Congenital malformations of the bladder (agenesis of the bladder) are caused by anomalies in the development of the urethra and genitalia and are rare. They are often accompanied by congenital malformations of the upper urinary tract and other systemic organs, and can be accompanied by renal agenesis. Male infants may be accompanied by absent prostate and seminal vesicles, and severe ectopic ureteral orifices can occur in both males and females. Even if they survive at birth, they often die due to upper urinary tract infection. A small bladder can be abnormal or underdeveloped. Abnormal development is often seen in duplicate bladder exstrophy or half bladder exstrophy, with small bladder, fibrosis, and difficult to expand. Underdeveloped bladders can have the potential to expand, seen in severe urinary incontinence, complete penile urethral fistula, and bilateral single ectopic ureteral orifices.