My son complains of lower abdominal pains, around the area of lower belly button. what could be the cause?

Many conditions: cause lower abdominal pain in children, and evaluation depends on the severity and duration of the pain. Progressive pain that starts around the navel and moves to the RLQ along with fever and nausea/V needs to be assessed for appendicitis, but more common are viral gastroenteritis, constipation, indigestion, gas from lactose intolerance, gluten sensitivity, imbalanced diet, or nervous stomach.