Ultrasound characteristics of extravaginal testicular torsion at different stages of disease progression

Introduction

Testicular torsion is a common urological scrotal emergency, with peak incidences in the neonatal and adolescent periods (1). Newborns, who have more fragile vascular tissue than children or adolescents, typically present with extravaginal torsion, in which twisting occurs outside the tunica vaginalis, while adolescents most often have intrathecal torsion, in which twisting occurs within the tunica vaginalis (2). Given their age and atypical clinical symptoms, the loss rate of affected testicles in newborns can be 92.4% to 100% (3,4). Many investigators have reported the ultrasound manifestations of intrathecal testicular torsion (2,5,6), but reports on extravaginal testicular torsion are limited to case reports and small clinical series (7,8). These studies lack a systematic description of the ultrasound manifestations of extravaginal testicular torsion, describing predominantly the ultrasound manifestations of a single disease stage (7-9). Herein we report data from 20 infants with surgically and pathologically confirmed extravaginal testicular torsion. The typical ultrasound features of extravaginal testicular torsion at various stages are summarized, aiming to improve the diagnostic accuracy of ultrasound for extravaginal testicular torsion, improving the rescue rate of testicular torsion, and demonstrating the value of color doppler ultrasound examination. We present this article in accordance with the STROBE reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-24-288/rc).

Methods

This retrospective cross-sectional study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by Biomedical Research Ethic Committee of Shandong Provincial Hospital (No. SWYX2024-016), and individual consent for this retrospective analysis was waived.

Study population

We performed a retrospective analysis of clinical and ultrasound examination data obtained from 20 infants ranging in age from 1 to 75 days (12 newborns; 8 aged >1 month) who were diagnosed with extravaginal testicular torsion both by surgery and pathology between January 2016 and December 2022. Medical history data spanned a mean of 16.3±17.5 days (range, 1–60 days). In 16 infants, testicular abnormalities were identified immediately after birth, while the remainder were identified within one month after birth. All testicular torsions were unilateral, with 10 on each side. Ten infants underwent a single ultrasound examination, nine underwent two ultrasound examinations, and one infant was examined three times (31 total). Based on the different ultrasound characteristics, they were divided into three stages: double-ring effusion (eight examinations), calcification of tunica vaginalis (15 examinations), and testicular atrophy (eight examinations). Four infants underwent surgery at the double-ring effusion stage, eight at the stage of calcification of the tunica vaginalis, and eight at the stage of testicular atrophy.

Examination method

Supine infants were settled until quiet, then underwent ultrasound examination utilizing the Toshiba Aplio500 ultrasound system (Toshiba Medical Systems Corporation, Tokyo, Japan) or the GE Logiq 9 ultrasound system (GE Medical Systems, Milwaukee, WI, USA) using a high-frequency linear transducer (L 5–12 MHz). The probe was placed on multiple portions of the scrotum to facilitate bilateral comparative scanning, with a focus on observing the testicular axis, size, shape, parenchymal echogenicity, and parenchymal blood flow signal distribution. Simultaneously, the epididymis and spermatic cord were observed, the presence or absence of paratesticular twisted masses (twisted spermatic cord tissue and epididymis) was assessed, and any fluid accumulation inside and outside the tunica vaginalis of the testicles was documented.

Ultrasound measurement

The longitudinal, antero-posterior, and transverse diameters of the affected and healthy testicles were measured. The longitudinal diameter was measured on the long axis section of the testicles, while the antero-posterior and transverse diameters were measured on the short axis section of the testicles, and the three diameters were multiplied by 0.52 to determine the volume of the testicle. The maximum depth of hydrocele inside and outside the tunica vaginalis was also measured.

