Incisional hernia refer to abdominal wall hernia at the site of previous surgical incision. It is a type of ventral hernia. Midline incisional hernias are more common than other sites. It can be definite hernia with all the hernia components of defect, sac and content. Or, it can be a weakness of the wall with shallow sac and occasional bulge of content. It is a common surgical problem. Surgeons are often asked to evaluate patients with incisional hernias as they can often be symptomatic to patients. The classical presentation is a bulge with positive cough impulse at the site of incision. Complicated incisional. Patients with incisional hernias are also at risk for incarceration, obstruction (if the content is bowel), or strangulation. This article reviews assessment and management principles of incisional hernia.
Incisional hernias can occur after any abdominal surgical procedure where the abdominal wall is incised. Incisional hernia have also been reported after traumatic abdominal wall injuries. Incisional hernias develop because of failure of the abdominal wall to close properly. Despite advancements in techniques for abdominal wall closure the incisional hernia rate following laparotomy is as high 15% to 20%. Although research is ongoing for the ideal closure methods to prevent incisional hernias, and recent guidelines have been published, surgeons are still often faced with incisional hernias. Reasons of failure to close properly include: patients related factors, disease related factors, and technical factors.
- Patient related factors that impair proper wound healing and affect strength of the new tissue to support the abdominal wall increase the incidence of incisional hernia. Systemic chronic diseases like DM, renal failure, obesity, smoking, and malnutrition conditions; or systemic long term medications intake like steroids and immunosuppressant increase the likelihoods of developing incisional hernia. Morbid obesity is a common associated risk factor.
- Disease related factors including incision site, timing and urgency of procedure, complications, and the underlying disease play important role in the occurrence of incisional hernia. Emergency surgeries, midline incisions, infection, and acute abdominal surgeries are associated with a higher incidence of incisional hernia development. Wound infection in particular is a common associated risk factor with incisional hernia.
- Technical factors related to the surgical technique or suture materials used for closure. Poor surgical technique may result in acute wound dehiscence or delayed healing failure in the form of incisional hernia. When the fascial edges are not approximated side to side appropriately with using the appropriate strength and length of suture material incisional hernia is more likely to occur. Despite advancements in techniques for abdominal wall closure the incisional hernia rate following laparotomy is as high 15% to 20%. Although research is ongoing for the ideal closure methods to prevent incisional hernias, and recent guidelines have been published, surgeons are still often faced with incisional hernias.
The exact pathophysiologic mechanism for development for an incisional hernia is not clearly known. It is believed to be multifactorial. Associated factors like technical factors, including those relating to suturing techniques of the fascia, disease factors, and patient factors contribute to the occurrence of an incisional hernia. Intimate edge to edge fascial healing is necessary to provide the strength of fascia against the development of hernia. Presence of gaps between the two healing edges that will be filled with healing scar predispose for incisional hernia. These gaps or poor healing sites can be caused by the above risk factors in variable combination. Chronically increased intraabdominal pressure predisposes more weak areas to develop hernias.
Non-midline incisional hernias are less common. Pathophysiologically, improper healing in more than one layer of the abdominal wall is required before hernia can fully develop. Less obvious or not well defined hernias may develop from weakness in one layer of the three abdominal muscles. Recognizing and treating this entity might be challenging. But, they not predispose to the classical complications of incarceration, obstruction or strangulation.
Incisional hernias are often noticed as a protrusion of the abdominal wall at the site of incision from previous abdominal surgery. This is typically more pronounced with increase intraabdominal pressure. Symptoms can range from no symptoms to discomfort, pain of symptoms of complications like bowel obstruction and or strangulation. In most people, hernias limit patients' physical activities either due to the associated symptoms or as a precaution to avoid worsening.
Physical exam involves abdominal palpation. In most of the cases hernial content can be palpated. Occasional the edges of hernial defect can be felt and the size can be estimated. Planing for surgical approach can be discussed with the patient on that visit. Although most cases of an incisional hernia are diagnosed with a history and physical, imaging is sometimes warranted like in early stages, obese patients, or complex cases. Computed Tomography (CT) scanning focused on the abdominal wall is not only helpful to confirm the diagnosis when it is not clear, but helps in planning the surgical approach and extent of repair.
