The utility of blood cultures in pyelonephritis

Kim Y, et al. Usefulness of Blood Cultures and Radiologic Imaging Studies in the Management of Patients with Community-Acquired Acute Pyelonephritis. Infect Chemother. 2017 Mar;49(1):22-30.

APN is diagnosed by clinical signs and symptoms of upper urinary tract infection, and isolation of the pathogen from urine [4]. In clinical practice, blood cultures and radiologic imaging studies such as CT are commonly used [5,6,13]. Although these tests have been performed on a substantial number of patients, there has been controversy as to their accuracy and usefulness. The purpose of this study was to evaluate the impact of blood cultures and radiologic tests on the management of CA-APN patients.

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Long B, Koyfman A. Best Clinical Practice: Blood Culture Utility in the Emergency Department. J Emerg Med. 2016 Nov;51(5):529-539.

“The utility of blood cultures has been a focus of controversy, prompting research evaluating effects on patient management. Bacteremia is associated with increased mortality, and blood cultures are often obtained for suspected infection. False-positive blood cultures are associated with harm, including increased duration of stay and cost. This review suggests that blood cultures are not recommended for patients with cellulitis, simple pyelonephritis, and community-acquired pneumonia, because the chance of a false-positive culture is greater than the prevalence of true positive cultures. Blood cultures are recommended for patients with sepsis, meningitis, complicated pyelonephritis, endocarditis, and health care-associated pneumonia. Clinical prediction rules that predict true positive cultures may prove useful. The clinical picture should take precedence. If cultures are obtained, two bottles of ≥7 mL should be obtained from separate peripheral sites.”

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Ledochowski S, et al. Relevance of blood cultures in acute pyelonephritis in a single-center retrospective study. Intern Emerg Med. 2015 Aug;10(5):607-12.

Pyelonephritides are frequently encountered diagnosis in Emergency Departments. Urinalyses have a central place in the management of this situation but the usefulness of blood cultures is not clear. We conducted a single-center retrospective study of 24 months to study the microbiological relevance of blood cultures in pyelonephritis. We included patients with blood cultures (BC) and urine cultures (UC) drawn at the same time, if they were not exposed to antibiotics prior to these tests. Of our 264 patients, 39 (15 %) had no bacteriological documentation. There were 83 (31 %) bacteremic patients. Seven patients had contaminated or sterile UC with positive BC. Four patients had positive UC and BC with the latter allowing identification of a pathogen absent from the UC (n = 1) or identifying the main pathogen in three cases. A total of 11 patients theoretically benefited from BC representing 4.2 % of our population. Excluding one patient who was known to be infected with multi-drug resistant bacteria, all empirical antibiotics regimens were effective against the identified pathogens. We did not reveal any significant therapeutic impact of blood cultures in the management of pyelonephritis, when BC and UC are performed before any antimicrobials treatment.

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