Location of the Deep Inguinal Ring
The ring is situated in the inferior part of the fascia transversalis, which lines the internal surface of the transversus abdominis muscle, forms the posterior wall of the inguinal canal, and is fused with the parietal peritoneum.
From the abdominal cavity perspective, the deep ring corresponds to the lateral inguinal fossa (fossa inguinalis lateralis). This fossa is paired and lies lateral to the lateral umbilical fold. An important anatomical landmark is the inferior epigastric vessels (a. et v. epigastricae inferiores): the deep inguinal ring is located lateral to them.
Structure
The structure is an oval opening in the fascia transversalis measuring approximately 2.5–3.0 × 1.0–2.5 cm.
The margins of the ring are reinforced by fibers of the transversfascia. At the site of the internal opening of the inguinal canal, the transversalis fascia forms a funnel-shaped projection extending into the canal.
This marks the origin of the internal spermatic fascia (fascia spermatica interna), an extension of the fascia transversalis that covers the spermatic cord and testis.
Topography and Relation to the Inguinal Triangle
The inguinal canal runs obliquely from inferolateral to superomedial: from the superficial inguinal ring posteriorly, superiorly, and laterally to the deep inguinal ring.
The roof of the inguinal canal is formed by the arched inferior margins of the internal oblique and transversus abdominis muscles.
The degree of protection provided to the deep ring depends on the shape of the inguinal defect:
- Slit-like oval shape: The internal oblique muscle adequately covers the deep inguinal ring. Upon contraction, it acts as a valve mechanism, arching to compress the spermatic cord, providing strong protection against hernias.
- Triangular shape: The internal oblique muscle runs horizontally toward the rectus sheath; the posterior wall of the canal lacks muscular coverage for a large extent, and the valvular mechanism is absent, predisposing the area to indirect inguinal hernias.
Contents of the Deep Inguinal Ring
The contents of the inguinal canal vary by sex:
- In males: The spermatic cord (funiculus spermaticus). Its constituents include: the ductus deferens, testicular artery, pampiniform plexus of veins, cremasteric artery and vein, artery of the ductus deferens, lymphatic vessels, genital branch of the genitofemoral nerve, and sympathetic/parasympathetic fibers.
- In females: The round ligament of the uterus (lig. teres uteri) along with accompanying vessels and nerves.
Clinical Significance: Hernias and Surgery
The deep inguinal ring serves as the pathway for indirect inguinal hernias: a hernia enters through the deep ring, traverses the entire inguinal canal, and exits via the superficial ring. An indirect inguinal hernia lies within the spermatic cord, enclosed by the internal spermatic fascia, with cord elements closely applied to the hernia sac. It may descend into the scrotum in males or the labium majus in females.
Surgical considerations:
- When incising the deep ring during the repair of strangulated hernias, the surgeon must account for the medially located inferior epigastric vessels to avoid injury.
- During anterior inguinal hernia repairs, it is critical to reconstruct the ring without compressing the spermatic cord structures. Traditionally, a surgeon's little finger is inserted into the deep ring as a gauge before placing the final suture.
- In radical tissue repairs (e.g., Bassini or Postempski techniques), the deep inguinal ring may be surgically relocated, or the canal completely obliterated while transposing the spermatic cord into the subcutaneous tissue.