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Inguinal hernia: latest developments

David L Sanders, Ashok R Gunawardene and Andrew N Kingsnorth
1 July, 2013  
The concept of ‘tailored hernia repairs’ rather than ‘one procedure for all’ is rapidly evolving and further improvements will result from attention to patient education, improving recovery patterns and patient flow
David L Sanders MRCS MBCHB
Ashok R Gunawardene MBChB(Hons) MRCS
Department of Upper GI Surgery
Royal Cornwall Hospital, Truro, UK
Andrew N Kingsnorth FRCS FACS MS MBBS
Plymouth Hernia Service,
Derriford Hospital, Plymouth UK
Advances in surgical practice and mesh technology have reduced recurrence rates in inguinal hernia repair to below 5%.(1) It has been estimated that more than 20 million repairs of inguinal hernia are carried out each year worldwide. Today, patients and surgeons have the choice between various techniques and prosthetic materials, and numerous publications (more than 6000 in the past ten years alone) confirm that many of them can be applied with success, providing that sufficient technical expertise is available. In the past five years, evidence-based clinical guidelines have been published by the European Hernia Society (EHS)(2) and the International Endohernia Society (IEHS)(3) on the diagnosis and management of inguinal hernia and provide excellent resources for clinicians. The aim of this article is to highlight the latest trends and developments in inguinal hernia surgery and discuss topics of ongoing controversy.
Medical imaging in diagnosis
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%.(4) However, in the case of diagnostic uncertainty or groin pain without a groin swelling, medical imaging may be useful in aiding the diagnosis.
According to the EHS guidelines, 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.(5–7) Ultrasonography should therefore only be used if appropriate expertise is available and where there is clinical diagnostic uncertainty. If ultrasonography fails to yield a diagnosis or appropriate expertise is not available, magnetic resonance imaging (MRI) should be the next line of investigation. The advantage of MRI is that other pathology can also be diagnosed (such as osteitis pubi, muscle inflammation or a tumour). 
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%.(8) 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 0.3–4%).(9) It has good sensitivity (100%) and specificity (98–100%) in diagnosing an occult hernia.(10) The EHS 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. Computed tomography scan does not have a significant role in diagnosis of inguinal hernia because it has a sensitivity of 83% and a specificity of 67–83%.(11) However, it may be useful in the rare case of involvement of the urinary bladder.(12)
Asymptomatic inguinal 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 does an elective operation (>5% versus 0.5%).(13,14) 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.(15) Moreover, the risk of a longstanding 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 in fact lead to a higher morbidity and mortality.(16)
 A multicenter randomised, controlled trial conducted at five North American centres included 720 men (364 watchful waiting, 356 surgical repair) followed up for 2 to 4.5 years. One watchful-waiting patient (0.3%) experienced acute hernia ‘incarceration’ without strangulation within two years, and a second had acute ‘incarceration’ with bowel obstruction at four years; there was a frequency of 1.8/1000 patient-years inclusive of patients followed for as long as 4.5 years.(17) Two independent systematic reviews both concluded that watchful waiting is safe, but most patients will develop symptoms (mainly pain) over time and will require an operation.(18,19)
Inguinal hernias in women
Women account for 8–9% of all groin hernias. Interestingly, re-operation rates after female open herniorraphy are higher, compared with males, independent of whether mesh was used.(20,21) A femoral recurrence is found in approximately 40% of re-operations.(21) 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.(22)
Should an open or laparoscopic technique be used?
In two meta-analyses comparing open and laparoscopic mesh techniques, 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 8–13 minutes), a lower incidence of seroma and recurrence.(23,24) The latter was strongly influenced by the Veterans Affairs Multicentre Trial, where the minimum mesh size in laparoscopic surgery was 7.6x15cm (a size that has been shown to be too small in later studies).(25,26) 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.
Bilateral hernias
For bilateral hernias, the meta-analyses comparing laparoscopic (totally extraperitoneal (TEP)) versus open surgery are based on few data; there is limited evidence showing no significant difference in persisting pain or recurrence.(22) Interestingly, the laparoscopic approach has been shown to be more cost effective than the open approach for bilateral hernias and is therefore recommended.(27)
Recurrent hernias
The laparoscopic approach after previous open repair (and vice versa) seems to have clear advantages because when another plane of dissection and mesh implantation was used in a randomised controlled trial (RCT), the laparoscopic approach significantly increased operative time (only TEP) but reduced perioperative complications, postoperative pain, analgesic requirement and time to return to normal activities.(28) Laparoscopic inguinal hernia techniques are recommended for repair of recurrent hernias after conventional open repair.(22) 
Trans-abdominal preperitoneal (TAPP) or TEP?
