purple urine

Coloured urine can be a dilemma to diagnose. Beeturia, red urine after eating beetroot is well known and the dark urine of dehydration also.
Purple urine has been reported after patient catheterisation. It is commoner in women, alkaline urine , constipation, plastic urinary catheterisation and certain bacteria e.g. E Coli , P mirabilis.
This phenomenon can also occur in alkaline urine as a result of the degradation of indican , a metabolite of dietary tryptophan into blue indigo and red indirubin by bacteria.
The urine returns to normal colour after eradicating the bacterial growth and acidification of the urine
Mumoli and Cei 2009 a case of purple urine.QJM 102 p 147.

Martin Eastwood
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