Appearance of the dilated bladder superior to obstructed male urethra is known as which sign?

• A. Keyhole sign
• B. Lemon sign
• C. Macroglossia
• D. Myelomeningocele

Answer: (A)

Keyhole sign arises from bladder outlet obstruction in a male fetus, most commonly due to posterior urethral valves. The bladder becomes dilated and the posterior urethra remains dilated as it exits the bladder neck, together forming a silhouette that looks like a keyhole on ultrasound. This distinctive appearance directly reflects the obstructed urethral segment and the resulting bladder dilation. Other options point to different conditions not described by this bladder–urethra configuration: the lemon sign is a skull contour change seen with open neural tube defects like anencephaly; macroglossia is an abnormally large tongue; myelomeningocele is a spinal defect associated with neural tube malformations, not the specific bladder-urethra appearance described here.