Abdominal hernias

Definitions & Key takeaways

A hernia is a protrusion of an organ or part of it through a weakened area in the wall that normally holds it in place. Abdominal wall hernias are a protrusion of the abdominal content through a defect in the abdominal wall. There exist various types of abdominal wall hernia, but ventral hernias are more common than other types and occur when the intestine, bladder, or other abdominal organs push through the abdomen wall.

Symptoms may include pain, swelling, and a feeling of weakness or pressure in the abdomen, with some of the rare but serious complications being incarceration or strangulation of an organ, mostly the bowels. A doctor can usually diagnose a hernia by examining the area and may order additional tests if needed. Abdominal wall hernias are generally treated with surgical repair of the defect.

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Introduction0:00–0:33

Abdominal hernias, also called external hernias, are when an abdominal organ, or part of an abdominal organ protrudes through the abdominal wall, usually at a site of weakness.
They can be classified into midline hernias and groin hernias. Most frequent types of midline hernias are the epigastric and umbilical hernias, while groin hernias can further be classified into inguinal and femoral hernias.
There’s also incisional hernias, which is when contents herniate through an incisional scar from a previous abdominal surgeryNow, the abdominal wall is made up of a few layers.

Anatomy0:33–1:15

The deepest layer is the visceral peritoneum, which covers many of the abdominal organs and lines the peritoneal space. That layer wraps around to form the parietal peritoneum.
Then, moving externally, there is the extraperitoneal fat, the transversalis fascia, the muscle layer with the internal and external oblique and transversus abdominis aponeurosis and a layer of fascia which has different names in different regions.
Ok, so anything that increases the pressure of the abdominal cavity may result in a sac that forms in the abdominal wall through which organs might protrude.

Pathophysiology1:15–3:28

When organs protrude through the midline, that results in a midline hernia. Midline hernias include the epigastric hernia, which is when abdominal organs herniate through the linea alba, or the part of the midline between the xiphoid process and the umbilicus.
With umbilical hernias, on the other hand, the organ protrudes through the umbilicus. And then there’s groin hernias, which can be classified into inguinal hernias, the more common type, and femoral hernias.
With inguinal hernias, the contents of the abdominal cavity, usually fat or part of the small intestine, protrude through the inguinal canal.The inguinal canal lies between the muscles of the anterior abdominal wall.
The canal is bound superiorly by the internal oblique and transversus abdominis muscles, anteriorly by the external and internal oblique aponeurosis, inferiorly by the inguinal ligament, and posteriorly by the transversalis fascia and conjoint tendon.
Finally, the inguinal canal also has two openings: an internal one, called the deep inguinal ring, which is an orifice of the transversalis muscle fascia, located lateral to the inferior epigastric vessels, and an external one, called the superficial inguinal ring, which is an opening in the external oblique muscle aponeurosis.
Now, remember that the inguinal canal forms during embryological development. The process begins when a projection of peritoneum called the processus vaginalis herniates through the abdominal body wall, to allow the gonads, testes in males, and ovaries in females, to descend from the abdomen, where they formed, to their final location in the scrotum, or pelvis, respectively.
When the gonads have descended completely, the processus vaginalis is obliterated, closing off the tunnel. But even though both males and females have inguinal canals, since the testes have a longer journey ahead, this makes the inguinal canals larger and more prominent in males, creating a physiological site of weakness in the abdominal wall.
This makes inguinal hernias far more common in genetically male individuals, so we’re going to be referring to this population moving forward.
Now, inguinal hernias can be classified as indirect, or direct. Indirect inguinal hernias occur when the processus vaginalis fails to close during after the testes have passed through it, so this is considered a congenital hernia.

Indirect inguinal hernia3:28–4:13

Due to the congenital aspect associated with it, indirect inguinal hernia typically occurs in infants and children, but it can also be discovered in adulthood.
When the processus vaginalis remains open, intra-abdominal organs, like the intestines, can herniate through the inguinal canal.
Specifically, with indirect inguinal hernias, the organs herniate lateral to the inferior epigastric vessels, through the internal and external rings of the inguinal canal, and end up in the scrotum.On the other hand, direct inguinal hernias are acquired hernias that result from the weakening of the transversalis fascia.

Direct inguinal hernia4:13–5:14

And since the abdominal walls weaken with age, direct hernias tend to occur in the middle-aged and elderly population. Most commonly, the transversalis fascia weakens in the posterior wall of the inguinal canal, within a region called Hesselbach triangle, an area defined medially by the lateral border of rectus abdominis, superolaterally by the inferior epigastric vessels and inferiorly by the inguinal ligament.
A hernia through the Hesselbach triangle may occur as a result of an increased abdominal pressure, such as when doing some heavy lifting or coughing that leads to continuous overstretching of the musculoaponeurotic tissue.
Eventually, with continued pressure, an organ such as the small intestine may bulge directly through parietal peritoneum, medial to the inferior epigastric vessels and lateral to the rectus abdominis muscles, going through the external inguinal ring only.

Femoral hernia5:14–5:43

Now, femoral hernias, on the other hand, are a relatively uncommon type of hernias. They occur just below the inguinal ligament, when abdominal contents pass through the femoral canal.
The canal lies medial to the femoral vein and lateral to the lacunar, or Gimbernat ligament. Inside the femoral canal, there are lymphatic vessels that drain the deep inguinal lymph nodes, as well as a deep lymph node known as the lacunar node.Now, normally, the content of the hernia is confined within a hernial sac, which is a pouch of peritoneum that covers the herniating organ.

Complications5:43–6:26

In uncomplicated hernias, the content can be reduced back into the abdomen by pressing on the hernial sac. However, sometimes the contents can’t be pushed back inside the abdomen and it’s called incarceration since the contents are “locked out” of the abdomen.
This result in decreased venous and lymphatic flow and, as a consequence, edema and swelling of the incarcerated tissue.
Eventually, the tissue can swell so much that arterial blood flow to the hernial sac contents is cut off. This is called strangulation, and it leads to ischemia and tissue necrosis.Now for symptoms, small hernias can be asymptomatic, but larger hernias appear with pain and a visible, palpable bulge.

Symptoms6:26–6:50

Incarceration may also interrupt passage of contents through the intestines, causing symptoms of bowel obstruction like nausea, vomiting and fever.
With strangulation, there may also be redness, because blood is trapped in the hernial sac.Diagnosis is usually established based on physical exam findings.

Diagnosis and treatment6:50–7:18

Sometimes, like in individuals with obesity, imaging studies, like an ultrasound, can be helpful. The ultrasound helps visualize the hernial orifice and possibly the hernial contents.
A CT or MRI scan may also be done to rule out other possible diagnoses.The definitive treatment of all hernias, regardless of origin or type, is surgical repair.
Ok, quick recap: Abdominal hernias, also called external hernias, are when an abdominal organ, or part of an abdominal organ protrudes through the abdominal wall, usually at a site of weakness.

Review7:18–8:11

Groin hernias are the most common type of abdominal hernias, and inguinal hernias are the most common subtype of groin hernias.
Clinically, hernias usually appear as a visible bulge and depending on the complications, symptoms like fever or tenderness might be present.
The diagnosis is commonly based on medical history and physical exam. Surgery is usually the treatment option for most hernias.
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