Lim, Yang, Kim, Kim, Kim, Lee, Moon, and Park: Ultrasonography of intrascrotal torsed appendages: size and interval between symptom onset and the ultrasonographic examination according to echogenicity

Abstract

Purpose

This study investigated the size of torsed appendages and the interval between symptom onset and the ultrasonographic examination according to the echogenicity of the torsed appendages.

Methods

This was a retrospective analysis of 54 cases in 46 patients with torsion of the testicular appendages between December 2008 and July 2021. Eight patients received follow-up ultrasonography 7-48 days after initial ultrasonography. The echogenicity of torsed appendages was classified into three groups: hypoechoic, hyperechoic, or isoechoic.

Results

The 54 torsed appendages were hypoechoic (n=40), hyperechoic (n=9), or isoechoic (n=5). The size of the torsed appendages ranged from 4 to 14 mm (8.0±3.1 mm) in hypoechoic torsed appendages and from 2.6 to 5.0 mm (3.7±0.9 mm) in hyperechoic torsed appendages. The interval between symptom onset and the ultrasonographic examination ranged from 0 to 17 days (4.2±4.4 days) in hypoechoic torsed appendages and from 8 to 48 days (29.8±16.0 days) in hyperechoic torsed appendages. The hyperechoic torsed appendages were smaller and had longer intervals between symptom onset and the ultrasonographic examination than the hypoechoic torsed appendages (P<0.05). Three hypoechoic torsed appendages and a single isoechoic torsed appendage on initial ultrasonography became hyperechoic on follow-up ultrasonography.

Conclusion

The size of the torsed appendages and the interval between symptom onset and the ultrasonographic examination varied according to the echogenicity of the torsed appendages. The hyperechoic torsed appendages were smaller and had longer intervals until the examination than the hypoechoic torsed appendages.

Introduction

The testicular appendages are vestigial remnants of the mesonephric and Müllerian duct systems. When the pedicle of the testicular appendage is torsed, sudden-onset scrotal pain and scrotal swelling develop.
Torsion of the testicular appendages is the most common cause of an acute painful scrotum in children [1-3]. The ultrasonographic findings of torsion of the testicular appendages are as follows: the appendages increase in size and present variable echogenicity (hypoechoic, isoechoic, or hyperechoic) [4,5]. However, there is an overlap between normal and torsed testicular appendages in size and echogenicity on ultrasonography [5,6].
Several studies have stated that the echogenicity of torsed testicular appendages is time-dependent [6-8]. However, the echogenicity of torsed appendages remains a matter of debate [4-8]. To the best of the authors’ knowledge, the relationship between the size of torsed appendages and the interval between symptom onset and the ultrasonographic examination according to the echogenicity of the torsed appendages has rarely been described [7]. In addition, no study has yet been published regarding changes in the echogenicity and size of torsed appendages on follow-up ultrasonography.
The purpose of this study was to evaluate the size of torsed appendages and the interval between symptom onset and the ultrasonographic examination according to the echogenicity of the torsed appendages.

Materials and Methods

Compliance with Ethical Standards

This retrospective study (Kyung Hee Univeristy Hospital at Gangdong, 2022-01-037-002) was approved by the institutional review board of the authors’ affiliated institution, and the requirement for informed consent from patients was waived.

Patients

The case files of 46 patients with testicular appendage torsion who were treated at Kyung Hee University Hospital at Gangdong between December 2008 and July 2021 were retrospectively reviewed.
The diagnosis of appendage torsion was based on pertinent ultrasonographic findings with clinical improvement after conservative treatment (n=46). Eight of the torsed appendages had follow-up ultrasonography after the initial diagnosis of testicular appendage torsion, with follow-up intervals ranging from 7 to 48 days (mean, 21.2 days). The total number of ultrasonographic examinations of torsed appendages was 54.
All ultrasonographic examinations were performed using high-resolution sonographic systems, such as an iU22 ultrasound machine (Philips Medical Systems, Bothell, WA, USA) equipped with a 5-12 MHz linear array transducer and a LOGIQ 700 MR system equipped with a 5-10 MHz linear array transducer (GE Healthcare, Milwaukee, WI, USA). Color Doppler ultrasonography was performed with optimized color Doppler parameters. The color gain control was adjusted so that the background color noise was minimal or absent.
The ultrasonographic findings were determined by a retrospective analysis of the images. Grayscale and color Doppler ultrasonographic images were interpreted via the consensus of two experienced radiologists: two experienced radiologists (D.M.Y. and S.H.L.) in the practice of ultrasonography.
Patients’ reports were analyzed to determine the echogenicity, size, and presence of blood flow of the torsed appendages and the interval between symptom onset and the ultrasonographic examination. The echogenicity of the torsed appendages was compared with that of the ipsilateral testis. When the torsed appendage was heterogeneous and had multiple tiny cystic foci separated by echogenic septa, it was considered hypoechoic. If symptom onset and the ultrasonographic examination were on the same day, the interval was regarded as 0.
The size of the torsed appendages and the interval between symptom onset and the ultrasonographic examination was analyzed according to the three echogenicity categories of the torsed appendages. In addition, initial and follow-up ultrasonographic examinations were compared to determine changes in the echogenicity and size of the torsed appendages and the interval between symptom onset and the ultrasonographic examination.
Analysis of variance (ANOVA) was used to compare the size of the torsed appendages and the interval between symptom onset and ultrasonographic examination according to the three echogenicity categories of the torsed appendages. Post hoc analysis with the Bonferroni correction was performed for all parameters identified as significant by ANOVA. The independent t-test was used to evaluate changes in the echogenicity and size of the torsed appendages between initial ultrasonography and follow-up ultrasonography. All analyses were performed with SPSS version 18 (SPSS Inc., Chicago, IL, USA). A P-value of less than 0.05 was considered statistically significant.

