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The inguinal canal is a passage in the anterior abdominal wall that transmits structures from the pelvis to the perineum formed by the fetal migration of the gonad from the abdomen into the labioscrotal folds.
The inguinal canal has an oblique course, is 4 cm in length and has two openings:
- deep inguinal ring: a round opening in the transversalis fascia found 1 cm superior to the inguinal ligament and 1 cm lateral to the inferior epigastric arteries
- superficial inguinal ring: a V-shaped opening in the external oblique aponeurosis that is superior and lateral to the pubic tubercle (within Hesselbach's triangle) 1,2
Deep inguinal ring
The deep inguinal ring is bounded by the following:
- laterally by the angle between the transversus abdominis and inguinal ligament.
- medially lies the inferior epigastric vessels.
Older authors and texts refer to the deep ring as the abdominal inguinal ring.
Superficial inguinal ring
The superficial inguinal ring, as described, is an inverted 'V' shaped, triangular opening in the medial end of the external oblique aponeurosis, above and lateral to the pubic tubercle. The lateral arm of the 'V' is the lateral crus and its medial arm, the medial crus. The spermatic cord (in males)/round ligament (in females) overlies the pubic tubercle.
- lateral crus of the 'V' is attached to the pubic tubercle
- medial crus of the 'V' is attached to the pubic crest, near the symphysis.
- posterior crus arises from the attachment of the lateral crus, whereby some fibers (reflected part of the inguinal ligament) pass up behind the cord to attach to the rectus sheath, blending with fibers of the opposite side
Older authors and texts refer to the superficial ring as the subcutaneous inguinal ring.
The following structures contribute to the walls of the inguinal canal 1:
- superior wall (roof): internal oblique muscle and transversus abdominis muscle
- anterior wall: external oblique aponeurosis and internal oblique aponeurosis
- inferior wall (floor): inguinal ligament and lacunar ligament
- posterior wall: transversalis fascia and conjoint tendon
MALT is a mnemonic to recall this.
- males & females: ilioinguinal nerve1,2, genital branch of genitofemoral nerve
- males: spermatic cord (and contents)
- females: round ligament
- 1. Bhosale PR, Patnana M, Viswanathan C et-al. The inguinal canal: anatomy and imaging features of common and uncommon masses. Radiographics. 2008;28 (3): 819-35. Radiographics (full text) - doi:10.1148/rg.283075110 - Pubmed citation
- 2. Shadbolt CL, Heinze SB, Dietrich RB. Imaging of groin masses: inguinal anatomy and pathologic conditions revisited. Radiographics. 2001;21 Spec No: S261-71. Pubmed citation