The presence of fever has long been a warning sign of severe urinary tract infection (UTI). However, we previously identified that inpatients with afebrile UTI had an increased risk of developing acute kidney injury (AKI). After expanding this cohort, 1132 inpatients with UTI diagnosed between January 2006 and April 2019 were analyzed. Overall, 159 (14%) of these patients developed AKI; bacteremia, urolithiasis, septic shock, hypertension, lower baseline renal function, marked leukocytosis, and the absence of fever were independently linked to AKI. When we further studied the cohort of inpatients with fever during hospitalization, we identified a group of "delayed fever" UTI inpatients who did not have fever as their initial presentation. Compared to patients presenting with fever at the emergency department, patients with delayed fever tended to be younger and have less frequent infection with Escherichia coli, more frequent AKI, upper tract infection, and a longer hospital stay. Despite the initial absence of fever, these patients demonstrated larger extents of elevations in both serum white blood cell counts and C-reactive protein levels. In short, besides UTI patients with lower baseline renal function that remain afebrile during their hospital stay, clinical awareness of the increased incidence of AKI in younger patients with "delayed fever" should also be noted.
Keywords: acute kidney injury; afebrile urinary tract infection; aging; baseline renal function; delayed fever; length of hospital stay; leukocytosis; urinary tract infection.