Abdominal pain is common and often due to diseases related to the digestive organs. Abdominal pain on the left side can be caused by all the organs nearby. It may follow a problem in the spleen, stomach, or pancreas. The colon is often involved in this kind of pain in older people in the case of diverticulitis, inflammation of small pouches in the colon wall. The kidney can sometimes cause left abdominal pain, but this often occurs nearer to the back. Constipation is the most common cause of pain in this location.