A hernia develops when an internal organ or tissue pushes through an abnormal opening or weak spot in the surrounding muscle or tissue wall. This condition can occur in various parts of the body, often in the abdomen or groin. This article explores the distinct types of hernias based on their location and characteristics.
Common Abdominal Wall Hernias
Abdominal wall hernias are the most frequently encountered, often presenting as a noticeable bulge. The most common type is an inguinal hernia, accounting for nearly three-quarters of all hernias and affecting men more often than women. It develops in the groin area, near the inguinal canal, which in men houses the spermatic cord and in women supports the uterus.
There are two primary forms of inguinal hernias: direct and indirect. An indirect inguinal hernia enters the inguinal canal through its top, often resulting from a congenital defect where the opening to the canal does not fully close during fetal development. Conversely, a direct inguinal hernia pushes directly through the posterior wall of the inguinal canal, developing in adults over time due to weakened abdominal muscles and chronic pressure.
A femoral hernia is another type, found in the upper thigh just below the groin crease. Less common than inguinal hernias, representing about 3% of all hernias, it is more prevalent in women, partly due to the wider female pelvis. A femoral hernia can manifest as a bulge or lump in the groin or upper thigh and may cause lower abdominal pain.
An umbilical hernia occurs at or near the navel, or belly button, where abdominal tissue or a portion of the intestine protrudes through a weak spot in the abdominal muscles. This type is very common in newborns and infants, often resolving naturally by age five. It can also develop in adults due to increased abdominal pressure from factors such as obesity or multiple pregnancies.
An incisional hernia forms at the site of a previous surgical incision, in the abdomen, where weakened muscles or tissues allow internal organs or tissue to protrude. These hernias often appear within three to six months after abdominal surgery, though they can develop years later. Factors such as excessive physical activity too soon after surgery, significant weight gain, or increased abdominal pressure can contribute to their formation.
Diaphragmatic and Hiatal Hernias
Diaphragmatic hernias are distinct from abdominal wall hernias, involving the muscular barrier separating the chest and abdominal cavities. A hiatal hernia is a specific type where a portion of the stomach pushes up into the chest cavity through the esophageal hiatus, an opening in the diaphragm where the esophagus normally passes.
The most common form, accounting for about 95% of cases, is a sliding hiatal hernia, where the junction between the esophagus and stomach intermittently slides up into the chest through the widened hiatus. A less common but potentially more concerning type is the paraesophageal hiatal hernia, where a part of the stomach pushes up into the chest alongside the esophagus, while the esophageal junction remains in its normal position. This type can carry a higher risk of complications, such as the stomach becoming “strangled” or obstructed.
Another diaphragmatic hernia involves abdominal organs protruding into the chest through a defect in the diaphragm. These can be congenital, meaning present at birth, or acquired, often resulting from trauma. Congenital diaphragmatic hernias are more common and occur due to incomplete fusion of diaphragmatic structures during fetal development, leading to abdominal contents entering the thoracic cavity. Acquired diaphragmatic hernias, while rarer, result from significant blunt or penetrating injuries to the diaphragm.
Other Less Frequent Hernias
Other hernia types occur less frequently than abdominal wall or diaphragmatic hernias. An epigastric hernia appears in the midline of the upper abdomen, between the breastbone (sternum) and the navel. These hernias are often small and may not cause symptoms, though pain or a visible bulge can occur. They form when fatty tissue protrudes through a weak spot in the abdominal wall along the linea alba.
A Spigelian hernia is a rare type occurring along the semilunar line, a specific anatomical line on the lateral edge of the rectus abdominis muscle. Developing deep within the abdominal wall, this hernia can be challenging to diagnose clinically as a visible bulge may not be present. Spigelian hernias account for approximately 0.12% to 1% of all abdominal wall hernias.
An obturator hernia is an extremely rare type, accounting for 0.07% to 1% of all hernias. It protrudes through the obturator canal in the pelvis, an opening formed by the ischial and pubic bones for nerves and blood vessels. This type is more common in elderly, frail women, partly due to anatomical differences in the female pelvis and factors like multiple childbirths or significant weight loss. Diagnosing an obturator hernia can be difficult due to its hidden location and non-specific symptoms, which often include signs of bowel obstruction.