Overview

Abdominal hernias: protrusion of intra-abdominal contents through a defect in the abdominal wall.

 

Classification of various hernias by anatomical location:

Location	Hernia type	Description
Anterior abdominal wall	Epigastric hernia	Hernia through the linea alba in the epigastric region (between the xiphoid and umbilicus)
	Umbilical hernia	Hernia through the umbilicus
	Incisional hernia	Hernia through a defect at a previous surgical site
	Parastomal hernia
Groin	Inguinal hernia	Hernia through the inguinal canal (can be direct or indirect)
	Femoral hernia	Hernia through the femoral canal
Pelvis	Obturator hernia	Hernia through the obturator foramen   Howship-Romberg sign (medial thigh pain due to obturator nerve compression)
	Sciatic hernia	Hernia through the greater or lesser sciatic foramen

Hernias that are not covered in this article are hiatal hernia

Inguinal Hernia

Definition

Inguinal hernia is the most common type of abdominal wall hernia in adults (~75% of abdominal wall hernias)

 

There are 2 types of inguinal hernias:

• Direct inguinal hernia: protrusion of abdominal content directly through the posterior wall of the inguinal canal
• Indirect inguinal hernia: protrusion of abdominal content into the inguinal canal, via the deep inguinal ring

Anatomy

Inguinal Canal Borders

• Roof: internal oblique and transversus abdominis muscle
• Floor: inguinal ligament (extends from the ASIS to pubic tubercle) primarily, also lacunar ligament (medial support)
• Posterior wall: transversalis fascia primarily, also aponeurosis of internal oblique and transversus abdominis (medial support)
• Anterior wall: external oblique aponeurosis primarily, also internal oblique muscle (lateral support)

Deep vs Superficial Inguinal Ring

Feature	Deep inguinal ring	Superficial inguinal ring
Structure	Transversalis fascia	External oblique aponeurosis
Surface anatomy	Midpoint of the inguinal ligament	Superior and lateral to the pubic tubercle
Function	Entrance of the inguinal canal	Exit of the inguinal canal

Pathophysiology

 Indirect inguinal hernia is more common than direct inguinal hernia in adults. While nearly all paediatric inguinal hernias are indirect.

Direct Inguinal Hernia

Caused by an acquired weakness of the transversalis fascia (posterior wall of the inguinal canal)

 

Key risk factors: ^[Ref]

• Male sex (~10x risk compared to female) – mainly due to the larger inguinal canal, as it contains the spermatic cord
• Advancing age
• Family history
• Causes of increased intra-abdominal pressure
  • Chronic coughing (e.g. COPD)
  • Smoking
  • Chronic constipation
• Low BMI (individuals with low BMI have less pre-peritoneal fat) (so obesity is actually protective against hernia)
• Connective tissue disorders (e.g. Marfan’s syndrome, Ehlers-Danlos syndrome)

Indirect Inguinal Hernia

Primarily caused by a patent processus vaginalis (a congenital defect)

 

While patent processus vaginalis increases the risk for indirect hernia, most adults with patent processus vaginalis do not develop hernias. This suggests that acquired risk factors play an important role: ^[Ref]

• Male sex (~10x risk compared to female) – mainly due to the larger inguinal canal, as it contains the spermatic cord
• Advancing age
• Family history
• Causes of increased intra-abdominal pressure
  • Chronic coughing (e.g. COPD)
  • Smoking
  • Chronic constipation
• Low BMI (individuals with low BMI have less pre-peritoneal fat) (so obesity is actually protective against hernia)
• Connective tissue disorders (e.g. Marfan’s syndrome, Ehlers-Danlos syndrome)

Clinical Features

Shared Clinical Features

Shared features of inguinal hernia:

• Lump in the groin area
  • More apparent when the patient stands / strains
  • May disappear on lying down
• +ve Cough impulse (a palpable impulse / bulge over the hernia location when the patient coughs)

 

Chronic pain in the groin (inguinodynia) with no palpable groin lump can be the sole presentation of an inguinal hernia.

Direct vs Indirect Inguinal Hernia

Location of the hernia:

• Direct hernia: lump within the Hesselbach’s triangle (medial border: lateral border of the rectus abdominis, lateral border: inferior epigastric vessels, inferior border: inguinal ligament)
• Indirect hernia: lump at the deep ring of the inguinal canal, or at the superficial ring (superior and medial to the pubic tubercle), or into the scrotum

 

The deep inguinal ring occlusion test can be performed to distinguish between direct and indirect inguinal hernias:

• Apply firm pressure over the deep inguinal ring (midpoint of the inguinal ligament), then ask the patient to stand and cough / perform Valsalva manoeuver
• Interpretation
  • If the hernia bulge does NOT appear → indirect inguinal hernia (as the herniated content is unable to pass through the deep ring)
  • If the hernia bulge still appears → direct inguinal hernia

Investigation and Diagnosis

Clinical diagnosis is sufficient in most cases.

 

If clinical evaluation is equivocal / an occult hernia is suspected:

• 1st line: ultrasound
• 2nd line: CT / MRI

Management

Note that the management doesn’t differ based on whether the hernia is direct or indirect. Therefore, although exams put a lot of emphasis on direct vs indirect inguinal hernias, it is of limited significance in practice.

