Hernias of the Abdominal Wall

A hernia is the abnormal protrusion of a viscus (or part of it) through a weak point or defect in the wall of the cavity that normally contains it. Abdominal wall hernias are among the highest-yield, most repeatedly tested topics in NEET PG surgery — anatomy of the inguinal canal, Hesselbach's triangle, direct versus indirect differentiation, and the complications cascade (irreducible → obstructed → strangulated) appear nearly every year.

Definition & Composition

Every hernia classically has three parts:

1. Sac — a diverticulum of peritoneum with a mouth, neck, body and fundus.
2. Coverings — the layers of the abdominal wall through which the sac passes.
3. Contents — most commonly omentum (omentocele) or small bowel (enterocele); may also contain bladder, ovary, or a Meckel's diverticulum.

High-yield: A Richter's hernia contains only part of the circumference (antimesenteric border) of the bowel wall — it can strangulate without causing intestinal obstruction, making it dangerously deceptive. Most commonly seen in femoral hernias.

High-yield: A Littre's hernia is a hernia containing a Meckel's diverticulum. A Maydl's hernia (hernia-en-W) has two loops in the sac with the strangulated loop lying inside the abdomen — easily missed at operation.

Classification

Type	Key feature
Reducible	Contents return to abdomen spontaneously or with pressure
Irreducible (incarcerated)	Cannot be reduced; no obstruction/ischaemia yet
Obstructed	Lumen blocked → intestinal obstruction, blood supply intact (initially)
Strangulated	Blood supply compromised → ischaemia, gangrene; surgical emergency
Sliding (hernia-en-glissade)	Posterior wall of sac formed by a retroperitoneal viscus (caecum on right, sigmoid colon on left, bladder)

Anatomy of the Inguinal Region (must-know)

The inguinal canal is an oblique passage ~4 cm long running from the deep to the superficial inguinal ring.

• Deep (internal) ring: defect in transversalis fascia, lateral to inferior epigastric vessels, ~1.25 cm above the midpoint of the inguinal ligament (mid-inguinal point is for the femoral artery — do not confuse).
• Superficial (external) ring: defect in external oblique aponeurosis, above and medial to the pubic tubercle.
• 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).

Hesselbach's Triangle (inguinal triangle)

Boundary	Structure
Lateral	Inferior epigastric artery
Medial	Lateral border of rectus abdominis
Inferior (base)	Inguinal ligament

High-yield: A direct inguinal hernia bulges through Hesselbach's triangle (medial to inferior epigastric vessels). An indirect hernia enters via the deep ring (lateral to inferior epigastric vessels). This single relationship answers most MCQs.

Direct vs Indirect Inguinal Hernia

Feature	Indirect	Direct
Frequency	Most common (~80%), commonest hernia overall	Less common
Age	Young, all ages; congenital basis (patent processus vaginalis)	Older, acquired (muscle weakness)
Relation to inferior epigastric vessels	Lateral	Medial
Path	Through deep ring, along canal, may reach scrotum	Bulges directly forward through posterior wall
Coverings	All three (passes through canal)	Fewer (does not traverse full canal)
Descent into scrotum	Common	Rare
Shape	Oval / pyriform	Round, hemispherical
Reduction & control	Reducible upwards, then laterally & backwards; controlled by deep-ring occlusion	Reduced directly backwards; not controlled by deep-ring pressure
Strangulation risk	Higher (narrow neck)	Lower (wide neck)

Deep ring occlusion test (clinical flow): Reduce hernia → occlude deep ring (1.25 cm above mid-inguinal point) → ask patient to cough → stays controlled = indirect; reappears medially = direct.

High-yield: A pantaloon (saddlebag / dual) hernia has both a direct and an indirect component straddling the inferior epigastric vessels.

Etiology & Pathophysiology

• Raised intra-abdominal pressure: chronic cough (COPD), straining (constipation, BPH with straining, stricture urethra), ascites, pregnancy, heavy lifting, obesity.
• Weak abdominal wall: ageing, collagen disorders, denervation, previous incision, smoking (collagen/elastin imbalance — increased risk of direct/recurrent hernia).
• Congenital: patent processus vaginalis → indirect inguinal hernia, congenital hydrocele, and (in females) hernia of the canal of Nuck.

Strangulation pathophysiology flow: Tight neck → venous + lymphatic obstruction → oedema → arterial inflow compromised → ischaemia → gangrene → perforation/peritonitis.

Clinical Features

• Swelling with expansile cough impulse; reducibility; positive "getting above the swelling is not possible" (distinguishes from a scrotal swelling, where you can get above it).
• Strangulated hernia: painful, tense, irreducible, no cough impulse, tender, with features of intestinal obstruction (colicky pain, vomiting, distension, constipation). Overlying skin may become erythematous.

