IF Finding Sign Keyhole Sign US Sagittal – Posterior Urethral Valves Keyhole Sign1-day old baby boy who was noted to have hydronephrosis on a prenatal ultrasound. Sagittal view of the thick-walled bladder and dilated proximal urethra is reminiscent of a keyhole. These findings are manifestations of a proximal severe obstruction of the posterior urethra with secondary dilation caused by posterior urethral valves, with secondary bladder outlet obstruction and hypertrophy of the bladder as a resultAshley Davidoff MD TheCommonVein.net 135747c US Sagittal – Posterior Urethral Valves Keyhole Sign1-day old baby boy who was noted to have hydronephrosis on a prenatal ultrasound. Sagittal view of the thick-walled bladder and dilated proximal urethra is reminiscent of a keyhole. These findings are manifestations of a proximal severe obstruction of the posterior urethra with secondary dilation caused by posterior urethral valves, with secondary bladder outlet obstruction and hypertrophy of the bladder as a resultAshley Davidoff MD TheCommonVein.net 135743c