56 HERNIAS
# 57 HERNIAS
What is a hernia?
A hernia is the abnormal protrusion of an organ or tissue through a defect in the wall that normally contains it — usually abdominal viscera (small bowel, omentum, pre-peritoneal fat) through a weakness in the abdominal wall.
Every hernia has a sac (peritoneum), contents, coverings, and a neck. The neck is the narrowest part — it determines strangulation risk. A tight, rigid-bordered neck cannot let bowel slip back and compresses the mesenteric vessels; this is why femoral and obturator hernias strangulate so readily and umbilical hernias rarely do.
Hernia terminology
| Term | Meaning |
|---|---|
| Reducible | Contents return to abdomen spontaneously or with gentle pressure — elective repair. |
| Irreducible (incarcerated) | Cannot be pushed back; no obstruction or ischaemia yet. |
| Obstructed | Bowel lumen blocked → colicky pain, vomiting, distension, constipation. |
| Strangulated | Blood supply compromised → tender tense erythematous lump, sepsis. Operate immediately. |
👩⚕️ Incarcerated ≠ strangulated. Incarcerated = stuck. Strangulated = stuck AND ischaemic. Every strangulated hernia is incarcerated; not every incarcerated hernia is strangulated.
The inguinal canal — the anatomy you must own
The inguinal canal is an oblique 4 cm passage in the lower anterior abdominal wall, running from the deep ring (lateral) to the superficial ring (medial). It transmits the spermatic cord (or round ligament in women) and the ilioinguinal nerve.
- Deep ring — at the mid-point of the inguinal ligament (halfway between ASIS and pubic tubercle); a defect in transversalis fascia; lies lateral to the inferior epigastric vessels.
- Superficial ring — a triangular split in the external oblique aponeurosis just above and medial to the pubic tubercle.
👩⚕️ Do not confuse the mid-point of the inguinal ligament (deep ring; ASIS → pubic tubercle) with the mid-inguinal point (femoral artery; ASIS → pubic symphysis). Same students, every year, lose this mark.
Walls of the inguinal canal
| Wall | Formed by |
|---|---|
| Anterior | External oblique aponeurosis (reinforced laterally by internal oblique) |
| Posterior | Transversalis fascia (reinforced medially by conjoint tendon) |
| Roof | Arching fibres of internal oblique & transversus abdominis |
| Floor | Inguinal ligament (medially, the lacunar ligament) |
The conjoint tendon is the fused aponeuroses of internal oblique + transversus abdominis inserting onto the pubic crest — it reinforces the posterior wall exactly where direct hernias try to push through.
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Inguinal hernias — direct vs indirect
Inguinal hernias account for ~75% of all abdominal wall hernias, two-thirds of which are indirect. Lifetime risk is ~27% in men vs 3% in women.
Indirect hernias pass through the deep ring → canal → superficial ring, lying lateral to the inferior epigastric vessels and following the cord. They may descend into the scrotum. Cause: patent processus vaginalis (congenital). Commoner in children and young men, but the commonest hernia at any age.
Direct hernias push forwards through a weakness in transversalis fascia within Hesselbach's triangle, medial to the inferior epigastrics. They do not traverse the deep ring and rarely enter the scrotum. Cause: acquired posterior wall weakness (chronic cough, BPH, constipation, heavy lifting). Typically older men.
Hesselbach's triangle: medial = lateral border of rectus; superolateral = inferior epigastric vessels; inferior = inguinal ligament.
Direct vs indirect — the comparison examiners expect
| Feature | Indirect | Direct |
|---|---|---|
| Aetiology | Congenital (patent processus vaginalis) | Acquired (weak transversalis fascia) |
| Relation to inferior epigastric vessels | Lateral | Medial |
| Passes through deep ring? | Yes | No |
| Path | Through canal, follows cord | Straight through posterior wall |
| Enters scrotum? | Often | Rarely |
| Age group | Any (commoner in young) | Older men |
| Cough impulse after reduction + finger on deep ring | Controlled (no bulge) | Not controlled (still bulges) |
| Strangulation risk | Higher (narrow neck at deep ring) | Lower (wide neck) |
👩⚕️ The deep-ring occlusion test. Reduce the hernia, press over the deep ring (mid-point of inguinal ligament), ask the patient to cough. If the hernia is controlled it is indirect; if it still bulges medially it is direct. Classic clinical exam question.
