Normal urine is clear and amber colored due to the presence of urochrome, an amorphous pigment1). Variations in color saturation are due largely to differences in urine concentration, but may also be caused by changes in pH, ingested substances and metabolic abnormalities2). It is unusual for urine to develop green discoloration without the addition of either exogenous substances such as medications and food dyes or endogenous pigments such as biliverdin. Here we report a case of green urine hue that developed after the ingestion of herbicides.

A 76-year-old woman was admitted to the hospital following the ingestion of approximately 150 cc of inorganic herbicide (proprietary name : Magma® ; mefenacet, imazosulfuron). She wan initially admitted to the local hospital 1 day before being transferred to our hospital. The patient presented to her local hospital with cyanosis of the lips and hands and her urine was noted to be a very distinctive green color (Figure 1). The patient was referred to our hospital because methemoglobinemia was suspected due to the symptoms of cyanosis and green urine. There was no other drug history. She was treated in the intensive care unit. On examination, her vital signs were blood pressure 140/70 mmHg; heart rate, 98 beats/min; a respiratory rate, 18 breaths/min; body temperature 36.6℃ Clinical examination confirmed cyanotic discoloration of her lips, tongue, fingers, and toes and that her urine was a green color.

Laboratory results were as follows: hemoglobin, 12.6 g/dL; total bilirubin 0.8 mg/dL; blood urea nitrogen, 6.4 mg/dL, and creatinine 0.7 mg/dL. Urinalysis revealed a green colored urine with a pH of 7.0, a specific gravity of 1.011, negative for bilirubin and protein and 5-9 red blood cells per high power field. Arterial blood gas analsyis showed a pH 7.42, pCO₂ 38 mmHg, HCO₃^-25 mEq/L, pO₂ of 132 mmHg and an oxygen saturation of 98.8%; the pulse oxymeter was 98% with oxygen supplied via a nasal canula. The urine culture was negative. Because the patient had cyanotic lips and hands, she was treated with methylene blue because methemoglobinemia was suspected. However, her methemoglobin level was normal and further hypoxia was not observed; therefore administration of methylene blue was stopped. After conservative treatment only, the cyanosis of the fingers and toes improved and the urine color returned to normal by the seventh day of admission.

Discoloration of the urine may be due to endogenous or exogenous substances. A red colored urine is observed with hemoglobinuria, myoglobinuria or porphyria, as well as drugs including metronidazole, phenytoin and rifampicin3). Green colored urine is an uncommon clinical finding that may have several possible causes including medications, dyes or infections (Table 1).

Ehrig et al.4) reported that blue dyes such as Food Dye and Color Blue Number 1, used for enteral feeding, are possible sources of green colored urine in patients with ulcerative colitis. In addition, there have been many reports on the association of greencolored urine with the administration of propofol after surgery5-7). Green urine may be due to the application of methylene blue or indigo blue4, 5), but our patient did not have any history to suggest an explanation for the green colored urine. Bilirubin has also been associated with green urine; however, our patient had a normal serum bilirubin level and the urinalysis was negative for bilirubin and urobilinogen. In addition, there were also no signs of urinary tract infection and the urine culture was negative.

We considered the possibility that mefenacet and imazosulfuron (Magma®) were the cause of the green discolored urine. Mefenacet and imazosulfuron are the main ingredients of magma®; these structures are shown in Figure 2. However, we do not know whether these two compoounds caused the green urine or alternatively whether metabolites of the main ingredients in the herbicides, or other components, were responsible for this change. A sample of the patient's urine was sent to a reference laboratory for spectrophotometric analysis, which showed an absorption peak at 630 nm. in the green color In conclusion, green urine in the setting of a patient admitted to the intensive care unit may reflect a serious condition such as methemoglobulinemia. However, the green urine that was observed after ingesting the herbicide Magma was clinically benign area of the wavelength spectrum (Figure 3).