Abnormal vaginal discharge may also not have a known cause. In one study looking at women presenting to clinic with concerns about vaginal discharge or a foul smell in their vagina, it was found that 34% had bacterial vaginosis and 23% had vaginal candidiasis (yeast infection).[6] 32% of patients were found to have sexually transmitted infections including Chlamydia, Gonorrhea, Trichomonas, or Genital Herpes.[6] Diagnosing the cause of abnormal vaginal discharge can be difficult, though a potassium hydroxide test or vaginal pH analysis may be used. When abnormal discharge occurs with burning, irritation, or itching on the vulva, it is called vaginitis.[2] The most common causes of pathological vaginal discharge in adolescents and adults are described below.