Direct inguinal hernia

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• Direct inguinal hernias
• Direct inguinal herniation
• Direct inguinal herniae

A direct inguinal hernia (alternative plural: herniae) is a type of groin herniation, that arises from protrusion of abdominal viscera through a weakness of the posterior wall of the inguinal canal medial to the inferior epigastric vessels, specifically through Hesselbach's triangle.

This type of hernia is termed direct as the hernial sac directly protrudes through the inguinal wall, in contrast to indirect inguinal herniae which arise through the deep inguinal ring and enter the inguinal canal. Since direct hernias do not have a guiding path, they seldom extend into the scrotum unless very large and chronic.

On this page:

• Epidemiology
• Pathology
• Radiographic features
• Treatment and prognosis
• Differential diagnosis
• Related articles
• References

• Cases and figures

Epidemiology

Direct inguinal herniae are a common type of abdominal hernia.

Pathology

Direct hernias are generally acquired and increase in incidence with age. They result from weakening of the transversalis fascia in Hesselbach's triangle. Therefore, they are often seen in the elderly with chronic conditions which increase intra-abdominal pressure over a long period, e.g. COPD, bladder outflow obstruction, chronic constipation, etc. Increased abdominal pressure is transmitted to both sides and as a result, direct hernias are usually bilateral. Compared to indirect hernias, they are less susceptible to strangulation as they often have a wide neck.

Radiographic features

CT

A lateral crescent of fat (lateral crescent sign) is a useful diagnostic sign of direct inguinal hernia. Also, they occur anteromedial to the origin of the inferior epigastric artery 2 .

Ultrasound

High-frequency linear transducers are preferred for sonographic interrogation of inguinal structures due to the superficial nature of the structures of interest. Examination of the patient supine, standing, and during a Valsalva maneuver increases the sensitivity of the examination. With the transducer aligned parallel to the inguinal ligament, a cranial sweep should be performed to identify the inferior epigastric artery arising from the external iliac artery, which will serve as a sonographic landmark to differentiate inguinal hernias. The peritoneal stripe will be visualized just deep to the inferior epigastric artery. A direct inguinal hernia will be identified with the following sonographic features 5 :

• deformation of the peritoneal stripe medial to the inferior epigastric artery
  • primarily visible when intra-abdominal pressure is increased
  • identified as a redundant, tubular structure with lamellated walls
  • may contain hyperechoic fat
  • release of Valsalva or probe pressure should restore continuity of peritoneal stripe
  • bowel should demonstrate peristalsis
  • blood flow, as demonstrated by power Doppler, should be present
  • bowel wall should be

  Treatment and prognosis

  Treatment is surgical repair which consists of reduction of the sac and reinforcement of the posterior wall of the inguinal canal, usually with a synthetic mesh.

  Differential diagnosis

  • indirect inguinal hernia
    • herniates lateral and superior to the inferior epigastric vessels
    • does not displace the canal, instead seems to get into it
    • exit below the inguinal ligament and caudal to the emergence of the inferior epigastric vessels