What causes sharp pains in lower abdomen?

Lots. The list is quite long from gynecological (cysts, infection, endometriosis, etc.), gastrointestinal (diverticulitis, appendicitis, irritable bowel, inflammatory bowel, etc.), anatomical (hernias etc.) among others. A proper history and physical exam will be necessary to narrow the options.
?kidney stones . Kidney stones, appendix, ovarian, colitis are possible. There are other possibilities like muscular or nerve compression. Please check with your doctor.