Inguinal hernias

What is an inguinal hernia?

An abdominal hernia comprises a protrusion of abdominal contents through the fascia of the abdominal wall; an inguinal hernia is where this protrudes through the internal inguinal ring. Hernias contain a portion of peritoneal sac and may contain viscera, usually small bowel and omentum.

Inguinal hernia

Inguinal hernia epidemiology

Inguinal hernias are common, making up 75% of all abdominal hernias.

Inguinal hernias are more common in men (the lifetime risk of an inguinal hernia is 27-43% in men and 3-6% in women).¹ Although they are much more common in men, women with a groin hernia are still more likely to have an inguinal than a femoral hernia.²

As well as male sex, risk factors include increasing age (although there is also a significant spike in cases below the age of 5 years) and a genetic predisposition.²

Other risk factors are thought to include: smoking, chronic obstructive pulmonary disease, lower body mass index, high intrabdominal pressure, thoracic or abdominal aortic aneurysm, patent processes vaginalis, history of open appendectomy, peritoneal dialysis, and collagen vascular disease.²

Inguinal hernia presentation

• An inguinal hernia will usually present as a swelling in the groin that may appear with lifting and be accompanied by sudden pain.

• There may be a cough impulse. The hernia may not be visible when lying flat but may appear on standing.

• The hernia may be reducible.

• Indirect hernias can cause pain in the scrotum and cause a 'dragging sensation'.

Congenital inguinal hernias are usually detected at birth and all need urgent outpatient referral for surgical repair.

Inguinal hernias in older children and adults usually develop gradually but can occur suddenly with an episode of heavy lifting:

• At first appearance, a hernia is usually easily reducible when the patient reclines. However, it may require manual replacement if large.

• With time, the hernia enlarges and becomes harder to replace, due to fibrous adhesions forming.

• When it can no longer be reduced, it is irreducible or incarcerated. This can occur at any time, as can strangulation. This occurs when visceral contents of the hernia become twisted or entrapped by the narrow opening. This compromises the blood supply, causing swelling and eventually infarction. Strangulation usually leads to bowel obstruction.

There are two types of inguinal hernia:

• Indirect: a protrusion through the internal inguinal ring passes along the inguinal canal through the abdominal wall, running laterally to the inferior epigastric vessels. This is the more common form accounting for 80% of inguinal hernias, especially in children. It is associated with failure of the inguinal canal to close properly after passage of the testis in utero or during the neonatal period.

• Direct: the hernia protrudes directly through a weakness in the posterior wall of the inguinal canal, running medially to the inferior epigastric vessels. It is more common in the elderly and rare in children.

Assessment³

• Examine the patient both standing and lying and ask them to cough or strain.

• Insert a finger through the top of the scrotum into the external inguinal ring and palpate for a lump when coughing - cough impulse.

• Sliding hernias are probable with large scrotal hernias.

Differential diagnosis

See also the separate Lumps in the groin and scrotum article.

• Femoral hernia.

• Hydrocele (when differentiating from an inguinoscrotal hernia, note that it is possible to get above a hydrocele on examination).

• Spermatic cord hydrocele.

• Lymph node swelling.

• Abscess.

• Saphena varix.

• Varicocele.

• Bleeding.

• Undescended testis.

Investigations

Whilst most specialists agree that imaging is not necessary to make the diagnosis, in the UK there are often local constraints on referrals for hernia repair which mean that the diagnosis needs to be confirmed by imaging. Ultrasound scan is the imaging option of choice.³⁴

Inguinal hernia treatment and management

Adults^{5 2}

If the inguinal hernia is small, the patient may only need reassurance. There is good recent evidence that "watchful waiting" is a safe option for many adults with inguinal hernias. Long-term follow-up of these patients suggests that around 68% proceed to surgical management eventually, usually due to worsening pain or lifestyle limitations from progression.²

Patients with pain, reduced mobility or other symptoms should be offered surgical management. Many patients with chronically incarcerated hernias may be asymptomatic but patients with obstruction or strangulation are a surgical emergency.

However, there is always the chance of it becoming a surgical emergency through obstruction and incarceration. Episodes of pain and tenderness suggest the need for urgent treatment but when these become prolonged and severe then emergency surgery is indicated for possible strangulation. The fundamentals of indirect inguinal hernia treatment are the same regardless of the patient's age. Reduction or excision of the sac and closure of the defect with minimal tension are the essential steps in any hernia repair.

Surgical guidelines recommend tailoring the choice of surgery to individual patient factors. Surgical options include either an open (tissue- or mesh-based) procedure or a minimally invasive (laparoscopic or robotic) procedure.

An open repair with mesh is associated with a 50%-75% lower risk of hernia recurrence, lower risk of chronic pain post-operatively, and an earlier return to work compared with a sutured repair. A tissue (sutured) repair is usually used where mesh is contraindicated, for example where there may be potential for infection from a contaminated field. Laparoscopic repair is recommended for bilateral inguinal hernias as the same port sites can be used.

Studies have shown no significant difference between mesh, laparoscopic and robotic procedures in terms of post-operative haematoma, surgical site infection, urinary retention, or hospital length of stay. However post-operative chronic pain appears to be lower in patients who have undergone laparoscopic procedures, though studies have been of questionable quality.

Inguinal hernias in children

The incidence of incarcerated or strangulated hernias in paediatric patients is higher than in adults, at around 7-11%.⁶ It is higher in infants than in older children. The risk increases with waiting time from diagnosis to procedure.⁶⁷

Surgical repair is usually recommended as early as possible in paediatric patients because of these risks.

Laparoscopic repair has been shown to have better outcomes than open repair though both have low risks of complications.⁸⁹¹⁰

Complications

These include:

• Post-operative chronic pain is reported to occur in between 8 and 16% of patients, though laparoscopic repair appears to reduce the risk.²

• Recurrence: 1.0% - most happening within five years of operation. Recurrence rate increases:

  • In children aged younger than 1 year.

  • In elderly patients.

  • After incarcerations.

  • In those with ongoing increased intra-abdominal pressure.

  • Where there is growth failure.

  • With prematurity.

  • Where there are chronic respiratory problems.

  • In girls with sliding hernias.

• Infarcted testis or ovary with atrophy.

• Wound infection.

• Bladder injury.

• Intestinal injury.

• A hydrocele from fluid accumulation in the distal sac usually resolves spontaneously but sometimes requires aspiration.

Prognosis

This is generally very good, depending on comorbidity.