It is not possible to detect a ruptured hymen if the hymen is only examined by leucorrhoea. Judgement of whether the hymen is ruptured needs to be made by a professional doctor based on symptoms and signs and cannot be based decisively on the presence of a bloody substance in the leucorrhoea.
If a patient has cervical erosion or is menstruating, both can have bloody leucorrhoea and cannot be identified as a ruptured hymen.