Final answer:
The congenital condition marked by the absence of the anterior wall of the urethra is known as hypospadias.
Step-by-step explanation:
In hypospadias, the urethral opening is located on the underside instead of at the tip. This condition can cause difficulty with urination and can be corrected surgically. Hypospadias occurs during fetal development when the tube that carries urine from the bladder to the outside of the body does not close completely. The exact cause is unknown, but it is thought to be a combination of genetic and environmental factors.
Treatment for hypospadias usually involves surgical repair to reposition the urethral. The surgery is typically done during early childhood, before the child starts school. After surgery, the child will be able to urinate normally and have a more typical appearance. So therefore hypospadias is the congenital condition marked by the absence of the anterior wall of the urethra, resulting in the urethral opening being located on the underside.