Joelson returned to the United States, his first stop being DC; after disembarking from the plane, he was directly taken to the Walter Reed Medical Center.
The Walter Reed Medical Center, formerly known as the United States Navy Medical Center, merged with the United States Army Medical Center in 2011 to form the Walter Reed National Military Medical Center, which falls under the jurisdiction of the Ministry of Defense.
In other words, this hospital is managed by the Pentagon.
The CIA headquarters is in Lanli and has its own hospital. Although it can't compare with the Walter Reed Medical Center in terms of size and capabilities, sending Joelson there clearly wasn't for medical reasons.
After being taken to the hospital, Joelson's blood was drawn, and he underwent a thorough and meticulous examination; they nearly redid the entire surgery, and they almost did.