What Causes Liver Enzymes Of 300 On A Child?

Hi. Blood tests have just shown that my 17-year-old, athletic, healthy son has liver enzymes of nearly 300. He s experiencing abdominal pain, extreme enough to keep him awake at night, and doctor found significant tenderness on palpitation. He has dark urine but no obvious blood in urine or stools. My son doesn t drink alcohol, doesn t use drugs, and is a bit of a health nut with regards to his diet. More blood tests are being run, and he s scheduled for an ultrasound -- what are doctors trying to rule out? (What are possible causes of his symptoms?) And what questions should we be asking to make sure that he s getting appropriate evaluation and treatment?