Pulmonary arteriovenous malformation (AVM) is a vascular anomaly that forms an abnormal direct connection between the pulmonary artery and pulmonary vein without a capillary bed. It creates right-to-left shunt physiology and leads to paradoxical embolism risk. Approximately 80-90% of cases are associated with hereditary hemorrhagic telangiectasia (HHT/Osler-Weber-Rendu syndrome). More common in lower lobes. The triad of feeding artery + draining vein + nidus (vascular mass) on CT is diagnostic.
Age Range
20-60
Peak Age
40
Gender
Female predominant
Prevalence
Rare
Pulmonary AVMs are congenital vascular developmental anomalies resulting from failure of regression of primitive vascular connections between pulmonary artery and vein during embryonic period. In HHT, mutations in endoglin (ENG) or ALK1 (ACVRL1) genes disrupt TGF-beta signaling pathway leading to abnormal angiogenesis. The nidus (vascular sac) bypasses capillary filter function and venous blood passes directly to the arterial system (right-to-left shunt). Hypoxemia develops due to this shunt, and oxygen saturation drops in orthopnea position (orthodeoxia since AVMs are predominant in gravity-dependent lower lobes). On CT, the feeding artery and draining vein opacify simultaneously with contrast. The nidus shows the same attenuation as vascular structures because contrast passes directly without capillary bed delay.
On CT angiography: dilated feeding artery from pulmonary artery branch, vascular nidus (sac/mass), and dilated draining vein to pulmonary vein. All structures opacify simultaneously with vessels. MIP and 3D reconstructions best demonstrate vascular anatomy. This triad is pathognomonic for pulmonary AVM.
Feeding artery originating from a pulmonary artery branch, vascular nidus (sac), and dilated draining vein draining into the pulmonary vein on CT angiography. All structures opacify simultaneously in the arterial phase. Feeding artery and draining vein are significantly wider than normal branch calibers.
Report Sentence
A vascular nidus measuring __ mm with associated dilated feeding artery and draining vein is noted in the right/left lower lobe, consistent with pulmonary arteriovenous malformation.
Well-defined, round or oval, homogeneous soft tissue density nodule or mass on non-contrast CT. Contains no calcification or fat. Usually located peripherally in lower lobes.
Report Sentence
A well-defined, round, soft tissue density nodule measuring __ mm is noted in the right/left lower lobe on non-contrast series; contrast-enhanced evaluation is recommended with initial consideration of vascular lesion (AVM).
Enhancement of the lesion simultaneous with and equal in density to pulmonary artery and aorta on contrast-enhanced CT. The nidus shows the same attenuation value as surrounding vessels (~200-400 HU). This pattern is specific to vascular lesions.
Report Sentence
The lesion enhances simultaneously and with equal density to the pulmonary artery and aorta on contrast-enhanced series; consistent with a vascular nature lesion (AVM).
Bilateral, multiple pulmonary AVMs may be seen in HHT patients. Variable in size (from a few mm to several cm), usually predominant in lower lobes. Concurrent hepatic AVM, cerebral AVM, and mucocutaneous telangiectasias support HHT diagnosis.
Report Sentence
Multiple pulmonary AVMs with lower lobe predominance are noted in both lungs; clinical evaluation with initial consideration of hereditary hemorrhagic telangiectasia (HHT) is recommended.
Contrast echocardiography evidence of right-to-left shunt with microbubbles in late opacifying left atrium after agitated saline injection. In correlation with CT, AVM nidus size and feeding artery diameter determine shunt volume.
Report Sentence
Right-to-left shunt has been confirmed on contrast echocardiography consistent with the AVM detected on CT; feeding artery diameter should be evaluated for embolization indication.
Criteria
Single feeding artery, single draining vein, single nidus segment. Comprises 75-80% of all AVMs.
Distinct Features
Easily treated with endovascular embolization (coil or Amplatzer plug) with high success rate (95%+). Recanalization rate is low.
Criteria
More than one feeding artery (2+) and/or more than one draining vein. Comprises 20-25% of all AVMs.
Distinct Features
Embolization is technically more challenging. Each feeding artery must be individually embolized. Risk of recanalization and incomplete occlusion is higher. 3D CT angiography is mandatory for vascular mapping.
Criteria
Bilateral multiple AVMs (>5-10), variable sizes, HHT clinical criteria (Curacao criteria) met
Distinct Features
Requires lifelong follow-up and treatment. AVMs with feeding artery diameter >3 mm are indicated for embolization (paradoxical embolism risk). Cerebral AVM screening is mandatory. Genetic counseling and family screening are recommended.
Distinguishing Feature
Metastases enhance as solid nodules but not simultaneously and equally with vascular structures. Feeding artery-draining vein triad is absent. AVM shows identical enhancement to vessels and vascular connections are demonstrated.
Distinguishing Feature
Granuloma is usually calcified, non-enhancing or minimally enhancing. AVM enhances with equal density to vessels and feeding artery-draining vein is demonstrated. Calcification is not expected in AVM.
Distinguishing Feature
Adenocarcinoma has spiculated margins, shows lower enhancement than vessels, and feeding artery-draining vein triad is absent. AVM has smooth borders and shows identical enhancement pattern to vessels.
Urgency
urgentManagement
interventionalBiopsy
Not NeededFollow-up
annualPulmonary AVM treatment is endovascular embolization (coil or Amplatzer plug). AVMs with feeding artery diameter of 3 mm or more are treatment-indicated (paradoxical embolism and brain abscess risk). Surgical resection is considered when embolization is not possible. Lifelong follow-up is needed in HHT patients with CT recanalization check at 6-12 months, then annual control. Cerebral AVM screening (MR angiography) is recommended in all pulmonary AVM patients. Curacao criteria should be evaluated for HHT diagnosis (epistaxis, telangiectasia, visceral AVM, family history).
PAVMs carry risk of paradoxical embolism (stroke, brain abscess) and hemoptysis. PAVMs with feeding artery diameter >3 mm should be treated with embolization. HHT screening is recommended.