Well as you describe,possible causes may include Gastritis/peptic ulcer,Kidney stone,Gastroenteritis.
He should try some self care measures including
OTC Prilosec and Emetrol.
Also eat a bland diet.
Avoid caffeine,carbonated beverages,alcohol,spicy,fried food.
Take OTC Mylanta gas and Motrin.
Hydrated himself with Oral rehydration solution.
Monitor his blood pressure.
Also start a probiotic and metamucil.
If pain'll persist then see your doctor for a clinical examination and undergo Urinalysis,Ultrasound whole abdomen.
Hope this helps.
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