Inguinal canal and hernias
Inguinal canal, spermatic cord and hernias: inguinal, femoral and others
Inguinal canal, spermatic cord and abdominal wall hernias for FCPS Part 1: direct, indirect, femoral, incisional and lumbar. Learn each hernia's route and its relation to the inferior epigastric vessels and the pubic tubercle.
The canal and its rings
An oblique passage about 4 cm long through the lower abdominal wall, created as the testis descends, running downwards and medially above the medial half of the inguinal ligament.
- Deep ring: an opening in the transversalis fascia, about 1.5 cm above the mid-point of the inguinal ligament (halfway between ASIS and pubic tubercle), immediately lateral to the inferior epigastric vessels, which form its medial margin. The internal spermatic fascia is drawn out from its edges.
- Superficial ring: a triangular gap in the external oblique aponeurosis, above and lateral to the pubic tubercle.
| Wall | Formed by |
|---|---|
| Anterior | External oblique aponeurosis (whole length); internal oblique (lateral third) |
| Posterior | Transversalis fascia (whole length); conjoint tendon (medial third) |
| Roof | Arching fibres of internal oblique and transversus |
| Floor | Inguinal ligament, with the lacunar ligament medially |
The conjoint tendon (fused aponeuroses of internal oblique and transversus) strengthens the back wall exactly behind the superficial ring.
Contents
- Male: spermatic cord and the ilioinguinal nerve (lying on the cord, outside its coverings, leaving through the superficial ring).
- Female: round ligament of the uterus and the ilioinguinal nerve.
- The ilioinguinal nerve can be compressed by a hernia in the canal, causing groin pain radiating to the scrotum or labium, and can be cut or trapped in a repair (numb root of penis, anterior scrotum and upper medial thigh).
Spermatic cord
| Group | Structures |
|---|---|
| Coverings | External spermatic fascia (external oblique), cremasteric muscle and fascia (internal oblique), internal spermatic fascia (transversalis fascia) |
| Arteries | Testicular (aorta), cremasteric (inferior epigastric), artery to the vas (superior or inferior vesical) |
| Nerves | Genital branch of genitofemoral (cremaster), sympathetic fibres |
| Other | Vas deferens, pampiniform plexus, lymphatics (to para-aortic nodes), remnant of the processus vaginalis |
Hesselbach (inguinal) triangle
- Lateral: inferior epigastric vessels. Medial: lateral border of rectus abdominis (linea semilunaris). Inferior: inguinal ligament.
- Its floor is the posterior wall of the canal (transversalis fascia, conjoint tendon medially); direct hernias push through it.
Inguinal hernias
| Feature | Indirect | Direct |
|---|---|---|
| Route | Through the deep ring and along the canal, inside the coverings of the cord | Through the posterior wall in Hesselbach triangle |
| Relation to inferior epigastric vessels | Lateral | Medial |
| Cause | Patent processus vaginalis (congenital sac) | Weak posterior wall (acquired, older men) |
| Reaches the scrotum | Often | Rarely |
| Controlled by pressure over the deep ring | Yes | No |
| Strangulation | More likely (narrow neck at the deep ring) | Less likely (wide neck) |
- The indirect hernia is the commonest hernia in both sexes and at all ages; children's hernias are almost always indirect. When abdominal contents pass along the processus vaginalis, they acquire all three coverings of the cord.
- Heavy lifting in the gym raises intra-abdominal pressure, but an indirect hernia appears because a patent processus vaginalis was already present; lifting reveals it.
- Pantaloon hernia: direct and indirect sacs straddling the inferior epigastric vessels.
- Sliding hernia: a viscus forms part of the sac wall (sigmoid colon on the left, caecum on the right, bladder).
- Richter hernia: only part of the bowel wall is trapped, so it can strangulate without obstruction. Littre hernia: contains a Meckel diverticulum.
- Position: inguinal hernias emerge above and medial to the pubic tubercle; femoral hernias below and lateral to it.
Remember Indirect is lateral to the inferior epigastric vessels; direct is medial.
Femoral hernia
- Through the femoral ring and canal: inguinal ligament in front, pectineal ligament behind, lacunar ligament medially, femoral vein laterally.
- Commoner in women than in men, though inguinal hernias are still the commonest hernia in women. The rigid, narrow ring makes strangulation common, so repair is always advised.
- When the neck is widened medially through the lacunar ligament, an abnormal obturator artery may be cut; the femoral vein lies just lateral to the sac and can be injured when the neck is dissected or sutured.
