Clinical features of misdiagnosed appendicitis in children. STUDY OBJECTIVE: To compare clinical features of children with misdiagnosed appendicitis with those of children with appendicitis initially diagnosed correctly. DESIGN: Retrospective review of hospital, emergency department, and clinic records. SETTING: University medical center with annual ED census of 40,000 patients. PARTICIPANTS: Children less than 13 years old admitted between May 1, 1979, and April 30, 1989, with a discharge diagnosis of appendicitis. MEASUREMENTS: Records were reviewed for historical, physical examination, laboratory, and pathologic features for all patients on their initial presentation to a physician and on final presentation during which the correct diagnosis was made. Using chi 2 analysis and Student's test, clinical features of misdiagnosed patients and patients diagnosed correctly were compared. RESULTS: One hundred eighty-one cases were identified with 50 initially misdiagnosed. On initial presentation, misdiagnosed patients were younger and more likely to have vomiting before pain onset, constipation, diarrhea, dysuria, and signs and symptoms of upper respiratory infections. Misdiagnosed cases were less likely to have right lower quadrant tenderness and documentation of bowel sounds, peritoneal signs, and rectal examinations. On final presentation, misdiagnosed patients were more likely to have pain duration of more than two days, temperature of more than 38.3 C, and to appear lethargic and irritable (P less than .05 for all measurements). CONCLUSION: Clinical features of children with misdiagnosed appendicitis differ from those of children with appendicitis initially diagnosed correctly. 