femoral vein

**Anatomy** - Course: The popliteal vein becomes the femoral vein as it passes through the adductor hiatus. The femoral vein ascends in the anterior thigh and becomes the external iliac vein at the inguinal ligament. - Tributaries: the deep femoral vein (profunda femoris), which joins in the proximal thigh; the great saphenous vein, which joins at the saphenofemoral junction (saphenous opening, about 3-4 cm inferolateral to the pubic tubercle); and the circumflex femoral veins. - Femoral triangle: The borders are the inguinal ligament (superior), sartorius (lateral), and adductor longus (medial). The contents from lateral to medial are Nerve, Artery, Vein, Empty space (femoral canal), Lymphatics (NAVEL). All of these sit within the femoral sheath except the femoral nerve. The femoral canal contains deep inguinal (Cloquet) lymph nodes and is the site of femoral hernias. - Naming: The femoral vein is part of the *deep* venous system, despite the name "superficial femoral vein" used in older terminology. This is a clinical trap, because a clot there is a true DVT and needs anticoagulation.

**Clinical significance** 1. DVT: The femoral and popliteal veins are the most common sites of proximal lower-extremity DVT. - Virchow triad: stasis, endothelial injury, hypercoagulability. - Risk factors: immobilization, surgery, malignancy, pregnancy, oral contraceptives, factor V Leiden, and others. - Presentation: unilateral leg swelling, pain, warmth, and erythema. - Diagnosis: Wells score, then D-dimer if low or moderate probability. Compression duplex ultrasound is the initial imaging test. - Complication: pulmonary embolism. Proximal DVT carries the highest PE risk. - Treatment: anticoagulation (DOAC, LMWH, or warfarin). An IVC filter is used if anticoagulation is contraindicated. 2. Central venous access: The femoral vein is accessed just medial to the femoral pulse, below the inguinal ligament. It is useful in emergencies and codes because it is compressible and does not interrupt chest compressions. Its drawbacks are the highest rates of catheter-related infection and DVT, and arterial puncture is possible. Inserting above the inguinal ligament risks retroperitoneal hemorrhage. 3. Femoral hernia: This is more common in women and has a high risk of incarceration and strangulation. The hernia passes through the femoral canal, which lies medial to the femoral vein and is inferior and lateral to the pubic tubercle. An indirect or direct inguinal hernia lies above the inguinal ligament. 4. Trauma or iatrogenic injury: Cardiac catheterization via the femoral artery can cause an AV fistula or pseudoaneurysm if the adjacent vein is punctured. 5. Chronic venous insufficiency: Valve incompetence at the saphenofemoral junction causes varicose veins of the great saphenous system. 6. Phlegmasia cerulea dolens: This is massive iliofemoral DVT with severe swelling, cyanosis, and risk of limb ischemia. It is an emergency. 7. May-Thurner syndrome: The right common iliac artery compresses the left common iliac vein. This causes left-leg iliofemoral DVT, typically in young women.

**High-yield pearls** - The femoral vein is medial to the artery, so the mnemonic for needle placement is "vein is medial to the artery" (from lateral to medial: NAVEL). - Venous drainage of the lower limb: superficial (great and small saphenous) and deep (femoral, popliteal, tibial) systems connect via perforator veins. DVT mainly involves the deep system. - Lymphatics: Superficial inguinal nodes drain the lower limb, perineum, and lower abdominal wall. Deep inguinal nodes lie medial to the femoral vein.