What tests/scans do they do to find the fistula?
Apparently impossible to pick up on MRI and CT.
The only options are valsalva test (unreliable), inspection (unreliable) or taking away fluid in the area for testing which is rarely done as requires surgery by which point you might as well patch (dogma)
Surgery is only performed if there is history of some kind of trauma and proof symptoms are mostly on one side mainly.
@T_T may have more thoughts.
90% are supposed to heal spontaneously but a hydrops can develop and leave you with MAV like symptoms for years.