Hernia: Clinical Classification, General Characteristics, and Rare Forms

1. Definition

2. General Characteristics of a Hernia

Predisposing Factors

• Chronic cough (e.g., COPD)
• Obesity, ascites, constipation, bladder outlet obstruction, heavy lifting
• Male sex, advancing age, low BMI
• Prior surgery, trauma, congenital defects, pregnancy, collagen disorders, smoking

3. Clinical Classification

3.1 By Anatomical Location

3.2 By Etiology

• Congenital — patent processus vaginalis (indirect inguinal), diaphragmatic (Bochdalek), umbilical
• Acquired — direct inguinal, incisional (up to 20% of laparotomy patients), most epigastric and femoral hernias

3.3 By Status of Contents (Clinical Urgency)

A Richter hernia is a special variant: only part of the bowel wall (not the full lumen) is incarcerated and strangulated, so complete bowel obstruction may be absent even with gangrenous bowel. Most often associated with femoral or inguinal hernias. — Mulholland & Greenfield's Surgery

3.4 By Direction (Groin Hernias)

3.5 By Recurrence Status

• Primary — first occurrence
• Recurrent — after previous repair (associated with much higher complication rates)

4. Formal Classification Systems

European Hernia Society (EHS) Groin Hernia Classification

• Location: L (lateral/indirect), M (medial/direct), F (femoral)
• Size: 0 (no defect), 1 (≤1 finger), 2 (1–2 fingers), 3 (≥3 fingers)
• Status: P (primary), R (recurrent), X (unknown)

Nyhus Classification of Groin Hernias (popular in the USA)

EHS Ventral/Incisional Hernia Classification

5. Ventral / Abdominal Wall Hernias (Overview)

6. Rare Forms of Hernia

6.1 Spigelian (Lateral Ventral) Hernia

• Site: Defect in the Spigelian aponeurosis (membranous portions of internal oblique + transversus abdominis), at the lateral edge of the rectus muscle at the semilunar line, almost always at or below the arcuate line
• Key feature: The external oblique is intact, so the hernia is interparietal — the bulge is covered by an intact muscle layer and may be invisible on exam. This makes clinical diagnosis challenging.
• Incarceration risk: Up to 20% (often contains omentum); repair is recommended even when asymptomatic
• Diagnosis: Dynamic ultrasound or CT of abdomen/pelvis
• Demographics: Typically ages 40–70

6.2 Obturator Hernia

• Site: Through the obturator canal (contains obturator nerve, artery, vein); exits medial to the femoral vein into the medial upper thigh
• Epidemiology: < 1% of all hernias; predominantly affects elderly, thin females due to their triangular pelvis and atrophy of preperitoneal fat
• Risk factors: COPD, constipation, ascites (raised IAP)
• Pathognomonic sign: Howship–Romberg sign — pain in the anteromedial thigh, relieved by hip flexion (compression of the obturator nerve)
• Presentation: Bowel obstruction in up to 50%; can mimic femoral or inguinal hernia
• Strangulation morbidity: As high as 14% due to delayed diagnosis
• Diagnosis: CT scan preferred; ultrasound limited by the bony pelvis

6.3 Lumbar Hernia

• Site: Posterior abdominal wall, between the 12th rib and iliac crest, through one of two triangles:
  • Superior lumbar (Grynfeltt's triangle): between the 12th rib and iliocostalis
  • Inferior lumbar (Petit's triangle): between the iliac crest, latissimus dorsi, and external oblique
• Most cases are acquired (post-surgical, trauma, infection); primary spontaneous lumbar hernias are rare
• Diagnosis: CT of the abdomen/pelvis

6.4 Sciatic Hernia

• Site: Through the greater sciatic foramen; three subtypes based on their relationship to the piriformis muscle:
  • Suprapiriformis (above piriformis)
  • Infrapiriformis (below piriformis)
  • Spinotuberous (in front of the sacrotuberous ligament)
• Extremely rare: Only ~99 patients in case reports from 1900–2008
• Presentation: Slowly enlarging gluteal mass, sciatic neuralgia, or acute bowel obstruction
• Repair: Minimally invasive (transabdominal) preferred; protect the obturator nerve/vessels and sciatic nerve; mesh sutured to Cooper's ligament