Results

The age of the patients ranged from 2 to 13 years (mean, 8 years). In all patients, the chief complaint was acute scrotal pain.
The 54 torsed appendages were hypoechoic (n=40), hyperechoic (n=9), or isoechoic (n=5) (Table 1, Figs. 1-3). Among the three echogenicity categories of the torsed appendages, hypoechoic torsed appendages were the most common. All hypoechoic torsed appendages showed heterogeneous echogenicity and had multiple tiny cystic foci (Figs. 1, 2).
The size of the torsed appendages ranged from 4 to 14 mm (8.0±3.1 mm) in hypoechoic torsed appendages, 2.6 to 5.0 mm (3.7±0.9 mm) in hyperechoic torsed appendages, and 5 to 6 mm (5.4±0.5 mm) in isoechoic torsed appendages. The hyperechoic torsed appendages were smaller than the hypoechoic torsed appendages (P<0.05).
The interval between symptom onset and the ultrasonographic examination ranged from 0 to 17 days (4.2±4.4 days) in hypoechoic torsed appendages, 8 to 48 days (29.8±16.0 days) in hyperechoic torsed appendages, and 1 to 3 days (1.6±0.9 days) in isoechoic torsed appendages. The hyperechoic torsed appendages had a longer interval between symptom onset and the ultrasonographic examination than the hypoechoic and isoechoic torsed appendages (P<0.05).
In the analysis of changes in the echogenicity between initial and follow-up ultrasonography in eight boys, six of the eight torsed appendages were hypoechoic and two were isoechoic (2/8) on initial ultrasonography, whereas four were hypoechoic and four were hyperechoic on follow-up ultrasonography (Table 2). Three hypoechoic torsed appendages and a single isoechoic torsed appendage on initial ultrasonography became hyperechoic on follow-up ultrasonography (Fig. 3). Additionally, one isoechoic torsed appendage on initial ultrasonography became hypoechoic on follow-up ultrasonography (Fig. 2).
The size of the torsed appendages ranged from 5 to 14 mm (9.4±3.9 mm) on initial ultrasonography and 2.6 to 16 mm (6.9±4.5 mm) on follow-up ultrasonography. The torsed appendages were larger on initial ultrasonography than on follow-up ultrasonography (P<0.05). The interval between symptom onset and ultrasonographic examination ranged from 0 to 9 days (9.4±3.9 days) on initial ultrasonography and 7 to 48 days (27.0±17.3 days) on follow-up ultrasonography.
On color Doppler ultrasonography, no blood flow was identified within the torsed appendages in any of the 54 cases (Fig. 1). An increase in periappendiceal blood flow was seen in 18 of the 54 torsed appendages (33.3%).

