The modern management of incisional hernias
BMJ 2012; 344 doi: https://doi.org/10.1136/bmj.e2843 (Published 09 May 2012) Cite this as: BMJ 2012;344:e2843
- David L Sanders, speciality trainee in upper gastrointestinal surgery1,
- Andrew N Kingsnorth, consultant surgeon2
- 1Upper Gastrointestinal Surgery, Royal Cornwall Hospital, Truro TR1 3LJ, UK
- 2Peninsula College of Medicine and Dentistry, Plymouth, UK
- Correspondence to: D L Sanders dsanders{at}doctors.org.uk
- Accepted 12 April 2012
Summary points
Incisional hernias are a common complication of abdominal surgery
Incisional hernias can occur many years after the index operation
Surgical site infection doubles the risk of incisional hernia
In case of uncertainty, ultrasonography can help confirm the diagnosis before specialist referral
Laparoscopic repair is generally reserved for small hernias (fascial defect <10 cm), although some surgeons report good results with larger defects
Before the introduction of general anaesthesia by Morton in 1846, incisional hernias were rare. As survival after abdominal surgery became more common so did the incidence of incisional hernias.1 Since then, more than 4000 peer reviewed articles have been published on the topic, many of which have introduced a new or modified surgical technique for prevention and repair. Despite considerable improvements in prosthetics used for hernia surgery, the incidence of incisional hernias and the recurrence rates after repair remain high. Arguably, no other benign disease has seen so little improvement in terms of surgical outcome.
Sources and selection criteria
We searched PubMed from 1970-2012 and Embase and the Cochrane Library from inception using the terms “hernia” and “incisional” (using the Boolean operator AND) and “ventral” (using the Boolean operator OR). The reference lists were also used to identify studies of interest. Both authors independently identified publications for inclusion and differences were resolved by discussion. We gave priority to research published in the past five years and highly regarded older publications.
Unlike other abdominal wall hernias, which occur through anatomical points of weakness, incisional hernias occur through a weakness at the site of abdominal wall closure. Why, unlike primary abdominal wall hernias, are the results after repair so poor? Perhaps it is because in the repair of incisional hernias several problems need to be overcome: a multilayered wall structure of different tissue properties in constant motion has to be sutured; positive abdominal pressure has to be dealt with; and tissues with impaired healing properties, reduced perfusion, and connective tissue deficiencies have to be joined.
This review, which is targeted at the general medical audience, aims to update the reader on the definition, incidence, risk factors, diagnosis, and management of incisional hernias.
Unravelling the terminology
Despite the size of the problem, the terminology used to describe incisional hernias still varies greatly. An internationally acceptable and uniform definition is needed to improve the clarity of communication within the medical community and enable publication data and future studies to be interpreted properly. Table 1⇓ lists the definitions of the commonly (mis)used terms.
Definitions of incisional hernia and the commonly (mis)used terminology
How common are incisional hernias?
Incisional hernias are one of the most common complications after abdominal surgery. The true incidence is difficult to determine, as shown by the wide range of published figures in the literature. The reasons for this discrepancy are the lack of standardised definition, the inconsistency of data sources used (which include self reporting by patients, audits of routine clinical examination, and insurance company databases), short length of follow-up (often one year), and the subjectivity of clinical examination.2 The reported incidence after a midline laparotomy ranges from 3% to 20% and is doubled if the index operation is complicated by wound infection.3 About 50% of incisional hernias are detected within one year of surgery, but they can occur several years afterwards, with a subsequent risk of 2% a year.3 4
Millions of abdominal incisions are created each year worldwide, so incisional hernias are a major problem, both in terms of morbidity and socioeconomic cost. Although exact figures are unknown, it is estimated that each year 10 000 repairs are performed in the United Kingdom and 100 000 are performed in the United States.5
Who is at risk?
Until recently, incisional hernias were thought to result mainly from a technical failure in the surgical closure of the abdominal wall.6 However, we now know that a complex array of patient related, surgical, and postoperative variables influence their development. These variables share a common denominator—they all influence normal wound healing (table 2⇓). Most of the evidence on risk factors has been determined by retrospective studies, and the relative importance of many of the proposed risk factors is poorly understood.
