What causes the spinning top urethra on voiding cystourethrography?
Let me know in the comments.
Click to reveal the answer
Answer:
The spinning top urethra is dilatation of the proximal female urethra with abrupt narrowing at the level of the external sphincter during voiding, producing a shape like a child’s spinning top. It is a functional finding of dysfunctional voiding, in which the child contracts the external sphincter and pelvic floor while the detrusor is contracting, and it is not a structural stricture or a distal urethral stenosis. Its associations are the ones that matter clinically: recurrent urinary tract infection, urgency and incontinence, constipation as part of the bladder and bowel dysfunction complex, and vesicoureteric reflux, which is why it is usually noticed on a study performed for infection. Historically the appearance was treated as evidence of distal urethral stenosis and led to urethral dilatation; that practice has been abandoned because the abnormality is behavioural and functional. Management is with bladder retraining, treatment of constipation, timed voiding and biofeedback, which improves both the radiographic appearance and the symptoms, with anticholinergics or alpha blockers in selected children. The finding should be reported alongside bladder wall thickening and trabeculation, post-void residual volume, reflux grade and any duplication or ureterocele, and a neurogenic cause should be considered when the appearances are severe or there are neurological or spinal signs.
Why is it called so?
The dilated proximal urethra tapering abruptly at the sphincter resembles the profile of a spinning top toy.
Pathophysiology
During normal voiding the detrusor contracts and the external urethral sphincter and pelvic floor relax in a coordinated fashion. In dysfunctional voiding this coordination is lost through learned behaviour, often after painful voiding, infection or constipation, so the sphincter contracts intermittently during detrusor contraction. Urine is forced against a partially closed sphincter, and the compliant proximal urethra above it dilates, while the sphincteric segment remains narrow, generating the characteristic outline. Repeated high-pressure voiding, incomplete emptying and residual urine promote infection, and sustained high pressures may cause bladder wall thickening and secondary reflux, so the functional problem produces structural consequences if it is not corrected.
Alternative names: Spinning top deformity of the urethra
Other associated named signs: Christmas tree bladder of neurogenic dysfunction and the lasso sign of a duplex system ureterocele
References
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
Improve Content And Help Your Colleagues!
Found an error in the post? Please let us know using our contact page and we will update it with due credits!
If you wish to contribute radiological images for this case (or any other article on the website), you can submit them here and you will be duly credited: Submit radiology case