Discussion

This study analyzed differences in the size of torsed appendages and the interval between symptom onset and the ultrasonographic examination according to the echogenicity of the torsed appendages.
Hypoechoic torsed appendages were larger than hyperechoic torsed appendages. The size of the torsed appendages ranged from 4 to 14 mm (8.0±3.1 mm) in hypoechoic torsed appendages and 2.6 to 5 mm (3.7±0.9 mm) in hyperechoic torsed appendages. Furthermore, hypoechoic torsed appendages had a shorter interval (4.2±4.4 days) between symptom onset and ultrasonographic examination than that of hyperechoic torsed appendages (29.8±16.0 days). All hypoechoic torsed appendages showed heterogeneous echogenicity and had tiny cystic foci. Heterogeneous hypoechogenicity may be due to a mixture of cystic lesions with background echogenic lesions [8]. The tiny cystic lesions may be represented by lymphatic dilatation, which may be the first histologic finding in early torsed intrascrotal appendages [9]. Park et al. [7] stated that torsed appendages diagnosed within 24 hours of symptom onset were primarily hypoechoic and that hypoechogenicity indicated edema of the torsed appendage without hemorrhage or infarction. Therefore, it is suggested that the first ultrasonographic findings after torsion of a testicular appendage are an enlargement of the appendage with heterogeneous hypoechogenicity.
Hyperechoic torsed appendages had a longer interval between symptom onset and the ultrasonographic examination than hypoechoic torsed appendages. A hyperechoic torsed appendage indicates hemorrhage or infarction on histopathology and usually is seen in a later stage of torsion [4,7]. As time goes on, torsion progresses from lymphatic dilatation and venous congestion to hemorrhage, ischemia, and infarction of the appendage [9]. These histologic changes can explain the change from hypoechogenicity into hyperechogenicity of torsed appendages. In two cases of torsed appendages that were hypoechoic on both initial ultrasonography and follow-up ultrasonography after 5 days, the peripheral portion of the appendages changed from hypoechogenic to hyperechogenic (Fig. 1). In addition, three hypoechoic torsed appendages on initial ultrasonography became hyperechoic on follow-up ultrasonography (Table 2, Fig. 3). However, the interval was quite long, making it difficult to know when the pattern changed from hypoechogenicity to hyperechogenicity.
The hyperechoic torsed appendages were smaller than the hypoechoic torsed appendages. Furthermore, the hyperechoic torsed appendages had a longer interval between symptom onset and ultrasonographic examination than the hypoechoic and isoechoic torsed appendages. It is suggested that the torsed appendages decreased in size because of reabsorption of the hemorrhage and necrotic tissue and the progression of fibrosis over time. However, Park et al. reported that torsed appendages did not differ in size between those evaluated within 24 hours of symptom onset and those for which more than 24 hours elapsed after onset [7]. This difference between studies likely reflects the different intervals that were analyzed: the interval between symptom onset and the ultrasonographic examination was 0-48 days in this study and 3 hours to 19 days in the previous study. The hyperechoic torsed appendages in this study had much longer intervals (29.8±16.0 days) than those in the previous study [7]. It is suggested that a longer interval increases the likelihood that a torsed appendage will be smaller.
Interestingly, previous studies have stated that torsed appendages in early stages were hyperechoic [4,5]. The reason for hyperechogenicity in earlier stages of torsed appendages may relate to the multiple interfaces generated by several tiny cystic lesions within the torsed appendage [8]. In torsed appendages with multiple tiny cysts, the echogenicity of the torsed appendages may be different according to the size of the interfaces generated by the multiple cystic lesions, with a hypoechoic pattern in larger interfaces and a hyperechoic pattern in smaller interfaces.
Isoechoic torsed appendages occur at a later stage after hemorrhage or infarction [7]. However, in this study, isoechoic torsed appendages had a shorter interval between symptom onset and the ultrasonographic examination than hypoechoic and hyperechoic torsed appendages. Isoechoic torsed appendages occurred earlier rather than hypoechoic and hyperechoic torsed appendages. In addition, one isoechoic torsed appendage on initial ultrasonography became hypoechoic 12 days later (Fig. 2). The cause of isoechoic torsed appendages in this study may have been less lymphatic dilatation and less edema due to an early stage or lesser degree of torsion. However, in the present study, the number of isoechoic torsed appendages was too small (n=5) for a definitive analysis. Further studies with large numbers of isoechoic torsed appendages will be necessary.
Color Doppler ultrasonography provides a simultaneous display of tissue morphological characteristics in grayscale and blood flow within the lesion [4,5,7,8]. In this study, no blood flow was found within the torsed appendages in any of the 54 cases. Periappendiceal hyperemia can be helpful for a diagnosis of torsed appendages and has been reported in 31%-80% of cases [4,7,8]. In this study, increased periappendiceal blood flow was seen in 33% of cases (18/54).
A number of limitations in this study should be considered. First, this study was limited by its retrospective design and small study population. Of the 46 patients, only eight received follow-up ultrasonography. In addition, all eight patients received only one follow-up ultrasonography examination, and the interval between initial and follow-up ultrasonography varied from 4 days to 48 days. It was not possible to establish when the torsed appendages changed from hypoechoic to hyperechoic and when the torsed appendages decreased in size. Therefore, to establish the relationship between echogenicity, the size of the torsed appendages and the interval between symptom onset and the ultrasonographic examination, further studies with larger study populations and follow-up ultrasonography at regular intervals are needed. Second, a radiologic-pathologic correlation was not possible because scrotal appendage torsion is a self-limiting condition.
In conclusion, the size of the torsed appendages and the interval between symptom onset and the ultrasonographic examination varied according to the echogenicity of the torsed appendages. Heterogeneous hypoechogenicity of torsed appendages was usually seen in the early stage of torsion. The hyperechoic torsed appendages had longer intervals between symptom onset and the ultrasonographic examination and were smaller than the hypoechoic torsed appendages. Knowledge of these ultrasonographic findings may be useful for the diagnosis of torsed intrascrotal appendages.

