A hernia is defined as the protrusion of part or whole of an organ or tissue through the wall of the cavity that normally contains it.
An inguinal hernia occurs when abdominal cavity contents enter into the inguinal canal. They are the most common type of hernia and account for 75% of all abdominal wall hernias, with a prevalence of 4% in those over 45 years.
In this article, we shall look at the classification, clinical features and management of aninguinal hernia.
There are two main subtypes of inguinal hernia:
- Direct inguinal hernia (20%) – Bowel enters the inguinal canal “directly” through a weakness in the posterior wall of the canal. They occur more commonly in older patients, possibly secondary to abdominal wall laxity or a significant increase in intra-abdominal pressure.
- Indirect inguinal hernia (80%) – Bowel enters the inguinal canal via the deep inguinal ring. They arise from incomplete closure of the processus vaginalis, an outpouching of peritoneum allowing for embryonic testicular descent, therefore are usually deemed congenital in origin. They may also occur due to stretching of the deep inguinal ring for the same reasons that direct hernias occur.
These two types of inguinal hernia can only be reliably differentiated at the time of surgery by identifying the inferior epigastric vessels. Indirect hernias will be lateral to the vessels whilst direct hernias will be medial to the vessels.
There are several factors that increase the risk of developing an inguinal hernia:
- Increasing age
- Raised intra-abdominal pressure
- Chronic cough, heavy lifting, or chronic constipation
The most common presenting symptom is a lump in the groin, which will initially disappear with minimal pressure or when the patient lies down. There may be mild to moderate discomfort which can worsen with activity or standing.
If the hernia is incarcerated, it can become painful, tender, and erythematous. If the bowel lumen becomes blocked, the patient may also present with symptoms of bowel obstruction (such as abdominal distention, vomiting, and / or absolute constipation).
You must examine any groin lump in a systematic and structured manner. Specific features of note include:
- Cough impulse
- Remember that a irreducible hernia may not have a cough impulse
- Location – Inguinal (superomedial to the pubic tubercle) or femoral (inferolateral to the pubic tubercle) – this is not always clear on examination.
- Reducible – On lying down +/- minimal pressure.
- If it enters the scrotum, can you get above it / is it separate from the testis?
Clinical Differentiation of Herniae
Theoretically, to differentiate a direct from an indirect inguinal hernia, the examiner must reduce the hernia and then place pressure over the deep inguinal ring (located at the mid-point of the inguinal ligament). The patient is then asked to cough:
- If hernia protrudes despite occlusion of the deep inguinal ring – indicates a direct hernia
- If hernia does not protrude – indicates an indirect hernia
However, as suggested earlier, this examination is unreliable and the only definite method to differentiate them is at the time of surgery.
There are several differential diagnoses for a lump in the groin. These include:
- Femoral hernia
- Saphena varix
- Inguinal lymphadenopathy
- Groin abscess
- Internal iliac aneurysm
If the mass extends into scrotum, consider a hydrocele, varicocele, or a testicular mass.
A hernia is typically a clinical diagnosis.
The Royal College of Surgeons Guidelines state that imaging should only be considered in patients if there is diagnostic uncertainty or to exclude other pathology. If necessary, an ultrasound scan is recommended as first line imaging.
Any patient with a symptomatic inguinal hernia (significant mass or discomfort) should be offered surgical repair.
However, a third of patients with an inguinal hernia will never experience any symptoms; these patients should be managed conservatively. Importance should be placed on likelihood of future surgical intervention and symptom of potential strangulation.
Hernia repairs can be performed via open repair (Lichtenstein technique most commonly used) or laparoscopic repair (either total extraperitoneal (TEP) or transabdominal pre-peritoneal (TAPP))
Open mesh repairs are preferred for those with primary inguinal hernias and is deemed the most cost-effective technique in this patient group. They can be done under general, spinal or local anaesthesia, dependent on patient fitness and surgeon preference.
A laparoscopic approach is preferred in those with bilateral or recurrent inguinal hernias. In can also be considered in certain patients with a primary unilateral hernia, mainly hose at a high risk of chronic pain (young and active, previous chronic pain, or predominant symptom of pain) or in females (due to the increased risk of the presence of a femoral hernia).
Laparoscopic repairs are associated with longer operating times but quicker post-operative recovery, fewer complications, and less post-operative pain.
The risk of strangulation is approximately 3% per year. Any patient presenting with evidence of strangulation (pain or obstruction) requires urgent surgical exploration.
The patient may require analgesia and IV fluids +/- the insertion of an NG tube for any bowel decompression. Patients presenting as a strangulated hernia should be made aware of the possibility of bowel resection and the formation of a stoma.
The main complications of an inguinal hernia are incarceration, strangulation, and obstruction.
Post-operative complications of hernia repair include:
- Pain, bruising, haematoma, infection, or urinary retention.
- Recurrence, approximately 1.0% within 5 years of surgery.
- Chronic pain (persisting 3 months after hernia repair), can occur in up to 30% patients and is disabling in ~2%
- Damage to vas deferens or testicular vessels, leading to ischaemic orchitis (and potentially sub-fertility).