Solution: Pseudoaneurysms are a relatively common complication after arterial access. The typical imaging finding is the yin-yang appearance seen in this case with to and fro flow seen on pulsed doppler imaging. Treatment used to be direct compression of the neck of the pseudoaneurysm for 30 minutes utilizing US guidance. If the first 30 minutes did not work, then repeat compressions would be necessary. Obviously, this was brutal for both the physician/technologist and the patient. It is now easily treated with thrombin injection. You mix up the thrombin at 1,000 units/ml and using US guidance and a tuberculin syringe, slowly inject. It usually takes between 0.5 and 1.5 ml to completely thrombose the pseudoaneurysm and you inject as far away from the neck as possible. The primary success rate is in excess of 90% and secondary success rate is around 100%. Complications are uncommon, but include thromboembolic phenomena (usually self-limited), and allergic reactions. Here is what it looked like 2 minutes later after treatment with thrombin injection.