Embryology relevant to ultrasound imaging of the male genitalia

Abstract

The male external genitalia include features (both normal and abnormal) that are direct consequences of the development of their embryologic precursors and demonstrable with ultrasound imaging. The testis and adnexa develop in close association with the kidney and ureter in the urogenital ridge. Portions of the early embryonic excretory system develop into the male reproductive ducts. Remnants of the Müllerian ducts may be encountered on the ultrasound examination of the male reproductive structures. The testes descend from the retroperitoneum to their final location in the scrotum. The scrotum develops in close association with the developing phallus. The bladder, prostate, and majority of the urethra are derived from an endodermal structure know as the urogenital sinus, which itself develops from the cloaca. The external phallus and testes have a blood supply that is well demonstrated and evaluated with ultrasound examination. An understanding of the development of the male reproductive structures aides in the interpretation of ultrasound findings during examination of these structures.