Splenomegaly, although associated with numerous diseases, remains one of the more elusive physical exam findings in the abdomen. Conditions such as infectious mononucleosis, thalassemia, and cirrhotic liver disease may all involve splenomegaly and as a result, the search for a reliable sign associated with this condition has been sought for generations. Currently, several such signs of splenomegaly exist, all of whose utility has been debated in medical literature. The presence or absence of splenomegaly, however, can be reliably appreciated on physical exam using Castell's sign in conjunction with other clinical information, increasing the positive predictive value of the test. When used in a decision-making rubric, Castell's sign becomes a valuable part of deciding whether to pursue further imaging.