👩⚕️ Relative to the pubic tubercle: inguinal hernias emerge above and medial; femoral hernias emerge below and lateral. Use the pubic tubercle as your anatomical anchor at the bedside and in the exam.
Femoral hernia
A femoral hernia descends through the femoral canal — the medial, empty compartment of the femoral sheath — appearing below and lateral to the pubic tubercle.
From lateral to medial the femoral sheath contains: femoral Artery, femoral Vein, femoral Canal (mnemonic NAVY — femoral Nerve sits outside the sheath laterally). The canal contains fat and the node of Cloquet.
Femoral canal borders: anterior = inguinal ligament; posterior = pectineal (Cooper's) ligament; medial = lacunar ligament; lateral = femoral vein.
Femoral hernias are commoner in women (wider pelvis, larger canal — though inguinal hernias remain commonest overall in women too). They carry the highest strangulation risk of all groin hernias because three of the four borders are rigid ligaments — ~40% present as emergencies. Repair urgently, even when asymptomatic.
Inguinal vs femoral hernia
| Feature | Inguinal | Femoral |
|---|---|---|
| Position relative to pubic tubercle | Above and medial | Below and lateral |
| Sex predominance | Male | Female |
| Strangulation risk | Lower | High — urgent repair |
| Anatomical defect | Inguinal canal / Hesselbach's triangle | Femoral canal |
Other hernias you must recognise
- Umbilical — through the umbilical ring; congenital; common in Afro-Caribbean infants; most close spontaneously by age 2.
- Paraumbilical — through the linea alba beside the umbilicus; acquired in obese, multiparous women.
- Epigastric — through the linea alba between xiphoid and umbilicus; usually extra-peritoneal fat.
- Incisional — through a previous surgical scar (~10–15% after midline laparotomy).
- Hiatus — stomach through the oesophageal hiatus; sliding (95%) or rolling (5%) (Lesson 44).
- Spigelian — through the semilunar line below the arcuate line; rare; tunnels between muscle layers, easily missed, high strangulation risk.
- Obturator — through the obturator canal; the "little old lady's hernia". Classic feature is the Howship–Romberg sign — pain down the medial thigh from obturator nerve compression. Often presents only when obstructed.
- Richter's — only the antimesenteric border of bowel is pinched in the sac. The lumen stays patent, so the patient strangulates without obstruction.
- Littré's — sac contains a Meckel's diverticulum.
- Amyand's — sac contains the appendix.
- Maydl's — a W-shaped loop of bowel; the strangulated portion lies intra-abdominally between the two limbs in the sac.
- Sliding — a retroperitoneal organ (caecum, sigmoid, or bladder) forms part of the wall of the sac. Important because the bowel can be injured during sac excision.
👩⚕️ Eponym shortcuts:
- Richter's → Rim of bowel (antimesenteric)
- Littré's → L for Meckel's (think "L" for "lump in the ileum")
- Amyand's → Appendix
- Maydl's → W (two limbs in, one out)
Repair principles and complications
- Open mesh (Lichtenstein) — gold standard for adult inguinal hernias. Tension-free polypropylene mesh reinforces the posterior wall; recurrence ~1–2%.
- Laparoscopic — TEP (totally extraperitoneal) or TAPP (transabdominal preperitoneal); preferred for bilateral and recurrent hernias.
- Emergency — for obstruction or strangulation; assess bowel viability, resect if necrotic, avoid mesh in contamination.
- Femoral hernia approaches — Lockwood (low), Lotheissen (inguinal), McEvedy (high). McEvedy is favoured in emergencies because it gives the best access for bowel resection.
Complications: chronic groin pain (10–12%, usually ilioinguinal nerve injury — numb upper scrotum/root of penis or mons pubis/labia majora), recurrence, mesh infection, haematoma, seroma, urinary retention, ischaemic orchitis, vas deferens injury.
[Image: MCQs banner]
Test yourself
A 55-year-old woman presents with a painless, reducible groin swelling with a cough impulse but no thrill, sitting below the inguinal ligament. Diagnosis?
- ((Femoral hernia::☑️ Below and lateral to pubic tubercle; commoner in women; high strangulation risk.))
- ((Inguinal hernia::Lies above and medial to pubic tubercle.))
- ((Saphena varix::Soft, bluish, disappears on lying flat — has a venous thrill on coughing.))
- ((Femoral artery aneurysm::Pulsatile and expansile, often with a bruit.))