High-yield: A previously reducible hernia becoming suddenly painful, tense and irreducible with loss of cough impulse = strangulation until proven otherwise → emergency surgery, do NOT attempt forceful reduction (risk of reduction-en-masse and perforating a gangrenous loop into the abdomen).

Specific Hernias

Femoral Hernia

• Protrudes through the femoral canal, the most medial compartment of the femoral sheath; appears below and lateral to the pubic tubercle (inguinal hernia is above and medial).
• Commonest in middle-aged/elderly women (wider pelvis, but indirect inguinal remains the commonest hernia even in women overall).
• Femoral ring boundaries: anterior — inguinal ligament; posterior — pectineal (Astley Cooper's) ligament + pubic bone; medial — lacunar (Gimbernat's) ligament; lateral — femoral vein.
• Highest risk of strangulation of all hernias because of the narrow, rigid, unyielding neck (lacunar ligament).

High-yield: Femoral hernia = highest strangulation risk + commonest site for a Richter's hernia. The mnemonic NAVEL (lateral→medial: Nerve, Artery, Vein, Empty space, Lymphatics) — the femoral hernia occupies the medial "empty space" (femoral canal).

High-yield: A Cloquet's node (deep inguinal lymph node) sits in the femoral canal and may mimic a femoral hernia.

Umbilical & Paraumbilical Hernia

• Congenital umbilical hernia: through the umbilical cicatrix in infants; most close spontaneously by 2 years; repair if persists beyond 2–3 years or > 1.5 cm.
• Paraumbilical hernia (adults): through the linea alba just above or below the umbilicus; commoner in obese multiparous women; contents often omentum/transverse colon; prone to strangulation due to fibrous, narrow neck.

Incisional (Ventral) Hernia

• Through an acquired weakness of a previous surgical scar.
• Risk factors: wound infection (most important), obesity, poor surgical technique, midline vertical incisions, steroids, malnutrition, raised intra-abdominal pressure, smoking.

Epigastric Hernia

• Through the linea alba between xiphoid and umbilicus; contains extraperitoneal fat (fatty hernia of the linea alba); may be painful and mistaken for peptic ulcer.

Obturator Hernia

• Through the obturator canal; classically in thin, elderly women ("the little old lady's hernia").
• Presents with intestinal obstruction; Howship–Romberg sign = pain along the inner thigh/knee (obturator nerve compression), relieved by thigh flexion. Hannington-Kiff sign = absent adductor reflex with preserved patellar reflex.

Spigelian Hernia

• Through the linea semilunaris at the arcuate line of Douglas (semilunar line, usually below the umbilicus); interparietal (between muscle layers) → easily missed; high strangulation risk.

Other named hernias

• Lumbar hernia — through superior (Grynfeltt) or inferior (Petit) lumbar triangle.
• Amyand's hernia — appendix within an inguinal hernia sac.
• Gibbon's hernia — hernia with a hydrocele.
• Phantom (Malgaigne) hernia — bulging of weak abdominal muscle, not a true hernia.

Diagnosis & Investigation of Choice

• Primarily clinical — inspection (standing & lying), palpation for cough impulse, reducibility, and the relationship to the pubic tubercle.
• Investigation of choice when in doubt / occult hernia: Ultrasound (dynamic, with Valsalva) is first-line imaging.
• CT abdomen is best for obscure/atypical hernias (Spigelian, obturator, internal) and to assess strangulation/obstruction.
• MRI for suspected sportsman's groin / occult hernia when USG equivocal.

Management & Repair (Drug/Procedure of Choice)

General principle: All hernias should ideally be repaired; surgery is the only definitive treatment. Trusses are reserved only for patients unfit for surgery.

Stepwise approach to inguinal hernia: Confirm diagnosis → assess reducibility & complications → optimise comorbidities (control cough, constipation, BPH) → elective repair → if strangulated → emergency surgery.

Inguinal hernia repair

Technique	Principle
Herniotomy	Sac excision only — operation of choice in children/infants (wall is healthy)
Herniorrhaphy (Bassini, Shouldice)	Tissue/darn repair, suturing conjoint tendon to inguinal ligament; Shouldice has lowest recurrence among pure tissue repairs
Lichtenstein	Tension-free mesh (polypropylene) repair of posterior wall — gold standard open repair in adults
Laparoscopic (TEP / TAPP)	Preperitoneal mesh; preferred for bilateral and recurrent hernias; less postoperative pain, faster recovery

High-yield: Lichtenstein tension-free mesh repair = standard open repair in adults. Herniotomy alone = treatment of choice in children. Laparoscopic TEP/TAPP = preferred for bilateral or recurrent inguinal hernias.