6.5 Perineal Hernia

• Site: Through the pelvic floor musculature; three types:
  • Anterior perineal — in front of the deep transverse perineal muscle
  • Posterior perineal — behind the deep transverse perineal
  • Ischiorectal (ischioanal) — through the levator ani into the ischioanal fossa
• Often occurs after abdominoperineal resection or pelvic exenteration

6.6 Interparietal (Interstitial) Hernia

• Herniation between the layers of the abdominal wall (not through all layers)
• Most are incisional; Spigelian hernia is the classic primary interparietal hernia
• Frequently causes intestinal obstruction; CT essential
• Two forms relevant after complex ventral repairs: posterior rectus sheath herniation (after Rives–Stoppa), and semilunar line herniation (after transversus abdominis release)

6.7 Hernia Through the Foramen of Winslow (Epiploic Foramen)

• An internal hernia with abdominal viscera passing posterior to the porta hepatis into the lesser sac
• Usually diagnosed at laparotomy for bowel obstruction

Summary Table: Rare Hernias

Hernia: Diagnosis and Treatment

PART I — DIAGNOSIS

1. History

• Symptoms: Presence, onset, and nature of a groin/abdominal bulge; pain (especially with exertion, coughing, Valsalva); nausea, vomiting, or signs of bowel obstruction
• Eliciting factors: Heavy lifting, chronic cough, constipation, straining to urinate
• Prior repairs: Operative details, type of mesh, dates, infections — operative reports are invaluable for planning
• Risk factors: Smoking, COPD, obesity, collagen disorders, pregnancy, prior abdominal surgery

2. Physical Examination

• Inspect for visible bulge or asymmetry with the patient standing and performing Valsalva
• Palpate the area at rest and during coughing/straining
• For males: invaginate the scrotal skin and pass a finger into the external inguinal ring — ask the patient to cough
  • Impulse at the fingertip → indirect hernia
  • Impulse at the dorsum/pulp → direct hernia
• Apply pressure over the mid-inguinal point (midway between ASIS and pubic tubercle): controlling an indirect hernia with this maneuver does not work for a direct hernia

Note: The accuracy of clinical differentiation between direct and indirect is only slightly better than chance; anatomical confirmation at surgery is definitive.

• Tender, warm, erythematous or discolored skin overlying the sac
• Fever, leukocytosis, hemodynamic instability
• Symptoms of bowel obstruction

3. Imaging

• Diagnosis is uncertain (occult hernia, obese patient)
• Differentiating recurrence from other causes of groin pain
• Preoperative planning for complex/recurrent hernias

MRI demonstrates the highest sensitivity, specificity, and negative predictive value for occult hernias compared with US and CT, and has increased sensitivity for neuromas or issues with implanted mesh. — Current Surgical Therapy, 14e

4. Differential Diagnosis of Groin/Abdominal Swelling

• Lymphadenopathy
• Lipoma of the cord / femoral pseudohernia (prominent fat pad)
• Hydrocele (transilluminates; examining hand gets above it)
• Varicocele ("bag of worms"; does not transilluminate)
• Saphena varix (below inguinal ligament; obliterated by compression over femoral hiatus)
• Femoral artery aneurysm (pulsatile, expansile; bruit)
• Psoas abscess, hematoma, ascites

PART II — TREATMENT

Decision Framework

Hernia Confirmed
      │
      ├── Strangulated? ──YES──► Emergency surgery (no taxis)
      │
      ├── Incarcerated (no strangulation)? ──► Attempt TAXIS; then repair
      │
      ├── Femoral / Symptomatic inguinal ──► Elective repair (early — femoral has
      │                                        22–45% strangulation risk at 2 years)
      │
      └── Asymptomatic / minimally symptomatic inguinal ──► Watchful waiting acceptable

