Inferior petrosal sinus sampling in the diagnosis of sellar neuropathology.

Because no single test is definitive for Cushing's disease (CD), establishing the diagnosis has remained a challenge that relies on building a critical mass of evidence. The differential diagnosis of corticotropin (ACTH)-dependent Cushing's syndrome (CS) traditionally has rested on noninvasive biochemical and radiologic testing. Bilateral inferior petrosal sinus sampling (BIPSS) is an invasive procedure that has become part of the diagnostic armamentarium surrounding CD. When used appropriately-that is, for patients who have biochemically confirmed ACTH-dependent CS but discordant biochemical or radiologic studies-BIPSS is the reference standard confirmatory test for CD.