Statistical analysis

Statistical analysis was performed using SPSS 19.0 software (SPSS Inc.; Chicago, IL, USA). The testicular measurements of each stage were represented by mean ± standard deviation. Paired sample t-tests were used to assess the differences between the affected and healthy testicles in double-ring effusion, tunica vaginalis calcification, or testicular atrophy, and the differences of the affected testicles among the three stages were analyzed using one-way analysis of variance (ANOVA). The consistency between the two ultrasound physicians was assessed using Pearson’s linear correlation analysis, and a P<0.05 was considered statistically significant.

Results

Testicular measurement and statistical analysis

Volume measurements of the affected and healthy testicles at each stage (double-ring effusion, tunica vaginalis calcification, and testicular atrophy) are shown in Table 1. The volumes of the affected testicles were greater than those of the healthy testicles at the double-ring effusion stage (P<0.05). At the tunica vaginalis calcification stage, the volumes of the affected testicles were smaller than those of the unaffected testicle (P<0.05). At the testicular atrophy stage, the volumes of the affected testicles were significantly smaller than those of the unaffected testicle (P<0.05). The volumes of the affected testicles gradually decreased from the stage of double-ring effusion to tunica vaginalis calcification, and then to testicular atrophy (P<0.05).

Characteristic sonograms

The typical ultrasound images of extravaginal testicular torsion are shown in Figures 1,2. The sonographic appearance of the double-ring effusion stage was characterized by enlargement and fullness of the affected testicles, with axial abnormalities, including uniform or uneven parenchymal echo, visualized in all 8 ultrasound examinations in the transverse position. Reduced blood flow signal was observed in the testicular parenchyma in two examinations, with absent blood flow signal on six studies. All eight examinations identified twisted paratesticular masses, with effusions present within the testicular sheath cavity and between the parietal sheath and the scrotal fascia layer, presenting as a “double-ring effusion sign” (Figure 1A), meanwhile no abnormalities were found in the contralateral testicle (Figure 1B).

Figure 1 Three consecutive ultrasound examinations of the same infant in the double-ring effusion, tunica vaginalis calcification, and testicular atrophy stages of extravaginal testicular torsion: (A) during the double-ring effusion stage (age: one day), fluid accumulation is seen both inside and outside the left testicular sheath cavity, presenting as a “double-ring effusion sign”; (B) no abnormalities are observed in the right testicle; (C) in the tunica vaginalis calcification stage (age: 22 days), the tunica vaginalis on the left testicle is seen to have a strong, eggshell-shaped echo signal; (D) in the testicular atrophy stage (age: 92 days), the affected testicle is markedly shrunken. White arrows: left testicle.

Figure 2 Two consecutive ultrasound examinations of the same infant in the tunica vaginalis calcification and testicular atrophy stages of extravaginal testicular torsion: (A) during the stage of tunica vaginalis calcification (age: 33 days), an eggshell-shaped strong echo signal is seen in the tunica vaginalis of the right testicle; (B) no abnormalities are observed in the left testicle; (C) during the testicular atrophy stage (age: 138 days), the right testicle is markedly smaller than the contralateral side; (D) no abnormalities are found in the left testicle. White arrows: right testicle.

At the tunica vaginalis calcification stage, the affected testicle was slightly smaller than the contralateral testicle. Axial abnormalities (in the transverse position) were observed in 14 studies, while one examination showed no axial abnormalities, and the parenchymal echo texture of the affected testicles was uniform or uneven. The parenchyma had absent blood flow, and the tunica vaginalis showed a strong echo signal in an eggshell-like pattern. Twisted paratesticular masses were observed on seven of 15 examinations. Fluid inside the tunica vaginalis was not observed, but two examinations identified fluid outside the parietal tunica vaginalis (Figures 1C,2A,2B).

At the testicular atrophy stage, there was a significant size reduction in the affected testicle, with regular or irregular morphology. Determination of the axial direction of the testis was challenging due to the significant size reduction. The echo texture of the tunica vaginalis and parenchyma was enhanced, without clear internal structure and no parenchymal blood flow. No obvious twisted paratesticular masses were observed, and no fluid was observed in the tunica vaginalis. One examination showed the presence of fluid outside the parietal tunica vaginalis (Figures 1D,2C,2D).

