Appendicitis/diagnosis; Abdomen, Acute/diagnosis; Abscess/etiology; Acute Disease; Adolescent; Adult; Age Factors; Appendectomy; Appendicitis/complications; Body Temperature; Cellulitis/etiology; Child; Chronic Disease; Diagnosis, Differential; Female; Fever/etiology; Humans; Hyperplasia; Intestinal Obstruction/etiology; Jaundice/etiology; Leukocytosis/etiology; Lymphoid Tissue; Male; Middle Aged; Pharynx; Respiratory Tract Infections/etiology; Sex Factors; Statistics as Topic; Tissue Adhesions/etiology; Urinary Tract Infections/diagnosis; Vomiting/diagnosis; Vomiting/etiology; Wound Infection/etiology