Notes · Anatomy · 23 October 2026

Femoral triangle anatomy

Definition

• The femoral triangle is a pyramidal space in the upper anterior thigh, situated just below the inguinal ligament.
• It serves as a conduit for neuro‑vascular structures passing from the abdomen into the lower limb and is a key landmark for clinical procedures such as femoral artery cannulation and lymph node biopsy.

Boundaries

Contents (from lateral to medial)

1. Femoral Nerve (L2‑L4) – the most lateral structure; lies outside the femoral sheath.
2. Femoral Artery – lies within the femoral sheath, just medial to the nerve.
3. Femoral Vein – positioned medial to the artery, also within the sheath.
4. Deep Inguinal Lymph Nodes – lie deep to the femoral vein, embedded in the femoral sheath.
5. Cloquet’s (Deep) Femoral Canal – a conical space medial to the femoral vein that contains the deep lymphatic vessels and the terminal portion of the great saphenous vein.

Mnemonic (L‑A‑V‑C): Lateral – Nerve, Artery, Vein, Cloquet’s canal (medial).

Femoral Sheath

• A fascial tube that encloses the femoral artery, femoral vein, and the femoral canal.
• It is divided into three compartments:
  • Lateral compartment – contains the femoral artery.
  • Intermediate (or medial) compartment – contains the femoral vein.
  • Posterior compartment – the femoral canal, which holds lymphatics and the terminal part of the great saphenous vein.

Clinical Significance

1. Vascular Access

• The femoral artery is commonly accessed for coronary angiography, cardiac catheterisation, and emergency resuscitation.
• Palpation of the pulsation just inferior to the inguinal ligament and lateral to the femoral vein confirms correct site.

2. Femoral Hernia (Rare)

• A femoral hernia protrudes through the femoral canal, appearing as a bulge inferior and lateral to the pubic tubercle.
• More common in women due to a wider bony pelvis.

3. Compression Syndromes

• Femoral nerve block (e.g., for knee surgery) is performed in the triangle, requiring knowledge of the nerve’s lateral position.
• Iliac artery aneurysm or deep vein thrombosis (DVT) can compress the femoral vein, leading to swelling of the lower limb.

4. Lymphadenopathy

• Enlarged deep inguinal nodes (e.g., in sexually transmitted infections or malignancy) are palpable deep to the femoral vein.

5. Trauma

• Penetrating injuries to the triangle can damage the femoral artery, leading to rapid exsanguination; immediate control with a vascular tourniquet or direct pressure is lifesaving.

Investigations

Management (Current Guidelines – 2023)

Vascular Access

• Guideline: American College of Cardiology (ACC) / American Heart Association (AHA) 2023 recommends ultrasound‑guided femoral puncture to reduce complications.
• Technique:
  1. Position patient supine with slight hip flexion.
  2. Identify the femoral pulse mid‑point between the ASIS and pubic tubercle.
  3. Use a high‑frequency linear probe to visualise the artery and vein.
  4. Insert needle below the inguinal ligament, lateral to the vein, and medial to the nerve.

Femoral Hernia Repair

• Guideline: European Hernia Society (EHS) 2022 recommends laparoscopic totally extraperitoneal (TEP) repair as first‑line for uncomplicated femoral hernias.
• Key steps: reduction of hernial sac, placement of mesh covering the femoral canal, fixation to the Cooper’s ligament.

Deep Vein Thrombosis (DVT) in the Triangle

• Guideline: ACCP 2022 suggests direct oral anticoagulants (DOACs) (e.g., apixaban 10 mg BID for 7 days, then 5 mg BID) for at least 3 months.

Femoral Nerve Block

• Guideline: ASA 2023 recommends ultrasound‑guided peripheral nerve block to improve block success and reduce vascular puncture.

Traumatic Vascular Injury

• Immediate direct pressure for arterial bleed.
• If uncontrolled, apply a proximal tourniquet above the inguinal ligament.
• Definitive repair: vascular surgeon for end‑to‑end anastomosis or graft interposition.

Complications

• Bleeding/Hematoma: due to arterial puncture; may compress the femoral vein causing secondary DVT.
• Arterial pseudo‑aneurysm: pulsatile mass after catheterisation; diagnosed by duplex US.
• Femoral nerve injury: presents as weakness of knee extension and loss of sensation over the anterior thigh; can occur from hematoma or iatrogenic needle trauma.
• Infection: catheter‑related sepsis; requires removal of the device and antibiotics.
• Lymphatic leak: after extensive node dissection; may cause a persistent seroma.

High‑Yield Exam Points

• Mnemonic for contents (L‑A‑V‑C) – remember the order from lateral to medial.
• Femoral pulse location: midway between the ASIS and pubic tubercle, just inferior to the inguinal ligament.
• Femoral sheath compartments: lateral (artery), intermediate (vein), posterior (femoral canal).
• Distinguish femoral vs. popliteal pulse: femoral is above the knee crease; popliteal is behind the knee.
• Femoral hernia emerges inferior to the inguinal ligament and lateral to the pubic tubercle – opposite of an inguinal hernia.
• Complication of femoral artery cannulation: pseudo‑aneurysm – look for a “to-and-fro” Doppler waveform.
• Clinical test for femoral nerve: ask the patient to extend the knee; weakness suggests nerve involvement.

Practice questions

1. Which structure lies lateral to the femoral artery within the femoral triangle?
   Answer: Femoral nerve — it is the most lateral structure, situated outside the femoral sheath.

2. A 45‑year‑old woman presents with a painless bulge inferior to the inguinal ligament, lateral to the pubic tubercle. Which hernia type is most likely?
   Answer: Femoral hernia — it protrudes through the femoral canal, appearing lateral to the pubic tubercle.

3. During ultrasound‑guided femoral artery cannulation, which landmark helps avoid accidental venous puncture?
   Answer: The femoral vein lies medial to the artery — keeping the needle lateral to the vein prevents venous injury.

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AI-assisted study material for exam revision. Always confirm with standard textbooks and current guidelines; not medical advice.