Patient related risk factors for developing an incisional hernia
Patient related factors
Associations between surgery for abdominal aortic aneurysm, the presence of other primary abdominal wall hernias, and the development of incisional hernias have repeatedly been documented.7 8 Similarly patients with certain connective tissue diseases (Marfan’s syndrome, osteogenesis imperfecta, and Ehlers-Danlos syndrome) have an increased incidence of incisional hernias.9 10 A review article published in 2011, which drew on evidence from 52 publications, concluded that collagen metabolism in patients with a hernia is altered at three levels. The ratio between type I (strong) and type III (weak) collagen is decreased, the quality of collagen is poorer, and collagen breakdown is increased via increased matrix metalloproteinase (MMP) activity.11 However, it has not been established whether these changes are localised to the site of hernia development or whether they affect all body tissues. The relative contribution of collagen deficiencies versus other patient related risk factors for hernia development is also not fully understood (table 2).
Surgical factors
Incisional hernias can occur after any type of laparotomy incision but are most common after midline (especially upper midline) and transverse incisions.4 An analysis of 11 publications assessing the incidence of incisional hernia after different abdominal incisions concluded that the risk was 10.5% for midline incisions and 7.5% for transverse incisions.12 However, many of these publications included variable closure techniques and disease processes.
Several clinical trials and meta-analyses have shown that a continuous closure technique with a simple running suture is the best option for closure of laparotomy incisions.13 14 15 The use of monofilament slowly resorbable suture material versus non-absorbable or braided material decreases the rate of incisional hernias and reduces the incidence of postoperative pain and wound infection.13 14 15
Experimental studies and randomised clinical trials have shown that a suture length to wound length ratio of at least 4:1, and not more than 5:1, minimises the risk of incisional hernia.16 17 18 Traditional surgical teaching recommends that continuous sutures are placed 10 mm from the wound edge and 10 mm apart.17 However, recently this technique has increasingly been challenged. The large tissue bites have been shown to be associated with an increase in the amount of necrotic tissue and slackening of the stitches, resulting in increased risk of wound infection and the development of an incisional hernia.19 20 In a large randomised controlled trial, small stitches placed 4-6 mm from the wound edge and 4 mm apart (in the aponeurotic layer only) minimised the risk of incisional hernias from 18% to 5.6% (P<0.001) and reduced wound infection rates by 50% (from 10.2% to 5.2%; P<0.02).21 This is currently being evaluated in a multicentre randomised controlled trial.16 Most surgeons still use the large bite method and adoption of the small bite technique will be a major shift in surgical practice.
Postoperative factors
Surgical site infection is commonly documented as the most important independent risk factor for the development of an incisional hernia and is thought to double the risk.4 A prospective cohort study showed that factors that increase intra-abdominal pressure in the immediate postoperative phase, such as postoperative ileus, the need for repeated urinary catheterisation, coughing, vomiting, and mechanical ventilation, also increase the risk of incisional hernias.22
Predicting the risk
A scoring system for predicting the development of early (less than six months after surgery) incisional hernia was published in 2010.23 The study used linear and multivariate regression models of 42 patient related, surgery related, and perioperative variables. Of these the most significant predictive factors, in order of importance, were fascial suture to incision ratio less than 4.2:1, surgical site infection, time to removal of skin sutures less than 16 days, and body mass index greater than 24. This may provide a useful future tool for preoperative risk assessment and the use of prophylactic mesh, but it still requires prospective and independent validation. Van Ramshorst and colleagues have also published a model for predicting wound abdominal dehiscence risk.24 They identified the major independent risk factors as age, sex, chronic pulmonary disease, ascites, jaundice, anaemia, emergency surgery, type of surgery, postoperative coughing, and wound infection.
Can an incisional hernia be prevented?