Other abdominal wall hernias
| Hernia | Site | Points |
|---|---|---|
| Incisional | Through a previous scar | Swelling with cough impulse near a scar (for example after several caesarean sections); fascial closure failed |
| Umbilical and paraumbilical | At or beside the umbilicus | Infants: usually close by themselves; adults: paraumbilical, often strangulate |
| Epigastric | Linea alba between xiphoid and umbilicus | Extraperitoneal fat through a small defect; tender lump |
| Diastasis recti | Midline ridge on lifting the head | Not a true hernia: no fascial defect, no strangulation |
| Spigelian | Linea semilunaris, near the arcuate line | Lies under external oblique, so easily missed |
| Inferior lumbar (Petit) | Triangle of iliac crest (base), latissimus dorsi (behind) and external oblique (in front) | Soft reducible flank swelling with cough impulse just above the iliac crest |
| Superior lumbar (Grynfeltt) | Between the 12th rib, internal oblique and quadratus lumborum | Rarer |
| Obturator | Obturator canal | Elderly thin women; pain down the medial thigh to the knee |
The triangle of auscultation lies on the back of the chest (trapezius, latissimus dorsi, medial border of scapula) and is not a hernia site.
Repairs and nerves at risk
- Lichtenstein tension-free mesh repair is standard for open surgery; laparoscopic TEP and TAPP use the preperitoneal space.
- Nerves at risk: ilioinguinal (numb root of penis, scrotum and medial thigh), iliohypogastric, genital branch of genitofemoral.
- Triangle of doom (laparoscopic view): between the vas medially and the testicular vessels laterally, containing the external iliac vessels. Triangle of pain: lateral to the gonadal vessels and below the iliopubic tract, containing the lateral cutaneous nerve of the thigh and femoral branch of genitofemoral; staples here cause chronic pain.
Children
- A patent processus vaginalis gives an indirect hernia, a communicating hydrocele or a hydrocele of the cord.
- Treatment is herniotomy (ligation of the sac at the deep ring) without repairing the wall.
Exam trap The ilioinguinal nerve passes through the superficial ring but lies outside the coverings of the spermatic cord.
Exam trap The deep ring lies above the mid-point of the inguinal ligament; the femoral pulse lies at the mid-inguinal point.
How FCPS asks about this
- Walls of the inguinal canal: external oblique in front, transversalis fascia and conjoint tendon behind, arching fibres above, inguinal ligament below.
- Deep ring is an opening in: transversalis fascia, lateral to the inferior epigastric vessels.
- Indirect hernia cause and relation: patent processus vaginalis; lateral to the inferior epigastric vessels, inside the cord coverings.
- Medial border of Hesselbach triangle: lateral border of rectus abdominis.
- Pain of an indirect inguinal hernia: compression of the ilioinguinal nerve in the canal.
- Swelling near caesarean scars with cough impulse: incisional hernia; midline ridge without a defect is diastasis recti.
- Reducible flank swelling just above the iliac crest: inferior lumbar (Petit) triangle hernia.
Test yourself on this topic
5 of the 67 questions in our bank on this topic. Choose an answer to see why every option is right or wrong.
At open inguinal hernia repair, thin loops of muscle are seen covering the spermatic cord. This layer is derived from:
Answer: Internal oblique
The cord gains three coverings as it passes through the abdominal wall. The internal spermatic fascia comes from transversalis fascia at the deep ring, the cremaster muscle and fascia from internal oblique as the cord passes under its lower fibres, and the external spermatic fascia from external oblique aponeurosis at the superficial ring. Transversus abdominis arches over the canal without contributing a covering, and the dartos is part of the scrotal skin.
Cord coverings
- Internal spermatic: transversalis fascia
- Cremaster: internal oblique
- External spermatic: external oblique
- Transversus: no covering
Remember Each layer passed gives one coat, except transversus.
Exam trap Transversus abdominis gives no covering to the cord.
Why the other options are wrong
- External oblique Gives the external spermatic fascia.
- Transversus abdominis Contributes no layer to the cord.
- Rectus abdominis Not related to the cord.
- Dartos muscle Smooth muscle of the scrotal wall, not a cord covering.
While narrowing the femoral ring during femoral hernia repair, which structure lying immediately lateral to the ring must not be compressed?
Answer: Femoral vein
The femoral canal is the medial compartment of the femoral sheath. Its upper opening, the femoral ring, is bounded in front by the inguinal ligament, behind by the pectineal ligament, medially by the lacunar ligament and laterally by the femoral vein in its own compartment. Sutures placed to close the ring must avoid narrowing the femoral vein, which can cause venous obstruction or thrombosis. The femoral artery lies further lateral, and the femoral nerve is outside the sheath.
