Hi. Thanks for your query. Noted the history about your son having stomach cramps, nausea, vomiting for the past 9 days, ruled out appendicitis, gall stones with infection, unable to work, severe pains radiating to the back, staying hydrated but eats very little and also has chills... This is most probably due to Gastroenteritis and I would advise him the following: Get the blood and stool tests so that your Doctor on clinical evaluation can assist you better in the following way. The most probable treatment for such an Abdominal Pain with Diarrhea , a waterborne disease can be a course of an antibiotic, Metronidazole, Tablets against worms, anti-spasmodics, Probiotics and supportive therapy. If there is no relief within a few days you can go for consultation of a Surgical Gastroenterologist and Investigations like that of stool, blood, urine, ultrasonography and CT scan of the abdomen. Colonoscopy and Upper GI Endoscopy. Treatment can be planned according to the clinical evaluation and reports. Additional treatment with a PPI like Omeprazole and Domperidone can help further.