Can someone help me with his diagnosis for care plan?

My patient came in with chronic abdominal pain. He's been having abdominal pain for years without known cause. He's been to doctors but they do not know what the problem is. I am trying to do my care plan.

P: chronic pain
E:
S: As evidenced by facial grimacing, pain level 9/10, no appetite

what do I put for the etiology? it's usually related to something like surgery, or cancer
but his cause is unknown
OK, you already said it yourself...r/t undiagnosed conditionso we know eg it's not his head that hurts, so, chronic abdominal pain... and you might AEB more specific do it by your assessment. Where is it, What causes the pain to be worse? Movement, position, palpation, eating, not eating, etc. How long has he had this pain?