately 40% of re-operations a femoral recurrence is found.25 It is not known whether these femoral recurrences represent hernias overlooked at the primary operation or de novo hernias. The high frequency of femoral recurrence after inguinal herniorraphy in women argues for the use of laparoscopic repair, covering both the inguinal and femoral orifices simultaneously.15

Suture versus mesh repair
Cochrane Reviews in 2002 and 2003 showed strong evidence that fewer hernias recur after mesh repair than following non-mesh repair, with a separate analysis for the Shouldice repair.26, 27 Mesh appeared to reduce the chance of chronic pain rather than increase it.

The Shouldice technique is the best non-mesh repair for primary inguinal hernia.28 The Lichtenstein technique is currently the best evaluated and most popular of the different open mesh techniques. This is because it is reproducible with minimal perioperative morbidity, it can be performed as a day case under local anesthesia and has low recurrence rates (<4%) in the long term.29,30 Other open mesh techniques (e.g. plug repairs) have very similar results compared with Lichtenstein repair, but tend to cost more.31–33

Laparoscopic repair has been shown to have similar recurrence rates to the shouldice technique but has a lower incidence of chronic pain (2.2% versus 5%).34 The European Hernia Society Guidelines conclude that all adult patients (>30 years of age) should be operated on using a mesh technique. When considering a non-mesh technique, the Shouldice repair should be used.15

Open versus laparoscopic repair
In two meta-analyses comparing open and laparoscopic mesh techniques it was shown that significant advantages for the laparoscopic approach included a lower incidence of wound infection, haematoma and chronic pain/numbness with earlier return to normal activities or work (six days). Conversely, significant advantages for Lichtenstein included shorter operation time (by eight to 13 minutes), a lower incidence of seroma and recurrence.35, 36

The latter was strongly influenced by the Veterans Affairs Multicentre Trial, where the minimum mesh size in laparoscopic surgery was 7.6x15cm (a size which has been shown to be too small in later studies).37, 38 When this study is excluded, there is no difference in recurrence rates between open and laparoscopic surgery.

There also appears to be a higher rate of rare but serious complications with respect to major vascular and visceral (especially bladder) with the laparoscopic approach. Most of these lesions were seen with transabdominal preperitoneal (TAPP) technique -0.65% versus 0%–0.17% for totally extra peritoneal (TEP) and open mesh repair.36 The transabdominal route of TAPP might also cause more adhesions leading to intestinal obstruction.39

When a mesh based repair is chosen, the best approach to the groin is still debated. This is mainly caused by discussion about recurrence on one end and chronic pain on the other. With adequate surgical technique and training, the recurrence rate, particularly after laparoscopic operations, can be reduced significantly. Currently, both the open Lichtenstein and laparoscopic (TEP rather than TAPP and minimum mesh size of 10cm x 15cm) inguinal hernia techniques are recommended as best evidence-based options for repair of a primary unilateral hernia, providing the surgeon is sufficiently experienced in the specific procedure.15 However, the open technique is currently more cost-effective for primary unilateral inguinal hernias.40

For bilateral hernias, the meta-analyses comparing laparoscopic versus open surgery are based on few data; there is limited evidence showing no significant difference in persisting pain or recurrence.15 However, interestingly, the laparoscopic approach has been shown to be more cost-effective than the open approach for bilateral hernias and is therefore recommended.40

For recurrent hernias, the laparoscopic approach after previous open repair (and vice versa) seems to have clear advantages, since another plane of dissection and mesh implantation is used. In a randomised control trial, the laparoscopic approach significantly increased operative time (only TEP) but reduced perioperative complications, postoperative pain, analgesic requirement and time to return to normal activities.41 Thus, for repair of recurrent hernias after conventional open repair, laparoscopic inguinal hernia techniques are recommended.15

Which mesh should be used?
There is a great variety of meshes available differing in textile parameters (polymer, filament, construction, pore size, elasticity, tensile strength, weight, surface). We do not know the parameters of the ideal mesh. In open inguinal hernia repair, the use of a monofilament polypropylene mesh is advised to reduce the chance of incurable chronic sinus formation or fistula which can occur in patients with a deep infection.15

Weight reduced mesh materials (>1000µm), macroporous and oligofilament structures seem to shrink less, cause less inflammatory reaction and induce less extensive scar-tissue formation and are therefore more likely to be integrated with less long-term discomfort and foreign body sensation when implanted in open hernia repair, but possibly they are associated with an increase risk for hernia recurrence.42-44

Should antibiotic prophylaxis be used?
In conventional hernia repair (non-mesh), antibiotic prophylaxis does not significantly reduce the number of wound infections (NNT 68).45 In open mesh repair in low-risk patients, antibiotic prophylaxis does not significantly reduce the number of wound infections (NNT 80).45 Similarly in laparoscopic repair, antibiotic prophylaxis does not significantly reduce the number of wound infections.

Therefore, in clinical settings with low rates (< 5%) of wound infection, there is no indication for the routine use of antibiotic prophylaxis in elective open or laparoscopic repair for low-risk patients. In the presence of risk factors for wound infection based on patient factors (recurrence, advanced age, immunosuppressive conditions) or surgical factors (expected long operating times, use of drains), the use of antibiotic prophylaxis should be considered.15

Day-case surgery and local anaesthesia
As early as 1955, the advantages of inguinal hernia repair as day surgery were already described in the literature: quicker mobilisation, patient friendly and lower costs.46 Several studies have showed that day surgery is just as safe and effective and, in addition, cheaper.47-49 Currently, there is a large variation in day-case rates, which is partly due to healthcare financing. All patients, irrespective of technique, should be considered for day-case surgery. This includes selected older patients and patients with an ASA grade of II 
or III.15

General anaesthetic can provide the surgeon with optimal operating conditions in terms of patient immobility and muscular relaxation. Modern general anaesthesia with short-acting agents and combined with local infiltration anaesthesia is safe and fully compatible with day-case surgery as is spinal anaesthesia. Disadvantages are the risk of airway complications, cardiovascular instability, nausea and vomiting.

Furthermore, urinary complications and recovery from central hypnotic effects may prolong the hospital stay. The use of local anaesthetic for the repair of primary inguinal hernia has been repeatedly shown to be safe, well accepted and cost-effective.50, 51 However, local anaesthetic rates are very variable between countries and hospitals, largely coming down to surgeon preference.

The future
Further improvements in inguinal hernia surgery will come about through increased use of outpatient facilities, attention to patient education, improving recovery patterns and patient flow. The concept of ‘tailored hernia repairs’ to the patients needs rather than ‘one procedure for all’ is rapidly evolving. Current research is concentrating on the improvement of prosthetic materials to enhance long-term patient comfort and the development of biological materials allowing for improved integration with host tissues.

In addition, the biological treatment of hernias as an adjuvant to surgical repair or as a stand-alone therapy is being investigated.52 The principle of such treatment is to strengthen the extracellular matrix using growth factors. This is currently being tailored towards incisional hernia surgery, but may be used in the future in the treatment of inguinal hernias.

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