Currently the risk of incisional hernia cannot be eliminated except by avoiding a laparotomy incision in the first place. However, the risk can be minimised by reducing systemic risk factors, especially smoking, obesity, and nutritional deficiencies, and by optimising diabetic management, even if surgery has to be delayed. The risk can be further minimised by careful attention to surgical technique when closing the abdominal wall. Surgeons should follow the 2008 National Institute for Health and Clinical Excellence guidelines for the prevention and treatment of surgical site infection.25 The guidelines provide a detailed review of preoperative, intraoperative, and postoperative measures to minimise the risk of infection. A systematic review of randomised controlled trials found that preoperative antibiotic prophylaxis (less than two hours before surgery) is beneficial in clean surgery involving a prosthesis, clean contaminated surgery, and contaminated surgery. The most significant difference was seen in colorectal surgery (12.9% surgical site infection with antibiotics versus 40.2% without antibiotics).w1
The role of prophylactic mesh placement in high risk patient groups is unclear. Promising results have been reported in a randomised controlled trial and case series for elective open abdominal aortic aneurysm surgery (rate of incisional hernias: 9.3% v 2.7% at three year follow-up) and after gastric bypass for obesity (rate of incisional hernias 4.4% at two year follow-up v 30% in matched controls).w2 w3 However, other small series have reported unacceptably high complication rates.w4 Two large multicentre trials assessing prophylactic mesh placement are currently being conducted.
Mention the postoperative risk of incisional hernia when obtaining informed consent from all patients undergoing laparotomy.
How should an incisional hernia be diagnosed?
Most incisional hernias can be diagnosed by a review of the patient’s history and by clinical examination. Patients typically present with an abdominal bulge in the region of the surgical scar. On examination the edges of the fascial defect can often be palpated, although an accurate estimation of the size of the defect may be difficult to discern clinically. The size of the peritoneal sac and associated contents is often large, although the fascial defect may be fairly small, particularly in obese patients and after multiple abdominal operations, where there may be numerous small fascial defects. Many incisional hernias are asymptomatic, but 20-50% present with pain. Skin changes as a result of pressure related capillary thrombosis and atrophic muscle fibrosis may occur in large and in longstanding hernias.w5
What diagnostic imaging should be used?
Ultrasonography is commonly used to confirm the clinical diagnosis. The sonographic image of a hernia is a fascial gap with protruding hernia contents. The hernia sac should increase in size or change location when the patient coughs. Intestinal structures are characterised by peristaltic movements and air bubbles, whereas the omentum appears as a stationary, highly reflective, space occupying structure.
More detailed diagnostic imaging is indicated in four patient groupsw6:
Obese patients (body mass index >35)
Patients with recurrent incisional hernias
Patients with large hernias with loss of domain (abdominal viscera permanently residing outside the abdominal cavity in the hernia sac)
Patients with pain within the abdominal wall but with no clinically detectable hernia.
In these patients computed tomography (with or without valsalva) and particularly multidetector computed tomography, which allows three dimensional reconstruction, is useful. Occult defects are accurately delineated, the contents of the sac defined, and an estimate can be made of the abdominal contents that have lost domain.w7
Does an incisional hernia have to be repaired?
Not every patient who presents with an incisional hernia is suitable for surgical repair, and the risk of surgery must be balanced against the risk of complications if the hernia is left untreated. Between 6% and 15% of incisional hernia repairs are performed because of strangulation or obstructive symptoms.w5 However, little information is currently available on the risk of major complications from untreated incisional hernias. Small hernias invariably enlarge with time as a result of the continuous intra-abdominal pressure, diaphragmatic contractions, and increased pressure from coughing or straining.w8
A commonsense approach is advocated. If the patient can safely have general anaesthesia and the chance of successful repair is reasonable, then surgery is indicated. If the patient presents a high anaesthetic risk or surgical repair will be technically difficult, then the size of the fascial defect relative to the hernia, the symptom complex, the patient’s age, and the patient’s preferences must be carefully considered. In such cases, conservative management may be more appropriate. This decision making process is patient specific and therefore we recommend that all patients are referred for a specialist opinion.
What methods of surgical repair are available?
