Case11

Pink Red Urine in a Child Who Ingested Prenatal Vitamins

Background

A 2-year-old boy is brought to the emergency department (ED) several hours after ingesting an unknown number of his mother's prenatal iron tablets.
His parents report that the child has been vomiting bright-red blood and has had 1 episode of bloody diarrhea. He has no history of medical problems and does not currently take any medications on a regular basis.
On physical examination, the child appears lethargic and irritable. His temperature is 99.0ºF (37.2ºC), with a heart rate of 150 bpm, a respiratory rate of 24 breaths/min, and a blood pressure of 88/55 mm Hg. His cardiorespiratory findings are otherwise unremarkable. On abdominal examination, he has diffuse, mild tenderness to palpation. The child is moving all of his extremities.
Acute iron toxicity is diagnosed, and the patient's hemodynamic status is stabilized with boluses of isotonic intravenous fluid. A plain radiograph of the abdomen does not reveal any retained tablets. Laboratory studies, including a serum iron level measurement, are performed, and the child is admitted to the intensive care unit for further treatment. Upon noting the gastrointestinal symptoms, acidemia, and continued lethargy with confusion, the consulting toxicologist recommends treatment with a specific pharmacologic agent. Shortly after the agent is administered, the child's urine changes from yellow to pink-red (see Figure 1). The laboratory result for the serum iron level that was obtained approximately 4 hours after the iron-tablet ingestion was 1200 µg/dL.

What is the cause of the pink-red urine seen in this iron toxicity case?
Hint: Chelation therapy was administered for the iron toxicity.

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