Inguinal Hernia - Comprehensive Overview

Definition

Anatomy of the Inguinal Canal

• Males: spermatic cord (testicular artery, veins, vas deferens, lymphatics, cremasteric muscle), ilioinguinal nerve, iliohypogastric nerve, genital branch of genitofemoral nerve
• Females: round ligament, same nerves

• Medial border: lateral edge of rectus abdominis
• Inferior border: inguinal ligament
• Lateral border: inferior epigastric vessels

Types

1. Indirect (Lateral) Inguinal Hernia

• Most common type overall
• Protrudes lateral to the inferior epigastric vessels, through the deep inguinal ring
• Follows the path of the processus vaginalis into the scrotum
• Can be congenital (patent processus vaginalis) or acquired
• All congenital hernias in children are indirect by definition
• Higher risk of incarceration and strangulation due to narrow neck

2. Direct (Medial) Inguinal Hernia

• Always acquired; results from weakness/stretching of the posterior inguinal canal wall
• Protrudes medial to the inferior epigastric vessels, directly through Hesselbach's triangle
• Broad-based neck - unlikely to strangulate
• More common in elderly males
• The urinary bladder can be dragged into a direct hernia (sliding)

3. Sliding Hernia

• Retroperitoneal structures (sigmoid colon on left, caecum on right, bladder) form part of the sac wall
• Surgeons must take extra care not to damage bowel during repair

4. Pantaloon Hernia

• Both direct and indirect hernia coexist simultaneously, straddling the inferior epigastric vessels (resembles a pair of trousers)

Classification

EHS (European Hernia Society) Classification

• P = Primary, R = Recurrent
• L = Lateral (indirect), M = Medial (direct), F = Femoral
• Defect size: 1 = ≤1 fingerbreadth (~1.5 cm), 2 = 1-3 fingerbreadths, 3 = ≥3 fingerbreadths
• Example: A primary indirect hernia with 3 cm defect = PL2

Nyhus Classification

Epidemiology & Risk Factors

• Lifetime prevalence: 15% at age 25-34 rising to 47% at age 75+ in males (Schwartz's)
• Male:female ratio approximately 10:1
• Right > left side
• Higher incidence in premature infants (processus vaginalis not yet obliterated)

• Increased intra-abdominal pressure (chronic cough, constipation, heavy lifting, BPH/straining)
• Collagen deficiency
• Prematurity
• Family history
• Prior ipsilateral hernia (recurrence)

Embryology

Clinical Features

Symptoms

• Groin bulge, often described as a "lump in the groin"
• Ache or dragging discomfort, worse on standing/coughing/lifting
• Reducible: disappears on lying down, reappears on standing or Valsalva
• May present as scrotal swelling (indirect hernia reaching the scrotum)

Examination

1. Examine the patient standing and supine
2. Identify bony landmarks: ASIS and pubic tubercle
3. Locate the deep inguinal ring (just above the midpoint of the inguinal ligament)
4. Ask patient to cough - feel for an impulse
5. Reduce the hernia and apply pressure at the deep ring:
   • Controlled by pressure at deep ring → indirect
   • Appears medial to pressure point → direct

• Indirect hernia: sac lies superomedial to the pubic tubercle, within the spermatic cord
• Direct hernia: sac lies directly in front of the pubic tubercle
• Cannot "get above" a scrotal hernia (distinguishes from hydrocele; also transillumination negative unless omentum not present)

Complications

Diagnosis

• Ultrasound: first-line imaging when clinical diagnosis is uncertain; identifies occult hernia, distinguishes from lymph node, lipoma, varicocele
• CT scan: for large/irreducible hernias, recurrent hernias, or suspected sliding hernia
• MRI (dynamic): for chronic groin pain, occult hernia, athletic pubalgia

• Femoral hernia (inferomedial to pubic tubercle)
• Hydrocele (transilluminates, can get above it)
• Lymphadenopathy
• Lipoma of the cord
• Varicocele ("bag of worms")
• Undescended testis
• Femoral artery aneurysm
• Psoas abscess

Management

Watchful Waiting

• Asymptomatic or minimally symptomatic hernias in high-risk patients may be observed
• Risk of acute incarceration/strangulation is low (~0.3-0.5% per year for reducible hernia)
• Symptomatic hernias and hernias in children always require repair

Surgical Repair - Principles

1. Herniorrhaphy: tension repair with sutures (tissue-based)
2. Hernioplasty: mesh-reinforced tension-free repair (preferred in adults)

Open Anterior Repairs

• Opens external oblique aponeurosis, dissects the cord
• Sac excised/ligated; sutures placed between conjoint tendon and inguinal ligament
• Historical gold standard; over 150 modifications described
• Associated with tension - higher recurrence

• Transversalis fascia is opened, then double-breasted (two-layer closure) to reconstruct the posterior wall
• External oblique similarly double-breasted
• Best tissue repair: expert centres report <2% lifetime failure
• Technically demanding

• Polypropylene mesh placed as a flat patch over the inguinal floor, sutured to the inguinal ligament below and the conjoint tendon above
• Introduced in the 1980s; dramatically reduced recurrence rates
• Recurrence <1-2% in most series
• Performed under local, regional, or general anaesthesia
• Recommended by 2018 EHS guidelines as the standard open repair

• Mesh plug placed into the defect + flat mesh overlay
• Simple but risk of meshoma, plug migration into bladder/bowel
• Not recommended by 2018 EHS guidelines

• Large mesh placed in preperitoneal plane via midline or Pfannenstiel incision
• Useful for complex/recurrent hernias and bilateral repairs
• Largely superseded by laparoscopic TEP

Laparoscopic Repairs

• Balloons/blunt dissection develop the preperitoneal space without entering the peritoneal cavity
• No peritoneal breach; lower risk of intra-abdominal injury
• More technically challenging to learn

• Peritoneal cavity entered; peritoneal flap raised; mesh placed in preperitoneal space; peritoneum closed over mesh
• Better visualisation; easier learning curve
• Risk of intra-abdominal injury (bowel, bladder)

• Less post-operative pain
• Faster return to work/activity
• Better for bilateral hernias (both sides repaired simultaneously)
• Better for recurrent hernias after open anterior repair (avoids previously dissected tissue)
• Lower incidence of chronic groin pain vs. open

• Requires general anaesthesia
• Longer operating time
• Risk of rare but serious vascular/visceral injury
• Recurrence rates similar to open Lichtenstein in experienced hands

Repair Approach - Decision Making

Complications of Surgery

Special Populations

Children

• All hernias are indirect by definition; repair as elective herniotomy
• Contralateral exploration debated (~30% have patent processus vaginalis on opposite side; rate decreases with age)
• Laparoscopic approach increasingly used under age 2
• Emergency repair if incarceration cannot be reduced

Females

• Hernias may contain the ovary and fallopian tube (often a sliding hernia)
• Risk of ovarian torsion if not repaired promptly
• Femoral hernias are relatively more common in women than men (though still less common overall)

Elderly

• Direct hernias more common
• Higher risk of recurrence with tissue repairs
• Mesh repair preferred
• Local anaesthesia is well tolerated

Key Anatomical Relationships to Remember