Testicular torsion with preserved flow: key sonographic features and value-added approach to diagnosis
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Testicular sonography has contributed greatly to the preoperative diagnosis of testicular torsion in the pediatric patient and is the mainstay for evaluation of acute scrotal pain. Despite its high sensitivity and specificity, both false-negative and false-positive findings occur. Presence of documented Doppler flow within the testis might be a dissuading factor for surgical exploration with resultant testicular loss in the false-negative cases. Our goal is to illustrate key sonographic features in the spectrum of testicular torsion with preserved testicular flow, and to describe how to differentiate testicular torsion from epididymitis in order to avoid the under-diagnosis of testicular torsion. We simplify the anatomy of the bell clapper testis. We also describe our sonographic protocol for testicular torsion and share valuable tips from our approach to challenging cases.
KeywordsBell clapper anomaly Children Epididymis Scrotum Testis Torsion Ultrasound Whirlpool sign
Recent investigators have emphasized the concept of intermittent and partial testicular torsion, which can be difficult to diagnose with sonography because these cases have either subtle decreased flow or flow that appears to be symmetrical with the contralateral testis, and symptoms can wax and wane . Such cases might present diagnostic dilemmas for both the pediatric radiologist and urologist. Testicular torsion is not an all-or-none phenomenon and can be of complete, partial or intermittent types. The incidence of each type of torsion in isolation is unknown. In a study in which all children with symptoms of acute scrotum underwent surgical revision, torsion of the appendix testis was the most common pathology (57%), followed by torsion of the spermatic cord (27%) and much less commonly epididymitis (11%) .
Complete torsion occurs when the testis twists 360° or greater, usually leading to absence of intratesticular flow on color Doppler exam; however sometimes the flow is preserved or decreased. Intermittent torsion is defined as sudden onset of unilateral testicular pain of short duration with spontaneous resolution. In partial or incomplete torsion, the degree of spermatic cord twist is less than 360°, allowing for some residual perfusion to the testis. However there is no spontaneous resolution of pain .
Testicular torsion has been reported to have a bimodal distribution, an initial peak in the first year of age where the torsion is of extravaginal type, and a second surge in adolescence where intravaginal torsion is common. Cases of intravaginal torsion with preserved flow and their critical sonographic findings are described in this review. Preserved flow indicates these cases did not have completely absent flow (which is typically straightforward and diagnostic for testicular torsion) on color Doppler exam. Instead, the affected testis had either decreased or symmetrical preserved flow compared to the contralateral unaffected side, sometimes even increased flow . In many of our cases, it was extremely difficult to decide whether the flow was truly symmetrical to the contralateral side or was subtly decreased. Of all the cases with preserved flow, decreased flow in the affected testis was more commonly observed than symmetrical or increased flow. The patient age in our cases ranged from 3 years to 19 years, the majority being 12 years and older. While studying some of our youngest patients (3–6 years), we noted that they all presented with abdominal pain, nausea and vomiting, and received the typical workup for pain including ultrasound examination to rule out appendicitis. The nonspecific symptoms resulted in a delayed diagnosis. It is important to remember that intravaginal torsion can occur even in such young patients, though less frequently compared to adolescents, and when presentation is right-sided it can mimic appendicitis. A clinical examination of the scrotum is recommended in all boys with right lower quadrant pain and a low threshold for a scrotal ultrasonography.
Anatomy of the bell clapper testis
Normally, the epididymis extends along the full length of the testis posterolaterally so that the upper and lower poles of the testis are covered and the tunica vaginalis parietal lamina is anchored to the epididymis. In a bell clapper anomaly, not only is there a lack of posterior attachment of the tunica vaginalis parietal lamina to the epididymis, but the epididymis–testis connection is also incomplete and the epididymis might be detached from the testis lower pole . Depending on the degree of epididymal detachment, the entire unit comprising the testis, epididymis and distal spermatic cord hangs freely in the intravaginal space and can twist, resulting in the horizontal lie or testicular torsion. There is wide consensus that bell clapper anomaly is the primary risk factor for acute intravaginal torsion. An autopsy study revealed bell clapper anomaly in 12% of testes . It was found to be bilateral in most cases. In a study of adolescent boys with acute testicular torsion, all torsion was intravaginal and was associated with ipsilateral bell clapper anomaly, and with contralateral bell clapper anomaly in 78% of the cases .
