Abdominal wall hernias
Abdominal wall abnormalities and hernias
A hernia is a protrusion of a viscus through a defect in its containing wall; inguinal hernias are the commonest, femoral hernias carry the highest strangulation risk, and umbilical and incisional hernias have their own features. Knowing the anatomy of the inguinal canal and the indications for repair is essential.
Definitions
- Reducible (contents return to abdomen), irreducible (incarcerated) — cannot be reduced but blood supply intact, obstructed (bowel obstruction without ischaemia), strangulated (blood supply compromised, leading to ischaemia, gangrene — surgical emergency: tender, tense, red, irreducible, no cough impulse, systemic upset).
- Richter hernia: only part of the bowel wall (antimesenteric border) is trapped, so strangulation without obstruction (femoral and obturator hernias).
- Maydl hernia (W loop): two loops in sac, strangulated loop inside abdomen.
- Littre hernia: contains a Meckel diverticulum. Amyand hernia: contains the appendix (inguinal); de Garengeot: appendix in femoral hernia.
- Sliding hernia: a viscus (sigmoid, caecum, bladder) forms part of the sac wall — risk of injury during repair.
- Pantaloon hernia: combined direct and indirect.
Inguinal canal anatomy
- About 4 cm long, from deep ring (midpoint of the inguinal ligament, lateral to inferior epigastric vessels; defect in transversalis fascia) to superficial ring (above and medial to the pubic tubercle; defect in external oblique aponeurosis).
- Anterior wall: external oblique aponeurosis (+ internal oblique laterally). Posterior wall: transversalis fascia (+ conjoint tendon medially). Roof: arching fibres of internal oblique and transversus abdominis. Floor: inguinal ligament (+ lacunar ligament medially).
- Contents: spermatic cord (vas deferens, testicular artery, pampiniform plexus, artery to vas, cremasteric artery, genital branch of genitofemoral nerve, lymphatics, processus vaginalis remnant) or round ligament in women; ilioinguinal nerve (runs through canal but outside the cord — at risk in repair).
- Hesselbach triangle: inferior epigastric artery (lateral), lateral border of rectus abdominis (medial), inguinal ligament (inferior) — direct hernias arise here.
Indirect versus direct inguinal hernia
| Feature | Indirect | Direct |
|---|---|---|
| Frequency | Commonest hernia in both sexes (about two-thirds of inguinal) | One-third |
| Age | Any; children (patent processus vaginalis), young adults | Older men (weak posterior wall) |
| Route | Through deep ring, along canal, lateral to inferior epigastric vessels; can descend into scrotum | Through posterior wall (Hesselbach triangle), medial to inferior epigastric vessels; rarely into scrotum |
| Deep ring occlusion test | Controlled by pressure over the deep ring | Not controlled |
| Strangulation risk | Higher (narrow neck) | Lower (wide neck) |
| Bilateral | Less often | Often bilateral |
- The definitive distinction is made at operation (relation to inferior epigastric vessels).
- Inguinal hernia emerges above and medial to the pubic tubercle; femoral hernia below and lateral.
Femoral hernia
- Through the femoral canal (medial compartment of femoral sheath): boundaries — anterior: inguinal ligament, posterior: pectineal ligament (Cooper), medial: lacunar ligament (sharp edge — strangulation), lateral: femoral vein.
- More common in women (wider pelvis) — though inguinal hernia is still the commonest hernia in women; elderly, multiparous.
- Highest risk of strangulation (narrow rigid neck), so repair all femoral hernias promptly (urgent).
- Differentials of a groin lump: inguinal hernia, lymph node, saphena varix (cough thrill, disappears lying down, bluish), femoral artery aneurysm (expansile pulsation), psoas abscess (TB spine — lateral to femoral artery), ectopic/undescended testis, lipoma, hydrocele of cord/canal of Nuck.
- Repair: low (Lockwood — crural), high (McEvedy — for strangulation, allows bowel resection), inguinal (Lotheissen) approaches; laparoscopic.
