Computed tomographic features of urinary bladder torsion in two dogs.

Urinary bladder torsion is rare in dogs. It is characterised by rotation of the organ along its longitudinal axis and is potentially life-threatening because of urinary flow obstruction with subsequent urine retention, hydroureter, hydronephrosis and azotaemia. This report describes the computed tomographic features of urinary bladder torsion in two dogs. In both cases, the hallmark indicative of torsion was the "whirl sign," originating from the twisted pelvic urethra and urinary bladder neck encircling the ureters, blood vessels and bladder ligaments in a characteristic spiral pattern. The imaging features correlated well with surgical findings, demonstrating high sensitivity of computed tomography in the preoperative diagnosis of urinary bladder torsion.