- ((Obturator hernia::Not externally palpable; presents with Howship–Romberg sign.))
👩⚕️ Use the pubic tubercle as your anatomical anchor: above-and-medial vs below-and-lateral decides the diagnosis.
What forms the posterior border of the femoral canal?
- ((Pectineal (Cooper's) ligament::☑️ Posterior border; anchor point used in McVay repair.))
- ((Inguinal ligament::Anterior border of the femoral canal.))
- ((Lacunar ligament::Medial border; the sharp edge that strangulates femoral hernias.))
- ((Femoral vein::Lateral border.))
Which structure lies immediately lateral to the neck of a femoral hernia, and is therefore at risk during repair?
- ((Femoral vein::☑️ Lateral border of the femoral canal.))
- ((Femoral artery::Lateral to the vein, outside the canal.))
- ((Lacunar ligament::Medial border of the canal.))
- ((Femoral nerve::Outside the femoral sheath altogether.))
Which structure forms the medial border of the femoral canal, accounting for its high strangulation risk?
- ((Lacunar ligament::☑️ Sharp, unyielding edge that strangles incarcerated bowel.))
- ((Pectineal ligament::Posterior border.))
- ((Inguinal ligament::Anterior border.))
- ((Femoral vein::Lateral border.))
Which hernia carries the highest risk of strangulation?
- ((Femoral hernia::☑️ Rigid borders around a narrow neck; ~40% present as emergencies.))
- ((Direct inguinal hernia::Wide neck through Hesselbach's triangle; low strangulation risk.))
- ((Indirect inguinal hernia::Higher risk than direct but lower than femoral.))
- ((Umbilical hernia (adult)::Wide neck; rarely strangulates.))
- ((Incisional hernia::Variable; usually wide-necked.))
👩⚕️ All femoral hernias should be repaired — even asymptomatic ones — because of strangulation risk.
Which structure forms the anterior wall of the inguinal canal?
- ((External oblique aponeurosis::☑️ Reinforced laterally by internal oblique; first layer opened in herniorrhaphy.))
- ((Transversalis fascia::Posterior wall.))
- ((Conjoint tendon::Reinforces posterior wall medially.))
- ((Inguinal ligament::Floor.))
The conjoint tendon is formed by the fusion of which two structures?
- ((Internal oblique and transversus abdominis aponeuroses::☑️ Inserts on pubic crest; reinforces posterior wall medially.))
- ((External oblique and internal oblique::External oblique forms the anterior wall and inguinal ligament, not the conjoint tendon.))
- ((Transversus abdominis and transversalis fascia::Fascia is not aponeurotic.))
- ((Rectus sheath and inguinal ligament::Anatomically unrelated.))
A direct inguinal hernia passes through which anatomical defect?
- ((Weakness in the transversalis fascia within Hesselbach's triangle::☑️ Pushes forwards medial to inferior epigastric vessels.))
- ((Deep inguinal ring::Site of indirect hernias.))
- ((Femoral canal::Site of femoral hernias.))
- ((Linea alba::Epigastric and paraumbilical hernias.))
What is the relationship of a direct inguinal hernia to the inferior epigastric vessels?
- ((Medial::☑️ Mnemonic: direct = medial; mid (Mid) = direct.))
- ((Lateral::This is the path of indirect hernias.))
- ((Anterior::Vessels lie deep to the hernia, not in front.))
- ((Posterior::Hernia bulges forwards through transversalis fascia.))
Which structure forms the lateral edge of the deep inguinal ring?
- ((Transversalis fascia::☑️ Deep ring is an opening in the transversalis fascia.))
- ((Inferior epigastric vessels::Form the medial border of the deep ring.))
- ((Inguinal ligament::Lies inferiorly, forming the floor of the canal.))
- ((Conjoint tendon::Reinforces the posterior wall medially.))
A 30-year-old man has an inguinal swelling that descends into the scrotum and lies lateral to the pubic tubercle. Most likely diagnosis?
- ((Indirect inguinal hernia::☑️ Passes through deep ring, follows the cord into the scrotum.))
- ((Direct inguinal hernia::Bulges forwards; rarely enters the scrotum.))
- ((Femoral hernia::Sits below and lateral to the pubic tubercle, not within the inguinal canal.))
- ((Hydrocele::Confined to the scrotum, transilluminates, no cough impulse to the abdomen.))
