Discrimination of culture negative pyelonephritis in children with suspected febrile urinary tract infection and negative urine culture results.

BACKGROUND

We investigated whether the C-reactive protein (CRP) level, urine electrolytes, and urine sodium-potassium ratio (uNa/K) could be useful markers for discriminating children with culture negative pyelonephritis (CNP) from children with suspected febrile urinary tract infection (fUTI) and negative urine culture results.

METHODS

We examined 264 children experiencing their first fUTI consecutively admitted to our hospital between January 2011 and October 2014. Blood tests (CRP, white blood cell count [WBC], erythrocyte sedimentation rate [ESR], electrolytes) and urine tests (urine protein to creatinine ratio [uProt/Cr], electrolytes, uNa/K) were performed upon admission. All children with fUTI underwent 99m-dimercaptosuccinic acid (DMSA) scanning at admission. Data were compared between children with acute pyelonephritis (APN), CNP, lower UTI and controls. Using multiple logistic regression analysis (MLRA), the ability of these parameters to predict a cortical defect on DMSA scan (APN and CNP) was analyzed.

RESULTS

The laboratory findings of CNP children were similar with those of APN children except uProt/cr. The CRP level, WBC count, and ESR were higher in children with CNP, while uNa and uNa/K were lower than in children with lower UTI and control. By MLRA, CRP levels and uNa/K were the most relevant factors for predicting a cortical defect on DMSA scan (P = 0.002, <0.001, respectively).

CONCLUSIONS

We conclude that the combination of CRP or WBC and uNa/K are useful for discriminating children with CNP from children with suspected fUTI and negative urine culture results.