Joseph, a previously healthy 20-year-old male, presented to the emergency department with complaints of severe abdominal pain. He described the pain as starting around his umbilicus and gradually migrating to the right lower quadrant over the past 24 hours. He rated the pain as 8 out of 10 on a numeric pain scale, exacerbated by movement and coughing. He reported associated symptoms of nausea and loss of appetite, but denied any vomiting, diarrhea, or fever. There were no urinary symptoms, and he feels constipated. What is the most likely diagnosis?
1) Appendicitis
2) Gastritis
3) Kidney stones
4) Gallstones