Gastrointestinal bleeding: an accessory spleen causing a false-positive Tc-99m-sulfur colloid study.

A Tc-99m-sulfur colloid abdominal scan was performed on a 12-year-old girl to localize the site of gastrointestinal bleeding. The study was normal. When bleeding recurred two weeks later, a repeat study revealed a focal abnormality in the upper abdomen. This was thought to be compatible with a small bleed. However, at surgery an accessory spleen was found, accounting for the abnormal scan.