Threads and Streaks Sign

Abstract

A 65 years old male patient visited our hospital with the complaint of diffuse pain in the upper abdomen since 2 months with no associated vomiting, melena or weight loss. Preliminary blood investigations of the patient were normal. Ultrasound  was done subsequently for the patient which showed cirrhotic appearance of liver with diffusely infiltrative mass lesion was seen in bilateral lobes of liver extending within the left and the right portal vein with prominent arterial supply on color doppler images (Figure 1a).  A subsequent Contrast enhanced ultrasound (CE-US) was performed to characterize the lesion which showed the characteristic “threads and streaks sign” also known as "striated vascular sign" which was earlier classically described on Angiography¹ for hepatocellular carcinoma.

Threads and streaks sign is the specific appearance of multiple tortuous arterial collaterals supplying the tumoral thrombus forming arterioportal shunts which directly drain into the portal vein leading to early “chain –like” filling of the portal vein in arterial phase. Multiple small and thin blood spaces which develop inside as well as between the tumour and vessel wall are responsible for this appearance.  The presence of this sign indicates the growth of the tumour within the vessels especially in cases with hepatocellular carcinoma². We demonstrated this sign on CE-US (Figure 1b) which helped us clinch the diagnosis of hepatocellular carcinoma on ultrasound. On subsequent triple phase CT this appearance was replicated (Figure 1c) hence confirming the findings.

Hepatocellular carcinomas are hypervascular tumours with predominant arterial supply which is often evident on Multiphase contrast CT/ MRI³. Arterioportal shunting is one of the most characteristic finding in these tumours and its correlates with the histopathological grade of the tumour as these shunts are seen more in well differentiated tumours⁴. Multiple antemortem and postmortem studies by Okuda et al⁵ suggest involvement of the inferior vena cava and the hepatic veins should be sought for in patients with hepatocellular carcinoma when the thread and streak sign is visible at either angiography or contrast-enhanced computed tomography (CT). We were able to demonstrate this sign on CE-US and hence its utility in patients with suspected liver lesion in patients with renal failure and non-availability of modalities like CT/ MRI to diagnose HCC is emphasized.

This appearance however needs to be differentiated with bland thrombus of portal vein which shows no arterial phase enhancement and arterioportal shunting as well as other causes of arteriovenous shunts like regenerating liver in liver cirrhosis. Another limitation while evaluating this sign is that the similar appearance can also occur in other hypervascular tumours that might grow into a portal vein and develop arteriovenous shunting.