Muscle strain, an injury to back muscles, ligaments or joints are few common causes of back pain. Compression of one of the lumbar nerves, the sacral nerve or the sciatic nerve may also be cause of lower left back pain. Kidney stones, kidney infection, irritable bowel syndrome are few other possibilities. Gynecological causes like ovarian cyst, fibroids can all lead to lower back ache. It is important to evaluate the cause of pain before initiating treatment. A clinical examination and ultrasound abdomen may be helpful. I hope you find this information useful.
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