Hernia Anatomy – The layers of the Abdominal Wall

The first concept to understand is the basic layers of the abdominal wall. These layers are a bit different between the umbilical region and the groin, but overall the basic layers are the same. From the outside to the inside is the skin, then a layer of fat. Underneath the fat is the layer of muscles which provide the strength to the abdominal wall. Under the muscles is a thin layer called peritoneum which serves as a barrier between the muscles and the internal organs which live underneath the peritoneum. 

Inguinal Hernia Anatomy

In inguinal or groin hernias a hole forms in the internal oblique and transversus muscles. If this hole forms lateral (or away from the middle) to the inferior epigastric blood vessels, an indirect inguinal hernia forms. If the hole forms medial (or towards the middle) to the inferior epigastric blood vessels, a direct inguinal hernia is formed. Regardless, in open surgery, the external oblique muscle layer is opened over the hernia (weakened internal and transversus muscle). The hole (or holes) in the internal oblique and the transversus muscle are found. A dual sided mesh is used to reinforce the hernia defect and the muscle around the hole.

The image below shows the anatomy of the inguinal region looking from the inside of the body outwards. This would be the view from inside the right groin. The right ‘indirect’ hernia is lateral or away from the middle of the patient. The left ‘direct’ hernia is medial or towards the middle compared to the inferior epigastric vessels.

Umbilical Hernia Anatomy

The CT image below shows a cross section of a patient. You can see a clear hole in the muscle at the level of the belly button, or umbilicus. This hole is considered an umbilical hernia. The image below shows a normal umbilicus with no evidence of a hole, or a hernia. Although CT scans can be helpful in determining whether there is a hernia, most often examining the patient is all that is needed to determine whether there is a hernia present.

Tension Vs. Tension-Free Hernia Repair

The term ‘tension’ or ‘tension-free’ is commonly used when describing a particular hernia surgery. Hernias are caused by a weakening of the abdominal muscles which over time develops into a true hole. For patients who desire a no mesh repair, the muscles surrounding the hernia defect are sewn back together to close the hernia. This pulling together of the muscles creates tension which his why primary (no mesh) repairs are considered ‘tension repairs’.

In many patients, whether due to the size of the hernia or the patient, it’s not advisable for a surgeon to simply pull the muscles back together. In those cases, most hernia specialists today utilize a mesh to help strengthen the muscles and the hernia repair. When using a mesh, the muscles themselves are often not sewn together limiting the tension on the tissues providing a ‘tension free’ repair. Instead, a mesh is placed over or under the hole in the muscle to prevent anything from pushing through the abdominal wall.

Mesh Versus No Mesh Hernia Repairs

While a no mesh hernia repair is an option for some patients, many others will strongly benefit from the use of a mesh. Some patients have heard or read negative information about mesh surgery. However, the unbiased government agency The National Institutes of Health performed a study of whether mesh should or should not be used for hernia surgery and found that in the vast majority of patients, a mesh is the recommended approach to repairing a hernia. They also found that in the right hands, the use of a mesh causes little if any additional risks to the patient. Read the article by clicking on the logo below:

Patients can read more on our ‘Truths About Hernia Mesh‘ page.

Our Approach

Our office specializes in the surgical repair for all hernia types. We provide patients with the full spectrum of treatment options from open no mesh hernia repairs to advanced minimally invasive laparoscopic techniques. Dr. Harris and our team perform over 500 hernia repairs each year making us the busiest center on the West Coast, and one of the top 3 in the country.

For over 10 years we have partnered with the Abdominal Core Health Quality Collaborative (ACHQC) to track the outcome of every surgery we perform. Year over year, our nationally leading outcome data shows a lower chance of hernia recurrence and a lower risk of developing chronic pain – data which we actively publish on our website. Our commitment to cutting edge hernia care, the full spectrum of surgical options, as well as research and transparency in our data, helps ensure you will have the best outcome after your hernia surgery.