What is an inguinal hernia?

Inguinal Hernia

An inguinal hernia is a protrusion of intra-abdominal contents through a defect in the groin area, specifically through the inguinal canal, resulting from incomplete involution of the processus vaginalis or weakness in the abdominal wall. 1

Types and Anatomy

Inguinal hernias are classified into two main types:

• Indirect inguinal hernias: Result from a patent processus vaginalis and represent more than 90% of pediatric inguinal hernias in boys 2, 1
• Direct inguinal hernias: Occur through a weakness in the posterior wall of the inguinal canal

The embryology of inguinal hernias is closely related to testicular descent, which involves two phases:

• Intra-abdominal phase
• Extra-abdominal phase

During fetal development, the processus vaginalis (an outpouching of peritoneum) forms and normally obliterates after testicular descent. Failure of this obliteration can lead to inguinal hernia formation 2.

Epidemiology

• Incidence is approximately 3-5% in term infants 2
• Higher incidence (13%) in preterm infants born at less than 33 weeks gestational age 2
• More common in males than females 3
• Risk factors include:
  • Family history
  • Previous contralateral hernia
  • Male gender
  • Abnormal collagen metabolism
  • Prostatectomy
  • Low body mass index 4

Clinical Presentation

Inguinal hernias typically present as:

• A bulge or swelling in the groin area
• The bulge may increase with physical effort, straining, or crying
• May be associated with pain or discomfort
• Can be reducible (contents can be pushed back into abdomen) or irreducible

Diagnosis

In most cases, inguinal hernias can be diagnosed through physical examination alone 3. However:

• Ultrasonography is recommended as the first-line imaging when diagnosis is uncertain, with a sensitivity of 92.7% and specificity of 81.5% 1
• Ultrasound is particularly useful in:
  • Female patients
  • Suspected recurrent hernias
  • Evaluation of complications 1
• MRI has higher sensitivity and specificity than ultrasound and is useful for diagnosing occult hernias when clinical suspicion is high despite negative ultrasound findings 3

Common Pitfalls in Diagnosis

• Failing to distinguish between direct and indirect inguinal hernias 1
• Relying solely on physical examination in women and children, which can lead to missed diagnoses 1
• Overlooking femoral hernias, especially in women (femoral hernias have a higher risk of strangulation) 5
• Mistaking other groin masses (hydrocele, varicocele) for hernias 3

Management Considerations

The management of inguinal hernias depends on several factors:

• Symptomatic hernias: Should be treated surgically 4
• Asymptomatic or minimally symptomatic hernias in men: May be managed with "watchful waiting" since risk of hernia-related emergencies is low, though most will eventually require surgery 4
• Femoral hernias: Should be treated surgically as soon as diagnosis is made due to high risk of strangulation 5
• Pregnant women: Watchful waiting is suggested as groin swelling most often consists of self-limited round ligament varicosities 4

Surgical approaches include:

• Open repair (Lichtenstein technique is most common)
• Laparoscopic repair (TEP or TAPP techniques)

Laparoscopic repair is associated with:

• Shorter recovery time
• Earlier resumption of activities of daily living
• Less pain
• Potentially lower recurrence rates compared to open repair 6

However, surgical approach should be tailored to the surgeon's expertise, patient characteristics, and hernia-related factors 4.