A 45-year-old woman gives a four-month history of abdominal pain after eating. She has no weight loss, no change in bowel habit and is well in-between the episodes of pain. When she gets the pain, it is severe, lasting between half an hour to a few hours. It tends to radiate round from the right of her abdomen around to the back. She reports feeling quite nauseous with the pain when it comes on. Could this be gallstones?