5-year-old boy who was noted to have hydronephrosis on ultrasound. VCUG in the RAO oblique-lateral view shows dilated proximal urethra caused by posterior urethral valves, with secondary bladder outlet obstruction. The resulting shapes are reminiscent of a keyhole – and hence the “keyhole sign”. Distal to the obstruction the penile urethra assumes a normal caliber
Ashley Davidoff MD TheCommonVein.net 135754c