False-positive "halo" sign on testicular scintigraphy in a 5-year-old boy with epididymitis and hydrocele.

Scintigraphic differentiation between acute torsion, hydrocele and testicular or scrotal abscess can be difficult. Doppler sonography may provide useful complimentary information toward diagnosis. The authors describe a 5-year-old child where epididymitis with hydrocele was misdiagnosed as testicular torsion on scrotal scintigraphy.

INTRODUCTION

99mTc pertechnetate scintigraphy is routinely used to detect testicular torsion and differentiate this condition from acute epididymo-orchitis. However, differentiation of torsion from hydrocele and testicular or scrotal abscess may be difficult. In this report, we present a 5-year old child in whom epididymitis with hydrocele was misdiagnosed as testicular torsion on scrotal scintigraphy.

CASE REPORT

A 5-year-old boy presented to the pediatric emergency department with a complaint of left scrotal swelling and local tenderness for 7 h. Doppler ultrasound (US) imaging showed mild hydrocele of the left scrotum with no e/o torsion of the left testis. Scrotal scintigraphy was then performed after intravenous injection of 10 mCi of 99mTc pertechnetate. Static images at 5 and 10 min showed a halo-like pooling of tracer in the periphery of the left hemi-scrotum with a photopenic center and normal tracer uptake in the right hemi-scrotum [Figure 1]. A scintigraphic diagnosis of mid-phase testicular torsion of the left testis was made and the patient was immediately operated. However, it was discovered intraoperatively that the patient had epididymitis with a hydrocele and not torsion of the left testis.

Figure 1

Scrotal scintigraphy following intravenous injection of 10 mCi of 99mTc pertechnetate. Static images at 5 and 10 min show a halo-like pooling of tracer in the periphery of the left hemi-scrotum (arrow) with a photopenic centre. Normal tracer uptake is seen in the right hemi-scrotum

Differentiation by scintigraphy between acute torsion, hydrocele, testicular or scrotal abscess, or even inguinal hernia can be difficult, and images must be interpreted in conjunction with clinical findings from scrotal transillumination. In this situation, sonography can provide useful complementary information.[1-4] In a previous study comparing scintigraphy and US in children with scrotal pain, Doppler US was able to provide the diagnosis of epididymo-orchitis in cases of false-positive scintigraphy.[1] A peri-testicular hyperemic rim on radionuclide scrotal scintigraphy is not pathognomonic of missed testicular torsion.[5] Epididymitis and hydrocele have also been reported to mimic testicular torsion on scintigraphy in adults.[6-8] The present study describes a halo-like appearance on scrotal scintigraphy caused by epididymitis with co-existing hydrocele in a clinical setting, suggestive of testicular torsion in a child.