This will be a single-cohort prospective interventional study. It will not interfere with the usual procedures, consisting of clinical examination in the Emergency Department (ED) and execution of the following exams at the physician's discretion: complete blood count with differential, C reactive protein, abdominal ultrasound, abdominal CT. Patients admitted to Emergency Department with Lower Abdominal and suspicion of Acute Appendicitis not needing immediate surgery, are requested by informed consent to undergo observation and non operative treatment with antibiotic therapy (Amoxicillin and Clavulanic Acid). The patients by protocol should not have received any previous antibiotic treatment during the same clinical episode. Patients not undergoing surgery will be physically examined 5 days later. During this follow-up visit, the patient will be given information about the study, will be invited to participate, and will be asked to sign an informed consent form. If the patient is under the age of 18 years, consent will be obtained from a parent or other legal guardian.