Other hernias
| Hernia | Features |
|---|---|
| Umbilical (true, children) | Congenital defect at umbilical ring; common in black infants, prematurity, Down syndrome, hypothyroidism; most close spontaneously by 3–5 years — repair if persists beyond ~4–5 years or large |
| Paraumbilical (adults) | Through linea alba just above/below umbilicus; obese, multiparous women; narrow neck — strangulation risk, so repair (mesh) |
| Epigastric | Linea alba between xiphoid and umbilicus; small, extraperitoneal fat, painful |
| Incisional | At previous surgical scar (about 10–20% after laparotomy); risk factors — wound infection (strongest), obesity, poor technique, midline incisions, emergency surgery, steroids, malnutrition, smoking, raised intra-abdominal pressure, diabetes; wide neck usually, but can obstruct; repair with mesh (onlay, sublay — retromuscular, intraperitoneal, laparoscopic); suture-to-wound length ratio 4:1 small bites reduces risk |
| Spigelian | Through linea semilunaris at the arcuate line level, below umbilicus; interparietal (under external oblique) — hard to feel; ultrasound/CT |
| Obturator | Through obturator canal; elderly thin women; Howship–Romberg sign (pain down medial thigh — obturator nerve); presents with SBO (Richter); diagnosed on CT |
| Lumbar | Petit (inferior) and Grynfeltt (superior) triangles |
| Hiatus hernia | Sliding (commonest, GORD) and rolling (paraoesophageal — risk of volvulus/strangulation) |
| Parastomal | Common complication of stomas |
| Congenital diaphragmatic hernia | Bochdalek (posterolateral, left), Morgagni (anterior) |
| Gastroschisis/exomphalos | See embryology |
- Divarication (diastasis) of recti: separation of rectus muscles along linea alba (pregnancy, obesity) — ridge on straining; not a true hernia, no strangulation risk; reassure/physiotherapy.
Management of inguinal hernia
- Symptomatic hernias: elective repair; asymptomatic minimally symptomatic in men: watchful waiting acceptable (most become symptomatic).
- Children: herniotomy (ligation and excision of the sac — no mesh) promptly (high incarceration risk, especially in infants/prematurity).
- Adults: tension-free mesh repair — Lichtenstein open repair (commonest; polypropylene mesh) or laparoscopic (TEP — totally extraperitoneal; TAPP — transabdominal preperitoneal) — preferred for bilateral and recurrent (after open) hernias, women (detect femoral). Tissue repairs (Bassini, Shouldice) without mesh in contaminated fields or where mesh unavailable.
- Complications: haematoma/seroma, wound infection, urinary retention, chronic post-herniorrhaphy groin pain (ilioinguinal, iliohypogastric, genital branch of genitofemoral nerve), recurrence, testicular atrophy/ischaemic orchitis (pampiniform plexus thrombosis), vas injury, bladder/bowel injury (sliding hernia), mesh infection.
- Emergency: strangulated hernia: resuscitation, urgent surgery, assess bowel viability; avoid forceful reduction (taxis) of a possibly strangulated hernia (reduction-en-masse).
- Risk factors: male sex, age, chronic cough (COPD), constipation, prostatism/straining, heavy lifting, obesity, ascites, peritoneal dialysis, collagen disorders, family history, previous hernia, smoking — look for and treat causes of raised intra-abdominal pressure.
Scrotal swellings (related)
- Hydrocele: fluid in tunica vaginalis; transilluminates, can get above it, testis not separately palpable (surrounded); children — communicating (patent processus vaginalis; most resolve by 1–2 years; herniotomy if persisting); adults — idiopathic, or secondary to testicular tumour/infection/trauma (ultrasound to examine testis) — Jaboulay or Lord repair.
- Epididymal cyst/spermatocele: separate from and above/behind testis; transilluminates.
- Varicocele: "bag of worms", left side (left testicular vein drains into left renal vein at right angle); disappears lying down; subfertility; sudden left varicocele in older man suggests renal cell carcinoma.
- Inguinoscrotal hernia: cannot get above it, cough impulse.
How FCPS asks it
Recalls test: definitions (incarcerated, obstructed, strangulated, Richter, Littre, Amyand, sliding); inguinal canal walls, rings and contents; Hesselbach triangle; indirect versus direct (relation to inferior epigastric vessels, age, scrotal extension, deep ring occlusion); inguinal versus femoral relation to pubic tubercle; femoral canal boundaries and highest strangulation risk; umbilical hernia in children (wait until 4–5 years); paraumbilical in adults; incisional hernia risk factors (wound infection); Spigelian and obturator hernias (Howship–Romberg); divarication of recti; herniotomy in children; Lichtenstein versus laparoscopic repair (bilateral, recurrent); nerve injury causing chronic pain; groin lump differentials (saphena varix); hydrocele and varicocele features.
Exam trap Indirect inguinal hernias pass lateral to the inferior epigastric vessels; direct hernias pass medial (Hesselbach triangle).
Exam trap Femoral hernias have the highest strangulation risk — repair promptly.
Exam trap Children's umbilical hernias usually close by age 3–5; adult paraumbilical hernias need repair.
Test yourself on this topic
5 of the 21 questions in our bank on this topic. Choose an answer to see why every option is right or wrong.
Where does a Spigelian hernia occur?
