An incisional hernia is the protrusion of the contents of a cavity (usually the abdomen) through a previously made incision in the compartment’s wall.
They occur (by definition) after an operation, and are an extremely common complication of abdominal surgery, with recent data reporting a prevalence after 1 year at 5.2% and 2 years of approximately 25%.
In this article, we shall look at the risk factors, clinical features and management of an incisional hernia.
The layers of the anterior abdominal wall are normally strong, and act to maintain the integrity of the abdominal cavity. However, once these layers are interrupted by a surgical incision, their continuity is disrupted and they are structurally weakened.
In the presence of increased intra-abdominal pressure and/or certain risk factors (such as smoking, infection or emergency surgery), the contents of the abdomen are able to herniate through the weakness, forming an incisional hernia.
As with any hernia, complications can occur, such as incarceration (hernia is irreducible), strangulation (blood supply to the hernia is compromised), or bowel obstruction.
The risk factors for incisional hernia following abdominal surgery include (ranked by relative risk):
- Emergency surgery
- Emergency surgery carries double the risk of elective surgery.
- Wound type
- BMI >25
- Obese patients are more likely to develop an incisional hernia
- Midline incision
- There is a 74% risk increase compared to non-midline
- Wound infection
- This increases incisional hernia risk by 68%.
- Pre-operative chemotherapy
- Intra-operative blood transfusion
- Advancing age
Other less common risk factors include chronic cough, diabetes mellitus, steroid therapy, smoking, and connective tissue disease.
The characteristic clinical feature of an incisional hernia is a non-pulsatile, reducible, soft and non-tender swelling at or near the site of a previous surgical wound.
If the hernia is incarcerated, it can become painful, tender, and erythematous. In cases of bowel obstruction, the patient may also present with symptoms of abdominal distention, vomiting, and/or absolute constipation.
On examination, a mass is palpable at or near the site of the surgical incision, which may be reducible (depending on its severity). Assess the patient for any signs of bowel ischaemia (strangulation), such as rebound tenderness or involuntary guarding.
A history of previous surgery with herniation at or near the site of incision is characteristic of an incisional hernia and leaves a very narrow differential diagnosis. Other causes of abdominal lumps, such as lipoma, should also be considered.
In most cases of incisional hernia, the diagnosis is made on a clinical basis, with no laboratory or imaging studies required (however any features of complications from the hernia should be investigated accordingly)
Ultrasound*or CT imaging can be used to investigate a hernia if the diagnosis is unclear, demonstrating the potential a fascial gap with protruding abdominal contents.
*The sonographer often requests the patient to cough or Valsalver while scanning to demonstrate this
The management of an incisional hernia should be considered on a case-by-case basis. The majority of incisional hernias are asymptomatic and can be managed conservatively.
Surgery is indicated in patients with painful hernias who are clinically fit enough for surgery. The size of the hernia, the clinical features, the patient’s age and co-morbidities, and the patient’s preferences should all be taken into account.
Incisional hernias can be repaired using a variety of techniques, including suture repair (for very small hernias), laparoscopic mesh repair, and open mesh repair.
The common complications of incisional hernia repair are pain (particularly after laparoscopic surgery due to the tacks used to hold the mesh in place), bowel injury and seroma formation (after open surgery; this may take several weeks or months to settle).
Many incisional hernias remain asymptomatic life-long; 6-15% of them will incarcerate and 2% will progress to strangulation.
Despite recent advances in techniques, recurrence rates remain high. They can be as high as 54% in suture repair and 36% in mesh repair, with an overall average at around 15%.
Chronic pain is a recognised but poorly understood complication of incisional hernia repair, affecting around 10-20% cases. It is thought to involve a combination of mesh inflammation, nerve damage and entrapment, and tension in the mesh.
- An incisional hernia is a hernia that occurs through a previously made incision in the abdominal wall
- Diagnosis is typically clinical, however imaging can help to confirm the diagnosis and elucidate the anatomy
- Management is decided on a case-by-case basis, however if suitable most patients will warrant surgical intervention