Concentric folds in the bladder: a new sign of chronic outlet obstruction and neurogenic bladder.

The finding of concentric folds in the bladder on excretory urography is a hitherto unreported but reliable sign of chronic urinary retention, usually due to outlet obstruction or neurogenic bladder. In a study of 152 consecutive patients with urinary retention, the presence of typical concentric folds alone was found to be as common and, therefore, as sensitive an indicator as trabeculation. The sign is useful in evaluating the significance of the incompletely emptied bladder on the post-void film, and in detecting unsuspected disease. A false-positive rate of 1.5% was found in a control series of 190 women, and no false-positive findings were seen in 214 men concurrently studied. A hypothesis concerning the mechanism of concentric fold formation is advanced.