Answer: Along the linea semilunaris
A Spigelian hernia passes through the Spigelian fascia, the aponeurosis between the lateral border of rectus abdominis (linea semilunaris) and the transversus abdominis muscle, usually below the umbilicus near the arcuate line. It often lies between the muscle layers under an intact external oblique aponeurosis (interparietal), so it is hard to feel. Ultrasound or CT helps diagnosis; the narrow neck carries a risk of strangulation.
Spigelian hernia
- Along linea semilunaris
- Below umbilicus, near arcuate line
- Interparietal, hard to feel
- Narrow neck: strangulation risk
Remember Lateral rectus edge, hidden hernia.
Exam trap Obturator hernias cause the Howship–Romberg sign (medial thigh pain).
Why the other options are wrong
- Through the umbilical ring Umbilical hernia.
- Through the lumbar triangle of Petit Lumbar hernia.
- Through the obturator canal Obturator hernia; medial thigh pain.
- Through the femoral ring Femoral hernia.
An 8-month-old boy has a soft, reducible umbilical swelling that bulges when he cries. Why is surgery usually not needed at this age?
Answer: The umbilical ring usually closes
Infantile umbilical hernias protrude through the umbilical ring, the opening where the umbilical vessels passed through the linea alba. After birth the ring continues to contract and the fascia strengthens, so most hernias close on their own within the first few years. Strangulation is rare because the ring is wide relative to its contents. Surgery is advised if the hernia persists beyond about 4 to 5 years or becomes very large.
Infantile umbilical hernia
- Through the umbilical ring
- Most close spontaneously
- Strangulation rare
- Repair if persisting beyond 4–5 years
Remember Infant umbilical hernia: wait and watch.
Exam trap Strapping the umbilicus with a coin does not help and can damage the skin.
Why the other options are wrong
- The sac contains only fluid It usually contains bowel or omentum.
- Strangulation cannot occur in infants Rare, but it can occur.
- The defect is in the rectus muscle The defect is in the umbilical ring of the linea alba.
- The swelling is a hydrocele of the cord A hydrocele of the cord lies in the groin, not the umbilicus.
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.
A 35-year-old man has a small, tender, irreducible lump in the midline halfway between the xiphoid and the umbilicus. At operation there is no peritoneal sac. What does the lump consist of?
Answer: Fat protruding through a linea alba defect
This is an epigastric hernia. Small defects occur in the linea alba above the umbilicus where it is crossed by small vessels, and extraperitoneal fat protrudes through them. Most contain only fat and have no peritoneal sac at first, though a sac can develop later. The fat can be nipped in the defect, so these small lumps are often tender and irreducible. Repair closes the defect in the linea alba.
Epigastric hernia
- Midline, xiphoid to umbilicus
- Defect in the linea alba
- Contains extraperitoneal fat
- Often no sac, tender
Remember A small tender upper midline lump is usually fat through the linea alba.
Exam trap Multiple small defects are common, so look for more at operation.
Why the other options are wrong
- Omentum in a paraumbilical hernia sac Lies at the umbilicus, with a peritoneal sac.
- Divarication of the rectus muscles A broad midline bulge, not a small tender lump.
- A lipoma of the rectus sheath Would not pass through a defect in the linea alba.
- A herniated loop of transverse colon Bowel in a small epigastric hernia is unusual, and it would have a sac.
Femoral hernias are much more common in women than in men, although inguinal hernias remain the commonest groin hernia in both sexes. What explains the female excess?
Answer: Wider pelvis with a larger femoral canal
The femoral canal is the medial compartment of the femoral sheath, lying medial to the femoral vein and bounded by the inguinal ligament in front, the pectineal ligament behind and the lacunar ligament medially. In women the wider pelvis makes the femoral ring and canal larger, and pregnancy stretches the surrounding tissues. This leaves more room for extraperitoneal fat and then a peritoneal sac to enter. The narrow, rigid ring makes these hernias likely to strangulate.
Femoral hernia in women
- Wider pelvis
- Larger femoral ring and canal
- Stretched by pregnancy
- Rigid ring: strangulation risk
Remember Wider pelvis, wider femoral canal.
Exam trap Even in women, an inguinal hernia is still more common than a femoral one.
Why the other options are wrong
- Absence of the inguinal canal in women Women have an inguinal canal containing the round ligament.
- Weaker conjoint tendon in women Not the reason for femoral hernias, which pass below the inguinal ligament.
- Larger deep inguinal ring in women The deep ring is smaller in women.
- Higher intra-abdominal pressure in women Intra-abdominal pressure is not generally higher in women.
Where this sits in the CPSP syllabus
- Surgery & Allied, Paper 2: Surgical conditions: pathology and investigation, Abdominal wall abnormalities and hernias