Torsion of the Appendices and Epididymis Workup

Updated: Oct 20, 2016
  • Author: Jason S Chang, MD; Chief Editor: Erik D Schraga, MD  more...
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Laboratory Studies

Lab studies include urinalysis and CBC with differential.


Imaging Studies


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 the "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 (AT), the best predictor was a positive blue dot sign. [9]

Color Doppler ultrasonography

Color Doppler sonography (CDS) is the imaging modality of choice for evaluation of the acute scrotum. [10, 11, 7]  In torsion of the testicular appendage, CDS shows normal blood flow to the testis, with an occasional increase on the affected side that possibly is due to inflammation. In prepubertal patients, this method of imaging is somewhat controversial because the prepubertal testis has low-velocity blood flow, and CDS is less accurate in these instances.

Standard US of the scrotum should include both grayscale and Doppler studies. Linear high-resolution transducers should be used, and te 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. [12]

Some studies suggest that CDS has 90% sensitivity and 98% specificity in diagnosing acute testicular torsion. However, variability exists in the sensitivity of color Doppler ultrasonography. As a result, a negative ultrasonographic result does not necessarily exclude testicular torsion.

A study by Pepe et al demonstrated that CDS specificity may not be as high as previously reported for testicular torsion. [13] In a subset analysis of 42 adolescents with diagnostic suspicion of testicular torsion by CDS, only 22 had surgical confirmation of this diagnosis, while 16 were found to be normal and 4 had torsion of the testicular appendage. In fact, clinical examination alone had sensitivity and specificity of 100% and 50%, respectively, while CDS had sensitivity and specificity of 95.7% and 48.7%, respectively. In a patient presenting with an acute scrotum, a negative CDS result may provide supportive evidence that the patient has a benign condition like torsion of an appendage, but it does not exclude the diagnosis of testicular torsion. In high clinical suspicion, surgical exploration may still be warranted.

Radionuclide imaging

Since the acceptance of Doppler US as the primary imaging for evaluation of acute scrotum, radionuclide scrotal imaging (RNSI) is uncommonly used. [12] The positive sign for testicular appendix torsion is the hot-dot sign, which is 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 fewer than 5 hours. Positive results are seen in only 45% of patients whose symptoms have lasted 5-24 hours. [14] The test is reported to be 68% sensitive and 79% accurate. [14]

Magnetic Resonance Imaging

MRI techniques are not typically used for the acute scrotum because of the limited availability of equipment and the long examination time involved. However, the use of MRI in scrotal diseases is increasing, and future studies are necessary to help determine the role of MRI in patients who have acute scrotal pain but equivocal CDU findings. [12]