Uncomplicated Inguinal Hernia

Management approach: ^[Ref]

• Symptomatic inguinal hernia is an indication to offer surgery
• Asymptomatic / minimally symptomatic inguinal hernia may be managed with watchful waiting or surgery
  • There is a low risk of complications with watchful waiting, but most patients will eventually require surgery
  • Guidelines emphasise discussing the risks and benefits of watchful waiting vs surgery in a shared decision-making process

 

Definitive management for inguinal hernia: surgical mesh repair ^[Ref]

• Unilateral inguinal hernias are commonly repaired with open mesh repair (e.g. Lichtenstein repair)
• Bilateral inguinal hernias are commonly managed with laparoscopic mesh repair

Post-Operative Advice

Key advice: ^[Ref]

• Early mobilisation and resumption of normal daily activities as tolerated
• Stay off work for at least 1 to 2 weeks (or up to 6 weeks if your job involves heavy lifting)
• Avoid heavy lifting or strenuous activity for at least 4-6 weeks

Surgery Complications

The most significant long-term complication is chronic post-operative inguinal pain (~10%) ^[Ref]

• It can be neuropathic (due to nerve injury, entrapment, or neuroma) or nociceptive (due to meshoma, scarring, or inflammation)

 

Hernia recurrence

• Risk is significantly lower with mesh repair (1-4% at 2-5 years of follow-up ^[Ref])
• Previous repair with direct suturing carries a significant risk of recurrence

 

Structure at risk of injury intra-operatively:

• Ilioinguinal nerve – most common
  • The ilioinguinal nerve runs just along the outer surface of the spermatic cord
  • Ilioinguinal nerve injury would present as neuropathic pain at the groin, upper medial thigh, root of the penis
• Genitofemoral nerve
• Iliohypogastric nerve
• Vas deferens
• Inferior epigastric vessels

Complicated Inguinal Hernia

Urgent surgery (within 6 hours) is necessary for ALL patients with complicated hernia (esp. if there are signs of strangulation or bowel obstruction) ^[Ref]

• Surgery is similar to an uncomplicated hernia – mesh repair open or laparoscopically

Femoral Hernia

Femoral hernias are uncommon (~5% of all abdominal hernias)

Anatomy

The femoral canal lies medial to the femoral vein within the femoral triangle, it is a space enclosed within the femoral sheath

• In a femoral hernia, abdominal contents can protrude through the femoral ring into the femoral canal

 

Femoral canal borders:

• Medial border: lacunar ligament
• Lateral border: femoral vein
• Anterior border: inguinal ligament
• Posterior border: Cooper’s ligament (pectineal ligament) and the superior pubic ramus

Pathophysiology

Femoral hernias are primarily acquired (unlike in inguinal hernias where congenital patent processus vaginalis plays a role)

 

Risk factors: ^[Ref]

• Female (due to a wider femoral canal) (NB male is risk factor for inguinal hernia but female is a risk factor for femoral hernia)
  • Although femoral hernias are more common in females compared to males, inguinal hernias remain ~5x more prevalent than femoral hernias even in female patients
• Multiparity

 

• Other shared-risk factors as an inguinal hernia
  • Advancing age
  • Causes of increased intra-abdominal pressure
    • Chronic coughing (e.g. COPD)
    • Smoking
    • Chronic constipation
  • Low BMI (individuals with low BMI have less pre-peritoneal fat) (so obesity is actually protective against hernia)
  • Connective tissue disorders (e.g. Marfan’s syndrome, Ehlers-Danlos syndrome)

Clinical Features

Femoral hernia presents as a lump inferior and lateral to the pubic tubercle (in the upper thigh region)

• Groin / pelvic pain is common
• 35-40% cases first present as bowel obstruction / strangulation ^[Ref]

 

Femoral hernia carries a higher risk of incarceration and strangulation (compared to inguinal hernias) due to the narrow and rigid boundaries of the femoral canal ^[Ref]

Investigation and Diagnosis

Clinical diagnosis is sufficient in most cases.

 

If clinical evaluation is equivocal / an occult hernia is suspected:

• 1st line: ultrasound
• 2nd line: CT / MRI

Management

Surgical repair is indicated in ALL cases of femoral hernia ^[Ref]

• Due to the high risk of complications, watchful waiting is NOT advised even if the patient is asymptomatic
• Standard surgical technique: open mesh repair

Incisional Hernia

Aetiology

Patient-dependent risk factors: ^[Ref]

• Advancing age
• Obesity
• COPD
• Surgical wound infection
• Classic risk factors for poor wound healing
  • Diabetes
  • Immunosupression
  • Smoking
  • Malnutrition

 

Operation-dependent risk factors: ^[Ref]

• Mindline incision (significant risk factor)
• Long incision
• Open laparotomy
• Emergency surgery

Clinical Features

A visible / palpable lump at the site of a previous abdominal incision ^[Ref]

• More apparent on standing or performing Valsalva manoeuvres
• Asymptomatic in up to 60% of patients
• If symptomatic, pain is the most common symptom

Investigation and Diagnosis

Clinical diagnosis is typically sufficient

 

If necessary, ultrasound or CT can be used to confirm diagnosis.

Management

Mesh repair (open or laparoscopic) is indicated if:

• Symptomatic
• High risk of incarceration / strangulation

 

Asymptomatic, small hernias in high-risk surgical candidates may be managed non-operatively with observation and lifestyle modification

Rare Miscellaneous Hernias

Overview

Hernia	Description	Learning tips
Sliding hernia	Hernia that involves a partially retroperitoneal structure (e.g. caecum, sigmoid colon)
Littre’s hernia	Hernia that contains the Meckel’s diverticulum	Meckel’s diverticulum is only seen in Littre (little) children
Spigelian hernia (lateral ventral hernia)	Hernia that protrudes through lower lateral edge of rectus abdominis (below / lateral to umbilicus)   At the level of the arcuate line at the semilunaris
Amyand hernia	Hernia that involves the vermiform appendix	A in amyand = A in appendix
Richter’s hernia	Partial herniation of the bowel wall (bowel continuity is maintained, does not cause full bowel obstruction)
Maydl’s hernia	The hernia contains 2 loops of bowel	Like an M (2 bowel loops form a shape similar to the letter M)