Surgery and follow-up

All 20 infants underwent surgery, with varying degrees of testicular torsion observed intraoperatively. Four infants had testicular surgery at the double-ring effusion stage, with recovery of testicular blood flow during the surgery and good recovery after a 3-month follow-up in two of them. The other two patients had no recovery in testicular blood flow during the procedure and had partial necrosis, and so underwent testicular resection. Eight infants had surgery at the tunica vaginalis calcification stage, and their testicles were found to be black or purple in color (Figure 3); blood flow did not recover, and testicular resection was performed. Eight infants underwent surgery at the testicular atrophy stage, during which significant testicular atrophy was observed and testicular resection was performed.

Figure 3 Intraoperative picture of extravaginal testicular torsion in the tunica vaginalis calcification stage: the testicle is twisted at the upper end of the spermatic cord, and the testicle and epididymis are black/purple in color.

The affected testicular blood flow, parenchymal heterogeneity and testicular preservation rate of the 20 infants are shown in Table 2.

Discussion

Neonatal testicular torsion (NTT) refers to testicular torsion occurring within the first month of life, also known as perinatal testicular torsion. Approximately 70% to 80% of cases occur in utero, and NTT accounts for 10% to 12% of testicular torsion in children (10). NTT develops outside the tunica vaginalis (11). NTT pathogenesis may be related to perinatal relaxation of the testicular and spermatic cord sheath attachment to the scrotal fascia layer, and to the incomplete attachment of the testicular cord to the scrotal wall. During pregnancy or delivery, changes in uterine pressure and compression of the infant in the birth canal can easily lead to testicular torsion developing outside the tunica vaginalis (11).

Due to the lack of corresponding clinical features in NTT, it is difficult to determine precisely when the torsion occurred. By the time testicular abnormalities are detected, torsion is often long-standing, and the opportunity for surgical reduction has been missed, resulting in an extremely low rate of successful testicular rescue. At the different disease stages following testicular torsion, the testicles generally go through a process from swelling to shrinking, followed by atrophy, due to changes in testicular blood supply, resulting in different ultrasound characteristics at each stage. Therefore, controversy remains on whether, and when, to treat (12-15).

Based on the distinct ultrasound characteristics of NTT at the different disease stages, we divided extravaginal testicular torsion into three stages: double-ring effusion, tunica vaginalis calcification, and testicular atrophy. Previous studies predominantly described NTT as having one or two stages, with some studies reporting simultaneous involvement of both testicles (7,8), However, in this study, the NTT cases were all unilateral.

The double-ring effusion stage is characterized sonographically by the “double-ring effusion sign” that gives the stage its name. The distinguishing point, aside from age of presentation, between extravaginal testicular torsion and intrathecal testicular torsion is that the latter’s hydrocele develops solely between the visceral and parietal layers of the testis, with no hydrocele between the parietal and scrotal testicular fascia layers. Complicating diagnosis, the “double-ring effusion sign” is not specific for extravaginal testicular torsion, and can be mistaken for the physiological double-ring effusion sign in healthy newborns. Their etiology is distinct, though physiological double-ring effusion is also due to the loose attachment of both the tunica vaginalis and scrotal fascia layer of the testis and spermatic cord in the perinatal period, resulting in a potential cavity into which abdominal fluid can enter. Simultaneously in neonates, due to the open sheath process, fluid may accumulate between the testicular visceral and parietal tunica vaginalis (16), forming a “double-ring effusion sign” with both internal and external fluid accumulation in the parietal tunica vaginalis of the testicle. The difference between physiologic and pathologic double-ring effusion is that the double-ring effusion sign of extravaginal testicular torsion is formed by exudate from the two cavities developing after torsion. Moreover, the physiologic double-ring effusion sign is typically bilateral, and is not associated with alterations in the size, axis, internal echo texture, or blood flow of the testis, and paratesticular twisted masses are absent. Testicular torsion with ultrasonographic double-ring effusion indicates that the torsion time typically has not been long-standing. Therefore, surgical exploration is recommended to restore testicular function and improve testicular rescue rate.

