Hello! Thank you for the query. Lower left abdominal pain can be caused by urinary tract infection, inguinal hernia, ovarian cyst or strained adductor muscle. Urinary issues usually give also frequent urinating, burning while urinating. Blood in the urine can be present. Inguinal hernia usually gives a lump in the groin which can be more visible (or only visible) when standing and coughing. That is why it can be missed in the CT. Ovarian cyst does not give any other specific symptoms and should be visible in the CT. Strained adductor muscle gives hernia-like pain in the groin. The pain usually appears after regular exercises like running. I suggest you to have urine analysis, general surgeon consult for hernia (and ultrasound of the groin in case of doubts), gynecologist consult with trans-vaginal ultrasound and if nothing will be found, MRI to check for chronic muscles inflammation. Hope this will help. Regards.