Atypical clinical features of pediatric appendicitis.

BACKGROUND: The diagnosis of appendicitis remains challenging in children. Delays in diagnosis, or misdiagnosis, have important medical and legal implications. The typical, or classic, presentation of pediatric appendicitis has been modeled after adult disease; however, many children present atypically with subtle findings or unusual signs.
OBJECTIVES: To determine the frequency of atypical clinical features among pediatric patients with appendicitis and to investigate which atypical features are the strongest negative predictors for appendicitis among patients being evaluated for appendicitis.
METHODS: Children and adolescents with suspected appendicitis were enrolled over 20 consecutive months. Pediatric emergency physicians completed standardized data collection forms on eligible patients. Final diagnosis was determined by pathology or follow-up telephone call. Typical and atypical findings were defined strictly a priori.
RESULTS: Seven hundred fifty-five patients were enrolled. The median age was 11.9 years (interquartile range [IQR]: 8.5, 14.9 yr); 36% of patients were diagnosed with appendicitis. Among patients with appendicitis, the most common atypical features included absence of pyrexia (83%), absence of Rovsing's sign (68%), normal or increased bowel sounds (64%), absence of rebound pain (52%), lack of migration of pain (50%), lack of guarding (47%), abrupt onset of pain (45%), lack of anorexia (40%), absence of maximal pain in the right lower quadrant (32%), and absence of percussive tenderness (31%). Forty-four percent of patients with proven appendicitis had six or more atypical characteristics. The median number of atypical features for patients with proven appendicitis was five (IQR: 4.0, 7.0). The greatest negative predictors, on the basis of likelihood ratios, were as follows: white blood cell count (WBC) of <10,000 per cubic millimeter (likelihood ratios [LR], 0.18), absolute neutrophil count (ANC) of <7,500 per cubic millimeter (LR, 0.35), lack of percussive tenderness (LR, 0.50), lack of guarding (LR, 0.63), and no nausea or emesis (LR, 0.65).
CONCLUSIONS: Appendicitis in pediatric patients is difficult to diagnose because children present with a wide variety of atypical clinical features. Forty-four percent of patients with appendicitis presented with six or more atypical features. Two atypical features are the strongest negative predictors of appendicitis in children: WBC of <10,000 per cubic millimeter and an ANC of <7,500 per cubic millimeter.