Hospitalization for urinary tract infections in Japan, 2010-2015: a retrospective study using a national inpatient database.

Background: Urinary tract infections (UTI) are common and can have severe consequences. However, there are few recent large-scale studies about them. We aimed to determine the incidence of hospitalization for UTI and to elucidate patient characteristics, clinical practice, and clinical outcomes by drawing on a Japanese nationwide database.

Methods: This was a retrospective observational study using a national database that covers half the acute care inpatients in Japan. Patients aged ≥ 15 years who were hospitalized for UTI were eligible. We did not include patients with lower UTI such as cystitis. We investigated the annual number of patients hospitalized in Japan, those patients' characteristics, and risk factors for in-hospital mortality.

Results: We identified 232,396 eligible patients from 31 million records of discharge between April 2010 and March 2015. The average age was 73.5 years and 64.9% of patients were female. The estimated annual number of hospitalizations because of UTI was 106,508. The incidence was 6.8 per 10,000 for men and 12.4 for women. The median medical care cost was 4250 USD. In-hospital mortality was 4.5%. Risk factors of poor survival included male sex, older age, lower bed capacity, non-academic hospital, admission in winter, higher Charlson Comorbidity Index score, low body mass index, coma on admission, ambulance use, disseminated intravascular coagulation, sepsis, renal failure, heart failure, cerebrovascular diseases, pneumonia, malignancies, use of anti-diabetic drugs, and use of corticosteroid or immunosuppressive drugs.

Conclusions: We found that older patients of both sexes accounted for a significant proportion of those hospitalized for UTI. The clinical and economic burden of UTI is considerable.