Femoral herniae are relatively uncommon but are are an important problem due to their high rate of strangulation (because of their narrow neck).
Femoral hernia occur 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 (ratio 3:1), because of the wider anatomy of the female bony pelvis. It is very rare for a femoral herniation to occur in a child.
Femoral Canal Anatomy
The femoral canal (Fig. 1) 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).
The rigidity of the borders of the femoral ring, especially the concave margin of the lacunar ligament, results in femoral hernias being very prone to complications requiring urgent surgical intervention.
The main risk factors for developing a femoral hernia include:
- Pregnancy (higher incidence in multiparous women)
- Raised intra-abdominal pressure (e.g. heavy lifting, chronic constipation)
- Increasing age
Femoral hernias will commonly present as a small lump in the groin. Whilst a femoral hernia is usually asymptomatic (aside from the lump) at presentation, due to the anatomy of the femoral canal, around 30% of femoral hernia cases will present as an emergency (either 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 although often, particularly in obese patients, it is not clear.
- Femoral hernia – found infero-lateral to the pubic tubercle (and medial to the femoral pulse)
- Inguinal hernia – found supero-medial to the pubic tubercle
- A femoral hernia can roll up superiorly and in front of the inguinal ligament and are often misdiagnosed as inguinal
The tightness of the femoral ring means that the hernia is unlikely to be reducible.
The differential diagnoses for a lump in the groin include low presentation of inguinal hernia, femoral canal lipoma or lymph node, saphena varix*, or a femoral artery aneurysm. Athletic Pubalgia occurs following a small tear in rectus sheath through which impingement of abdominal wall musculature can occur, most often in young athletes,
*Saphena varix will disappear when lying flat, have palpable thrill when coughing, and there will be the presence of varicose veins elsewhere
All patients with a femoral hernia need surgical intervention (as discussed below), hence routine pre-operative investigations should be performed if possible.
Whilst the diagnosis can be made clinically, additional imaging is often required.
Ultrasound scanning can demonstrate a femoral hernia (Fig. 2) but these are operator dependent and a high index of suspicion is necessary. A CT abdomen-pelvis scan will also demonstrate a femoral hernia, as well as delineate any differential diagnosis.
If there is significant doubt in the diagnosis or evidence of complications, then the lump should be surgically explored.
All femoral hernias should be managed surgically, ideally within 2 weeks of presentation, due to the high risk of strangulation.
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 is the preferred technique in an emergency intervention due to the easy access to compromised small bowel
The operation involves reducing the hernia and then narrowing the femoral ring with sutures medially between the pectineal and inguinal ligaments or with a mesh plug .
Emergency Presentation and Management of a Hernia
The serious complications of a hernia that require urgent intervention are:
- Irreducible / incarcerated – 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 that has strangulated will present as an irreducible and tender tense lump, the pain often being out of proportion to clinical signs. This may be accompanied with clinical features of obstruction.
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.
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 obstructed.
An acute presentation of femoral hernia carries an increased morbidity and 20 times higher mortality than that of elective surgery, as well as the associated risks of bowel resection, wound infection, and cardiorespiratory complications.
- Female gender and pregnancy increase the risk of developing a femoral hernia
- Femoral hernias commonly present as an emergency; any patient (particularly older females) presenting with vomiting must have their groins examined as it is commonly missed
- Femoral hernias have a high rate of strangulation, urgent surgery is therefore mandatory
- Surgical management can be taken via a low or high approach