An inguinal hernia is a protrusion of all or part of a viscus through the wall of the abdominal or pelvic cavity in which is normally contained, causing a visible or easily palpable bulge.

Male sex, elderly patients (above 75 years old), family history of collagen defects such as Ehler-Danlos syndrome are risk factors for developing inguinal hernias.

Inguinal hernias lie superior and medially to the pubic tubercle. Right-sided hernias are more common clinical presentations than left (due to descend of the testis or previous appendectomy).

Patients who develop strangulated hernias typically presents with an acute onset of symptoms such as irreducible groin mass, pain in their groin and/or abdomen, nausea, and vomiting. Many other patients will be asymptomatic but regular clinic follow-up is needed as symptoms could develop over a 5-10 year period.

The management of inguinal hernias depends on the severity of the presentation of clinical symptoms. For mild/asymptomatic hernias, the treatment management plan would be conservative such as weight loss, smoking cessation etc. For symptomatic hernias, referral to secondary care for management.

There are various classification methods for inguinal hernias as there is no universal classification available at this moment in time yet. The anatomical classification is widely recognised. However, this classification method is not as clinically useful in the secondary care management as compared to the Nyhus classification and European Hernia Society (EHS) classification.

Anatomical classification:

• Direct inguinal hernia lies medially to the inferior mesenteric artery.
  • The hernia extends through the deep inguinal ring, inguinal canal and superficial ring. Complete hernia sac extends all the way in the fundus, the incomplete sac can be limited to the canal or inguinoscrotal or inguinolabial.

• Indirect inguinal hernia lies laterally to the inferior mesenteric artery.
  • The hernia passes through the defect in fascia transversalis (posterior wall of the inguinal canal). The hernia normally does not run alongside the cord to the scrotum.

Inguinal hernia may be further sub-classified into the following groups:

• Reducible:
  • Manual pressure allows the contents of the hernia to be returned to their original compartment.

• Irreducible or incarcerated:
  • If the bowel is incarcerated, the hernia contents may not be reduced into the peritoneal cavity, but blood supply to hernia contents have not been compromised.

• Strangulated:
  • When the blood supply to the hernia contents is compromised, this can lead to ischemia, gangrene and perforation of the affected bowel segment.

European Hernia Society (EHS) classification:

• Type of hernia
  • Primary
  • Recurrent

• Anatomical location of the hernia
  • Lateral
  • Medial
  • Femoral

• Size of hernia orifice
  • <1.5 cm (one finger)
  • 1.5 cm to 3 cm (two fingers)
  • >3 cm (more than two fingers)

Nyhus classification:

• Type I: indirect inguinal hernia with the normal internal ring
  • Congenital, as seen in paediatric patients

• Type II: indirect inguinal hernia
  • Dilated internal inguinal ring with posterior inguinal wall intact

• Type III: posterior wall defects
  • 3A) Direct inguinal hernia
  • 3B) Indirect inguinal hernia
  • 3C) Femoral hernia

• Type IV: recurrent hernia
  • 4A) Direct hernia
  • 4B) Indirect hernia
  • 4C) Femoral hernia
  • 4D) Combination of 4A, 4B, and 4C

The aetiology for inguinal hernias and their risk factors:

• Male sex: this is common in older patients above 75 years old, especially for direct hernias.
• Family history: this is common in collagen defect medical conditions such as Ehlers-Danlos syndrome, Marfan’s syndrome.
• Previous right lower quadrant abdominal incisions: appendectomy and prostatectomy
• Premature babies
• Less common causes:
  • Abdominal aortic aneurysm
  • Defective transversalis fascia

Patients with inguinal hernias have demonstrated to have decreased collagen levels and abnormal collagen metabolism → progressive degeneration of elastin-related fibres in transversalis fascia of abdomen and groin area → the changes of the structure of transversalis fascia lead to the dilation of the opening of transversalis fascia (where the deep inguinal ring passes through) and/or weakness of the posterior wall of the inguinal canal → the protrusion of abdominal and/or pelvic contents occur in the inguinal area, creating a visible bulge.

• For direct inguinal hernia patients, the degeneration in the changes of the structure of the aponeurosis of the transversalis fascia. This allows the hernia to bulge through the posterior wall of canal medial to the inferior epigastric artery through Hesselbach’s triangle, which consists of the inferior epigastric artery (lateral), inguinal ligament (inferior) and lateral border of rectus abdominals (medial).
• For indirect inguinal hernia patients, the failure of processus vaginalis to close leads to the formation of an empty peritoneal sac lying in the inguinal canal. The hernia passes through the deep inguinal ring along the inguinal canal and into the scrotum and covered by the layers of the cord. The hernia becomes clinically evident when bowel or other abdominal content fills and enlarges the empty sac.
• Indirect hernias are more likely to be strangulated as compared to direct hernias. This is because the structural defect in a direct hernia is usually a widespread weakness of the inguinal floor tissues, rather than a discrete, defined ring-like defect.
  • The indirect hernia passing through a tight internal ring allows segments of the intestine to prolapse through the defect in the anterior abdominal wall → this process causes the sequestration of fluid within the lumen of the herniated bowel.
  • The impairment of lymphatic and venous drainage occurs → which further aggravates the swelling of the bowel → leading to the impairment of the arterial supply, which subsequently causes ischemia. If left untreated, gangrene occurs, and eventually the perforation of the bowel.

