Acute pyelonephritis in adults: a case series of 223 patients

Background Acute pyelonephritis (APN) is a common disease which rarely evolves into abscesses. Methods We prospectively collected clinical, biochemical and radiological data of patients hospitalized with a diagnosis of APN from 2000 to 2008. Results Urinary culture was positive in 64/208 patients (30.7%) and blood cultures in 39/182 cases (21.4%). Two hundred and thirteen patients were submitted to computed tomography (CT) or nuclear magnetic resonance (NMR): confirmation of APN was obtained in 196 patients (92%). Among these, 46 (23.5%) had positive urine culture, 31 (15.8%) had positive blood culture and 15 (7.6%) had positive cultures of both urine and blood. In 98 patients, either urine or blood cultures were negative, but CT/NMR were positive for APN. Fifty of the 213 patients submitted to CT/NMR (23.5%) had intrarenal abscesses: only 2 were evidenced by ultrasound examination. No differences were found between patients with positive or negative CT with regards to fever, leucocytosis, C-reactive protein, pyuria, urine cultures and duration of symptoms before hospitalization. No differences were found between patients with or without abscesses with regards to these parameters and risk factors. Patients with abscesses had a longer duration of treatment and hospitalization. Conclusions Our data suggest that in APN it is not always possible to routinely document urinary infection in a clinical setting. This finding could be explained by previous antibiotic treatment, low bacterial growth or atypical pathogens. Systematic CT or NMR is necessary to exclude evolution into abscesses, which cannot be suspected on clinical grounds or by ultrasound examination and may also develop in the absence of risk factors.