Spinning-Top Urethra

Spinning top urethra refers to the appearance of a widened posterior urethra that is seen mainly in girls with urodynamic abnormalities. It is thought to be due to involuntary bladder contractions that are resisted by a voluntary increase in distal sphincter tension (to prevent urine leakage), resulting in distention of the posterior urethra.

The images, obtained in two different patients during voiding, show an irregular contour of the urinary bladder (more so on the bottom image), which is due to trabeculations. The widening of the posterior urethra gives us the spinning top urethra.

Vaginal reflux of contrast during voiding may mimic spinning top urethra on anteroposterior views, as contrast in the vagina is superimposed on the contrast-filled urethra. Look for the irregular walls of the vagina to steer clear of this confusion. Oblique views will also help by showing a contrast-filled vagina posterior to the urethra.

References

• Fernbach SK, Feinstein KA, Schmidt MB. Pediatric voiding cystourethrography: a pictorial guide. Radiographics. 2000 Jan-Feb;20(1):155-68;
• Saxton HM, Borzyskowski M, Mundy AR, Vivian GC. Spinning top urethra: not a normal variant. Radiology. 1988 Jul;168(1):147-50.