Despite recent advances in the management of incisional hernias, recurrence rates remain high. The recurrence rate after open suture repair can be as high as 54%, and as high as 36% for open mesh repair; however, in general, recurrence rates are slightly lower, with a mean of about 15%.w9 Recurrence rates for laparoscopic repair seem to be comparable to open mesh procedures but laparoscopic repair requires a shorter hospital stay.w10 The method of choice for repair of incisional hernias is still debatable. Figure 1⇓ shows the anatomy of the different methods of repair.
Fig 1 Simplified anatomy of a midline incisional hernia and options for surgical repair
Interestingly, in a comparative retrospective study of more than 400 incisional hernia operations over 25 years, the most important prognostic factor was found to be the surgeon’s experience rather than the repair method used.w11
Mesh versus suture repair
A systematic review found that hernia repair without prosthetic mesh is associated with unsatisfactory recurrence rates of 12-54%, whereas hernia repair with mesh results in recurrence rates of 2-36%.w9 It is now accepted that only the smallest (less than 3 cm) incisional hernia should be repaired by primary tissue approximation with sutures.w12 w13 A population based study of 10 882 patients in the US found an increase in the frequency of synthetic mesh use from 35% in 1987 to 65% by 1999.w14 A recent Cochrane review of open procedures for the repair of incisional hernia concluded that open mesh repair is superior to suture repair in terms of recurrence but inferior in terms of wound infection and seroma formation on the basis of evidence from three trials.w15
Laparoscopic mesh repair versus open mesh repair
Laparoscopic incisional hernia repair is an emerging technique with promising initial results. A composite or coated mesh (to reduce visceral adhesions) is placed in the intraperitoneal position and the hernia defect is usually not closed. This is referred to as an intraperitoneal onlay mesh (IPOM; fig 1). The advantages of the laparoscopic approach are that it allows the whole of the previous incision to be visualised and small fascial defects to be identified, but it has the disadvantage of relying fully on the strength of the mesh and its fixation.
A 2002 meta-analysis identified 83 studies comparing open and laparoscopic incisional hernia repair from a structured Medline search; it was able to compare 390 patients having open repair with 322 patients having laparoscopic repair.w16 Perioperative complications and length of stay were reduced in the laparoscopic group. Another meta-analysis identified 53 studies with a total of 5227 laparoscopic incisional hernia repairs. The rate of hernia recurrence was 3.98%.w17 Most of the studies were carried out in specialty centres that carried out large numbers of minimally invasive procedures, the authors concluded that the true recurrence rate is probably higher. Laparoscopic repair has been criticised for producing cosmetically worse results than the open repair because the hernia sac is not excised and the defect is not closed. Furthermore, laparoscopic repair is not always possible for large incisional hernias or when the hernia extends towards the costal margin or pelvis because adequate mesh overlap cannot easily be achieved.w17 A 2011 Cochrane review of 10 randomised control trials (including 880 patients) concluded that laparoscopic repair is a safe technique that has a lower risk of wound infection, shorter hospital stay, and is associated with fewer (albeit more severe) complications than open repair.w18 However, the data were heterogeneous and most trials had a short length of follow-up.
A patient’s perspective
A few years after having a hysterectomy for endometriosis, which was complicated by a bowel perforation, relaparotomy, and subsequent wound infection, I gradually noticed that I had a bulge in the lower part of my abdomen and that some of my clothes no longer fitted. The bulge started to get much bigger and to cause discomfort, making it difficult for me to complete my normal daily activities. It’s hard to explain, but I had a strange sensation that my bowel was spilling out.
I was referred to a specialist, who diagnosed a large and complex incisional hernia. We discussed the options for treatment and I was placed on the waiting list for an open incisional hernia repair, which involved releasing the muscles to fix the hernia (a component separation; fig 1). I was apprehensive because of the problems I had after my original operation, but I knew that I couldn’t go on like as I was.
I was in hospital for a week after the operation and had wound drains in. It was difficult after the operation and I took three months to recover fully. I am now getting back to normal and am very grateful to the team that looked after me.
Techniques for open mesh repair
Three principal types of repair have been described for the open repair of incisional hernia with mesh—the inlay, onlay, and sublay techniques.