A. Non-Operative Management

Femoral hernias should not be managed with watchful waiting — emergency operation carries a sevenfold increase in all-cause mortality over elective surgery (Swedish Hernia Registry, n = 107,838). — Schwartz's Principles of Surgery

B. Manual Reduction (Taxis)

1. Administer analgesics and light sedation
2. Place patient in Trendelenburg position (aids reduction by gravity)
3. Elongate the hernia sac with both hands
4. Apply gentle circumferential countertraction in a stepwise fashion to ease contents back into the abdomen

Taxis is contraindicated when strangulation is suspected — reducing gangrenous bowel into the abdomen causes intraabdominal catastrophe.

C. Surgical Repair — Principles

1. Reduce hernia contents
2. Reapproximate the fascial defect
3. Reinforce with mesh using wide overlap (≥3–5 cm) while preserving adjacent neurovascular structures

D. Inguinal Hernia Repair

Open Approaches

• Oblique/horizontal groin incision; Scarpa's fascia divided; external oblique aponeurosis opened
• Spermatic cord isolated; hernia sac identified and reduced
• A flat polypropylene mesh is sutured over the inguinal floor, covering the myopectineal orifice with wide overlap
• Standard of care for primary inguinal hernia repair in most centers

• Bassini: Approximation of the transversalis fascia, transversus abdominis, and internal oblique to the inguinal ligament
• Shouldice: Multi-layer running suture repair of the posterior inguinal wall; lowest recurrence among pure tissue repairs (~1%)
• Higher recurrence than mesh repairs; now used mainly when mesh is contraindicated

• Large mesh placed in the preperitoneal space via open approach; covers the entire myopectineal orifice
• Useful for bilateral, complex, or recurrent hernias

Laparoscopic/Minimally Invasive Approaches

E. Femoral Hernia Repair

• High priority for repair due to high strangulation risk
• Approaches: anterior (via inguinal canal), low (directly below inguinal ligament), preperitoneal (best exposure for strangulated/recurrent cases)
• Mesh plugs or flat mesh placed in the femoral canal or over the myopectineal orifice

F. Ventral / Incisional Hernia Repair

Open Repair

• Primary suture repair: Only for small defects (<2 cm); high recurrence rate
• Mesh sublay (Rives-Stoppa): Mesh placed in the retromuscular (retrorectus) space posterior to the posterior rectus sheath — the current gold standard for open incisional hernia repair; wide mesh overlap in extraperitoneal plane
• Component separation (anterior CS): Release of the external oblique aponeurosis lateral to the linea semilunaris, allowing medial advancement of myofascial flaps to close large midline defects; used for complex, large, or recurrent hernias
• Transversus Abdominis Release (TAR / posterior CS): Division of the transversus abdominis muscle to access the retromuscular space; allows massive mesh overlap; particularly suited to recurrence after anterior CS

Laparoscopic Ventral Hernia Repair (LVHR)

• Greatest value: reduced wound complications due to small access incisions; applies "sublay" mesh technique without large open dissection
• Advantages: decreased blood loss, lower wound infection, shorter hospital stay
• Indications: high wound complication risk, small-to-moderate defects, multiple "swiss cheese" defects
• Contraindications: intolerance of pneumoperitoneum/GA, open wounds, extensive adhesions, large defects >10 cm
• Current trend: close the fascial defect during laparoscopic repair (not just "bridge" it) to prevent eventration/pseudorecurrence

G. Mesh Selection

Mesh should not be used in grossly infected fields unless biologic mesh is chosen. In resource-limited settings, sterilized polypropylene mosquito nets have demonstrated similar short-term complication and recurrence rates to commercial meshes.

