Why would a vascular study be recommend by a surgeon for chronic idiopathic peripheral neuropathy/neuralgia (severe left foot) and pudendal neuralgia?

Rule out other cause: Idiopathic means that we really do not know the underlying cause of the neuropathy. In working up pain or numbness in the extremity, vascular studies, like an ultrasound, can help look for some occlusive disease. Nerves need blood to function and the lack of oxygen can cause injury. Discuss with the doc who ordered the test.

Vascular study nerve: A vascular study, such as an ankle / brachial index, is often done in the setting of unilateral pain, even if it is felt to be due to a peripheral nerve condition.

Complete: These types of conditions are not straight forward. There are many interconnecting bodily systems so this test is being ordered to rule out all potential causes. For examples, some of my pudendal neuralgia patient's have had disorder of varicose veins that compress and aggrevate the nerve.