CHAPTER 20 Male Reproductive System
ANATOMY OF THE MALE REPRODUCTIVE SYSTEM
NORMAL IMAGING APPEARANCE OF THE MALE REPRODUCTIVE SYSTEM
Scrotal Contents
An echogenic line (the mediastinum testis) can usually be identified with US, bisecting the testis along its long axis asymmetrically (Fig. 20-4). A mediastinal artery is visible about 50% of the time and can mimic a small cyst or mass when viewed in cross section. Elongating the vessel and use of color Doppler imaging confirm the vascular nature of this finding (Fig. 20-5). Capsular arteries underlie the tunica albuginea and give rise to centripetal branches that radiate inward. Spectral Doppler demonstrates a low-resistance arterial waveform, with resistive indices typically between 0.50 and 0.75.
Prostate and Seminal Vesicles
Typical appearance of the prostate on CT is an ovular soft-tissue density, often difficult to separate from the surrounding fascia and musculature. Large BPH nodules and global prostatic enlargement are sometimes evident as irregular soft-tissue nodules seen encroaching into the bladder base, often with associated bladder wall thickening. Crude zonal anatomy can be appreciated on contrast-enhanced images in patients with BPH, as the central gland enhances heterogeneously, delineating it from the surrounding hypovascular peripheral zone (Fig. 20-7). Calcification within the prostate gland is common and usually asymptomatic, although it is more common in men with recurrent prostatitis, BPH, and a variety of metabolic disorders. Calcification of the seminal vesicles and vas deferens are also common and are associated with diabetes mellitus.

Figure 20-7 Enhanced axial computed tomography in a 42-year-old man demonstrates some limited zonal anatomy.
T2-weighted MR images provide improved definition of multiplanar prostatic zonal anatomy compared with other imaging modalities (Fig. 20-8). The peripheral zone consists of glandular tissue high in water content, giving it a bright appearance on T2-weighted images. The transitional and central zones of the central gland are difficult to delineate as separate structures in the young male individual, but together appear as intermediate signal intensity on T2-weighted imaging. As the patient ages, the transitional zone and periurethral glandular tissues enlarge, compressing the central zone and creating the surgical pseudocapsule between the hyperplastic transitional zone and the surrounding peripheral zone.
SCROTAL PAIN
Differential Diagnosis and Triage of Patients with Scrotal Pain
The main goal of imaging for acute scrotal pain is to identify those disease processes that require urgent surgical therapy. Sonographic evaluation usually allows effective triage of patients into one of three categories as shown in Table 20-1.
Table 20-1 Triage of Patients with Scrotal Pain According to Ultrasound Findings
Management | Ultrasound Diagnosis |
---|---|
No treatment necessary | |
Medical therapy usually sufficient | |
Surgical intervention should be considered | |
Urgent surgical intervention required |
Table 20-2 Differentiating Common Causes of Scrotal Pain
Diagnosis | Clinical Discriminators | Ultrasound Discriminators |
---|---|---|
Epididymitis | ||
Orchitis | ||
Testicular torsion | ||
Segmental infarction of the testis | History of sickle cell disease, vasculitis, polycythemia vera, torsion/detorsion | |
Varicocele | Palpable enlargement on physical examination that increases with Valsalva maneuver or standing | |
Torsion of testicular or epididymal appendage | ||
Hernia | Peristalsis of bowel or movement of fat with Valsalva maneuver | |
Fournier gangrene | Echogenic foci of soft-tissue gas |
Torsion or Infection?
Fortunately, the imaging findings of infection and torsion are also usually quite disparate (Table 20-3). Typical sonographic features of epididymitis include an enlarged epididymis with increased blood flow on color Doppler (Fig. 20-10). In epididymoorchitis, there is also increased blood flow to the testis, which is often enlarged and mildly hypoechoic (Fig. 20-11). Although the testis and epididymis are typically enlarged and hypoechoic with torsion as well, blood flow is decreased or absent (Fig. 20-12). When evaluating blood flow for possible torsion, it is essential to keep in mind that there is often hyperemia surrounding an ischemic or infarcted testicle, so flow within the testicular parenchyma must be present to exclude torsion (Fig. 20-13). A spiral appearance of the spermatic cord vessels has also been described as a sign of torsion. Spectral Doppler evaluation usually demonstrates a low-resistance arterial waveform in orchitis and a high-resistance arterial waveform with decreased, absent, or reversed diastolic flow in testicular torsion. With torsion, loss of venous flow may precede loss of arterial flow on spectral Doppler imaging.
FOCAL TESTICULAR LESIONS
Benign or Malignant?
Table 20-4 Focal Testicular Lesions: Ultrasound Findings That Favor Benign Disease
Finding | Comments |
---|---|
Anechoic with smooth margins | Cyst of tunica albuginea or true intratesticular cyst depending on location |
Absence of flow on color Doppler | |
Enlargement of epididymis or thickening of the scrotum | Common with infection or inflammation including granulomatous orchitis |
Tubular shape | |
Concentric rings (laminated) | Epidermoid cyst |
Straight margins or wedge shape | Focal testicular infarct |
Pronounced mediastinal adenopathy with small testicular lesions | Consider sarcoidosis |