Fundamentally, a hernia is a hole. It is a hole in a barrier that allows things from one side of the barrier to get out and enter the other side of the barrier. A hole anywhere in the abdominal wall that allows contents from the inside of the abdomen to get out of the abdomen through that hole is a hernia. Think of your abdomen as a barrel. The spine and the muscles around the spine constitute the back wall of the barrel. The sidewalls of the barrel are made up of your abdominal muscles. This includes the rectus muscle (the six-pack muscle) and the oblique muscles, which wrap around the sides. The top of the barrel is the diaphragm, which separates the abdomen from the chest. The bottom of the barrel is the pelvic floor. Holes anywhere in this barrel can allow contents from the inside to get outside. And these can occur in multiple locations.
The hole in your diaphragm through which your esophagus passes is called the hiatus. When this becomes enlarged and portions of the abdomen such as the stomach slip through this into the chest, this is called a hiatal hernia. There are multiple potential holes that can occur in the groin. The most common is called an inguinal hernia. In men, this most commonly develops at the location where the blood vessels to the testicle exit the abdominal wall and travel down into the scrotum. It is also possible to develop a hole near the blood vessels that travel into your thigh. This is called a femoral hernia. There are multiple locations on the front of the abdominal wall where hernias can develop. A hole at the bellybutton, or umbilicus, is called an umbilical hernia. A hole in the midline between the umbilicus and the xiphoid process (the bottom of your breastbone) is called an epigastric hernia. Both umbilical and epigastric hernias are known as primary hernias, which means that they develop on their own and are not a result of an incision. Incisional hernias are holes that develop where previous abdominal incisions have failed to heal completely. Incisional hernias are a quite common type of hernia and can be particularly challenging to fix definitively.
The most common symptom of a hernia is pain.
It hurts when the herniated contents push through the abdominal wall. Life-threatening complications are thankfully rare and include intestinal obstruction and intestinal strangulation. When the intestines pass through a hernia opening, it is possible that they might get pinched off and cause an obstruction. This can lead to nausea and vomiting with abdominal distention and failure to pass gas and stool from below. If the intestines are pinched tight enough, their blood supply may be blocked, leading to strangulation and bowel death. Intestinal obstruction and strangulation occurs in less than 1% of hernias.
The odds of an excellent recovery are great.
A hernia is called reducible if it is possible to push the abdominal contents back into the abdomen through the hole. If it is not possible abdominal contents back into the abdomen through the whole, this is called incarcerated hernia. This is not the same as an obstructed or strangulation of hernia. Many incarcerated hernias include herniated intestine that is still healthy and works fine. Incarceration can occur for multiple reasons. Sometimes this is because the volume of herniated contents becomes too large for the size of the hole. Sometimes this is because the herniated contents have developed adhesions to the inside of the hernia sac outside of the abdominal wall, preventing them from going back in. A hernia sac is simply the inner lining of the abdominal wall that has ballooned out through the hernia opening and is now adherent to the fatty layer between the skin and the abdominal wall. Think of it as a windsock or a bubblegum bubble. When there are no adhesions, abdominal contents can slip from the abdominal sack up into the hernia sac, and back and forth depending on pressure.
Fundamentally, repairing a hernia involves returning the abdominal contents to their appropriate location inside the abdomen and closing the hole. Most of the time, closing the hole includes suturing the abdominal wall back together. The larger the hole, the more tension is necessary to sew it together. The greater the tension, the higher the likelihood that the tissues will not heal well and will pull apart, leading to hernia recurrence.
Larger hernias are often reinforced with mesh to prevent the tissues from pulling apart.