PYURIA AND BACTERIURIA IN URINE SPECIMENS OBTAINED BY CATHETER FROM YOUNG-CHILDREN WITH FEVER

Results of urinalysis and culture of 2181 urine specimens obtained by catheter from febrile children aged less than 24 months were analyzed to determine the following: (I) an optimal cutoff point in considering a bacterial colony count clinically ''significant,'' (2) the accuracy of leukocyte esterase and nitrite tests in identification of pyuria and bacteriuria, and (3) the utility of pyuria (defined as greater than or equal to 10 leukocytes/mm(3)) in the discrimination of urinary tract infection from asymptomatic bacteriuria. Among 110 urine cultures with greater than or equal to 10,000 colony-forming units per milliliter, 92 (84%) had greater than or equal to 100,000 CFU/ml, 10 (9%) had 50,000 to 99,000 CFU/ mt, and 8 (7%) had 10,000 to 49,000 CFU/ml. Urine specimens with 1000 to 49,000 CFU/ml were more likely than specimens with greater than or equal to 50,000 CFU/ml to yield Grampositive or mixed organisms (36/60 vs 7/109; p < 0.001). A count of < 10 leukocytes/mm(3) was almost invariably associated with a sterile culture; a count of greater than or equal to 10 leukocytes/mm(3) was found in 93 of 102 patients with greater than or equal to 50,000 CFU/ml. The dipstick leukocyte esterase test had sensitivities of 52.9% and 66.7% in detecting greater than or equal to 10 leukocytes/mm(3) and greater than or equal to 20 leukocytes/mm(3), respectively. The dipstick nitrite test had a sensitivity of 31.4% in detecting bacteriuria (greater than or equal to 50,000 CFU/ml). Acute pyelonephritis was diagnosed by a renal scan with dimercaptosuccinic acid labeled with technetium 99m in 50 (77%) of 65 patients with greater than or equal to 10 leukocytes/mm(3) but in none of five patients with < 10 leukocytes/mm(3) (p < 0.01). The findings in these five patients were consistent with colonization of the urinary tract rather than infection. For urine specimens obtained by catheter, we believe that urinary tract infection is best defined by both a leukocyte count greater than or equal to 10/mm(3) and a CFU count greater than or equal to 50,000/ml. This definition almost always discriminates among true urinary tract infection, bacteriuria resulting from contamination of the urine specimen, and asymptomatic bacteriuria.