Excerpt from Testicular Torsion

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Background

Testicular torsion, also termed torsion of the spermatic cord, is a relatively common and potentially devastating acute condition due to obstruction of the arterial blood supply to the testis.¹ Fortunately, this entity is relatively well known, and it usually occurs with enough discomfort to lead to its diagnosis and subsequent testicular salvage. However, atypical presentations of testicular torsion, delayed recognition of the condition, and its confusion with other causes of acute scrotum can potentially delay diagnosis and lead to testicular necrosis necessitating orchiectomy. Diagnostic imaging, particularly Doppler ultrasonography, plays an important role in the assessment of the patient with acute scrotal pain.²

Pathophysiology

Two types of testicular torsion are recognized, and each has slightly different etiologies. Extravaginal torsion occurs in fetuses and in neonates. With this type of testicular torsion, the testis, epididymis, and tunica vaginalis twist on the spermatic cord.³ In the neonatal period, the testicle is often undescended, and this condition may delay the diagnosis of testicular torsion.

Intravaginal torsion occurs more commonly in the peripubertal period than at other times. This type of testicular torsion is associated with a bell-clapper deformity in which the tunica vaginalis completely surrounds the testis. With the absence of the normal posterior anchoring, the testicle can twist freely. This congenital anomaly occurs in approximately 12% of males.

Frequency

United States

Testicular torsion has a prevalence of approximately 1 case per 4,000 population or 1 case per 125 males.⁴

Mortality/Morbidity

The salvage rate of torsed testes is fully dependent on the time between the onset of torsion and surgical detorsion.

• If torsion is repaired within 6 hours of the initial insult, salvage rates of 80-100% are typical. These rates decline to nearly 0% at 24 hours.
• Approximately 5-10% of torsed testes spontaneously detorse, but the risk of retorsion at a later date remains high.

Sex

Testicular torsion is an exclusively male phenomenon, although the female version, ovarian torsion, is well recognized and commonly associated with an ovarian mass.

Age

• Testicular torsion is predominantly an affliction of childhood, with three quarters of the cases occurring in those younger than 20 years.
• Two distinct age peaks that loosely correspond to differing congenital anomalies are the neonatal period and 13 to 17 years of age.
• Less than 10% of affected patients are older than 30 years.

Anatomy

The evaluation of ultrasonographic findings requires a detailed understanding of the scrotal anatomy. The testes are paired structures suspended in the scrotum by the spermatic cord. They measure approximately 2.0 X 3.0 X 4.0 cm in the adult and weigh 15-20 g.

Each testis is surrounded by a fibrous capsule called the tunica albuginea. The testis contains seminiferous tubules, which are tightly coiled and arranged in wedge shaped lobules. The margins of the lobules are formed by septations arising from inner layers of the tunica albuginea. The seminiferous tubules converge toward the mediastinum testis and unite to form larger tubules, which in turn form a network of tubules, the rete testes. The rete testes unite to form efferent tubules at the superior pole of the testes. These efferent tubules (10-15 in number) constitute the head of the epididymis. The efferent tubules then unite to form a single lumen structure called ductus epididymis.

The ductus epididymis forms the body and the tail of the epididymis, which is located on the posterolateral aspect of the testis. The tail of the epididymis undertakes an acute turn and continues as the vas deferens, which joins the spermatic cord. The testis and epididymis are vested by an extension of the peritoneum called the tunica vaginalis; this covers all but the posterior side.

The blood supply to the testis is mainly from the testicular artery, a branch of the abdominal aorta. Contribution is also made by the deferential artery, a branch of the hypogastric or superior vesical artery; it primarily supplies the vas deferens. In addition, the cremasteric branch of the inferior epigastric artery forms a network over the tunica and forms an anastomosis at the testicular mediastinum. The testicular artery enters the testis through the mediastinum and branches under the tunica albuginea to form capsular arteries. The capsular arteries send radial branches, known as the centripetal arteries, into the substance of the testis. The centripetal arteries form U loops near their ends, increasing the effective area of supply.

