Millions of Americans have peripheral artery disease, a disorder primarily caused by fatty deposits that can narrow arteries and block blood flow to the legs. Often, the first symptom they feel is leg pain. Experts say that most treatments are safe, but some have expressed a growing sense of alarm that doctors may be doing procedures that patients don’t need, exposing them to unnecessary risks.

ProPublica looked into artery procedures and found that some doctors are making millions of dollars doing a questionable number of treatments. Government insurers pay well for vascular procedures that are done outside of hospitals, and doctors can bill tens of thousands of dollars for treatments done in a single office visit.

One doctor in Maryland made millions of dollars from the federal government for performing thousands of vascular procedures. A state medical board investigation found that his inappropriate treatments put patients at risk of serious harm. One man had to have his leg amputated after invasive treatments for mild pain, according to filings in a settled lawsuit. A grandmother bled out and died shortly after the same doctor cut into her, according to another ongoing lawsuit. The doctor denied the allegations in legal filings, but declined to be interviewed and did not respond to emailed questions.