Puncture sites for femoral lines should lie between the groin crease and the inguinal ligament; punctures outside of these zones risk complications. The inguinal ligament stretches from the anterior superior iliac spine down to the pubic symphysis and marks the inferior border of the peritoneum. Hence, punctures above this point will likely enter the peritoneal cavity, with potential visceral injury and bacterial seeding. Aspiration of enteric contents or ascitic fluid should immediately alert the operator of this eventuality, and a general surgical team should be alerted.

Conversely, attempting cannulation too inferiorly (below the groin crease) risks laceration of branch vessels. The common femoral artery branches into the superficial femoral and deep femoral arteries at this point. Similarly, in the venous system, the greater saphenous vein joins the deep femoral vein roughly 3 cm inferior to the inguinal ligament, forming the femoral vein. Although the operator may obtain a “flash” of blood into the syringe at a distal site, there may be difficulty threading the wire through the junction of the superficial to the common femoral artery. More significantly, the needle may lacerate the femoral artery “through and through” and also injure the vein, eventually leading to an arteriovenous fistula (usually >2 days after the injury). A patient with diminished distal pulses, a groin bruit, pulsatile mass, and potentially a drop in blood pressure after attempts at femoral cannulation should be suspected of an arteriovenous (AV) fistula, and a high-quality vascular duplex study should be ordered. Evidence of
flow between the artery and vein should prompt an immediate vascular surgery consult.