Differentiating Kawasaki disease from urinary tract infection in febrile children with pyuria and C-reactive protein elevation

BACKGROUND: Kawasaki disease (KD) is sometimes confused with urinary tract infection (UTI) because both can present with pyuria and C-reactive protein (CRP) elevation. The present study investigated the clinical and laboratory findings that can differentiate KD from UTI in febrile children with pyuria and CRP elevation. METHODS: Medical records were retrospectively reviewed for children with KD and those with UTI. The clinical and laboratory findings between the KD with pyuria group (n = 48) and the UTI group (n = 118) were compared. RESULTS: The KD with pyuria group had older age (P < 0.001) and longer duration of fever (P < 0.001) than the UTI group. In blood tests, both groups showed increased CRP level, but the value of CRP was higher in the KD with pyuria group than in the UTI group (P < 0.001). The KD with pyuria group also showed higher values for liver enzymes than the UTI group (P < 0.001); > 70.0% of children in the KD with pyuria group, but < 20.0% of children in the UTI group possessed elevated liver enzymes (P < 0.001). On urinalysis, 40.7% of the UTI group had a positive nitrite test, but 0.0% of the KD with pyuria group had a positive nitrite test (P < 0.001). CONCLUSIONS: Elevated liver enzymes are more specific to KD than to UTI, whereas a positive nitrite test is more specific to UTI than to KD. Our findings can be used as diagnostic clues to differentiate KD from UTI in febrile children with pyuria and CRP elevation.