Testicular torsion in the tunica vaginalis calcification stage sonographically shows a mild reduction in size of the affected testicle compared to the contralateral healthy testicle. Typically, a slight axial change is present, the echo texture of the parenchyma can be uniform or uneven, and parenchymal blood flow is absent. The tunica vaginalis has a bead-like, eggshell-like, or annular strong echo. Occasionally, paratesticular twisted masses are observed, and a small amount of fluid may be present outside the tunica vaginalis cavity. The tunica vaginalis calcification stage must be differentiated from testicular teratoma or epidermoid cyst (17,18), which can also exhibit eggshell like or patchy strong echogenicity within the testicles or around lesions, but rarely on the tunica vaginalis. Moreover, testicular teratomas or epidermoid cysts typically have a clear boundary, with normal testicular tissue observed. Testicular torsion observed by ultrasound in the tunica vaginalis calcification stage is indicative of long-standing testicular torsion, and is accompanied by mild size reduction of the affected testicle. The affected testicle may be necrotic, and the surgical exploration is often non-contributory.

In the testicular atrophy stage, ultrasound identifies a significant reduction in testicular size, with regular or irregular morphology. The testicular axis is difficult to determine, and the echo texture of the tunica vaginalis and parenchyma are enhanced. The internal structure of the affected testicle is difficult to discern, and parenchymal blood flow is absent. The differential diagnosis includes cryptorchidism (19-21), since affected testicles in this stage are markedly smaller, with enhanced echoes and unclear internal structures, so they can be missed or mistaken for the soft tissue in the scrotum, leading to the diagnosis of cryptorchidism. However, the diagnosis of cryptorchism requires identification of ectopic testicles in the inguinal area or pelvic cavity, distinguishing the condition from testicular atrophy. When ectopic testicles are not detected, the diagnosis of cryptorchidism is suspected, and surgical exploration is likely unnecessary. The affected testicles are markedly smaller at this stage, and are non-viable, so surgical exploration is not recommended.

However, there are some limitations in this study. Firstly, the sample size is relatively small, especially with only one case showing three stages of the disease; further cases will be identified in the future. Secondly, there are some difficulties in identifying the blood flow signal of the testicles of newborn, and it is necessary to adjust the blood flow range and color gain parameters of the ultrasound instrument.

Conclusions

In summary, extravaginal testicular torsion has distinct sonographic manifestations at different disease stages. Recognizing these sonographic features can aid in the diagnosis and clinical rescue rate of the affected testes. Color doppler ultrasound examination is extremely helpful diagnostically.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://qims.amegroups.com/article/view/10.21037/qims-24-288/rc