Occasionally small incisional hernias are identified intraoperatively when the patients undergo another abdominal surgery. Incisions made at the same scar site or laparoscopic approach may show the fascial defects with occasional fat incarceration.
History and physical exam will allow for diagnosis of incisional hernias in the vast majority of cases. In cases of occult hernias, either small incisional hernias or hernias in obese patients, further workup with imaging is warranted. The computed tomography (CT) scan is the most commonly used method to diagnose an incisional hernia and can be useful in complex cases as well in helping plan operative management. Ultrasound techniques have also been described for evaluation of abdominal wall hernias (Dynamic Ultrasonography Assessment for Hernia-DASH). MRI can also be used to assess abdominal wall hernias but are less commonly used and is institution dependent.
Complete evaluation of incisional hernias include confirming the diagnosis, sizing the defect, identifying the herniated content, and assessing the abdominal cavity to plan the surgical treatment in complex hernias. CT scan imaging is a useful to obtain these details.
Treatment strategies for an incisional hernia involve surgical repair or conservative nonoperative treatment. In this section, a general review of the treatment principles will be discussed. The decision to choose between the two options depends on a few factors like symptoms, the size of a hernia, complications and patients' preference. Small and asymptomatic hernias can be observed safely with a low risk of complication, 2.6% annually in some studies. Unless contraindicated, large or symptomatic hernias should be surgically repaired to avoid complications, relief symptoms, and improve quality of life.
Open, laparoscopic, and robotic techniques have been commonly used to repair incisional hernias and must be tailored to the patient and hernia characteristics. In general, the mesh should be used to repair the majority of incisional hernias as they reduce the rate of recurrence compared to primary suture repair. Mesh provides the strength for the repair and scaffold for the healing tissue. There are different options of mesh placement. Onlay (above the fascial defect), inlay (between the fascial edges), sublay (below the fascial defect but above the posterior rectus sheet), and underlay or Intraperitoneal onlay (intraperitoneally below the fascial defect).
Several different types of meshes are available. Meshes are characterized as permanent vs. absorbable, and synthetic vs. biologic. Permanent synthetic meshes are commonly used. Absorbable meshes are used in contaminated or infected field. Biologic meshes can be used for the same reasons when longer standing support is needed and for other special indications.
In general, the fascial closure should be performed when the defect is 10 cm or smaller, and the closure augmented with mesh. If fascial closure cannot be achieved secondary to tension, other techniques such as component separation have been used. Details of the surgical repair are discussed in other articles.
Natural history of incisional hernia is progressive enlargement over a variable time period. It can be asymptomatic or produce one or a combination of symptoms as discussed above. Possible complications include:
- Incarceration. Incarceration can be chronic nonsymptomatic as in large defect hernias, or acute and likely symptomatic incarceration. It can be reducible or irreducible, associated with other complications like obstruction or with no complication. In chronically incarcerated hernias, adhesions develop between the hernial content and the sac. While in acutely incarcerated hernias the small defect size the cause of the incarceration.
- Obstruction. Luminal obstruction of bowel is an acute complication that may lead to more serious complications like strangulation or perforation.
- Strangulation. Incarceration or obstruction can lead to strangulation, a more serious and acute complication. Strangulation should be relieved emergently.
Prevention of an incisional hernia is an important concept in abdominal surgery. There are several principles and recommendations that should can minimize the risk of incisional hernias. Some of these recommendations are: using slowly absorbing monofilament suture, suture to wound length ratio not less than 4:1 has been shown to decrease incisional hernia rates, prevention of infections, less tissue traumatic techniques, and optimizing patient postoperative care.
In some high-risk patients and cases, the incisional hernia rate is extremely high despite the adequate closure. Open abdominal aortic aneurysm (AAA) repair and formation of permanent colostomies are associated with high incisional/ parastomal hernia rates. Prophylactic mesh augmentation has been used in these cases.