Sonographic features most reliable for diagnosing testicular torsion
Spermatic cord whirlpool sign
Redundant spermatic cord
Horizontal or altered lie
Sonographic features concerning for testicular torsion but also seen in other conditions
Globular testicular enlargement
Varying degrees of heterogeneous parenchymal echotexture might be seen in testicular torsion, and significant heterogeneity indicates late torsion and testicular nonviability (Fig. 6). Homogeneous echotexture portends extremely well for testicular viability . Careful mapping of the testicular echotexture can lead to early diagnosis of potential segmental infarction and can also help during follow-up exam, when the echotexture might return to normal.
Epididymal enlargement without hyperemia
Role of spectral Doppler in testicular torsion:
Intratesticular arteries characteristically have a low resistance pattern with a mean resistive index of 0.62 (range, 0.48–0.75) . Asymmetrical dampened spectral waveform in the affected testis and absence or reversal of diastolic flow suggests testicular torsion in the proper setting . Documenting Doppler waveforms and calculating resistive indices on both the affected and non-affected sides can be useful in determining differences in testicular perfusion.
Torsion versus Epididymitis: Approach to diagnostic challenges
The clinical features considered predictive for testicular torsion include pain <24 h, nausea/vomiting, abnormal cremasteric reflex, and high position of the testis . The best predictors for epididymitis include dysuria, a painful epididymis on palpation, altered epididymal echogenicity and increased peritesticular perfusion found on ultrasound exam . Torsion of the appendix testis can be identified by the presence of the blue dot sign, a palpable nodule on the upper pole of the testis, or visualization of a relatively avascular nodule on ultrasound .
Sonographic protocol for suspected testicular torsion
Transducer - Use the linear high-frequency 6- to 15-MHz probe. The linear 9-MHz probe can be used to obtain greater depth. In infants, the hockey-stick probe can be used. Start the examination by asking where it hurts.
First obtain a midline gray-scale transverse view to document lie of both testes.
Take transverse static color Doppler image of both testes.
While holding the probe still (do not sweep) in midline transverse mid-testis position, take a 3-s color cine clip of both testes side-by-side to show real-time intrinsic flow.
Take gray-scale longitudinal images in central, medial and lateral aspect of each testis.
Take gray-scale transverse images at superior, mid and inferior portions of each testis.
Document testis volume on each side.
Start with asymptomatic side in order to optimize color Doppler parameters, and then move to the affected side. Perform color Doppler of each testis.
Color Doppler exam with pulsed Doppler tracing of arterial and venous flow (angle correct if possible, and use power Doppler if flow is difficult to document). Try to measure testicular arterial resistive index.
Take gray-scale and color images of the epididymis in longitudinal and transverse planes.
Take gray-scale and color images of the spermatic cord in longitudinal plane. Follow the cord meticulously in its entire extent in the sac and through the inguinal canal till the internal ring.
Take cine sweeps of each testis in longitudinal and transverse planes.
Take cine sweep of each spermatic cord in longitudinal plane.
In case of any pathology, save images as needed.
Swollen epididymis and testis with testicular flow that is only minimally decreased, normal, or increased in boys with incomplete or intermittent testicular torsion can mimic epididymo-orchitis. The most common cause of acute scrotal pain in children is torsion of appendix testis, which can also mimic epididymo-orchitis. Therefore it is important to evaluate for the presence of avascular nodule that might represent the torsed appendage (Fig. 8; videos 9, 10 and 11, online supplementary material). Any time a child presents with acute scrotal pain, and findings resembling epididymitis without findings of torsed appendage, testicular torsion should be excluded. Suspicion of intermittent or incomplete testicular torsion should be raised in a child with a history of recurrent epididymitis or epididymo-orchitis, or abrupt pain that resolved or decreased at the time of diagnosis.
