Sciatica pain is caused by pressure on the sciatic nerve, which runs from the lower back down through the hips, buttocks and back of the leg. If the pressure presses on the nerves that are responsible for bowel control, it can lead to incontinence or constipation. This condition is known as cauda equina syndrome. Cauda equina syndrome is a surgical emergency. If you experience pain, numbness, tingling or weakness in one or both of your legs, and if you lose control of your bowels or bladder, seek medical attention immediately.