H. Emergency Repair (Strangulated Hernia)

• IV fluid resuscitation
• Nasogastric decompression
• IV prophylactic antibiotics
• Urgent theatre booking

• Reduce hernia contents and assess bowel viability
• Viable bowel → left in situ
• Non-viable bowel → resection + anastomosis or stoma
• In the context of contamination (necrotic bowel/spillage): avoid permanent synthetic mesh; use tissue repair or biologic mesh; two-stage approach may be necessary

I. Postoperative Complications to Anticipate

Causes of Hernia

I. Fundamental Mechanism

"Especially where the connective tissue is weakened, as occurs in elderly persons, it occasionally fails to resist intra-abdominal pressure and becomes a site of hernia. Triggering events include lifting heavy objects or even coughing." — THIEME Atlas of Anatomy: General Anatomy and Musculoskeletal System

II. Congenital Causes

1. Patent Processus Vaginalis (PPV) — most important congenital cause

• In preterm infants, the processus is almost always patent → very high incidence of indirect inguinal hernia (up to 30% of premature neonates)
• In full-term infants, ~5% have an inguinal hernia
• In children and young adults, most hernias are indirect inguinal hernias of congenital origin
• The overall risk of developing a symptomatic hernia in the presence of a known PPV during childhood is relatively low — many PPVs close spontaneously

2. Other Congenital Defects

• Umbilical hernia in infants — failure of the umbilical ring to close after birth; most close spontaneously by age 4–5
• Congenital diaphragmatic hernia (Bochdalek, Morgagni) — failure of diaphragm development/closure
• Omphalocele / gastroschisis — failure of normal abdominal wall formation in embryonic development
• Naturally weak anatomical points in the abdominal wall where muscle is absent and only connective tissue spans the gap (inguinal canal, femoral canal, umbilical ring, obturator foramen) — these are pre-formed sites of vulnerability

III. Acquired Causes

A. Increased Intraabdominal Pressure (IAP)

B. Connective Tissue / Collagen Disorders

• Microscopic examination of skin from inguinal hernia patients shows significantly decreased ratios of type I : type III collagen
  • Type I collagen = major structural tensile-strength collagen
  • Type III collagen = weaker, more distensible — does not contribute to tensile strength as significantly
• Disaggregated collagen tracts with decreased fiber density are found in hernia tissue
• Matrix metalloproteinase (MMP) dysregulation: elevated concentrations of extracellular matrix elements and altered MMP activity impair structural integrity of fascial tissues
• This explains why hernias can occur even without obvious mechanical triggers

A positive family history confers an eightfold lifetime incidence of inguinal hernia. — Schwartz's Principles of Surgery

C. Cigarette Smoking

• Tobacco smoke inhibits α₁-antitrypsin, increases systemic protease activity, and impairs collagen synthesis and cross-linking
• Associated with both inguinal hernia formation and poor wound healing → higher incisional hernia rates

D. Age and Loss of Tissue Elasticity

• Advancing age causes progressive loss of tissue elasticity and collagen quality
• Muscle atrophy and thinning of fascial layers
• Direct inguinal hernias are overwhelmingly acquired and increase markedly with age
• Obturator hernias preferentially affect elderly, thin women (loss of preperitoneal fat protecting the obturator canal)

E. Sex

• Male sex is the dominant risk factor for inguinal hernia (male : female ratio = 7.5–10 : 1)
  • Men have a 25–27% lifetime risk; women 3–5%
  • The inguinal canal in males is larger and has the spermatic cord passing through it — inherent weakness
• Female sex is a risk factor for femoral hernia (though inguinal hernia is still more common even in women)

F. Prior Surgery (Incisional Hernia)

G. Trauma

• Blunt or penetrating abdominal injury can create fascial defects → traumatic hernia
• Also includes sports hernias (athletic pubalgia) — disruption of the posterior inguinal wall from repetitive strain without a true peritoneal sac

H. Neurological / Muscular Disease

• Conditions causing denervation or paresis of the abdominal wall musculature (e.g., post-polio, spinal cord injury) leave the abdominal wall unsupported → hernia at weak anatomical points

IV. Cause Summary by Hernia Type