Torsion of the Testicular Appendices and Epididymis Workup

Updated: Feb 02, 2022
  • Author: Jason S Chang, MD; Chief Editor: Erik D Schraga, MD  more...
  • Print

Imaging Studies

Imaging of the scrotum in the setting of acute symptoms such as pain or swelling is commonly performed emergently to differentiate between patients who require immediate surgery and those who do not. Acute scrotal symptoms generally are caused by infectious, traumatic, or vascular etiologies. [6]

Ultrasonography is the well-established first-line imaging modality for acute scrotum. Contrast-enhanced ultrasound and MRI can be useful as problem-solving tools when ultrasound studies are inconclusive or equivocal. [6]

Lab studies include urinalysis and CBC with differential.


Torsion of the testicular appendages represents the most common cause of acute scrotum in prepubertal boys. Torsion of the testicular appendages has a set of features on multiparametric ultrasonography. Awareness of these features can facilitate diagnosis of torsion of the testicular appendages with no need for unnecessary surgical scrotal exploration or unwarranted antibiotic treatment. [18]

Ultrasonography can be useful in distinguishing torsion of a testicle and torsion of an appendix testis. Testicular appendage torsion appears as a lesion of low echogenicity with a central hypoechogenic area. The presence of a large appendix adjacent to the epididymis (in the absence of clinically detectable inflammation) may signify testicular involvement. If the edematous appendix and the head of the epididymis are close enough, this condition will have a "Mickey Mouse" appearance on transverse view.

In a retrospective study of 241 boys with acute scrotal pain, the best predictors for epididymitis were dysuria, a painful epididymis on palpation, and altered epididymal echogenicity and increased peritesticular perfusion on ultrasound studies; for appendix testis, the best predictor was a positive blue-dot sign. [19]

Color Doppler ultrasonography

Color Doppler ultrasonography (CDU) is the imaging modality of choice for evaluation of acute scrotum. [16, 20, 21]  In torsion of the testicular appendage, CDU shows normal blood flow to the testis, with an occasional increase on the affected side that may be due to inflammation. In prepubertal patients, this method of imaging is somewhat controversial because the prepubertal testis has low-velocity blood flow, and CDU is less accurate in these instances.

Standard ultrasonography of the scrotum should include both grayscale and Doppler studies. Linear high-resolution transducers should be used, and studies should include both the scrotum and inguinal areas. In patients with torsion, a normal homogeneous echo pattern is likely to indicate a viable testis, whereas a hypoechoic or inhomogeneous testis is likely to be nonviable. [22]

Some studies suggest that CDU has 90% sensitivity and 98% specificity in diagnosing acute testicular torsion. However, variability in the sensitivity of CDU has been noted. As a result, a negative ultrasonographic result does not necessarily exclude testicular torsion.

A study by Pepe et al demonstrated that CDU specificity may not be as high for testicular torsion as was previously reported. [23] In a subset analysis of 42 adolescents with diagnostic suspicion of testicular torsion by CDU, only 22 had surgical confirmation of this diagnosis; 16 were found to be norma,l and 4 had torsion of the testicular appendage. In fact, clinical examination alone had sensitivity and specificity of 100% and 50%, respectively, and CDU had sensitivity and specificity of 95.7% and 48.7%, respectively. In a patient presenting with an acute scrotum, a negative CDU result may provide supportive evidence of a benign condition such as torsion of an appendage, but it does not exclude the diagnosis of testicular torsion. In cases of high clinical suspicion, surgical exploration may be warranted.

Radionuclide imaging

Since Doppler ultrasonography has been accepted as the primary imaging modality for evaluation of acute scrotum, radionuclide scrotal imaging (RNSI) is used uncommonly. [22] The positive sign for testicular appendix torsion is the hot-dot sign, which shows an area of increased tracer uptake. This sign is pathognomonic for testicular appendix torsion. Radionuclide images do not show a positive result if symptoms have been present for less than 5 hours. Positive results are seen in only 45% of patients whose symptoms have lasted 5-24 hours. [24] This test is reported to be 68% sensitive and 79% accurate. [24]

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) techniques typically are not used for assessment of the acute scrotum because of limited availability of equipment and the long examination time involved. However, use of MRI in scrotal disease is increasing, and future studies will help determine the role of MRI in patients who have acute scrotal pain but equivocal CDU findings. [22]