The Twinkling Trap: Mistaking Hydatid Cysts for Vascular Soft Tissue Masses

Abstract

Hydatid disease is a parasitic infection that can mimic various pathologies on imaging, leading to diagnostic challenges. We present a case of a 37-year-old woman with chronic abdominal pain whose hepatic lesions were initially misinterpreted as vascular soft tissue masses due to the presence of twinkling artifacts on color Doppler ultrasound. Subsequent imaging with CT and contrast-enhanced MRI revealed characteristic features of hydatid cysts, including peripheral calcifications, internal membranes, and a T2 hypointense rim. Notably, the twinkling artifact was present even in lesions without calcification, likely due to rough internal surfaces, and was probe- and machine-dependent. This artifact, while useful in detecting small calcifications, may be misleading when mistaken for vascular flow, potentially leading to hazardous interventions like biopsy. This case underscores the importance of integrating multimodal imaging and using spectral Doppler to distinguish artifacts from true vascular signals, especially in endemic areas where hydatidosis should be a key differential.

Keywords

twinkling artifact - color Doppler imaging - hydatid cyst

Introduction

The twinkling artifact is a relatively common phenomenon observed in color Doppler ultrasound imaging. It manifests as rapidly alternating red and blue colors posterior to a stationary object with certain surface characteristics. First described by Rahmouni et al in 1996 in relation to calcifications, it was noted that this artifact is not exclusive to calcified structures and may also be observed with rough surfaces.[1]

Despite multiple studies, the mechanisms underlying twinkling artifacts remain incompletely understood, though they are thought to result from a complex interplay of object properties and machine settings. Importantly, this artifact may mimic vascular flow and can be misleading, particularly to the untrained eye.[2]

Case Report

A 37-year-old female presented to the surgical outpatient department with complaints of chronic, dull-aching abdominal pain and occasional chest discomfort.

Ultrasound examination revealed a round heteroechoic lesion in the right liver lobe and a similar but exophytic lesion in the left lobe. Color Doppler imaging demonstrated rapidly alternating red and blue signals within both lesions ([Fig. 1]). This was initially misinterpreted as vascular flow, leading to a provisional diagnosis of vascular soft tissue hepatic masses. Additionally, a chest radiograph revealed a mass-like opacity in the left lower lung zone.

Fig. 1 Color Doppler of the lesions in the right lobe of the liver (A) and left lobe (B), showing alternating red and blue colors akin to color flow.

These findings raised suspicion of metastatic malignancy. A liver biopsy was planned; however, to further evaluate the lung lesion and assess for other potential metastatic sites, computed tomography (CT) was performed. CT revealed peripheral stippled and internal curvilinear calcifications within the left liver lobe lesion, characteristic of hydatid cysts ([Fig. 2]).[3] Notably, the right lobe lesion did not show calcifications. No significant internal enhancement was observed on CT, arguing against the diagnosis of a vascular soft tissue mass.

Fig. 2 Axial (A) and coronal (B) noncontrast computed tomography images of the patient showing peripheral stippled and internal curvilinear calcifications.

Contrast-enhanced MRI was performed for further characterization. It demonstrated well-defined T2 hyperintense lesions with a hypointense rim (the “rim sign”) in both hepatic lobe lesions. Multiple internal membrane-like structures were identified, with no significant diffusion restriction or internal enhancement ([Fig. 3]).[4] The lesion in the left lung demonstrated similar features ([Fig. 4]). These imaging features were diagnostic of disseminated hydatidosis.[5]

Fig. 3 Axial T2 (A) and postcontrast T1 (B) MRI images showing right liver lobe lesion with T2 hypointense rim and internal detached membranes with no significant internal enhancement. Images (C, D) depict similar characteristics of the lesion in the left liver lobe.

Fig. 4 Axial CT (A) image, axial T2 (B), and postcontrast T1 (C) MRI images showing a hydatid cyst in the left lung.

Review ultrasound examination confirmed the presence of twinkling artifacts in both hepatic lesions, including the right lobe lesion, which did not show calcification on CT. This suggests that the artifact likely resulted from the rough surfaces formed by detached germinal membranes within the cysts. Interestingly, the artifact was visible when using a curvilinear probe but absent with a linear probe ([Fig. 5]).[6]

Fig. 5 Lesion in the right lobe of the liver, scanned using a linear probe in color Doppler mode, showing no twinkling artifact.

Discussion

Twinkling artifacts on ultrasound, although widely studied, remain poorly understood. In this case, the artifact was observed with a curvilinear probe but not with a linear probe, likely reflecting the influence of machine-dependent factors such as probe frequency, pulse repetition frequency, focal zone, and beam shape.[7] [8]

Generally, a twinkling artefact is better visualized with:

1. Placing the focal zone below the rough surface.

2. Increasing the priority of white color.

3. Reducing the grey scale.

4. Reducing the pulse repetition frequency. However, these cannot be generalized owing to variations in color-white priority dictated by the manufacturer's design of the ultrasound machine.[2]

Some studies, however, argue that scale and PRF have minimal impact on twinkling artifact generation.[9]

While the artifact is helpful in detecting small calcifications, particularly in renal imaging, its misinterpretation as vascular flow, especially in unusual locations, may significantly alter the diagnosis and treatment plan. In this case, it nearly led to the biopsy of hydatid liver lesions, which could have resulted in an anaphylactic reaction.

Conclusion

Therefore, when a twinkling artifact is seen, spectral Doppler analysis should be employed. The absence of a discernible waveform can help differentiate the artifact from true vascular flow.

Conflict of Interest

None declared.

Note

The content of this article is not presented or published in part or whole.

• References

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• 6 Lee JY, Kim SH, Cho JY, Han D. Color and power Doppler twinkling artifacts from urinary stones: clinical observations and phantom studies. AJR Am J Roentgenol 2001; 176 (06) 1441-1445
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• 9 Bacha R, Gilani SA, Manzoor I. Relation of color Doppler twinkling artifact and scale or pulse repetition frequency. J Med Ultrasound 2019; 27 (01) 13-18

Publication History

Article published online:
10 February 2026