Hernia & Abdominal Wall

A hernia is the protrusion of a viscus, or part of one, through a defect in the wall of the cavity that normally contains it.

Candidates lose marks in this chapter by learning long lists of named hernias and then being asked a management question they cannot answer. The examination is rarely testing whether you can name a Littre hernia. It is testing whether you know which hernia will kill the patient this week.

The organising tool is this: the neck decides the danger, not the size. A narrow neck permits the contents to enter but not to return, and once they cannot return, venous drainage fails and strangulation follows.

That is why a femoral hernia the size of a grape is more dangerous than an inguinoscrotal hernia the size of a melon.

1. The Parts of a Hernia

Every hernia has three components, and the vocabulary of the subject depends on them.

The sac is the peritoneal outpouching, with a mouth, a neck, a body and a fundus. The coverings are the layers of abdominal wall the sac has pushed in front of it. The contents are whatever has entered the sac.

The terms describing behaviour are worth defining precisely, because examiners use them exactly.

Richter hernia is the trap in that table. Only part of the circumference of the bowel wall is caught in the defect, so the lumen remains patent. The patient strangulates without ever obstructing, passes stool normally, and presents late with dead bowel and no distension.

Littre hernia contains a Meckel diverticulum, and Maydl hernia contains a W-shaped loop in which the strangulated segment lies inside the abdomen rather than in the sac.

Sliding hernia is a distinct concept: part of the sac wall is formed by a retroperitoneal viscus, usually caecum on the right or sigmoid colon on the left. It matters because dissecting the sac blindly risks opening the bowel.

2. Why the Neck Decides

Constriction at a narrow neck first obstructs venous return, because veins are thin-walled and collapse at lower pressure than arteries.

Venous obstruction with continued arterial inflow produces engorgement, then oedema, which tightens the neck further. This is a self-reinforcing loop, and it explains why strangulation progresses quickly once it begins.

Arterial supply fails last, so a strangulating hernia is exquisitely tender and dusky before it is pulseless, and waiting for signs of infarction means waiting too long.

The clinical signs of strangulation are a tense, tender, irreducible lump that has lost its cough impulse, with overlying skin changes, and systemic features of tachycardia, fever and eventually peritonitis.

A strangulated hernia is never reduced manually, because reducing dead bowel into the peritoneal cavity converts a treatable emergency into peritonitis with no visible source.

Femoral hernias strangulate most often because the femoral ring is bounded by the inguinal ligament in front, the pectineal ligament behind, the lacunar ligament medially and the femoral vein laterally, three of which are unyielding.

3. The Inguinal Canal

The canal runs from the deep to the superficial ring, transmitting the spermatic cord in men and the round ligament in women. Its boundaries are examined directly and are worth learning as a set.

The reinforcement pattern is not arbitrary. The anterior wall is strongest laterally, exactly where the deep ring lies, and the posterior wall is strongest medially, exactly where the superficial ring lies, so each ring is backed by strength on the opposite side.

Hesselbach triangle is bounded by the inferior epigastric vessels laterally, the rectus sheath medially and the inguinal ligament inferiorly. A hernia pushing through it is direct.

4. Indirect Against Direct

The distinction rests entirely on the relationship to the inferior epigastric vessels.

The deep ring occlusion test follows directly from the anatomy. Pressure over the deep ring, a finger's breadth above the midpoint of the inguinal ligament, blocks the route of an indirect hernia but not that of a direct one, which emerges medial to it.

The test is unreliable in practice and the distinction is frequently only made at operation, but the reasoning is examined.

Clinically, an indirect hernia descends obliquely and may reach the scrotum; a direct hernia bulges forwards through the posterior wall and rarely does.

Distinguishing an inguinal from a femoral hernia is more important than distinguishing indirect from direct, because it changes the urgency rather than only the operation.

An inguinal hernia emerges above and medial to the pubic tubercle; a femoral hernia emerges below and lateral to it. Femoral hernias are commoner in women, though inguinal hernias remain the commonest hernia in women too.

5. Repair

Watchful waiting is safe for asymptomatic or minimally symptomatic inguinal hernias in men, on high-quality evidence, though most patients eventually come to surgery because symptoms develop.

That position does not extend to femoral hernias, which are repaired promptly whether or not they are symptomatic, because of their strangulation risk.

Mesh repair is the standard of care, because tissue repairs recur substantially more often. The mesh works by inducing fibrosis that reinforces the posterior wall rather than by relying on sutured tension.

The Lichtenstein tension-free open mesh repair is the recommended open technique and remains the reference operation worldwide. Open preperitoneal mesh techniques are now accepted alternatives where the expertise exists.

Laparoscopic repair, whether totally extraperitoneal or transabdominal preperitoneal, gives comparable recurrence rates with less chronic pain and faster return to work, at the cost of a longer learning curve and general anaesthesia.

Laparoscopic repair is particularly favoured for bilateral and recurrent hernias, and for a recurrence after open repair it avoids operating through scarred tissue.

In low-resource settings the recommended approach is high-volume standardised Lichtenstein repair under local anaesthesia with a low-cost mesh, which is directly relevant to Indian practice.

