Direct inguinal hernia

An inguinal hernia is a protuberance of intra-abdominal tissue through the abdominal wall where it is weakened by the presence of the inguinal canal. There are two main types:

• indirect (75%) - these originate lateral to the inferior epigastric artery and follow the path of the spermatic cord or round ligament through the internal inguinal ring and along the inguinal canal
  
  
• direct (25%) - these originate medial to the inferior epigastric artery and push through a weakness in the posterior wall of the inguinal canal rather than down the canal itself

In both, the sac usually contains omentum or small bowel; less often, large bowel or appendix; and occasionally, diseased tissue - carcinoma, appendicitis, or peritoneal secondaries.

Notes:

• very small inguinal hernias which are difficult to diagnose on clinical examination are defined as 'occult inguinal hernias'
  • occult inguinal hernias are can often present with groin pain. However there are many causes of groin pain and therefore it is important to differentiate it from other causes. Occult inguinal hernias are often difficult to diagnose clinically from just history and examination and therefore there is a need for imaging prior to proceeding to surgery or further management
  • study evidence has shown that ultrasound to have a sensitivity of 94% in detection of 'occult inguinal hernias'. Ultrasound used with clinical judgment has a positive predictive value of 73% (1)

Reference:

• 1) Light D, Ratnasingham K, Banerjee A, Cadwallader R, Uzzaman MM, Gopinath B. The role of ultrasound scan in the diagnosis of occult inguinal hernias.Int J Surg. 2011;9(2):169-72. Epub 2010 Nov 5