There are clinical features specifically to look out for in different inguinal hernias. The determinant of the type of inguinal hernia is usually during surgery.

The rate of strangulation for inguinal hernias increases at 0.3-2.9% per year, increase risk if hernias are irreducible or indirect. Up to 60% of adult male inguinal hernias are indirect.

The presentation of symptoms in patients with acute strangulated hernias usually occurs within a few hours, whereas for patients who are asymptomatic or have mild symptoms could take years to develop.

In general, patients with inguinal hernias typically present i.e. an asymptomatic lump, groin mass (reducible or not), groin and/or abdominal pain, previous surgical scars, nausea, vomiting, and constipation.

During the physical examination, there are tests that can be performed to differentiate between direct or indirect inguinal hernias.

• To test for indirect inguinal hernias, finger pressure should be applied over the deep inguinal ring. The finger pressure will control the hernia when the patient coughs.
  • The deep inguinal ring anatomical location: 1cm superior to the inguinal ligament, midway between ASIS and pubic tubercle.
• To test for direct hernias, instruct the patient to cough, and a bulge should appear medial to point of finger pressure.

The clinical presentation for strangulated hernias are usually acute and require immediate treatment. The common symptoms presented are:

• Pain
• Groin discomfort
• Irreducible groin mass
• Tender distended abdomen with lack of bowel sounds
• Abdominal pain
• Nausea
• Vomit
• Constipation

Most inguinal hernias are diagnosed clinically, through observation and physical examination of the abdomen and groin. However, it may be useful in certain clinical scenarios such as suspected recurrent hernia or possible hydrocele, uncertain diagnosis, and surgical complications, especially chronic pain.

• If diagnosis in doubt or in complex cases, there are imaging available such as:
  • Ultrasound scan of the groin
  • CT/MRI scan of the groin and abdomen
  • Herniography of the groin (but rarely use in practice now)
• For strangulated hernias, investigations in acute scenarios include FBC, U&Es, LFTs, CRP, lactate, urinalysis, group and save, CT, MRI, ultrasound scan of the groin and abdomen.

Inguinal hernias may easily be confused with other causes of groin masses.

Possible differential diagnoses:

• Femoral hernia:
  • Similarities: clinical symptoms presentation similar to inguinal hernia.
  • Differences: anatomically the femoral hernia is situated inferior and laterally to the pubic tubercle.
• Saphena varix:
  • Similarities: groin mass and cough impulse present.
  • Differences: saphena varix is a localised protrusion of saphenous vein at the groin region, where it joins the femoral vein, always reducible, and disappears when the patient lying down whereas inguinal hernias are not always reducible.
• Femoral aneurysm:
  • Similarities: groin mass.
  • Differences: pulsatile swelling in the groin with a continuous murmur, weak peripheral pulse.
• Lymphadenopathy:
  • Similarities: groin mass.
  • Differences: firm and round texture, usually presented with lower limb infections, abrasions, wound in the peritoneum, carcinoma.
• Psoas abscess.
• Lipoma.
• Undescended testis (cryptorchidism).
• Varicocele or hydrocele.

The management of inguinal hernias depends on the severity of the presentation of clinical symptoms.

For mild/asymptomatic hernias, the treatment management plan would be conservative. For symptomatic hernias, referral to secondary care for management.

Acute hernias require immediate attention and can be life-threatening.

Conservative management for inguinal hernias depends on the presentation of clinical symptoms:

• Patients with mild/asymptomatic hernias: watchful waiting if the risk of bowel obstruction and strangulation is low. However, 6-months regular clinic follow-up usually needed as some patients move on to develop symptoms over the 5-10 year period.
• Acute hernia (strangulation/ incarceration): refer to secondary care (general surgery) immediately.

Secondary care management for inguinal hernias include patient counselling and surgical repair procedures.

Patient counselling:

• Encourage patients to lose weight (if overweight) before surgery.
• Stop smoking.
• Postoperatively: the patient's expectations should be managed on the risk of hernia recurrence and the chronic pain that the patient may experience.

Surgical repair procedures:

According to the European Hernia Society Guidelines for Inguinal Hernia in Adults (2009), the surgery procedure depends on the presentation of the hernia:

Primary unilateral/ bilateral hernia:

• Mesh repair (Lichtenstein’s or endoscopic repair), the mesh repair uses polypropylene mesh to reinforce the posterior wall. A recurrence rate of 2-10% for both procedures.

Recurrent inguinal hernia:

• If previous anterior hernia repair: open preperitoneal mesh or endoscopic approach
• If previous posterior hernia repair: Lichtenstein’s totally extraperitoneal (TEP). A minimally invasive procedure where the mesh is used to seal the hernia from outside the peritoneum.

Clinical presentation of the severity of hernia:

• Elective surgery is suitable for indirect hernias, symptomatic for direct hernias.
• Emergency/ prompt treatment is suitable for painful irreducible hernias (presenting complaint of onset less than 4 weeks).

There are various complications associated with inguinal hernias, mostly related to:

Post-operation:

• Haematoma: internal bleeding due to trauma of surrounding viscus and blood vessels
• Infection of wound and mesh.
• Recurrence of inguinal hernias can be between 10-30%.
• Testicular atrophy/ ischemic orchitis as a result of spermatic cord damage in males.
• Urinary retention problems in male patients
  • Patients with pre-existing prostatic symptoms such as BPH.

Rare complications:

• Bowel obstruction.
• Incarceration and strangulation of hernia contents.