Black Coloured Urine following Organophosphorus Poisoning: Report of Two Cases

Organophosphorus poisoning is common in rural Asia. Clinical features result from overactivity of acetylcholine receptors. Blackish discoloration of urine is not a feature of organophosphorus poisoning. Only one case of black colored urine following quinalphos poisoning has been reported in literature. We report two cases of organophosphorus poisoning from two different compounds, following which patients passed black colored urine, in the absence of haemolysis or rhabdomyolysis. These cases indicate that blackish discoloration of urine in organophosphorus poisoning might not be as uncommon as it was believed to be. Besides, urinary excretion of metabolites might be an underlying mechanism, rather than hemolysis. 1. Introduction The public health importance of organophosphorus poisoning is reflected in the huge number of deaths due to suicidal and accidental toxicity from these compounds [1]. History of exposure, characteristic signs and symptoms of toxicity, and low serum cholinesterase levels make the diagnosis almost certain [2]. Intermediate syndrome causing respiratory failure is one of the most dreaded complications [3]. Although atypical complications like pancreatitis and haemolysis have been described [4, 5], only one case of blackish discoloration of urine has been reported in literature, following quinalphos poisoning [6]. This report describes two cases sharing this atypical manifestation, but due to different compounds. 2. Case Report The first patient was a 26-year-old male farmer, brought to the emergency room 3 hours after intentional ingestion of 100？mL of monocrotophos (organophosphorus compound). He was conscious and oriented with a heart rate of 56/minute and blood pressure of 110/60？mm？Hg. His pupils were pinpointed and he had fasciculations. Examination of chest revealed bibasal fine crackles. Gastric lavage was administered and he was started on infusion of atropine sulfate titrated according to clinical response. In view of diaphragmatic weakness, he was intubated and ventilated. His investigations showed haemoglobin of 13.5？g% with normal leucocyte and platelet counts. Renal and liver functions were normal. Serum cholinesterase levels were low (650？U/L; normal: 3500–8500？U/L). After 6 hours of hospitalization, he started passing black colored urine (Figure 1). We evaluated this uncommon manifestation and found no evidence of haemoglobin or myoglobin in the urine. Besides, creatine phosphokinase levels were found to be normal, ruling out the possibility of rhabdomyolysis. The patient developed ventilator associated pneumonia on