Lateral artery, middle vein and medial femoral canal with lymphatics
Mnemonic
NAVEL, from lateral to medial in the femoral triangle:
- N - femoral Nerve (outside the sheath)
- A - femoral Artery
- V - femoral Vein
- E - Empty space, the femoral canal
- L - Lymphatics, and the lymph node of Cloquet
The femoral canal is the empty space, and it exists to let the vein expand. It is also where a femoral hernia descends, and because its neck at the femoral ring is narrow and rigid, femoral hernias have a high risk of strangulation.
“The nerve is outside the sheath” is the point most often missed: the sheath is a continuation of transversalis and iliac fascia and contains only the artery, vein and canal.
Femoral versus inguinal hernia is decided by the pubic tubercle: a femoral hernia is below and lateral, an inguinal hernia above and medial.
Expansion
The femoral sheath has three compartments, lateral to medial:
- Lateral - femoral artery
- Middle - femoral vein
- Medial - the femoral canal, containing a lymph node (of Cloquet), fat and lymphatics
The femoral canal allows the vein to expand and is the weak point through which a femoral hernia protrudes, below and lateral to the pubic tubercle. The femoral nerve lies outside the sheath.