In the inlay technique the mesh is placed between the muscles in a bridging position. The mesh is in contact with the viscera (fig 1). Polypropylene mesh anchors to all adjacent tissues and can therefore induce extensive adhesions to viscera if placed in a position where it becomes adjacent to the bowel. Erosion of the mesh then can occur into the intestines—a well recognised drawback of this technique.w12 A non-randomised prospective study reported good results with this technique, but these impressive results have not been repeated elsewhere.w19 A smaller retrospective analysis compared the inlay, onlay, and sublay techniques. The recurrence rate for the inlay technique was 44%, and two of 23 patients developed enterocutaneous fistulas.w20 Inlay techniques, therefore, are not generally recommended. Furthermore, the force needed to dislocate a bridged mesh is much lower than for a closed defect, and bridging should be a last resort only.w21
In the onlay technique (fig 1), the mesh is placed over the abdominal wall closure in the subcutaneous prefascial space.w22 In a systematic review, recurrence rates after this technique varied from 5.5% to 14.8%, with a mean follow-up of one to 6.7 years.w23 The main criticisms of this technique are the high rates of wound infections and seroma formation.w12 w15
In the sublay technique, the mesh is placed over the closed posterior rectus sheath and peritoneum (fig 1).w24 If the hernia is large and the posterior sheath cannot be closed, the mesh is sometimes used to bridge the defect (fig 1). A systematic review found that the recurrence rate after sublay repair varied from 1% to 23% at a mean follow-up of 1.7 to 6.7 years.w23 The European Hernia Society has adopted sublay mesh repair as the gold standard open repair; however, the procedure has been reported as technically more difficult than the onlay technique, with a steeper learning curve and a requirement for more operative time.w12 w25
Chronic pain after incisional hernia repair
Chronic pain (for more than three months postoperativelyw26) after incisional hernia repair is poorly documented. A review reported that clinically important pain after open mesh repair of incisional hernia has an incidence of 10-20%.w27 The causes of the pain are poorly understood but probably include a combination of mesh associated inflammation, nerve damage from mesh fixation, nerve entrapment or damage, visceral adhesions to the mesh and fixation points, and tension in the repair. Whether the pain relates to the preoperative symptom complex (as with inguinal hernia repair) is not yet established. The importance of chronic pain is difficult to gauge because of the lack of prospective high quality studies. Patients may think that mild postoperative discomfort is an acceptable consequence of surgery for an unsightly and uncomfortable abdominal swelling, whereas pain that limits daily activity after repair of a small asymptomatic incisional hernia may not be thought acceptable.
Patients who present with chronic pain should be referred back to the operating surgeon. A computed tomogram may be useful to assess whether the pain is related to a recurrence of the hernia or a port site hernia (after laparoscopic repair). If there is no evidence of recurrence, many surgeons adopt a watch and wait approach with referral to chronic pain services. Other surgeons have reported removing fixation tacks or sutures or replacing the mesh, with successful outcome.w28 w29 However, no high quality evidence is available to recommend the best way to manage this problem.
Special circumstances
Giant incisional hernias
Patients with giant incisional hernias (fascial defect >10 cm in transverse diameter) and obese patients (body mass index >35) present a surgical and anaesthetic challenge. These patients often have poor quality abdominal wall musculature coupled with multiple comorbid medical problems. A further problem that has to be overcome is the risk of serious “loss of domain” once the hernia is repaired, which can result in abdominal compartment syndrome. Loss of domain implies that a proportion of the abdominal contents resides permanently (in a hernia sac) outside the natural abdominal cavity. Returning the contents requires considerable physiological adaption (predominantly respiratory) if the volume exceeds 20% of the size of the abdominal cavity.w8
Preoperative pneumoperitoneum has been used to overcome the problems of loss of domain by increasing the size of the abdominal cavity before surgery.w30 Although this technique may be effective, it has not been widely adopted in the UK. Patients and the surgical technique must be carefully selected, and the team will usually include a hernia specialist, anaesthetist, and plastic surgeon. Patients often need postoperative care in the intensive treatment unit. Dumainian and Denham have updated an algorithm for the management of complex incisional hernias.w31
The component separation technique allows a flap of the rectus muscle, anterior rectus sheath, internal oblique, and transversus abdominus muscle to slide medially, enabling giant hernia defects (up to 20 cm) to be closed (figs 1 and 2⇓).w32 This can be reinforced with a prosthetic mesh to supplement the attenuated layers of the abdominal wall and is the technique of choice for giant midline incisional hernias.
