A 61-year-old man with a history of nephrolithiasis presented to the emergency department with left flank pain and pyelonephritis. Results of abdominal imaging revealed multiple radiodense opacities scattered throughout the patient's colon (panel A). The patient denied macroscopic evidence of foreign bodies in his stool. No clinical or laboratory findings consistent with systemic toxicity from heavy metal ingestion were evident. The patient later recalled using liquid mercury to make batteries. The metal spilled in his toolbox, and, 8 days before presentation, he placed screws from the toolbox intermittently into his mouth. An abdominal radiograph obtained 9 days after presentation revealed colonic transit of the metallic densities (panel B). In patients with healthy gastrointestinal anatomy and transit, metallic mercury ingestion poses minimal risk of tissue injury or systemic absorption. No specific treatment is warranted, and radiologic evidence of metallic mercury is typically no longer present after 1 week.