Tissue repairs retain a role where mesh is contraindicated, principally in a contaminated field with dead bowel. The Bassini and Shouldice repairs belong here, with Shouldice giving the best results of the non-mesh operations.

6. Groin Swellings and the Child

Not every groin lump is a hernia, and two bedside questions separate most of them.

Can you get above the swelling? If you can, the lesion is confined to the scrotum and is not a hernia, because a hernia is continuous with the inguinal canal. If you cannot, the swelling arises from the canal.

Does it transilluminate? A hydrocele contains clear fluid and transilluminates brilliantly; a hernia containing bowel does not, although it may transmit a cough impulse and gurgle on reduction.

The remaining common causes are lymph nodes, which are multiple and do not extend into the canal, a saphena varix, which is soft, has a fluid thrill on coughing and disappears on lying down, and a femoral artery aneurysm, which is expansile.

Paediatric inguinal hernia has a different mechanism and a different operation. It is almost always indirect, arising from a patent processus vaginalis that failed to obliterate, so the defect is a persistent congenital tract rather than an acquired weakness.

The repair is therefore herniotomy alone, meaning high ligation and excision of the sac. No mesh and no wall reconstruction are used, because the abdominal wall itself is normal.

Infant hernias are repaired promptly rather than watched, since the risk of incarceration is highest in the first year of life and the tissues tolerate obstruction poorly.

A communicating hydrocele in a child shares the same cause, a patent processus that is too narrow to admit bowel, and it is treated in the same way if it persists beyond about two years.

7. Hiatus Hernia

Herniation of the stomach through the oesophageal hiatus of the diaphragm is conventionally grouped with abdominal wall hernias, although the mechanics are quite different.

A sliding hiatus hernia accounts for the great majority. The gastro-oesophageal junction itself moves up into the chest, disrupting the antireflux mechanism, so the presentation is gastro-oesophageal reflux and the treatment is medical in most patients.

A rolling or paraoesophageal hernia is the dangerous one. The junction stays in place while the fundus rolls up alongside the oesophagus, so reflux may be absent, but the herniated stomach can volvulate, obstruct and strangulate.

That difference reverses the management. A sliding hernia is treated for its symptoms; a paraoesophageal hernia is considered for repair on anatomical grounds even in a relatively well patient, because the complication it risks is catastrophic.

Surgical repair, usually laparoscopic, involves reducing the stomach, excising the sac, closing the crura and adding a fundoplication.

8. Complications of Repair

Recurrence rates are low with mesh but never zero, and recurrence after a mesh repair is usually medial, at the pubic tubercle, where fixation is most difficult.

Chronic groin pain is now a more common problem than recurrence, affecting a meaningful minority of patients, and it may be neuropathic from nerve entrapment or nociceptive from the mesh itself.

Three nerves are at risk and each has a recognisable sensory territory: the ilioinguinal, the iliohypogastric and the genital branch of the genitofemoral nerve.

Ischaemic orchitis follows thrombosis of the pampiniform plexus, presenting with a painful swollen testis in the first days, and testicular atrophy may follow. It is commoner after repair of a recurrent or large inguinoscrotal hernia.

Seroma and haematoma are common and usually self-limiting. Mesh infection is uncommon but difficult, often requiring mesh removal.

Urinary retention is frequent, particularly in older men after general or spinal anaesthesia.

9. Ventral and Other Hernias

Umbilical hernia in infants is common, usually closes spontaneously by about four years, and is repaired only if it persists, becomes very large or complicates.

Paraumbilical hernia in adults is a separate condition, occurring through the linea alba adjacent to the umbilicus, with a narrow fibrous neck that makes strangulation relatively likely. It does not close spontaneously.

Epigastric hernia passes through the linea alba above the umbilicus, is often small, and typically contains only extraperitoneal fat, which is why it can be disproportionately painful.

Incisional hernia follows a failure of the abdominal wall closure to heal, and its risk factors are the reasons wounds fail: wound infection, obesity, diabetes, corticosteroids, chronic cough, malnutrition and poor surgical technique.

It is the commonest hernia complicating surgery, and repair is by mesh, increasingly laparoscopically, with recurrence far commoner than after groin hernia repair.

Spigelian hernia occurs through the semilunar line at the lateral border of rectus abdominis, usually below the arcuate line where the posterior rectus sheath is deficient. It lies deep to the intact external oblique, so it is easily missed clinically and often needs imaging.

Obturator hernia is the classic hernia of the thin elderly woman, presenting as bowel obstruction with no visible lump, and the Howship-Romberg sign of pain along the inner thigh from obturator nerve compression.

Lumbar hernias occur through the superior triangle of Grynfeltt or the inferior triangle of Petit, and a parastomal hernia is an incisional hernia at the site where a stoma passes through the abdominal wall.

Divarication of the recti is not a hernia and must not be repaired as one. The linea alba is stretched and thinned so the muscle bellies separate, producing a midline ridge on sitting up, but the fascia is intact and there is no defect through which bowel can pass.

