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. A femoral hernia occurs when abdominal viscera or omentum passes through the femoral ring and into the potential space of the femoral canal.
Femoral hernias account for 5% of abdominal hernias and are more common in women than men (3:1), secondary to the wider anatomy of the female bony pelvis. It is very rare for a femoral herniation to occur in a child.
In this article we will revise the anatomy of the femoral ring and canal before analysing the clinical diagnosis and management of femoral hernias.
Femoral Canal Anatomy
The femoral canal is an anatomical compartment, located in the anterior thigh. It contains lymphatic vessels, lymph nodes and some loose connective tissue.
The superior border of the femoral canal is the femoral ring, which is covered by the femoral septum (a connective tissue layer).
It is important to appreciate the rigidity of the borders of the femoral ring, especially the concave margin of the lacunar ligament (Fig.1) – as without any laxity in the walls of the borders, femoral hernias are subsequently very prone to strangulation.
Risk factors for developing a femoral hernia include:
- Increasing age
- The incidence is higher in multiparous than nulliparous women
- Increased intra-abdominal pressure (heavy lifting, chronic constipation)
Femoral hernias will commonly present as a lump in the groin. Whilst a femoral hernia is usually asymptomatic (aside from the lump) at presentation, around 30% of femoral hernia cases will present as an emergency (obstruction or strangulation).
It is important to identify the exact location of the lump in the groin in order to decide which type of hernia is present:
- Femoral hernia – found infero-lateral to the pubic tubercle and medial to the femoral pulse.
- Inguinal hernia – found superomedial to the pubic tubercle.
However, a femoral hernia can migrate superiorly to the inguinal ligament and are sometimes misdiagnosed as inguinal. The tightness of the femoral ring means that the hernia is unlikely to be reducible.
More details for the examination of a hernia can be found here.
The differential diagnoses for a lump in the groin include:
- Low presentation of inguinal hernia
- Femoral canal lipoma
- Femoral lymph node
- Saphena varix
- Disappears when lying flat, palpable thrill when coughing, presence of varicose veins elsewhere
- Femoral artery aneurysm
- Athletic Pubalgia
- Small tear in rectus sheath through which impingement of abdominal wall musculature occurs (common in young athletes)
All patients with a reducible femoral hernia will eventually need surgical intervention (as discussed below), hence routine pre-operative investigations will be needed (e.g full blood count, baseline liver and kidney function tests).
Whilst the diagnosis is usually clinical, the gold standard is via an ultrasound scan. US scans are 96% accurate in identifying the specific type of hernia but are operator dependent.
Magnetic resonance imaging (MRI) has been shown to be more accurate than US scans in the diagnosis of inguinal hernias, yet there is currently a lack of evidence supporting its use in differentiating between the origin of groin lumps overall.
However, if there is significant doubt in the diagnosis, then the lump should be surgically explored.
All femoral hernias should be surgically managed, due to the increased risk of strangulation of the hernia (compared to inguinal hernia).
Surgical intervention requires the reduction of the hernia and then surgical narrowing of the femoral ring with the use of interrupted sutures (extra care should be taken to avoid narrowing the femoral vein in the process)
Two different approaches can be taken with the femoral hernia surgical reduction:
- Low approach – the incision is made below the inguinal ligament, which has the advantage of not interfering with the inguinal structures but does result in limited space for the removal of any compromised small bowel.
- High approach – the incision is made above the inguinal ligament, via the posterior wall of the inguinal canal, and is the preferred technique in an emergency intervention due to the easy access to compromised small bowel. Its main limitation is the need to repair the inguinal canal on closure, thus providing an obvious new area of weakness and potential secondary herniation.
The risk of strangulation of femoral hernias increases with time following initial diagnosis; after 3 months the risk of strangulation is 22% and reaches 45% after 21 months. As with any hernia, there is also a risk of becoming irreducible or obstructed.
An acute presentation of femoral hernia carries an increased morbidity and 20 times higher mortality than elective surgery, as well as increased risk of bowel resection, wound infection, and cardiorespiratory complications.
Emergency Presentation and Management of a Hernia
The serious complications of a hernia that require urgent intervention are:
- Irreducible – the contents of the hernia are unable to return to their original cavity.
- Obstruction – the bowel lumen has become obstructed, leading to the clinical features of bowel obstruction.
- Strangulation – compression of the hernia has compromised the blood supply, leading to the bowel becoming ischaemic.
A hernia which has strangulated will present as a tender tense lump that is irreducible (for both patient and clinician). Signs and symptoms of bowel obstruction may be present (depending on the time delay to presentation).
A strangulated hernia is a surgical emergency, due to the time-dependent risk of bowel infarction. The diagnosis is typically a clinical one and requires urgent access to theatres for surgical exploration; due to the time critical nature of the condition, rarely will further imaging be requested.
The specific management for strangulated hernia will vary depending on the type of hernia involved. However, mortality is much higher in emergency cases compared to elective operations for all hernia.