Radiology, Vol 182, 81-85, Copyright © 1992 by Radiological Society of North America
Nonobstructive posterior urethral widening (spinning top urethra) in boys with bladder instability
HM Saxton, M Borzyskowski and LB Robinson
Department of Radiology, Guy's Hospital, London, England.
Seven boys between the ages of 5 and 10 years with symptoms of urinary
frequency and urgency and daytime wetting were studied with urodynamics and
were shown to have bladder instability and a dilated posterior urethra. In
two the dilatation occurred predominantly during bladder filling. Unstable
contractions caused filling of the posterior urethra, and leakage was
prevented by voluntary contraction of the distal urethral sphincter; with
voiding, the urethra showed a more normal appearance. In the remaining
five, there were similar changes during filling, but dilatation persisted
during voiding. In six the measured urine flow rate was normal, and none
showed any evidence of anatomic obstruction. The mechanism of urethral
distention appears to be similar to that previously shown in girls with
spinning top urethra: Unstable contractions resisted by voluntary sphincter
contraction cause posterior urethral dilatation. Boys with dilated
posterior urethras who have urinary frequency and urgency and daytime
wetting and normal urine flow rates should be assumed to have bladder
instability.