• TEP = Totally Extra-Peritoneal; TAPP = Trans-Abdominal Pre-Peritoneal.
• Strangulated hernia: resuscitate → emergency exploration → assess bowel viability (colour, peristalsis, mesenteric pulsation, sheen) → resect non-viable bowel → repair defect (avoid prosthetic mesh in a contaminated field; use tissue repair or biological mesh).

Specific repairs

• Femoral hernia: Lockwood (low/infra-inguinal), Lotheissen (trans-inguinal), or McEvedy (high/abdominal — preferred in emergency as it allows bowel resection).
• Incisional/ventral hernia: mesh repair (open sublay/retrorectus per Rives–Stoppa, or laparoscopic IPOM); component separation for large defects.

Complications

• Of the hernia: irreducibility → obstruction → strangulation → gangrene → perforation, peritonitis, sepsis. Also reduction-en-masse (sac reduced with contents still strangulated).
• Of surgery: recurrence, chronic groin pain (ilioinguinal/genitofemoral/iliohypogastric nerve injury), seroma/haematoma, wound infection, mesh infection, testicular atrophy/ischaemic orchitis (from cord vessel injury), injury to vas deferens, urinary retention.

High-yield: Ischaemic orchitis results from thrombosis of the pampiniform plexus, not the testicular artery; it is more common after repair of recurrent or large/sliding hernias.

Key Differentials (groin swelling)

• Inguinal vs femoral hernia (pubic tubercle relationship).
• Vaginal hydrocele / encysted hydrocele of cord — can get above the swelling, transilluminant.
• Undescended/ectopic testis, lipoma of the cord (commonest cause of a fatty swelling mistaken for hernia).
• Saphena varix (saphenofemoral junction) — soft, disappears on lying down, fluid thrill on coughing, bluish.
• Femoral artery aneurysm, psoas abscess/bursa, enlarged inguinal lymph nodes.

Recently asked / exam angle

• Boundaries of Hesselbach's triangle and the direct vs indirect distinction (lateral vs medial to inferior epigastric vessels) — perennial favourite.
• Richter's hernia strangulating without obstruction; Littre's = Meckel's; Maydl's = W-loop; Amyand's = appendix; Littre vs Richter confusion.
• Femoral canal boundaries and why femoral hernia strangulates most; NAVEL mnemonic; lacunar (Gimbernat) ligament as the medial, unyielding boundary.
• Howship–Romberg sign → obturator hernia in a thin elderly woman with bowel obstruction.
• Lichtenstein = gold standard open; herniotomy in children; McEvedy approach for emergency femoral hernia.
• Deep ring located lateral to inferior epigastric vessels and ~1.25 cm above the mid-inguinal point (vs mid-point of inguinal ligament).
• Distinguishing mid-inguinal point (femoral artery) from midpoint of the inguinal ligament (deep ring) — classic trap.
• Spigelian hernia at the linea semilunaris/arcuate line; sliding hernia contents (caecum right, sigmoid left).

Mnemonics:

• Femoral sheath contents lateral→medial = NAVEL (Nerve, Artery, Vein, Empty space "femoral canal", Lymphatics).
• Indirect = Lateral to inferior epigastric (think "I" goes the Indirect, lateral route through the canal).
• Strangulation triad worsening: Painful, Irreducible, no Cough impulse (= PIC → emergency).

Rapid revision

1. Indirect inguinal hernia = commonest hernia overall; lies lateral to inferior epigastric vessels.
2. Direct hernia bulges through Hesselbach's triangle, medial to inferior epigastric vessels.
3. Hesselbach's triangle: inferior epigastric artery (lateral), rectus (medial), inguinal ligament (base).
4. Femoral hernia = below & lateral to pubic tubercle; highest strangulation risk; commonest in elderly women.
5. Richter's = part of bowel circumference; strangulates without obstruction.
6. Littre's = Meckel's diverticulum; Maydl's = W-loop with intra-abdominal strangulated segment; Amyand's = appendix.
7. Deep ring = lateral to inferior epigastric vessels, 1.25 cm above mid-inguinal point.
8. Lichtenstein tension-free mesh = gold standard open inguinal repair; herniotomy in children.
9. TEP/TAPP laparoscopic repair preferred for bilateral & recurrent hernias.
10. Howship–Romberg sign (inner-thigh pain) = obturator hernia.
11. Strangulated hernia: painful, tense, irreducible, no cough impulse → emergency surgery; never force reduction.
12. McEvedy (high) approach = preferred for strangulated/emergency femoral hernia (allows bowel resection).