Serum C-reactive protein and the site of urinary tract infections.

Elevated surum levels of C-reactive protein have been found regularly in girls with acute clinical pyelonephritis but only infrequently in those with clinical cystitis. Based on these data, the suggestion has been made that elevated serum CRP concentrations may be useful in identifying patients with upper urinary tract infections. In a study in which the bladder washout test was used to localize the site of urinary tract infections, we identified nine girls with renal bacteriuria who did not have clinical findings suggesting acute pyelonephritis; four of these girls had serum CRP concentrations less than 10 micrograms/ml. Twenty-eight girls had bladder washout-proven lower urinary tract infections; three of these had serum CRP values greater than 30 micrograms/ml. These studies show that an elevated serum CRP concentration is not accurate in localizing the site of a urinary tract infection in girls who do not have clinical signs of acute pyelonephritis.