[A case of infravesical obstruction caused by prostatic stones as diagnosed by transrectal ultrasonography at voiding].

A 69-year-old patient, who had been treated using alpha 1-blocker for benign prostatic hyperplasia (BPH) at another clinic, visited our clinic due to persistent difficulty in urination. Total International Prostate Symptom Score (IPSS) was 32 points and quality of life (QOL) index was 5. Uroflowmetry demonstrated maximum urinary flow rate and average urinary flow rate to be 9.2 ml/sec and 5.1 ml/sec, respectively, with 3 ml of residual urine volume. Transrectal ultrasonography (TRUS) revealed prostatic stones but not BPH. Retrograde urethrography demonstrated nothing abnormal other than prostatic stones. TRUS at voiding phase using linear probe (voiding TRUS) revealed poor opening of the urethra surrounded by prostatic stones. As a result, the cause of urinary disturbance was diagnosed to be due to urethral obstruction caused by prostatic stones, and transurethral resection of prostatic tissue with stones was performed. Postoperatively, IPSS decreased to 10 points and QOL index to 2. Maximum urinary flow rate also improved to 18.1 ml/sec and mean urinary flow to 8.4 ml/sec. Thus, voiding TRUS is likely the best urodynamic test for clinical use in determining the etiology of obstruction at posterior urethra.