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 |
Do NOT mix up the following surface anatomy:
- Midpoint of the inguinal ligament: midpoint between ASIS and pubic tubercle (landmark for deep inguinal ring)
- Mid inguinal point: midpoint between ASIS and pubic symphysis (landmark for femoral pulse)
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.
If a hernia is reducible, it is uncomplicated and less worrying
- A reducible hernia refers to a hernia in which the lump can be returned to the abdominal cavity either spontaneously or with gentle manual pressure
If a hernia is not reducible, it suggests a complicated inguinal hernia:
| Incarcerated hernia | Strangulated hernia | |
|---|---|---|
| Definition | Contents are trapped and cannot be reduced back into the abdominal cavity | Incarcerated hernia with compromised blood supply to the herniated tissue, leading to ischemia and potential necrosis |
| Clinical features |
|
|
Incarcerated hernia can progress to mechanical bowel obstruction; in fact hernias are the most common cause of small bowel obstruction.
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
The most definitive way to distinguish between direct and indirect inguinal hernias is during surgery or laparoscopy by visualising the relationship of the hernia sac to the inferior epigastric vessels:
-
An indirect inguinal hernia is lateral to the inferior epigastric vessels
-
A direct inguinal hernia is medial to the inferior epigastric vessels
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
Key differential diagnosis of groin swelling, apart from hernias:
- Inguinal lymphadenopathy
- Undescended testis
- Lipoma
- Cellulitis / abscess
- Saphenous varix
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.
Manual reduction of a strangulated hernia should NOT be attempted because it risks returning non-viable, ischemic, or necrotic bowel to the abdominal cavity, which can lead to sepsis and delayed recognition of bowel compromise.
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
If the inguinal hernia recurs, offer further mesh repair with a different approach to avoid operating at the same anatomical tissue plane twice [Ref]
- If the hernia is first repaired openly, and it now recurs, perform the repair laparoscopically
- If the hernia is first repaired laparoscopically, and it now recurs, perform the repair openly
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
If a complicated hernia progresses to bowel perforation with diffuse peritonitis, sepsis, or haemodynamic instability, an urgent exploratory laparotomy via a midline incision is required.
See the Gastrointestinal (GI) Perforation article for more details.
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]
If a hernia is reducible, it is uncomplicated and less worrying
- A reducible hernia refers to a hernia in which the lump can be returned to the abdominal cavity either spontaneously or with gentle manual pressure
If a hernia is not reducible, it suggests a complicated inguinal hernia:
| Incarcerated hernia | Strangulated hernia | |
|---|---|---|
| Definition | Contents are trapped and cannot be reduced back into the abdominal cavity | Incarcerated hernia with compromised blood supply to the herniated tissue, leading to ischemia and potential necrosis |
| Clinical features |
|
|
Incarcerated hernia can progress to mechanical bowel obstruction; in fact hernias are the most common cause of small bowel obstruction.
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
Key differential diagnosis of groin swelling, apart from hernias:
- Inguinal lymphadenopathy
- Undescended testis
- Lipoma
- Cellulitis / abscess
- Saphenous varix
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
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
If a complicated hernia progresses to bowel perforation with diffuse peritonitis, sepsis, or haemodynamic instability, an urgent exploratory laparotomy via a midline incision is required.
See the Gastrointestinal (GI) Perforation article for more details.
Manual reduction of a strangulated hernia should NOT be attempted because it risks returning non-viable, ischemic, or necrotic bowel to the abdominal cavity, which can lead to sepsis and delayed recognition of bowel compromise.
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
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
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) |