Imaging modalities of the male reproductive system

Main imaging modalities

The diagnostic radiologist has several key approaches at their disposal to evaluate the male reproductive system:

• Ultrasonography (US). This is the absolute first and main modality (method of choice) for evaluating scrotal structures. Due to its high availability and safety, it is used for any initial suspicion of pathology.
• Color Doppler mapping (CDM). This is an ultrasound technique for assessing blood flow that has completely replaced radionuclide methods in diagnosing acute conditions such as testicular torsion. Doppler ultrasonography also holds high potential to replace invasive examinations in diagnosing vascular impotence.
• Magnetic resonance imaging (MRI). It is ordered in complex diagnostic situations. MRI is indispensable when it is necessary to detail a mass lesion (to determine whether it consists of solid, cystic, or adipose tissue) and to reliably differentiate pathology of the testis itself from lesions of adjacent tissues (paratesticular masses).
• Computed tomography (CT). Along with MRI, it plays a major role in oncologic screening—for precise staging of malignant neoplasms. In addition, CT or MRI is used to localize undescended testes (cryptorchidism) if they cannot be visualized by ultrasound in the inguinal canal.
• Radiocontrast methods. Contrast venography is used to study the anatomy in detail for varicocele (dilation of the spermatic cord veins). Often this procedure transitions from diagnostic to therapeutic: the examination is supplemented with vein embolization, which avoids full-scale surgery. Intravascular examinations with iodine-based contrast (arteriography and venography) sometimes play a role in evaluating impotence.

Normal testicular anatomy

Testis (testis) is a paired organ whose normal dimensions are 3–5 cm in length and 2–3 cm in transverse and anteroposterior sections (depth).

The parenchyma of the organ is predominantly formed by seminiferous tubules (seminiferous tubules). Externally, the testis is covered by a very dense fibrous tissue—the tunica albuginea (tunica albuginea). Thin septa extend from this capsule deep into the parenchyma, dividing the internal space into several hundred lobules.

All septa converge toward the center of the organ—the mediastinum testis (mediastinum testis). During ultrasound scanning, this mediastinum is clearly visualized as a bright linear hyperechoic (ultrasound-reflecting) structure.

The seminiferous tubules head toward the mediastinum and merge there, forming the rete testis (rete testis). Efferent tubules (efferent tubules) extend from the rete, piercing the tunica albuginea and carrying seminal fluid outward into the epididymis.

At the upper pole of the testis, a remnant of the Müllerian duct can often be found—the appendix testis, or hydatid of Morgagni (appendix testis). This is a small formation measuring 3–5 mm, similar in echogenicity to the testicular tissue itself. The appendix of the epididymis may also be located nearby.

Epididymis and membranes

The epididymis (epididymis) is normally located posterior to the testis. However, anatomical variability should be considered during US: the epididymis may be visualized anteriorly or laterally. Anatomically, it is divided into three parts:

1. Head—adjacent to the upper pole. It is formed by the convergence of the rete testis ductules into a single duct of the epididymis (ductus epididymis).
2. Body—the middle part running along the organ.
3. Tail—located at the lower pole. Here, the duct bends, courses cranially (upward), and continues as the vas deferens (vas deferens).

Membranes. During the prenatal period, descending through the inguinal canal into the scrotum, the testis pulls along peritoneal layers—the processus vaginalis (processus vaginalis). Normally, this process should obliterate (close). The remaining isolated layers (visceral and parietal) surrounding the testis and appendices form the tunica vaginalis (tunica vaginalis).

Blood supply and venous drainage

The male gonad has a triple arterial blood supply system:

• Testicular artery (testicular artery). It is the main source of nutrition. It branches directly from the abdominal aorta (below the level of the renal arteries) and descends through the inguinal canal. It branches into capsular arteries that wrap around the tunica albuginea. From these, centripetal arteries extend inward toward the mediastinum, which then loop around and return back into the parenchyma as small capillaries.
• Deferential artery (deferential artery). This is a branch of the inferior vesical artery. It accompanies the vas deferens and ends in a branching capillary network in the region of the epididymal tail.
• Cremasteric artery (cremasteric artery). A branch of the inferior epigastric artery. It accompanies the spermatic cord and forms a rich network of anastomoses with the other two arteries.

Venous drainage from the testicular tissue itself occurs through a dense pampiniform plexus (pampiniform plexus), which ultimately collects into the gonadal vein. Drainage from the scrotal wall and epididymis occurs separately via the cremasteric plexus.

Diagnosis of mass lesions

All scrotal mass pathologies in diagnostic radiology are strictly divided into two categories:

• Intratesticular (originating directly from the organ parenchyma).
• Extratesticular (originating from the epididymis, membranes, or spermatic cord).

Differentiating these two groups is critically important for prognosis. Distinguishing them from each other is quite easy both clinically and using ultrasound (the method has 100% sensitivity for determining localization).

However, if a mass is localized within the testis, reliably distinguishing a malignant process from a benign one based solely on ultrasound data is more difficult. The specificity of the method decreases here: the rate of false-positive diagnoses of malignant neoplasms on ultrasound reaches 22%. Therefore, in questionable cases, the protocol is expanded with MRI.

Briefly: answers to topical questions

What else to study on this topic

• Malignancy criteria for intratesticular masses on MRI.
• The role of CT and MRI in testicular cancer staging and lymph node evaluation.
• Embolization technique for varicocele: indications and performance procedure.
• Algorithm for diagnostic imaging of an undescended testis (cryptorchidism) in the inguinal canal and abdominal cavity.
• Ultrasound characteristics and penile vascular hemodynamics in impotence.

Other topics in the section "Diagnostic Radiology of the Abdominal Organs"

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