Hi, The possible causes of your problem are: Sclerosing stromal tumor of ovary is benign sex cord tumor of ovary. Though these tumors are hormonally inactive, sometimes after removal of the ovary it may take sometime for the regularization of hormones and fluctuations in menstrual flow can be seen. Stress and strain of surgery and blood loss during surgery can also affect the menstrual cycles. Dark colored flow usually indicated collected blood in uterus, so color may not be that much significant. During menstruation cramps and increased frequency of micturition due to increased blood supply to pelvic organs can be seen. Usually these symptoms will subside soon. If these symptoms persist, better to consult your Gynecologist once, get examined and go for ultrasound to rule out other possibilities like postoperative infection, pelvic collection etc. This will help in finding the possible cause of the problem and treatment can be taken accordingly. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr. Sree Gouri SR