Spinning top urethra is non-obstructive posterior urethral dilatation seen on voiding cystourethrography, mainly in females. It was initially considered as an indicator of distal urethral narrowing/stenosis. However, it is now believed to be due to functional discoordinate voiding or bladder instability. Although some women have this appearance of the urethra as a normal variant 4, the finding necessitates a detailed search for a functional voiding disorder.
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Epidemiology
Children are more commonly affected with higher incidence seen in females. It is more common in females as they have tendency to and are trained to hold urine for longer periods.
Clinical presentation
Clinical manifestations vary depending on the disorder with daytime and night enuresis, recurrent urinary tract infections, urgency and frequency commonly encountered. Commonly vesicoureteric reflux, non-compliant bladder and behavioral disorders are associated with it.
Pathology
The underlying pathology of this entity is not clearly known. Initially it was believed to be due to distal urethral narrowing/stenosis, with post-stenotic dilatation or a dilated segment between the urethral meatus and bladder neck due to voluntary contraction of striated sphincter. It is now believed that the dilatation results from bladder instability, however voiding dysfunction may not necessarily be demonstrated in all such cases. The literature suggests an association of functional voiding disorder with spinning top urethra 2.
A congenital bladder neck anomaly may also predispose to spinning top urethra.
Rarely it may be considered as a normal variant when an extensive physical and laboratory evaluation fails to reveal bladder instability.
Radiographic features
Voiding cystourethrography (VCUG)
VCUG demonstrates dilatation of posterior urethra just distal to the internal sphincter. It may sometimes be only demonstrable during bladder filling wherein unstable bladder contractions lead to filling of urethra while leakage is prevented by voluntary contraction of distal urethral sphincter. The dilatation may persist or disappear during voiding.
It is important to recognize additional findings (as listed below) to facilitate diagnosis and differentiate between functional disorders like urge syndrome or detrusor-external sphincteric dyssynergia:
bladder capacity
bladder wall trabeculations
sacculations and diverticulum
vesicoureteric reflux
post-void residue
Treatment and prognosis
Treatment includes management of behavioral disorder with voiding retraining and biofeedback training. Frequent and relaxed voiding is encouraged as behavioral modification.
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