A recent prospective trial of 4552 well-matched patients undergoing TEP (n=3457) and TAPP (n=1095) found that patients undergoing TEP had a significantly higher rate of intraoperative complications (TEP 1.9% versus TAPP 0.9%; p=0.029) and surgical postoperative complications (TEP 2.3% versus TAPP 0.8%; p=0.003). The postoperative length of stay was longer for patients undergoing TAPP whereas the duration of the operation was longer for TEP (66.6 versus 59.0min; p<0.001) and the conversion rate was higher (TEP 1.0% versus TAPP 0.2%; p=0.011).(29) These findings are in opposition to other publications and the EHS guidelines, which describe TEP as the safer and more cost-effective procedure. The reality probably is that the two techniques are comparable, provided that appropriate expertise is available.
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). Lower rates of chronic pain with the use of a lightweight mesh compared with standard heavyweight polypropylene or multifilament mesh have been attributed to a reduced inflammatory response, less scar tissue and less restriction of abdominal wall movement.(30) In previous RCTs comparing lightweight mesh with standard polypropylene mesh, two indicated that the use of lightweight mesh was associated with significantly less pain on exercise after six months(31) and less pain of any severity at 12 months in the lightweight group.(30)
 A recent meta-analysis including eight prospective RCTs of good quality found no significant difference concerning severe pain (odds ratio (OR) 0.99%; 95% CI, 0.48–2.02; p=0.97); however, the incidence of any pain and the foreign body sensation was significantly lower in the lightweight group (OR 0.65; 95% CI 0.5–0.84; p=0.001).(32)  Consequently, EHS guidelines recommend the use of a lightweight mesh (Grade A recommendation).
The exception to this is in cases where there is a high risk of recurrence (for example, poor tissue constitution, complete abdominal wall reconstruction, history of multiple recurrences), in which case a heavyweight material might be preferable.
Should antibiotic prophylaxis be used?
In conventional hernia repair (non-mesh), antibiotic prophylaxis does not significantly reduce the number of wound infections (number needed to treat (NNT) 68).(33) In open mesh repair in low -risk patients, antibiotic prophylaxis does not significantly reduce the number of wound infections (NNT 80).(33)
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 (recurrence, advanced age, immunosuppressive conditions) or surgical (expected long operating times, use of drains) factors, the use of antibiotic prophylaxis should be considered.(22)
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.(34) Several studies have shown that day surgery is just as safe and effective and, in addition, less costly.(35–37) 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.(22)
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 hospital stay. The use of local anaesthetic for the repair of primary inguinal is safe, well accepted and cost effective.(38,39) However, local anaesthetic rates are very variable between countries and hospitals largely coming down to surgeon preference.
Chronic pain and nerve handling
The reported frequency of postoperative pain following inguinal hernia repair varies widely. This is in part a reflection of the discrepancy of the descriptors used for pain. Two systematic reviews of chronic pain after inguinal hernia repair found incidence ranging from 0% to 63%.(40,41) The authors identified a cumulative prevalence of chronic pain of 30% at three years post-surgery. One- third of this 30% reported moderate-to- unbearable pain.
However, these data included mesh and non-mesh repairs and several studies had incomplete follow up of patients. In both reviews, the overall data suggested more chronic pain following repair without prosthetic material. When the pain is classified by severity, 3–4% of patients report severe chronic pain that affects daily activities, such as walking, work, sleep, relationships with other people, mood and general enjoyment of life.(42)  
The ilio-inguinal, ilio-hypogastric nerves and the genital branch of the genitofemoral nerve may contribute to chronic post-inguinal neuropathic pain. Traditional surgical teaching dictates that the nerves should be preserved at all times during inguinal hernia repair because of the supposed morbidity associated with cutaneous sensory loss and chronic groin pain following nerve injury. Various surgical etiquettes have been proposed to reduce the incidence of unintentional intra-operative nerve injury.(43) Cohort studies have shown that routine ilio-inguinal neurectomy is associated with a lower incidence of chronic groin pain and subjective paraesthesia is usually temporary.(44-46)
However, RCTs comparing the preservation versus elective neurectomy of the ilio-inguinal nerve have shown conflicting results.(47-50) A systematic review, including three RCTs assessing ilio-inguinal nerve handling, found similar outcomes in patients receiving nerve preservation or division.(51)  Other reviews have suggested that better results are obtained if the nerves are identified and either protected from injury or systematically divided if they are in danger of suffering incidental damage during surgery.(52-57) For litigation purposes, it is important that nerve identification and handling be documented in the operation note.
Future management
Further improvements in inguinal hernia surgery will come about through 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 whether laparoscopic repair should be offered to all patients or is more suited to certain patient groups, that is, active patients and those more at risk of chronic pain. In addition, the biological treatment of hernias as an adjuvant to surgical repair or as a stand-alone therapy is being investigated.(58) 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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