Given the paucity of physical exam findings to evaluate possible splenomegaly, Castell's sign is the most sensitive, and is thus a good tool to teach in an advanced-type physical diagnosis course. Castell's has been shown to be superior in sensitivity to other spleen percussion signs as well as palpation, which is not likely useful due to the extreme enlargement necessary to feel the spleen below the costal margin. Castell's sign is thus, in the appropriate clinical scenario, an important part of the abdominal physical exam.