There are many causes of left-sided back pain, and of course kidney stones can also cause pain in the left side of the back. But this pain is usually very severe and is a deep internal colic. It is possible to roll around when in pain, to shed tears when in pain, and often to curl up in a certain position to relieve the local pain. In most cases, lumbar pain is not caused by kidney stones. Long periods of time in one position, long repetition of certain movements, excessive exposure to cold, sleeping in a soft bed, prolonged sitting and standing, and overexertion and weight bearing can all lead to stimulation of the muscle fibers in the lumbar region or repeated strain, resulting in local congestion and edema and the formation of sterile inflammation, which can also lead to pain in the lumbar region. Lumbar disc herniation causes changes in the pressure in the spinal canal, so it is reflected to the lumbar region through the sinus spinal nerve, causing pain in the lumbar region. Ankylosing spondylitis, septic infection of the lumbar spine, and tumor-occupying disease can also cause pain in the left side of the low back.