Incomplete/partial testicular torsion is a difficult diagnosis both clinically and sonographically. Arce et al.  showed that rotated cord structures were visualized with gray-scale ultrasound in all six of their patients with surgically proven testicular torsion, despite the presence of intratesticular color flow, suggesting a diagnosis of incomplete testicular torsion. The torsion knot has been reported on MR imaging in an adult with 6 weeks of symptoms . Both testicular MRI and contrast-enhanced sonography in the future might be a useful complement to clinical and baseline imaging in difficult/sonographically equivocal cases, although there are no prospective studies in the pediatric population . In a retrospective study by Galina et al. , the epididymis was always sonographically abnormal in boys with testicular torsion, being minimally or grossly displaced in relation to the testis and spermatic cord.
Clinical correlation is essential. Severe nausea and vomiting and abrupt onset of pain favor torsion. A more common clinical mimic of testicular torsion is an acutely torsed testicular appendage, which is treated conservatively . Presence of subcutaneous superficial soft-tissue swelling favors inflammatory etiology, either epididymitis or appendage torsion, rather than testicular torsion, in which case the subcutaneous edema is typically seen later in the presentation. Scrotal exploration should be considered whenever there is suspicion for testicular torsion, even if the ultrasound findings are not specific.
Likelihood of salvage of the testis is directly related to the time between symptom onset and detorsion . However in our experience salvage is unpredictable depending on how tightly or loosely the cord was twisted, and hence surgery should not be delayed after the diagnosis of torsion is established, even if the time to presentation exceeds the 6- to 10-h window. A testis might become nonviable as early as 4 h after a 720° twist, or it might remain viable for several days if the torsion is incomplete. In one of our cases, salvage was achieved after 3 weeks from initial diagnosis of epididymitis to final diagnosis of incomplete torsion (Fig. 9). Anatomical variability might account for differences in the duration of viability of the torsed testis . Initially after salvage, the testes sometimes appear in good condition; however long-term follow-up of salvaged testes post orchiopexy can be helpful in determining the effects of torsion. Manual detorsion of the testis can restore blood flow while the boy awaits surgical correction. In a study of 133 patients with testicular torsion, successful manual detorsion was associated with a salvage rate of 97% compared with 75% salvage in patients in whom detorsion was not attempted or not successful .
Testicular gray-scale ultrasound is the modality of choice for the imaging evaluation of acute scrotal pain. The presence of intratesticular flow does not exclude testicular torsion. Testicular vascularity can look symmetrical with the contralateral asymptomatic side with preserved arterial and venous flow and still represent testicular torsion. An integral part of the exam is to look for an abrupt change in configuration of cord at the external inguinal ring or in the scrotal sac. The presence of redundant spermatic cord within the scrotum is highly suspicious for testicular torsion. An enlarged epididymal-cord complex representing the torsion knot/pseudomass is more frequently identified at the sonographic examination compared to the more classic whirlpool sign of twisted spermatic cord. Residual flow might be preserved in parts of the cord when the twist is not tight enough to completely obliterate the flow. An astute analysis of the cord and lie of the testis can prevent the overdiagnosis of epididymitis. We encourage the use of simultaneous cine clips of testes side-by-side at the start of the exam to document lie and assess inherent flow. A group discussion among the radiologist, emergency room physician and urologist is recommended for proper management; manual detorsion of the testis might be considered to improve chances of salvage while the patient awaits surgery.
We would like to express our sincere appreciation to our stellar sonographers — Tara Cielma, Danyelle Holley, Kadine Linden, Lesley Demshur, Megan Aluri, Cathy Jones, Suella Jones, Steve Hoefer, Courtney Ruiz, Cara Hill, Gail McClain, Teela Durfee, Roza Zenelaj — for their expertise and insight.
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Conflicts of interest
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