DOI: 10.1148/radiol.2361030114
(Radiology 2005;236:284-285.)
© RSNA, 2005
The Thread and Streak Sign1
Björn-Werner Raab, MD
1 From the Department of Diagnostic Radiology, Georg-August-Universität Goettingen, Robert-Koch-Strasse 40, D-37073 Goettingen, Germany. Received January 22, 2003; revision requested April 11; final revision received December 15; accepted January 5, 2004.
Address correspondence to the author (e-mail: bwraab{at}med.unigoettingen.de).
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APPEARANCE
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The thread and streak sign is described as a thin linear or chainlike opacification in the portal vein at angiography after the injection of contrast material. The abnormal enhancement associated with this sign develops during early hepatic arteriography (Fig 1).
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Figure 1. Hepatic arteriogram obtained 3 seconds after injection of 30 mL of iodinated contrast material (iopromide, Ultravist 300; Schering, Berlin, Germany) (flow, 6 mL/sec) shows catheter placed in right main hepatic artery. Note initial retrograde opacification of portal vein (arrows), with linear opacification showing thread and streak sign.
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EXPLANATION
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The thread and streak sign represents blood spaces and vessels (both veins and arteries) located in and around a tumor cast that is growing in a large branch and trunk of the portal vein (1,2). The tumor cast contains many small, narrow blood spaces inside, as well as between, the tumor and vessel wall. The spaces are lined with a layer of endothelium and extend along the long axis of the vein (1). Arterial blood enters the tumor thrombus, flows through and around the thrombus longitudinally, and mixes with the portal vein blood near the portal hilum (3). The thread and streak sign therefore reflects the growth of tumor, such as hepatocellular carcinoma, into the portal vein (4). The thread and streak sign may be seen in other hypervascular tumors that grow into a large vein and demonstrate arteriovenous shunting. The thread and streak sign has also been noted in patients with renal neoplasms, as well as in a case of retroperitoneal osteosarcoma with growth into the inferior vena cava, and has an appearance similar to that of malignant liver tumors (5–7).
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DISCUSSION
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In most cases, hepatocellular carcinomas are vascular hepatic lesions with small abnormal vessels throughout the tumor; the presence of abnormal vascular spaces is often seen at hepatic angiography (2,8). Another characteristic finding of hepatocellular carcinoma is intrahepatic arteriovenous shunting with abnormally early opacification of portal branches that can be seen during the arterial phase of angiography (2,3). Of the various angiographic findings, arterioportal shunting seems to be one of the most characteristic and is consistent with the histopathologic appearance (9,10). According to Kido et al (9), the angiographic abnormalities of hepatocellular carcinoma correlate well with histopathologic findings and are typically seen in well-differentiated tumors.
Retrograde opacification of the portal vein at angiography is most clearly seen 3–4 seconds following hepatic arterial injection of a contrast material bolus (10) and may be mistaken for a collection of fine arteries (1). The appearance of the thread and streak sign is not related to the injection pressure (10).
Although both reflect the same phenomenon of intraportal tumor growth, retrograde flow of contrast material into the portal vein during hepatic arteriography and the thread and streak sign may have a somewhat different importance with regard to the extent of tumor growth in the lumen of the portal vein (1,4). The thread and streak sign with early enhancement of the portal vein reflects a direct connection between the arterial and venous system within the tumor and does not—as formerly proposed—represent markedly enlarged vasa vasora in the involved segments (6).
In several studies by Okuda et al (1,3,11,12), antemortem and postmortem findings demonstrated that, in patients with hepatocellular carcinoma, involvement of the inferior vena cava and the hepatic veins should be considered when the thread and streak sign is visible at either angiography or contrast-enhanced computed tomography (CT).
The thread and streak sign can be differentiated from thrombosis of the portal vein, which appears as a filling defect in the portal venous phase or as nonopacification within the lumen of the portal vein (13) and absence of the typical linear enhancement pattern during the early phase. Arteriovenous shunts may also appear in regenerating liver, liver cirrhosis, and portocaval shunting, with a normal course of the vessels in such instances.
