Postvoid Residual Urine as a Clue to the Diagnosis of Acute Bacterial Prostatitis: A Case Report

Acute bacterial prostatitis (ABP) typically presents with fever and urinary symptoms; however, its diagnosis can be challenging in patients who lack characteristic findings such as perineal pain or prostatic tenderness. Although postvoid residual (PVR) urine may be associated with voiding dysfunction in ABP, its potential role as a diagnostic clue has received little attention. A 44-year-old man presented with a 2-day history of fever ranging from 38 to 39°C, irritative urinary symptoms, back pain, and difficulty initiating urination. At presentation, the patient was afebrile and had no perineal tenderness. Noncontrast computed tomography (CT) performed approximately 1 min after urination revealed an estimated PVR volume of 170 mL. The CT also showed an enlarged prostate with irregular margins and a low-density area. Laboratory tests showed a white blood cell count of 17,700/μL, a C-reactive protein level of 7.01 mg/dL, and 3+ leukocytes on urinalysis. Urine culture subsequently yielded Escherichia coli. Based on the clinical, imaging, and laboratory findings, ABP was diagnosed, and antibiotic therapy was administered for 28 days. Following treatment, inflammatory markers and urinary findings improved, and the follow-up PVR volume was 36 mL when measured 10 min after urination. In this case, PVR volume measurement immediately after urination provided a clue to the presence of voiding dysfunction associated with ABP, despite the absence of typical clinical findings. Furthermore, the reduction in PVR volume following treatment was temporally associated with improvement in inflammatory findings and urinary symptoms, although a causal relationship cannot be established. In patients with urinary symptoms and suspected ABP despite the absence of characteristic clinical findings, assessment of PVR volume may provide additional information regarding associated voiding dysfunction and support the overall clinical assessment.