Fig 2 Photographs of a patient with a large complex incisional hernia before (A) and after (B) laparostomy
Incisional hernia repair and pregnancy
Repair of large incisional hernias in premenopausal women presents special problems because elasticity and expansion of the abdominal wall will be required if the patient subsequent becomes pregnant. Few data are available on the required compliance of the abdominal wall during pregnancy or whether prosthetic mesh reduces the elasticity enough to cause complications during pregnancy.w33 There have been a few case reports of successful pregnancies in which the uterus has been within (or part of) the hernia sac.w34-w36 Small, asymptomatic incisional hernias can probably be safely left until the completion of a family. Large or symptomatic hernias should be fixed, and in these cases it may be better to avoid the use of mesh and to use a sutured repair such as the shoelace technique.w33 Patients must be warned of the high risk of recurrence with subsequent pregnancy.
Additional educational resources
Resources for patients
Patient UK (www.patient.co.uk/health/Hernia.htm)—An overview of all types of hernia, risk factors, and management
For healthcare professionals
Sauerland S, Walgenbach M, Habermalz B, Seiler CM, Miserez M. Laparoscopic versus open surgical techniques for ventral or incisional hernia repair. Cochrane Database Syst Rev 2011;3:CD007781
Den Hartog D, Dur AHM, Tuinebreijer WE, Kreis RW. Open surgical procedures for incisional hernias. Cochrane Database Syst Rev 3008;3:CD006438
Muysoms FE, Miserez M, Berrevoet F, Campanelli G, Champault GG, Chelala E, et al. Classification of primary and incisional abdominal wall hernias. Hernia 2009;13:407-14 (European Hernia Society classification for incisional hernias)
Sanders DL, Kingsnorth AN. Prosthetic mesh materials used in hernia surgery. Expert Rev Med Devices 2012;9:159-79
Medscape (http://emedicine.medscape.com/article/1297226-overview)—An overview of abdominal wall reconstruction and complex hernias
Tips for non-specialists
Refer all incisional hernias for a specialist opinion and urgently refer painful hernias and large hernias in which a small fascial defect is suspected
Divarication of the rectus muscles (separation of the rectus muscle with an intact fascia, which usually does not need surgery) may resemble an epigastric hernia; if the diagnosis is uncertain, ultrasonography is useful before referral
Optimise weight, smoking status, and diabetic control before surgery
The positioning of the mesh depends on the type of repair; a small postoperative bulge after laparoscopic hernia repair is normal because the fascial defect is not closed
Ongoing research
Watchful Waiting Versus Repair of Oligosymptomatic Incisional Hernias (AWARE) http://clinicaltrials.gov/ct2/show/NCT01349400
Prevention of Incisional Hernia by Mesh Augmentation After Midline Laparotomy for Aortic Aneurysm Treatment (PRIMAAT) http://clinicaltrials.gov/ct2/show/NCT00757133
Prophylactic Mesh Implantation for the Prevention of Incisional Hernia (ProphMesh) http://clinicaltrials.gov/ct2/show/NCT01203553
Laparoscopic Versus Open Incisional Hernia Repair (COLIBRI) http://clinicaltrials.gov/ct2/show/NCT01420757 (completed but not yet published)
Notes
Cite this as: BMJ 2012;344:e2843
Footnotes
Contributors: Both authors contributed with the literature review. DLS wrote the article and ANK reviewed the article and made amendments. DLS is guarantor.
Funding: None received.
Competing interests: All authors have completed the ICMJE disclosure form at http://www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years, no other relationships or activities that could appear to have influenced the submitted work.
Provenance and peer review: Not commissioned; externally peer reviewed.
Patient consent obtained.