Aetiology of inguinal hernias
Although the main contributing factor causing inguinal hernias has yet to be defined, it is likely to be multifactorial. The integrity of the transversalis fascia, where there is a weakness of the abdominal wall due to changes in the components of the extracellular matrix, which promote a loss of resistance and elasticity of the transversalis fascia, as well as other fascial layers, is thought to contribute along with a congenital pathogenesis with the failure of the processus vaginalis to regress and peritoneal developmental defects.
These factors along with other predisposing factors such as an acquired weakness of the abdominal wall through surgery causing scaring, muscle wasting due to age and strenuous activities are also thought to be contributing factors. |
Increased intra-abdominal pressure can stretch the abdominal wall vertically and horizontally around the defect, increasing its size. This can be caused by a number of factors which include coughing, vomiting, pregnancy and childbirth, straining during urination and defecation, heavy lifting or straining, obesity and ascites.
Although the inguinal canals oblique direction and the mechanisms of the inguinal canal, such as the musculoaponeurotic arcades that descend during increased intra-abdominal pressure, aid in maintaining its integrity, if there is weakness from either a congenital or acquired defect the risk of developing an inguinal hernia is higher. |
Anatomical classification of inguinal hernias
Inguinal hernias are more common in males than females and this is thought to be related to the development of the gubernaculum, which thickens as it progresses through the abdominal wall as the testes descend. Subsequently this thickening increases the size of the superficial inguinal ring and weakens the wall resulting in a higher frequency of inguinal hernias in males.
The myopectineal orifice is a region of the antero-inferior abdominal wall and the site of all inguinal hernias, which are defined as a protrusion of the peritoneum and/or viscera through a weakened region of the abdominal wall into the inguinal canal.
The myopectoneal orifice is an anatomic defect, seen in Figure 17 (Moore et al. 2010) that superiorly allows the passage of the spermatic cord structures in males and the round ligament in females and inferiorly the femoral vessels.
Scroll over both the labels and the structures in the image below to highlight them and/or reveal where they are located. By clicking on various structures descriptions will appear under some areas.
The myopectoneal orifice is an anatomic defect, seen in Figure 17 (Moore et al. 2010) that superiorly allows the passage of the spermatic cord structures in males and the round ligament in females and inferiorly the femoral vessels.
Scroll over both the labels and the structures in the image below to highlight them and/or reveal where they are located. By clicking on various structures descriptions will appear under some areas.
Figure 17. Formation of inguinal region, adapted from (Moore et al. 2010: p. 202).
The myopectoneal orifice is covered by the transversalis fascia and split into two by the inguinal ligament. Subsequently it must be protected for a successful hernia repair. It consists of four boundaries:
Superiorly:
Internal oblique and transversus abdominis muscles
Inferiorly:
Cooper ligament and the pubis
Medially:
Rectus abdominis muscle
Laterally:
Iliopsoas muscle and the iliopectineal arch
Internal oblique and transversus abdominis muscles
Inferiorly:
Cooper ligament and the pubis
Medially:
Rectus abdominis muscle
Laterally:
Iliopsoas muscle and the iliopectineal arch
Anatomically inguinal hernias can be defined by their relationship to the inferior epigastric vessels, seen in Figure 18 (Drake et al. 2010) and subsequently are classified either as an:
Direct (acquired) inguinal hernia
OR
Indirect (congenital) inguinal hernia
OR
Indirect (congenital) inguinal hernia
Additional classifications for Indirect (congenital) inguinal hernias include, bubonocele, funicular and complete (or scrotal) respectively.