Blood cultures in pyelonephritis: Do results change therapy?

OBJECTIVE: To determine how often blood culture results are instrumental in directing the therapy of patients with pyelonephritis. METHODS: Retrospective chart review of all patients admitted to Doctors Hospital with a diagnosis of pyelonephritis to ascertain whether the results of blood cultures were instrumental in the management of those patients. For study purposes, results of blood cultures were considered instrumental if the treatment regimen or diagnostic procedures were changed because of those results. RESULTS: 212 patients were admitted during the study period with a diagnosis of pyelonephritis. Of these, 105 (49.5%) had blood cultures ordered as part of their workup. Adult patients had at least 2 blood cultures ordered and some had as many as 4 or 6 sets ordered during hospitalization. Most pediatric patients had only a single blood culture ordered for diagnosis. Of the 105 patients, 88 (83.5%) had no growth on any of the tubes drawn. 17 patients had positive growth in at least one tube; however, 6 out of these 17 patients were judged by the treating physician to have contaminated cultures that were not diagnostically useful. Of the 105 patients, only 11 (10.4%) were considered to have positive culture results by their treating physician. The organism identified by blood culture was compared to that present in the patient's urine culture, and in only 2 patients did the results differ and were found to have a secondary site of infection. Only in these 2 cases were the antibiotic regimens changed because of the blood culture results. No patient without a second site of infection had a change in therapy based on the blood culture results. CONCLUSIONS: In patients admitted for pyelonephritis, blood cultures may not be needed.