Ventral Hernias

What is a Ventral Hernia?

A Ventral Hernia is a defect in the innermost connective tissue layer of the anterior abdominal wall called the Transversus Abdominal Fascia. Understanding why hernias occur in this area requires an understanding of the anatomy of the anterior abdominal wall.    As you can see, the abdominal wall is composed of several layers which vary depending on how medial or lateral or cephalad or caudal one is on the abdominal wall . 

Keep those images open as I explain.

In the lateral abdominal wall, deep to the skin and subcutaneous fat, there are three muscle layers, each invested in front and behind with a layer of fascia.  From outside to inside these are: The external oblique muscle, whose fibers run obliquely down from lateral to medial, The internal oblique muscle, whose fibers run obliquely downward from medial to lateral, and finally the transversus abdominal muscle whose fibers run directly horizontal across the abdomen.  The innermost layer of fascia is the transversus abdominal fascia.  A defect in this layer is a hernia. 

As we approach the midline, the fascia of the internal oblique splits in two.  Half goes anteriorly and half goes posteriorly around the rectus abdominus muscle.  That's the one that gives you the six-pack if you do a thousand sit-ups a day. Above the arcuate line the fascia of the transversus abdominal muscle stays posterior to the rectus muscle; whereas below the arcuate line this fascia goes anterior to the rectus muscle.  Thus, below the arcuate line the innermost layer is composed only of peritoneum and a thin layer of fascia.  The significance of this will be explained shortly.

Finally, in the midline, all of these fascial layers coalesce into the very tough linea alba.  The umbilicus, which is the vestigial remnant of fetal circulation, penetrates the midline.  Hernias occur where there are natural or man-made defects in the abdominal wall or more specifically the transversus abdominal fascia. 

Thus; abdominal surgery, where an incision is made in the midline or elsewhere may result in an incisional hernia.  Not everybody who has had an abdominal operation gets a hernia.  In fact, very few do.  Risk factors for incisional hernia will be discussed later. 

Umbilical hernias occur in or around the umbilicus because the umbilicus creates an area of weakness in the midline. 

Epigastric hernias occur because the midline fascia above the umbilicus may become attenuated over time with the effects of gravity and the pressure from the internal organs particularly in obese people. 

Finally, Spigelian or Semilunar hernias occur across that natural area of weakness at the arcuate line where the internal most layer of fascia is made weaker because the transversus abdominus muscle passes anterior to the rectus abdominus muscle instead of posterior to it.  This line is located a few centimeters below the umbilicus and the hernia usually occurs just lateral to the rectus muscle. 

What are the risk factors for getting a ventral or incisional hernia?

Incisional hernias or hernias following surgery may occur for a variety of reasons.  These risk factors may be divided into patient related factors and surgery related factors.

Patient related risk factors include co-morbidities present in the patient undergoing surgery that may increase the risk for developing a hernia after surgery.  Diabetes, cigarette smoking, obesity and use of steroids all have negative influences on wound healing.  Cancer patients are at an increased risk for post-operative hernia development because of the inherent immunologic abnormalities seen in some cancers, as well as the possible effects of cancer treatments like chemotherapy or radiation treatment.  Other chronic conditions such as asthma, Chronic Obstructive Pulmonary Disease (COPD), and other conditions which may increase intra-abdominal pressure may result in incisional hernia should a patient with one of these conditions require surgery.  Certainly patients with any connective tissue disorder or Collagen-Vascular diseases are at an increased risk of hernia development as these conditions all negatively impact wound healing.  Opiate pain medications all may slow down GI tract motility and cause constipation and abdominal distension and increased intra-abdominal pressure.  Over time this may result in hernia formation.  Finally, the patient's nutritional status can have profound effects on wound healing.  Malnourished patients with a depressed serum albumin may heal slowly and poorly.  This can have an obvious detrimental impact on the development of abdominal wall hernia after surgery.
 

Surgery related risk factors include such things as the nature of the underlying surgery.  Hernia development after elective surgery is far less common than after emergency surgery for conditions such as major trauma, severe infection or massive bleeding.  Surgical conditions that involve elements such as these are often associated with massive tissue swelling which may increase tension across a wound, infection which may directly break down a wound or significant anemia from surgical blood loss may decrease oxygen supply to a healing wound.  Major abdominal surgery often results in ileus which may exert pressure on the abdominal wall and wound.  The metabolic consequences of massive trauma or severe infection may also lead to diminished oxygen supply to a healing wound which later results in a hernia.  Certainly all attempts should be made to avoid closing an abdominal wound under tension, but at times this is unavoidable.  Hernia development after elective surgery may still occur in spite of all precautions to avoid tension in a wound if any or several of the patient factors mentioned are present.

Non-surgical ventral hernias such as epigastric, spigelian or umbilical hernias may occur through those natural areas of weakness already mentioned particularly if there are patient factors present.  In general, development of these hernias is related to intra-abdominal pressure, or gravity exerted against those natural weak spots over time. 

What are the Complications of a Ventral or Incisional Hernia?

As with inguinal and femoral hernias, the main risk that concerns us with ventral and incisional hernias is incarceration or entrapment of internal organs within the hernia.  Some will say that a large hernia has a lower risk of incarceration because there is more room for the organ in question to come and go.  While there is some truth to that I have seen many large hernias with incarceration of intestine occur.  What happens is that a large loop of intestine passes into the hernia but then within that loop a smaller cavity is created which then entraps another loop of intestine.  Incarceration of an organ within a hernia may result in strangulation.  In this situation, the blood supply to the organ (usually intestine) is cut off and that organ may become gangrenous. 

Even without incarceration, hernias may cause pain.  Often there are adhesions or scars that develop between the hernia sack and the intestine.  These adhesions may cause pain or may interfere with the normal function of the gastro-intestinal tract, even causing symptoms of obstruction. 

Finally, even patients without any of these complications, are simply unhappy with the cosmetic deformity in their abdominal wall resulting from the hernia.  In some cases the bulge can be quite large and may affect how they wear clothing.  Umbilical hernias may cause attenuation of the skin which may actually ulcerate and bleed.  This can be quite painful.  Attenuation of the linea alba in the midline above the umbilicus may cause a bulge which is not a true hernia.  Though the fascia is attenuated there is no defect and no risk of incarceration of abdominal organs. Here the issue is purely cosmetic yet many patients may seek repair of this abnormality.

What are the surgical options for ventral or incisional hernia repair?

If there were one perfect way of performing a surgical procedure that worked for every patient every time with every surgeon then there would be only one way of doing said procedure.  Nothing could be further from the truth when it comes to ventral hernia surgery.  There are several options that may be utilized depending on location of the hernia, size of the hernia, size and body type of the patient and of course, surgical expertise.  The development of newer mesh materials has also expanded the ability to repair complex hernias even under the most challenging of situations.  I will discuss all of these in the article entitled Surgical Options in the Repair of Ventral and Incisional Hernias.

I hope that I have answered most of the questions that you may have had, without adding to your confusion. As always, I welcome questions or comments.

Steven P. Shikiar, MD, FACS email