The testicular veins exit from the mediastinum and form a plexus called the pampiniform plexus. The plexus then combines into a dominant vein, which follows the testicular artery into the spermatic cord. The left testicular vein drains into the left renal vein, whereas the right testicular vein enters directly into the inferior vena cava.

Clinical Details

The classic presentation of testicular torsion includes the following: acute onset of scrotal pain, frequently at night; a previous painful episode (in as many as 40% of patients); scrotal swelling and erythema; and difficulty in palpating the testis.⁵

Variant presentations may involve abdominal pain that mimics appendicitis. Nausea and vomiting are frequently associated findings. Patients may also have flank pain radiating to the groin.

On physical examination, the affected hemiscrotum is swollen and frequently erythematous. The normal separation of the testis from the epididymis may not be palpable. An elevated, horizontal lie of the affected testis (Brunzel sign) and skin pitting at the scrotal base (Ger sign) may provide evidence in support of the diagnosis. With transillumination, the ischemic testicle may be visualized (blue-dot sign). Typically, no pain relief occurs with scrotal elevation (Prehn sign), as observed with acute epididymitis. The spermatic cord is typically thickened and tender. Tenderness alone may be indicative of acute epididymitis.

Clinical examination may be confusing, as in cases with 360° or 720° twists, in which the testicular lie (position) may be normal. Undescended testes are much more likely to torse than those normally positioned. Bilaterality occurs in 10% of patients and may cloud the clinical picture.

Differential considerations in the appropriate age group include acute epididymitis or epididymo-orchitis; abscess; torsion of the epididymal appendix; incarcerated hernia; hematoma; ruptured varicocele; or, rarely, scrotal tumor.^{6, 7}

Detorsion may occur spontaneously, with subsequent luxury perfusion of the involved testis. History taking and physical examination play even larger roles in the diagnosis in this scenario.

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Preferred Examination

In general, laboratory tests are not diagnostically useful in distinguishing torsion from other acute scrotal syndromes. Urinalysis results are negative in 98%, and a mild leukocytosis may occur in as many as 30% of patients.

Within the past decade, ultrasonography with color and power Doppler imaging has emerged as the primary imaging modality for the diagnosis of testicular torsion.^{8, 9, 10, 11, 12} It not only helps in corroborating the diagnosis by alteration of testicular echotexture but also provides valuable information on vascular perfusion of the testis. In addition, sonographic findings frequently allow other diagnoses to be made in those patients presenting with an acute scrotum who do not have torsion.¹³

Prior to the development of high resolution, real-time ultrasonography coupled with sensitive color Doppler, nuclear scintigraphy was the mainstay of tests available to evaluate the acute scrotum. Given associated radiation, less widespread availability, limited ancillary information, and the accuracy of color Doppler imaging, scrotal scintigraphy is no longer used as frequently.^{14, 15} In cases with a clinically ambiguous picture or with indeterminate sonographic findings, scintigraphy remains a viable imaging alternative.¹⁶

Information about the role of MRI in the diagnosis of torsion is limited, although MRI is likely to be highly sensitive.^{17, 18} However, with its limited availability, particularly at night, and its cost, MRI is unlikely to become a front-line examination for the patient presenting with acute scrotal pain.

Limitations of Techniques

Color Doppler ultrasonography is highly operator dependent. In the diagnosis of testicular torsion, gray-scale findings are combined with dynamic flow information. Inaccurate results may be obtained in the prepubertal patient with small testicular volume or in cases with multiple imaging and Doppler artifacts. Such imaging artifacts may result from inappropriate gain settings and the non-use of slow-flow techniques.¹⁹

Testicular scintigraphy is straightforward, although it requires intravenous access. An infiltrated radionuclide bolus prevents an adequate examination. False-negative results are unusual. False-positive results are more frequent because of the changing scintigraphic appearance of infarction over time and potential interpretation errors.

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