Splenomegaly

This radiograph shows a soft tissue opacity in the left upper quadrant without bowel gas. The stomach bubble is oriented vertically and deviated toward the midline, suggestive of mass effect. This appearance is expected in the right upper quadrant where the liver occupies the majority of the space, but the left upper quadrant typically has stomach or bowel gas. The differential for this appearance is broad and includes mass, splenomegaly, and ascites (if the bowel is sufficiently decompressed). Further investigation with CT or ultrasound would be advised. The rest of the exam is unremarkable.

This patient went on to CT which showed marked splenomegaly. Give their young age and reported history of recent illness, this was presumed to be sequela of prior mononucleosis.