What are the different types of abdominal hernias?

Types of Abdominal Hernias

Abdominal hernias are classified into three main categories: external (abdominal wall) hernias, internal hernias, and diaphragmatic hernias. 1

External/Abdominal Wall Hernias

These involve protrusion of abdominal contents through a defect in the abdominal wall 1:

Groin Hernias

• Inguinal hernias are the most common type of abdominal hernia, consistently representing the highest frequency across all time periods 2
• Femoral hernias have decreased in relative frequency over time, dropping from the second most common in the 1980s to the fifth most common by 2005-2008 2

Midline Hernias

The proportion of midline abdominal wall hernias has increased over time 2:

• Umbilical hernias are now the second most common type, representing the third most common abdominal hernia in adults 3
• Paraumbilical hernias are a subtype that occurs adjacent to the umbilicus and carry higher risk of complications including rupture, skin ulceration, and obstruction 3
• Epigastric hernias rank as the third most common, with 80% having a ring smaller than 25mm and 20% being multifocal 4

Other Abdominal Wall Hernias

• Incisional hernias occur at previous surgical sites and rank fourth in frequency 2
• Spigelian hernias are rare, with 90% located in the subumbilical region at the Monro line (semilunar line), and are asymptomatic in 90% of cases 4

Diaphragmatic Hernias

These involve protrusion of abdominal contents into the chest 1 and are classified as either congenital or acquired 5:

Congenital Diaphragmatic Hernias (CDH)

• Bochdalek hernia is the most common CDH (95%), occurring more commonly on the posterior left side of the diaphragm (85% left versus 15% right) 5
• CDH in adults has an incidence of 0.17% and presents at an average age of 40 years 5

Acquired Diaphragmatic Hernias (ADH)

These are categorized into three types 5:

Hiatal Hernias (classified into four types) 5:

• Type I (sliding hiatal hernia): Most common (90%), with migration of the gastroesophageal junction above the diaphragm
• Type II (paraesophageal): Accounts for 10%, with herniation of gastric fundus while gastroesophageal junction remains in normal position
• Type III: Combination of Type I and II
• Type IV: Large hernia accommodating additional viscera including stomach, colon, and spleen

Traumatic Diaphragmatic Hernias (TDH) 5:

• Occur in 2.1% of blunt trauma and 3.5% of penetrating trauma
• Penetrating trauma is the most frequent mechanism (65%), though defects are generally smaller than those from blunt trauma
• Left-sided injuries are more common (50-80% affect left hemidiaphragm, 12-40% right side, 1-9% bilateral) due to protective effect of the liver on the right side

Iatrogenic hernias: Result from surgical procedures 5

Internal Hernias

These involve protrusion of viscera through the peritoneum or mesentery into a compartment within the abdominal cavity 1. They are treated with prompt reduction, suture repair, and bowel resection if intestinal necrosis is present 5.

Current Frequency Ranking

The current relative frequency of hernia repair types is: inguinal, umbilical, epigastric, incisional, paraumbilical, femoral, and finally other rare types such as spigelian 2. This contrasts with traditional teaching that listed femoral hernias as more common than they currently are in clinical practice.