Femoral artery branches. Adapted from Ruiz Villareal 4 

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... risk factors for pseudoaneurysm formation include low femoral puncture, increased length of procedure, larger sheath size ‡ 7 French, difficult access, hypertension and simul- taneous arteriovenous access. 3 Traditionally, ultrasound has been the diagnostic modality of choice, often demonstrating tur- bulent flow or the to and fro sign that is considered pathagnomic and occurs as a result of diastolic reversal of flow in the aneu- rysm neck. There are multiple branches of the femoral and profunda femoris arteries ( Figure 5). Given this intricate arrangement of vessels in a relatively small space, the potential for injury is high. Lying adjacent and medial to the common femoral artery is the common femoral vein. In procedures such as this where the target vessel is the vein, the three arteries that are most at risk are the superficial epigastric, and the superficial and deep external pudendal arteries, which can be seen coursing medially off the artery in the diagram. The other vessel at risk is the medial circumflex femoral artery and its branches, as it leaves the profunda femoris medially before looping laterally to encircle the femoral neck. Injuries here are more common when the arterial puncture site is low. In our case, it is difficult to say exactly which vessel was damaged, but it is likely that it was the deep external pudendal artery or one of its branches. This is by no means a first report of such a case. Shannon et al 5 report a similar case, which was complicated by major retroperitoneal haemorrhage, managed by endovascular coiling. Waldherr et al 6 report superselective embolization of a deep femoral artery branch pseudoaneurysm sustained through both percutaneous coronary intervention and as a complication of hip surgery. The management of pseudoaneurysms depends on several factors including size and location. Small, superficial aneurysms may be treated with thrombin injection, whereas larger ones may require formal surgical excision and arterial repair. In cases such as this where the bleeding vessel is deeper, the first approach should be endovascular, as it is less invasive and carries a lower morbidity. Inspite of this injury not being a first report, this delayed presentation reminds us of several important points. First, with the increasing use of interventional techniques across all medical specialties, the use of image guidance to aid vessel access is paramount for safety; not all specialties currently practise this routinely. Furthermore, we should consider arterial injury in all patients, including those who have had venous puncture. Injuries may not necessarily occur at the anterior vessel wall, and may well be deeper. Finally, there should be a low threshold for alternative imaging if symptoms are out of context with clinical findings. We present an elusive complication of vascular access. Conven- tional first-line imaging techniques here can be falsely reassuring and a high suspicion of this type of complication is paramount in the face of on-going ...