Femoral ring boundaries
- Anterior: inguinal ligament
- Posterior: pectineal ligament
- Medial: lacunar ligament
- Lateral: femoral vein
Remember From outside in: nerve, artery, vein, empty space.
Exam trap Tight sutures laterally narrow the femoral vein.
Why the other options are wrong
- Femoral artery Lies lateral to the vein, not next to the ring.
- Femoral nerve Lies outside the femoral sheath, most lateral.
- Lacunar ligament Forms the medial boundary.
- Great saphenous vein Joins the femoral vein lower down at the saphenous opening.
A 25-year-old labourer has a reducible right groin swelling. After it is reduced, firm finger pressure just above the midpoint of the inguinal ligament stops it reappearing when he coughs. What type of hernia is this most likely to be?
Answer: Indirect inguinal hernia
The deep inguinal ring lies about 1–2 cm above the midpoint of the inguinal ligament, just lateral to the inferior epigastric vessels. An indirect hernia leaves the abdomen through this ring, so pressure over it holds the hernia reduced on coughing. A direct hernia pushes through Hesselbach triangle, medial to this point, and still bulges. A femoral hernia emerges below the ligament, lateral to the pubic tubercle.
Deep ring occlusion test
- Deep ring: above midpoint of inguinal ligament
- Lateral to inferior epigastric vessels
- Controlled on coughing: indirect
- Bulges medially despite pressure: direct
Remember Block the deep ring: indirect stays in.
Exam trap The deep ring is above the midpoint of the inguinal ligament, not the mid-inguinal point used for the femoral artery.
Why the other options are wrong
- Direct inguinal hernia Comes through the posterior wall medially; not controlled.
- Femoral hernia Emerges below the inguinal ligament.
- Spigelian hernia Lies along the linea semilunaris, higher up.
- Obturator hernia Passes through the obturator canal; not palpable here.
An elderly woman has a small, firm, irreducible tender lump in the groin, below and lateral to the pubic tubercle, with vomiting and distension. Which of the following is the most likely diagnosis?
Answer: Strangulated femoral hernia
Femoral hernias are commonest in older women and emerge through the femoral canal below the inguinal ligament, below and lateral to the pubic tubercle. The narrow, rigid femoral ring (lacunar ligament medially) makes strangulation and obstruction more likely than with inguinal hernias, so they are repaired urgently. Richter's hernia, involving only part of the bowel wall, may cause strangulation without full obstruction.
Femoral hernia
- Older women
- Below and lateral to pubic tubercle
- Narrow ring: strangulates often
- Repair urgently
Remember Below and lateral: femoral, and fix it fast.
Exam trap An aberrant obturator artery may run on the lacunar ligament and bleed if cut.
Why the other options are wrong
- Indirect inguinal hernia Emerges above and medial to the pubic tubercle.
- Saphena varix Soft, compressible with a cough thrill; disappears on lying.
- Psoas abscess Lies lateral, with fever and hip flexion.
- Inguinal lymphadenitis Several tender nodes with a source of infection.
What are the boundaries of Hesselbach's (inguinal) triangle?
Answer: Epigastrics, rectus, inguinal ligament
Hesselbach's triangle is the area of the posterior wall of the inguinal canal through which direct hernias emerge: laterally the inferior epigastric vessels, medially the lateral border of rectus abdominis (rectus sheath), and inferiorly the inguinal ligament. Its floor is transversalis fascia, reinforced medially by the conjoint tendon. The femoral triangle is bounded by the inguinal ligament, sartorius and adductor longus. Calot's triangle is the cystohepatic triangle.
Hesselbach's triangle
- Lateral: inferior epigastric vessels
- Medial: rectus abdominis border
- Inferior: inguinal ligament
- Site of direct hernias
Remember RIP: Rectus, Inferior epigastric, Poupart's ligament.
Why the other options are wrong
- Inguinal ligament, sartorius, adductor Femoral triangle.
- Pubic tubercle, deep ring, conjoint Not correct.
- Linea alba, umbilicus, symphysis Not correct.
- Cystic duct, CHD, liver Calot's triangle.
Where this sits in the CPSP syllabus
- Paper 1: Abdomen, Inguinal canal, spermatic cord and hernias (inguinal, femoral)
- Surgery & Allied, Paper 2: Abdomen, Inguinal canal, spermatic cord and hernias (inguinal, femoral)