BACKGROUND: Propofol is a short-acting, intravenous sedative-hypnotic agent that 
is widely used for the induction and maintenance of general anesthesia and 
sedation. An uncommon adverse effect of propofol is green discoloration of the 
urine, which has been reported not only under general anesthesia but also with 
sedation. Although it is assumed that the phenolic derivatives of propofol can 
cause green discoloration of the urine, the actual origin remains unknown. The 
aim of this report was to identify the origin of the green discoloration of the 
urine using liquid chromatography-mass spectrometry (LC-MS).
CLINICAL FEATURES: The patient, a 51-year-old man, was scheduled for his oral 
surgery under general anesthesia using propofol. Postoperatively, the color of 
his urine was observed to be green. We compared and analyzed both the green 
urine and the normal urine using LC-MS.
CONCLUSION: We experienced a case of a patient with green discoloration of the 
urine after general anesthesia using propofol. Although LC-MS analysis showed 2 
unique peaks in the green urine at 490 and 590 nm, obvious causes were not 
revealed.