Because there is no neck, there is no risk of strangulation, and the appropriate management is reassurance and abdominal wall exercise rather than mesh.

Rectus sheath haematoma is the other abdominal wall lump that mimics a hernia. It follows rupture of the inferior epigastric vessels after coughing or minor trauma, typically in an anticoagulated patient, and gives a tender mass that becomes more prominent on tensing the abdominal wall while an intra-abdominal mass becomes less so.

10. Managing the Emergency

An irreducible hernia with obstruction and no signs of strangulation may be treated with gentle taxis after adequate analgesia, though this is increasingly avoided.

Strangulation forbids reduction entirely. The specific danger is reduction en masse, in which the sac and its constricted contents are pushed into the abdomen together, so the lump disappears while the bowel remains strangulated inside.

Operation proceeds after resuscitation. The sac is opened, the contents inspected, and viability assessed by colour, peristalsis and mesenteric pulsation after warming with saline-soaked packs.

Non-viable bowel is resected. Mesh is avoided in a contaminated field, so a tissue repair is used where bowel has been resected.

The constricting agent must be released before the bowel is examined, and in a femoral hernia this means dividing the lacunar ligament medially, taking care because an abnormal obturator artery may cross it.

11. Worked Examples

Example 1. A 70-year-old thin woman has small bowel obstruction and pain radiating along the inner thigh. No lump is palpable.

The Howship-Romberg sign, obstruction and the demographic together describe an obturator hernia, which occurs through the obturator canal in thin elderly women who have lost the preperitoneal fat that normally occludes it.

The absence of a lump is expected, because the hernia lies deep to pectineus. Computed tomography makes the diagnosis, and operation is required.

Example 2. A patient has a tender irreducible groin lump below and lateral to the pubic tubercle, with vomiting. A junior doctor attempts reduction.

The position below and lateral to the pubic tubercle identifies a femoral hernia, which strangulates readily because three of the four boundaries of the femoral ring are unyielding.

Tenderness with irreducibility and vomiting indicates strangulation, and manual reduction is contraindicated. Reduction en masse would return dead bowel to the peritoneal cavity, removing the lump while leaving the strangulation and the patient with peritonitis and no visible source.

Example 3. A patient with a small femoral hernia develops fever, tachycardia and localised tenderness but is passing flatus and stool normally with no distension.

This is Richter hernia. Only part of the circumference of the bowel wall is trapped in the narrow femoral ring, so the lumen stays patent and the patient never obstructs.

The absence of obstruction is therefore not reassurance but the diagnostic clue, and these patients characteristically present late with dead bowel. Urgent operation is required.

Summary

• The neck decides the danger, not the size of the hernia.
• Venous drainage fails before arterial supply, so strangulation is self-reinforcing.
• Reducible, irreducible, obstructed and strangulated describe different states.
• Richter hernia strangulates without obstructing and presents late.
• Littre contains a Meckel diverticulum; Maydl is a W loop strangulated inside the abdomen.
• A sliding hernia has a viscus forming part of the sac wall.
• The anterior canal wall is strongest laterally and the posterior wall medially.
• Hesselbach triangle is bounded by epigastric vessels, rectus sheath and inguinal ligament.
• Indirect hernias are lateral to the inferior epigastric vessels; direct are medial.
• Indirect hernias descend into the scrotum and strangulate more readily.
• Deep ring occlusion controls an indirect hernia but not a direct one.
• Inguinal hernias lie above and medial to the pubic tubercle; femoral below and lateral.
• Femoral hernias strangulate most because three boundaries of the ring are rigid.
• Inguinal hernia remains the commonest hernia in women.
• Watchful waiting is safe for minimally symptomatic inguinal hernias in men.
• Femoral hernias are repaired promptly regardless of symptoms.
• Mesh repair is standard; Lichtenstein is the reference open operation.
• Laparoscopic repair gives less chronic pain and suits bilateral and recurrent hernias.
• Low-resource practice favours standardised Lichtenstein under local anaesthesia.
• Chronic groin pain is now commoner than recurrence.
• Ischaemic orchitis follows pampiniform plexus thrombosis.
• Infantile umbilical hernia usually closes by four years; paraumbilical hernia does not.
• Epigastric hernia often contains only fat and is disproportionately painful.
• Incisional hernia reflects failed wound healing and recurs frequently.
• Spigelian hernia lies deep to external oblique and is easily missed.
• Obturator hernia occurs in thin elderly women with the Howship-Romberg sign.
• Getting above a swelling excludes a hernia; transillumination suggests a hydrocele.
• Paediatric hernia is a patent processus and is treated by herniotomy alone, without mesh.
• Infant hernias are repaired promptly because incarceration risk is highest in the first year.
• Sliding hiatus hernia causes reflux; the paraoesophageal type risks volvulus and is repaired.
• Divarication of the recti has no defect and no neck, so it is not repaired.
• Rectus sheath haematoma becomes more prominent on tensing the abdominal wall.
• Strangulated hernias are never reduced manually.
• Reduction en masse hides strangulated bowel inside the abdomen.
• Mesh is avoided when bowel has been resected in a contaminated field.