Spinning top urethra on voiding cystourethrogram.

Received March 2013 Accepted June 2013 Department of Radiodiagnosis and Imaging, Post Graduate Institute of Medical Education and Research, Chandigarh 160012, India. A 10-year-old‎girl‎was‎ referred‎ for‎a‎voiding‎cystourethrogram‎(VCUG)‎with‎a‎history‎of‎ recurrent‎urinary‎ tract‎ infections.‎Examination‎including‎neurological‎evaluation‎was‎unremarkable.‎ Ultrasonography‎of‎the‎kidneys‎and‎bladder‎was‎normal.‎Voiding‎phase‎of‎VCUG‎was‎subsequently‎performed.‎Bladder‎ capacity‎and‎outline‎were‎normal‎(Figure‎1).‎There‎was‎marked‎dilatation‎of‎posterior‎urethra‎(Figure‎2)‎with‎smooth‎tapering‎towards‎ distal‎end‎resembling‎a‎“spinning‎top”.‎No‎vesicoureteral‎reflux‎or‎post-void‎residual‎urine‎was‎noted.‎Spinning‎top‎urethra‎(STU)‎ represents‎a‎widened‎posterior‎urethra‎seen‎mainly‎in‎girls.‎For‎a‎long‎time,‎it‎was‎considered‎a‎normal‎variation,‎due‎to‎contraction‎ of‎transverse‎fibers‎of‎urethral‎sphincter‎located‎in‎the‎distal‎urethra.(1)‎Proponents‎of‎STU‎as‎a‎pathological‎entity‎have‎attributed‎it‎ variably‎to‎meatal‎stenosis,‎urethral‎ring,‎distal‎sphincter‎dyssynergia,‎bladder‎instability‎and‎congenital‎wide‎bladder‎neck‎anomaly‎ (CWBNA).(2)‎‎Former‎three‎mechanisms‎were‎refuted‎by‎studies‎showing‎high‎urine‎flow‎rates‎in‎subjects‎with‎STU.‎For‎the‎latter‎two‎ mechanisms,‎controversy‎exists‎because‎majority‎of‎cases‎with‎instability‎and‎CWBNA‎do‎not‎show‎STU.‎Thus,‎one‎should‎consider‎ STU‎a‎normal‎variant,‎sometimes‎occurring‎in‎children‎with‎instability‎or‎CWBNA.‎Differential‎diagnosis‎includes‎Lyon1s‎(fibrous)‎ ring‎in‎girls‎and‎urethral‎valves‎in‎males.‎(3) PICTORIAL