Case PresentationA 72-year-old woman with a history of uterine prolapse presented to the emergency department with a fever and malaise that persisted for several days. The patient had well-controlled diabetes mellitus. The patient’s temperature was 39.7℃, and her respiratory rate was 24/min; the other vital signs were unremarkable. On physical examination, no findings suggestive of an infectious source were noted. Blood test results showed a normal white blood cell count of 7,309/μL, but an elevated C-reactive protein level of 6.07 mg/dL. Additionally, her renal function was decreased, with a creatinine level of 1.47 mg/dL. Pyuria was confirmed to be present. Contrast-enhanced abdominal computed tomography revealed bilateral hydronephrosis and ureteral obstruction due to compression by uterine prolapse (Figure 1). A urine culture tested positive forEscherichia coli . Thus, obstructive urinary tract infection associated with uterine prolapse was diagnosed. The uterine prolapse was repaired by inserting a pessary, which was performed by gynecologist, and antimicrobial therapy was initiated. On day 2, ultrasound examination showed resolution of the hydronephrosis. On day 3, the fever resolved, and the patient’s creatinine level improved (0.97 mg/dL). Antimicrobial therapy was completed in 10 days. The patient was discharged on day 13.Uterine prolapse is typically asymptomatic and rarely requires emergency interventions.1 However, it can be complicated by obstructive urinary tract infections and severe renal dysfunction.2-3 Although its treatment requires removal of the obstruction, few reports on obstructive urinary tract infections due to uterine prolapse exist, and management strategies vary. Previous reports have shown that urologic intervention is not required to release the obstruction, and pessary insertion can be effective. 3 Once the uterine prolapse is corrected, antimicrobial therapy is sufficient for improvement. In our case, pessary insertion was also effective, as evidenced by the rapid amelioration of hydronephrosis. Emergency physicians should be aware that uterine prolapse is a risk for obstructive urinary tract infections or renal failure and that pessary insertions can be effective.