For women with dysmenorrhea, if they only have pain on the left side during menstruation, it is often necessary to consider that the secondary dysmenorrhea may be caused by the presence of ovarian chocolate cysts on the left side, because in women with chocolate cysts, it is often due to the local atrophy and necrosis of the chocolate cysts that stimulates the local pain of the ovaries on the left side, so that when the pain occurs in such women, only In these women, when pain occurs, only the left side of the ovary is painful, but not the right side. For women with dysmenorrhea on the left side only, an ultrasound may be required to determine if the abnormality is due to a chocolate cyst on the left ovary.