Ultrasound is the primary imaging method for evaluating the scrotum.
Color Doppler is crucial for assessing testicular torsion and infection.
Ultrasound can accurately distinguish between intratesticular and extratesticular masses, as well as solid versus cystic masses.
Scrotum Anatomy Objective
Identify the normal anatomy of the scrotum.
Explain the vascular supply to scrotal contents.
Review content discussed.
Anatomy of the Scrotum - Testes
The testes are symmetric, oval-shaped glands located in the scrotum.
Adult testes typically measure 3-5 cm in length, 2-4 cm in width, and 3 cm in thickness.
Each testis is divided into >250-400 conical lobules containing seminiferous tubules.
The tubules converge at the apex of each lobule and connect to form the rete testis in the mediastinum.
The rete testis drains into the head of the epididymis through efferent ductules.
Anatomy of the Scrotum - Testes Sonographic Appearance
Sonographically, testes appear as smooth, medium gray structures with a fine echotexture.
The rete testis appears as tiny tubules.
Anatomy of the Scrotum - Epididymis
The epididymis is a 6-7 cm tubular structure that begins superiorly and courses posterolaterally to the testis.
It is divided into the head, body, and tail.
The head is the largest segment, and it's located superior to the upper pole of the testis.
The body is smaller than the head, and the tail is slightly larger than the body.
The appendix of the epididymis is a small protuberance from the head of the epididymis.
Anatomy of the Scrotum - Epididymis Ductal System
The epididymis contains 10-15 efferent ductules from the rete testis, which converge to form a single duct in the body and tail.
This duct is known as the ductus epididymis.
It becomes the vas deferens and continues in the spermatic cord.
Anatomy of the Scrotum - Epididymis Sonographic Appearance
The normal epididymis typically appears isoechoic or hypoechoic compared to the testes.
It has a coarser echotexture compared to the testes.
Anatomy of the Scrotum - Mediastinum Testes
The testis is covered by a dense, fibrous tissue called the tunica albuginea.
The posterior aspect of the tunica albuginea reflects into the testis to form a vertical septum known as the mediastinum testis.
The mediastinum supports vessels and ducts coursing within the testis.
Sonographically, it appears as a bright, hyperechoic line coursing craniocaudally within the testis.
Anatomy of the Scrotum - Tunica Vaginalis
The tunica vaginalis lines the inner walls of the scrotum, covering each testis and epididymis.
It consists of two layers: the parietal and visceral layers.
The parietal layer is the inner lining of the scrotal wall.
The visceral layer surrounds the testis and epididymis.
Hydroceles form in the space between the layers of the tunica vaginalis, and a small amount of fluid is normally seen in this space.
Anatomy of the Scrotum - Vas Deferens
The vas deferens is a continuation of the ductus epididymis.
It dilates at the terminal portion near the seminal vesicle, and this area is called the ampulla of the vas deferens.
The vas deferens joins the duct of the seminal vesicles to form the ejaculatory duct.
The verumontanum is the junction of the ejaculatory ducts with the urethra.
The urethra courses from the bladder to the end of the penis.
Anatomy of the Scrotum - Spermatic Cord
The spermatic cord consists of the vas deferens, testicular arteries, venous pampiniform plexus, lymphatics, nerves, and fibers of the cremaster muscle.
The spermatic cord extends from the scrotum through the inguinal canal.
The cord suspends the testis in the scrotum.
Anatomy of the Scrotum - Vascular Supply
The right and left testicular arteries arise from the abdominal aorta below the level of the renal arteries.
These arteries are the primary source of blood flow to the testicles.
They descend in the retroperitoneum and enter the spermatic cord in the deep inguinal ring, then course along the posterior surface of each testis and pierce the tunica albuginea.
The branching pattern of the testicular artery is as follows: Testicular artery - Capsular artery - Centripetal artery - Recurrent Rami artery (centrifugal arteries).
Vascular supply - Waveform
Approximately one half of normal testes has a transmediastinal or transtesticular artery
Large vein often identified adjacent to artery
Feeding testicular capsule therefore waveform will appear higher resistant
Sonographically appears as an anechoic or hypoechoic tube
Waveform from the intratesticular arteries Normal low resistant waveform
Anatomy of the Scrotum - Vascular Supply - Venous Drainage
Venous drainage of the scrotum occurs through veins in the pampiniform plexus.
The pampiniform plexus exits from the mediastinum testis and courses in the spermatic cord.
It converges into three sets of anastomotic veins: testicular, deferential, and cremasteric.
The left testicular vein joins the left renal vein (LRV).
The right testicular vein joins the inferior vena cava (IVC).