Detection of tumor invasion into the portal vein and evidence of the thread and streak sign at CT has been described previously (14). Opacified streaks in the dilated portal vein can easily be depicted in the early phase of contrast-enhanced CT (Fig 2).
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Figure 2. Transverse multi–detector row spiral CT scan obtained in arterial phase after intravenous injection of 110 mL of iopromide (flow, 3 mL/sec). Scan shows hepatocellular carcinoma of right hepatic lobe. Note several streaks of opacification within dilated portal vein.
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FOOTNOTES
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Author stated no financial relationship to disclose.
A trainee (resident or fellow) wishing to submit a manuscript for Signs in Imaging should first write to the Editor for approval of the sign to be prepared, to avoid duplicate preparation of the same sign.
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References
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- Okuda K, Musha H, Yoshida T, et al. Demonstration of growing casts of hepatocellular carcinoma in the portal vein by celiac angiography: the thread and streaks sign. Radiology 1975; 117:303–309.[Abstract]
- Reuter SR, Redman HC. Tumors. In: Reuter SR, Redman HC, eds. Gastrointestinal angiography. 2nd ed. Philadelphia, Pa: Saunders, 1977; 131–161.
- Okuda K, Musha H, Yamasaki T, et al. Angiographic demonstration of intrahepatic arterio-portal anastomoses in hepatocellular carcimoma. Radiology 1977; 122:53–58.[Abstract]
- Sörensen R, Trüber E, Apitzsch DE, Fiegler W. Angiographic appearance of intravenous tumor growth in the portal and hepatic veins ("thread and streaks sign") [in German]. Rofo Fortschr Geb Rontgenstr Neuen Bildgeb Verfahr 1978; 129:205–207.[Medline]
- Ferris EJ, Bosniak MA, O'Connor JF. An angiographic sign demonstrating extension of renal carcinoma into the renal vein and vena cava. Am J Roentgenol Radium Ther Nucl Med 1968; 102:384–391.[Medline]
- Gregg FP, Goldstein HM, Wallace S, Casey JH. Arteriographic demonstration of intravenous tumor extension. Am J Roentgenol Radium Ther Nucl Med 1975; 123:100–105.[Medline]
- Kahn PC. Epinephrine effect in selective renal angiography. Radiology 1965; 85:301–305.
- Reuter SR, Redman HC. The spectrum of angiographic findings in hepatoma. Radiology 1970; 94:89–94.[Medline]
- Kido C, Sasaki T, Kaneko M. Angiography of primary liver cancer. Am J Roentgenol Radium Ther Nucl Med 1971; 113:70–81.[Medline]
- Inoue Y, Tagawa K, Unuma T, Kubo T, Sakamoto M, Shichijo Y. Angiographic demonstration of venous tumour invasion in hepatocellular carcinomas: characteristic parallel linear vascular channels [in German]. Rofo Fortschr Geb Rontgenstr Neuen Bildgeb Verfahr 1982; 136:196–199.[Medline]
- Okuda K, Moriyama M, Yasumoto M, et al. Roentgenologic demonstration of spontaneous reversal of portal blood flow in cirrhosis and primary carcinoma of the liver. Am J Roentgenol Radium Ther Nucl Med 1973; 119:419–428.[Medline]
- Okuda K, Jinnouchi S, Nagasaki Y, et al. Angiographic demonstration of growth of hepatocellular carcinoma in the hepatic vein and inferior vena cava. Radiology 1977; 124:33–36.[Abstract]
- Parvey HR, Raval B, Sandler CM. Portal vein thrombosis: imaging findings. AJR Am J Roentgenol 1994; 162:77–81.[Abstract/Free Full Text]
- Suzuki M, Itoh H, Konsihi H, Ida M, Matsui O, Takashima T. Hepatocellular carcinoma involving the portal vein. J Comput Assist Tomogr 1982; 6:831–832.[Medline]
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