Feeding vessel sign | Radiology Signs

Answer:

The feeding vessel sign is a pulmonary vessel seen coursing directly into a peripheral pulmonary nodule on CT, and it indicates that the nodule reached the lung through the bloodstream. It is classically described with septic pulmonary emboli, where it accompanies multiple peripheral, often cavitating, nodules of varying age in the lower zones in a patient with right-sided endocarditis, an infected venous catheter or pacing lead, septic thrombophlebitis including Lemierre syndrome, or an infected deep venous thrombosis. It is also seen with haematogenous metastases, pulmonary arteriovenous malformations, granulomatosis with polyangiitis and pulmonary infarcts. High-resolution multidetector CT with thin sections and multiplanar reformats has shown that the apparent feeding vessel is often a pulmonary vein leaving the lesion rather than an artery entering it, which is why the sign is less specific than originally believed and why it should be read together with the distribution and morphology of the nodules rather than alone. The practical value is that it points the search toward a source: in septic emboli the imaging should be followed by echocardiography and blood cultures, and in suspected metastases by evaluation for a primary tumour, while in an arteriovenous malformation the demonstration of a single feeding artery and draining vein establishes the diagnosis and directs embolisation.

Why is it called so?

A vessel appears to run into and feed the nodule.

Pathophysiology

Organisms or tumour cells carried in the pulmonary arterial circulation lodge where the vessel calibre first becomes too small to allow passage, which is in the subpleural peripheral lung, and this is why haematogenous lesions are peripheral and basal, following the distribution of blood flow. In septic embolism the impacted infected material causes local infarction and suppuration, and central necrosis drains through a bronchus to produce cavitation. Because the lesion grows around the vessel that delivered it, the vessel is incorporated into the nodule and remains visible entering it. Thin-section imaging demonstrates that many lesions also recruit and displace adjacent veins, which accounts for the frequent identification of a venous rather than arterial connection.

Alternative names: Vessel sign; nodule with a feeding vessel

Other associated named signs: Cheerio sign of cavitating nodules, the halo sign and the hypodense vessel sign of septic thrombophlebitis

References

1. Dodd JD, Souza CA, Müller NL. High-resolution MDCT of pulmonary septic embolism: evaluation of the feeding vessel sign. AJR Am J Roentgenol. 2006;187(3):623-9. PMID: 16928922.