Hernia · Free article
Groin anatomy for FRCS (Gen Surg): the walls and rings of the inguinal canal, direct, indirect and femoral hernias, the nerves at risk, and the laparoscopic triangles of doom and pain.
The inguinal canal is an oblique passage about 4 cm long above the medial half of the inguinal ligament. It carries the spermatic cord in men and the round ligament of the uterus in women, and the ilioinguinal nerve in both. Its obliquity, the shutter action of the internal oblique and transversus, and the strength of the posterior wall medially protect it against herniation.
| Wall | Formed by |
|---|---|
| Anterior | The external oblique aponeurosis, reinforced laterally by the internal oblique |
| Posterior | The transversalis fascia, reinforced medially by the conjoint tendon |
| Roof | The arching fibres of the internal oblique and transversus abdominis |
| Floor | The inguinal ligament, with the lacunar ligament medially |
The cord carries the vas deferens, the testicular artery, the artery to the vas and the cremasteric artery, the pampiniform plexus, the genital branch of the genitofemoral nerve, sympathetic fibres, lymphatics and the remnant of the processus vaginalis. It gathers three coverings as it passes through the abdominal wall: the internal spermatic fascia from the transversalis fascia, the cremasteric fascia and muscle from the internal oblique, and the external spermatic fascia from the external oblique. The ilioinguinal nerve runs on the cord, outside these coverings, and leaves through the superficial ring; it does not pass through the deep ring.
| Row | Indirect inguinal | Direct inguinal | Femoral |
|---|---|---|---|
| Route | Through the deep ring, within the cord | Through the posterior wall in Hesselbach’s triangle | Through the femoral canal, beneath the inguinal ligament |
| Relation to the inferior epigastric vessels | Lateral | Medial | Below and lateral to the pubic tubercle |
| Origin | A patent processus vaginalis | Weakness of the transversalis fascia | Widening of the femoral ring |
| Typical patient | Any age; the usual hernia of children | Older men | Older women, though inguinal hernias are still commoner in women |
Hesselbach’s triangle is bounded by the inferior epigastric vessels laterally, the lateral border of rectus abdominis medially and the inguinal ligament below. A pantaloon hernia has both components, straddling the vessels.
The femoral canal is the medial compartment of the femoral sheath. Its ring is bounded by the inguinal ligament in front, the pectineal (Cooper’s) ligament behind, the lacunar ligament medially and the femoral vein laterally. The rigid medial and anterior borders explain why femoral hernias strangulate, why they should be repaired promptly rather than watched, and why the lacunar ligament may have to be divided to reduce one — taking care of an abnormal obturator artery that can run across it.
Identifying and preserving these nerves, and avoiding entrapment by mesh fixation, is the main way to prevent chronic postoperative inguinal pain. The HerniaSurge guidelines recommend identifying all three in open repair, and pragmatic neurectomy of a nerve already at risk rather than routine division.
From inside, the landmarks are the inferior epigastric vessels, the medial umbilical ligament, the vas deferens running medially and the gonadal vessels laterally, converging on the deep ring. The iliopubic tract is the posterior counterpart of the inguinal ligament.
Test yourself
A fit 52-year-old woman has a symptomatic, reducible lump in the right groin. On examination it appears to be an inguinal hernia, and ultrasound reports a fat-containing groin hernia without specifying the type.
Which is the most appropriate repair?
By their relation to the inferior epigastric vessels: indirect hernias pass through the deep ring lateral to them, direct hernias through Hesselbach’s triangle medial to them. Clinical tests are unreliable; the distinction is made at operation or on imaging.
The inguinal ligament in front, the pectineal ligament behind, the lacunar ligament medially and the femoral vein laterally.
The ilioinguinal nerve, which runs on the spermatic cord in the canal and supplies the skin of the upper medial thigh and the root of the penis or labium majus.
In laparoscopic repair, the triangle between the vas deferens and the gonadal vessels, with its apex at the deep ring, containing the external iliac vessels.
Written for revision in the FRCS (Gen Surg) style under our editorial standards. It is not clinical advice: always confirm against current guidance. Spotted an error? Tell us.
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