There are numerous etiologies of splenomegaly, which can be broadly categorized as hematological (anemias, hematological neoplasms), hemodynamic (such as portal vein obstruction), infectious (especially viral), metabolic, neoplastic (non-hematological metastases), and owing to connective tissue disorders.
Since the etiologies are so varied, the associated manifestations will also vary widely from patient to patient. In rare cases, you may be able to appreciate a palpably enlarged spleen on physical exam. Patients may also complain vaguely of dull LUQ pain, fatigue (from anemia), and abdominal fullness.
A healthy spleen has a homogeneous echogenicity, smooth capsular contours, and a craniocaudal length no more than 12cm in an adult (although taller males may have a spleen up to 14cm long). Any larger, and your patient likely has splenomegaly.
Other findings in splenomegaly include a rounded inferior splenic surface – note above how the spleen sort of “hugs” the kidney and is convex inferiorly, whereas in the image below, the bottom has become concave with respect to the kidney, also dwarfing it in size.