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-24-288/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. This study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by Biomedical Research Ethic Committee of Shandong Provincial Hospital (No. SWYX2024-016), and individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Zhao LC, Lautz TB, Meeks JJ, Maizels M. Pediatric testicular torsion epidemiology using a national database: incidence, risk of orchiectomy and possible measures toward improving the quality of care. J Urol 2011;186:2009-13. [Crossref] [PubMed]
2. Sharp VJ, Kieran K, Arlen AM. Testicular torsion: diagnosis, evaluation, and management. Am Fam Physician 2013;88:835-40.
3. Monteilh C, Calixte R, Burjonrappa S. Controversies in the management of neonatal testicular torsion: A meta-analysis. J Pediatr Surg 2019;54:815-9. [Crossref] [PubMed]
4. Yerkes EB, Robertson FM, Gitlin J, Kaefer M, Cain MP, Rink RC. Management of perinatal torsion: today, tomorrow or never? J Urol 2005;174:1579-82; discussion 1582-3. [Crossref] [PubMed]
5. Xiang H, Han J, Ridley WE, Ridley LJ. Snail shell sign: Testicular/ovarian torsion. J Med Imaging Radiat Oncol 2018;62:106. [Crossref] [PubMed]
6. Singhal A, Agarwal A, Metuge J, Olsavsky T. Neonatal testicular torsion with an unusual sonographic feature. J Clin Ultrasound 2012;40:243-6. [Crossref] [PubMed]
7. Bagci S, Bachour H, Woelfle JF, Mueller A, Bartmann P, Franz AR. Bilateral perinatal testicular torsion in an infant: a rare neonatal emergency. Pediatr Int 2010;52:e227-8. [Crossref] [PubMed]
8. Sommer-Jörgensen V, Künzli M, Holland-Cunz SG, Gros S, Frech M. A CARE-compliant article successful salvage of bilateral perinatal testicular torsion after delivery out of breech presentation: A case report and review of the literature. Medicine (Baltimore) 2020;99:e21763. [Crossref] [PubMed]
9. Yadav P, Erlich T, Zlotnik M, Khondker A, O'Kelly F, Traubici J, Chua ME, Koyle MA. Ultrasonographical features of perinatal testicular torsion: an assessment of interobserver variability among radiologists and pediatric urologists. Pediatr Surg Int 2022;38:2053-8. [Crossref] [PubMed]
10. Abraham MB, Charles A, Gera P, Srinivasjois R. Surgically managed perinatal testicular torsion: a single centre experience. J Matern Fetal Neonatal Med 2016;29:1265-8. [Crossref] [PubMed]
11. Sangüesa Nebot C, Llorens Salvador R, Picó Aliaga S, Garcés Iñigo E. Perinatal testicular torsion: ultrasound assessment and differential diagnosis. Radiologia 2017;59:391-400. [Crossref] [PubMed]
12. Ching CB, Jones JS. Incomplete prenatal torsion of the testicle--a successful salvage. Urology 2011;78:1182-4. [Crossref] [PubMed]
13. Yağız B, Hancıoğlu S, Balcı Ö, Demirel BD, Karaman A, Bıçakcı Ü, Özgüner İF, Karaman İ. Management of perinatal testicular torsion: experience of two tertiary centers. Pediatr Surg Int 2020;36:959-63. [Crossref] [PubMed]
14. Callewaert PR, Van Kerrebroeck P. New insights into perinatal testicular torsion. Eur J Pediatr 2010;169:705-12. [Crossref] [PubMed]
15. Kylat RI, Ahmed MN. Neonatal testicular torsion. Afr J Paediatr Surg 2022;19:1-4. [Crossref] [PubMed]
16. Patoulias I, Koutsogiannis E, Panopoulos I, Michou P, Feidantsis T, Patoulias D. Hydrocele in Pediatric Population. Acta Medica (Hradec Kralove) 2020;63:57-62. [Crossref] [PubMed]
17. Arkar RR, Umap RA, Jadhav S. Prenatal diagnosis of cryptorchid testicular teratoma. Indian J Radiol Imaging 2016;26:67-9. [Crossref] [PubMed]
18. Stemberger A, Zeffren M, Birbe R, Tan WP. Epidermoid cyst: An unusual presentation of a testicular mass. Curr Urol 2022;16:267-8. [Crossref] [PubMed]
19. Braga LH, Lorenzo AJ. Cryptorchidism: A practical review for all community healthcare providers. Can Urol Assoc J 2017;11:S26-32. [Crossref] [PubMed]
20. Longui CA. Cryptorchidism: diagnosis and treatment. Arq Bras Endocrinol Metabol 2005;49:165-71. [Crossref] [PubMed]
21. Ashley RA, Barthold JS, Kolon TF. Cryptorchidism: pathogenesis, diagnosis, treatment and prognosis. Urol Clin North Am 2010;37:183-93. [Crossref] [PubMed]