Notes

Author Contributions

Conceptualization: Yang DM. Data acquisition: Yang DM, Kim HC, Kim SW. Data analysis or interpretation: Lim SH, Yang DM, Kim H, Lee DI, Moon SK, Park SJ. Drafting of the manuscript: Lim SH, Yang DM, Kim, Lee DI. Critical revision of the manuscript: Kim HC, Kim SW, Moon SK, Park SJ. Approval of the final version of the manuscript: all authors.

Conflict of Interest

No potential conflict of interest relevant to this article was reported.

References

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A 9-year-old boy with a 2-day history of left scrotal pain.

A. Longitudinal color Doppler ultrasonography shows an enlarged heterogeneously hypoechoic torsed appendage at the upper portion of the left testis (arrow). Multiple tiny cystic lesions are noted within the appendage. There is no blood flow within the appendage. B. After 5 days, on longitudinal ultrasonography, a torsed appendage still shows a heterogeneously hypoechoic presentation (arrow). However, a peripheral portion of the torsed appendage became hyperechoic (arrowheads).
usg-22169f1.jpg
Fig. 1.

A 6-year-old boy with a 2-day history of right scrotal pain.

A. Longitudinal ultrasonography shows an enlarged isoechoic torsed appendage between the testis and the head of the epididymis (arrows). B. After 10 days, on longitudinal ultrasonography, a torsed appendage shows heterogeneous hypoechogenicity with tiny internal cysts (arrows).
usg-22169f2.jpg
Fig. 2.

A 9-year-old boy with a 5-day history of left scrotal pain.

A. Longitudinal color Doppler ultrasonography shows a heterogeneously hypoechoic torsed appendage with multiple tiny cystic foci at the upper portion of the left testis (arrow). Hydrocele and thickening of the tunica vaginalis are seen. B. After 32 days, longitudinal ultrasonography shows the decreased size and increased echogenicity of the torsed appendage (arrow).
usg-22169f3.jpg
Fig. 3.
Table 1.
The size of the torsed appendages and the interval between the symptom onset and ultrasonographic examination according to the echogenicity of the torsed appendages
Echogenicity Size (mm) Interval (day)
Hypoechoic (n=40) 8.0±3.1a) 4.2±4.4b)
Hyperechoic (n=9) 3.7±0.9a) 29.8±16.0b,c)
Isoechoic (n=5) 5.4±0.5 1.6±0.9c)

a) The post-hoc test showed statistically significant differences between hypoechoic torsed appendages and hyperechoic torsed appendages after the Bonferroni correction (P<0.05).

b) The post-hoc test showed statistically significant differences between hypoechoic torsed appendages and hyperechoic torsed appendages after the Bonferroni correction (P<0.05).

c) The post-hoc test showed statistically significant differences between hyperechoic torsed appendages and isoechoic torsed appendages after the Bonferroni correction (P<0.05).

Table 2.
Changes in echogenicity and size of torsed appendages, as well as the interval between initial and follow-up US
Patient No. Age (year) Initial US
Follow-up US
Echogenicity Size (mm) Interval (day)a) Echogenicity Size (mm) Interval (day)b)
1 9 Hypoechoic 13.0 2 Hypoechoic 16.0 7
2 12 Isoechoic 5.9 1 Hyperechoic 3.0 40
3 10 Hypoechoic 14.0 2 Hypoechoic 9.6 13
4 9 Hypoechoic 8.5 5 Hyperechoic 4.0 37
5 6 Hypoechoic 5.0 0 Hyperechoic 2.6 48
6 7 Hypoechoic 10.0 8 Hyperechoic 5.0 46
7 6 Isoechoic 5.0 2 Hypoechoic 6.0 12
8 11 Hypoechoic 14.0 9 Hypoechoic 9.0 13
Mean±SD 9 9.4±3.9c) 3.6±3.3 6.9±4.5c) 27.0±17.3

SD, standard deviation.

a) Interval between symptom onset and initial ultrasonography (US).

b) Interval between symptom onset and follow-up US.

c) The torsed appendages were larger on initial ultrasonography than on follow-up ultrasonography (P<0.05).

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