Which layer is the first to be incised when opening the inguinal canal during open herniorrhaphy (after skin and superficial fascia)?
- ((External oblique aponeurosis::☑️ Split along its fibres to expose the cord.))
- ((Internal oblique muscle::Lies deeper; forms part of the roof.))
- ((Conjoint tendon::Encountered medially at the posterior wall.))
- ((Transversalis fascia::Forms the posterior wall — deepest layer encountered.))
A 6-year-old boy presents with an intermittent scrotal swelling that appears on standing and disappears when he lies down. Most likely underlying cause?
- ((Patent processus vaginalis::☑️ Failure of obliteration → indirect hernia or communicating hydrocele.))
- ((Weakness of the transversalis fascia::Cause of direct hernia — exceedingly rare in children.))
- ((Patent urachus::Connects bladder to umbilicus; presents with umbilical discharge.))
- ((Cryptorchidism::Undescended testis, not a reducible swelling.))
Six months after open inguinal hernia repair, a 40-year-old man has persistent numbness over the upper scrotum, root of the penis and a small patch of medial thigh. Which nerve has most likely been injured?
- ((Ilioinguinal nerve (L1)::☑️ Supplies upper medial thigh, root of penis, anterior scrotum (or mons pubis and labia majora).))
- ((Iliohypogastric nerve::Supplies skin over the suprapubic region above the inguinal ligament.))
- ((Genitofemoral nerve (genital branch)::Supplies cremaster and a small area of scrotal skin; less commonly injured in open repair.))
- ((Femoral branch of genitofemoral nerve::Supplies a small area over the femoral triangle — not the scrotum.))
- ((Medial cutaneous nerve of thigh::Supplies medial thigh skin only, not scrotum or penis.))
👩⚕️ The ilioinguinal nerve runs on top of the spermatic cord inside the canal — it is the nerve most exposed to injury when the external oblique aponeurosis is opened.
An 82-year-old thin woman presents with small-bowel obstruction and pain radiating down the medial aspect of her right thigh to the knee. Most likely diagnosis?
- ((Obturator hernia::☑️ Howship–Romberg sign — obturator nerve compression by the hernial sac.))
- ((Femoral hernia::Palpable groin lump; no characteristic medial thigh pain.))
- ((Spigelian hernia::Through semilunar line; lateral lower abdominal wall, no thigh pain.))
- ((Direct inguinal hernia::Lump above the inguinal ligament; rarely obstructs.))
- ((Richter's hernia::Antimesenteric bowel pinched in sac; usually strangulates without obstruction.))
A patient with a small femoral hernia has localised tenderness and signs of strangulation, but no abdominal distension or vomiting. Which hernia type does this most likely represent?
- ((Richter's hernia::☑️ Antimesenteric knuckle of bowel — strangulates without luminal obstruction.))
- ((Littré's hernia::Sac contains a Meckel's diverticulum.))
- ((Maydl's hernia::W-shaped loop; strangulated portion lies intra-abdominally.))
- ((Amyand's hernia::Sac contains the appendix.))
- ((Sliding hernia::Viscus forms part of the wall of the sac, not a strangulation pattern.))
Revision summary
- Reducible → incarcerated → obstructed → strangulated. Incarcerated ≠ strangulated.
- Canal walls: anterior EO aponeurosis; posterior transversalis fascia + conjoint tendon; roof IO + TA; floor inguinal ligament.
- Deep ring — mid-point of inguinal ligament, lateral to inferior epigastrics. Superficial ring — above and medial to pubic tubercle.
- Indirect = lateral to inferior epigastrics, through deep ring, congenital (patent processus vaginalis), may enter scrotum.
- Direct = medial to inferior epigastrics, through Hesselbach's triangle, acquired.
- Inguinal = above and medial to pubic tubercle; femoral = below and lateral.
- Femoral canal: ant inguinal lig, post pectineal lig, med lacunar lig, lat femoral vein. Commoner in women, highest strangulation risk — always repair.
- Eponyms: Richter's (rim), Littré's (Meckel's), Amyand's (appendix), Maydl's (W-loop), Spigelian (semilunar line), obturator (Howship–Romberg).
- Repair: Lichtenstein open mesh; TEP/TAPP laparoscopic for bilateral/recurrent.
- Chronic post-op pain → ilioinguinal nerve (numb upper scrotum, root of penis, medial thigh).