Azygos vein thrombosis (AVT) and hemiazygos vein thrombosis (HVT) are rare entities. The etiopathogenesis is unknown, but these thromboses have been associated with predisposing factors, such as underlying azygos vein aneurysm (AVA)1 or other prothrombotic factors. AVT in a normal azygos and hemiazygos vein is exceptional.2 The azygos system provides the superior (SVC) and inferior vena cava (IVC) with an alternative access to the right atrium, so AVT is usually asymptomatic, making it difficult to diagnose and treat early. It can be complicated by pulmonary embolism (PE), vena cava syndrome (VCS) and even stroke in the case of cardiac shunt, which confers a worse prognosis.3 This paper reports an acute, symptomatic case of AVT and HVT and reviews the most relevant aspects of this rare entity.

A 60-year-old woman, former smoker, receiving chemotherapy for a diagnosis of ovarian adenocarcinoma, presented with sudden dyspnea, heaviness in the upper limbs, and syncope. Physical examination revealed blood pressure 110/60 mmHg, heart rate 110 bpm, oxygen saturation 95%, erythema and facial edema, and no signs of collateral circulation or lymphadenopathies. On laboratory tests, hemoglobin was only 8.6 g/dl. Chest CT-angiogram showed extensive thromboses in the azygos and hemiazygos veins, with no signs of PE or VCS (Fig. 1). No findings of interest were observed on lower limb ultrasound or echocardiogram. Thrombophilia tests, including antiphospholipid antibodies, were negative. The patient was given weight-adjusted tinzaparin treatment and anticoagulation continued until the end of chemotherapy (9 months), with complete resolution of her respiratory symptoms and no evidence of complications. Repermeabilization of the AVT was observed in the follow-up CT.

Figure 1.

Extensive azygos and hemiazygos vein repletion defects, with no signs of thrombosis in main, lobar, or segmental pulmonary arteries.

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We performed a Pubmed search for original and review articles using the term “azygos vein thrombosis”. Original articles were eligible for inclusion if AVT and/or HVT were identified. Abstracts, animal studies, and articles written in languages other than English or Spanish were excluded. The references for each article included in this review were also analyzed to identify other studies of interest. We found a total of 216 eligible studies, published up to June 2020. Nineteen studies met the inclusion criteria and all reported isolated clinical cases (Table 1). Of the 19 patients included, male sex was slightly more predominant (57.8%) and the mean age was 55 years. AVA was the most frequent predisposing factor in 47.3% of cases,1,4–11 followed by septic thrombosis (15.78%)2,12,13 and intravenous catheters (10.5%).14,15 Other etiologies included other prothrombotic factors3,16 and congenital malformations.17 Although the high prevalence of venous thromboembolism (VTE) in cancer patients is well known, AVT associated with cancer is unusual.18,19

Isolated AVT was conventionally considered as asymptomatic deep vein thrombosis (DVT) in an unusual site, until it was associated with complications such as PE or VCS. In our patient, the syncopal episode, together with the clinical picture suggestive of VCS, confirmed the presence of AVT and HVT in the imaging tests. In most cases included in the review, AVT was symptomatic (84.2%), with chest pain being the most frequent symptom (42.1%), followed by cough (26%) and dyspnea (21%). The most frequent complications included thrombosis in other sites (15.7%),15,16,19 followed by PE (10.5%),5,9 septic PE (10.5%),2,13 VCS (5.2%),16 and transient antiphospholipid syndrome (5.2%).12

Chest CT-angiogram is the test of choice for the diagnosis of AVT, while a CT-venography should be considered if VCS is suspected. In thrombosed AVAs, the use of dynamic multidetector CT with ECG to assess myocardial damage has been proposed.5

As AVT is considered thrombosis in an unusual site, the treatment recommendations have been extrapolated from published studies on VTE.20 Almost one third (31.6%) of AVT cases were treated with anticoagulants, while in 1 case, anticoagulation was ineffective and surgical resection was required.9 Antibiotics are the first line of treatment in AVT associated with infection and/or septic PE,2,12,13 although anticoagulation in these cases may be controversial. Some cases of endovascular treatment, thrombectomy, and removal of infected devices have been reported.11,12

Despite the association of AVA with AVT and PE, treatment of asymptomatic aneurysm is not well established, and experts recommend radiological follow-up.4 Furthermore, there is no established consensus for asymptomatic thrombosed AVA, and treatment can range from indefinite anticoagulation to surgical resection to prevent PE. In our series, 36.8% of the symptomatic and/or thrombosed AVAs underwent surgical resection without subsequent anticoagulation.1,4,6,7,9–11 In VCS secondary to AVT, the first-line treatment is anticoagulation. It is effective in up to 88% of patients and can be combined with percutaneous stent placement for immediate symptomatic relief and chemotherapy and/or radiotherapy with long-term curative or palliative intent. According to experts, anticoagulation for the treatment of VCS due to thrombosis should be maintained indefinitely.21 In the series reviewed, there were no deaths in follow-up.

In conclusion, the importance of this clinical case lies in the rare presentation of a DVT in an unusual site in an anatomically normal azygos system. This is an extremely rare presentation in isolation that we were able to diagnose and treat promptly due to the clinical presentation suggestive of VCS.