Congenital Absence of the Infrarenal Segment of the Inferior Vena Cava Associated with Azygous Continuation of Inferior Vena Cava and Pulmonary Embolism

Background: Congenital anomalies of the inferior vena cava (IVC) are present in 0.3 to 0.5% of young, healthy adults. The most common congenital abnormalities of the IVC are duplication and retroaortic left renal vein. Absent IVC has an incidence of 0.0005 to 1% in the general population. These congenital variants could create a challenging anatomical configuration for the treating interventionist and surgeons resulting in prolonged or even abortion of the procedure, thus previous knowledge of such anomalies can help guide the intervention into a safe and successful treatment route. In addition, deep vein thrombosis and pulmonary embolism are frequent findings in young patients with congenitally absent IVC, as they have been well reported in the literature which in turn alarm the treating physician to further investigate for these associated potentially life-threatening conditions which eventually will come into the patient benefit of early detection and management.

Case Report: A 59-year-old female known case of poorly differentiated thyroid cancer on concurrent chemoradiation therapy presented to the emergency department with a 1-day history of chest pain, shortness of breath, and cough upon presentation, she was hypotensive and hypoxic requiring 6 L of oxygen per minute, CTA of the pulmonary arteries were performed and revealed major (saddle) pulmonary embolism (massive) involving both main pulmonary arteries, as well as bilateral lower lobar arteries. The decision to perform catheter-directed thrombectomy and thrombolysis was made by the pulmonary embolism response team. She arrived at the interventional radiology theater shortly, after catheterization of the right femoral vein followed by upward advancement of the catheter, and many attempts were made to catheterize the right heart without success for approximately have an hour, later IVC venograms show the anomalous anatomy of the venous system, performed which demonstrate a dilated vascular structure in the mid of the abdomen, not at the normal location of the IVC. This venous structure was running up to the chest side to side with the thoracic aorta, as they pass through the diaphragm and finally drains into the right superior vena cava in keeping with an azygous continuation of the IVC. In addition, there was a small trunk that connects this large azygous vein into the native diminutive IVC which also has an absent infrarenal segment. Knowing the different anatomy, the team starts to move into the right path that trunk was catheterized to reach the anomalous native IVC and the route was to catheterize the right heart was feasible, from there through the pulmonary outflow tract and finally pulmonary arteries catheterization was in hand. Mechanical thrombectomy (utilizing Penumbra Indigo system), as well as injection of thrombolytic materials, was performed and EKOS catheters were left in both right and left main pulmonary, once the patient finishes the procedure and shifted back to the intensive care unit.

Results: Unfortunately, after 24 hours of the procedure and initiating thrombolysis treatment the patient died from cardiac arrest caused by cardiopulmonary failure from right ventricular overload in consequences of massive pulmonary embolism, a note to be mentioned, she was on a full therapeutic dose of IV heparin.

Discussion: Absent infrarenal IVC with azygous continuation is a rare congenital venous anomaly that results from embryogenic defects by obliteration of the right supracardinal vein which forms the infrarenal segment of IVC, on the other hand, the azygous continuation of IVC is a common associated anomaly, these are found incidentally in asymptomatic patients. Preoperative knowledge of anatomy is beneficial to avoid difficult catheterizing of the venous system. Among the commonest venous malformations are duplicated IVC and retroaortic left renal vein. Absent IVC has an incidence of 0.0005 to 1% in the general population. It is thought that IVC anomalies are underdiagnosed as in this case, despite her having an abdomen CT prior to the venography these anomalies went undetected. There were many reported cases of congenitally absent IVC in the literature where they linked these congenital anomalies with increased risk of deep venous thrombosis and pulmonary embolisms. Therefore, this was one additional risk factor for pulmonary embolism and deep venous thrombosis in addition to her other known risk factors which were malignancy and chemotherapy treatment. Chee et al similarly noted that up to 5% of 20- to 40-year olds presenting with DVT had an IVC anomaly (four in total of which three had complete absence of IVC). This was much higher than the expected 0.5%. Idiopathic deep venous thrombosis in young adults without risk factors should be further investigated for IVC anomalies. However, if these congenital anomalies were isolated no further treatment is required.

Learning Points: Most of the IVC anomalies are asymptomatic and usually first discovered during a procedure or incidentally at diagnostic imaging workup, and it can be a technical challenge during the endovascular procedure to the interventional radiologist and vascular surgeons. Congenital venous anomalies are associated with an increased risk of deep venous thrombosis and pulmonary embolisms.

Conclusion: In conclusion, this lady was presented with massive pulmonary embolism and discovered to have congenital anomalies of the IVC which are additional risk factors for thrombosis in the combination of her known malignancy and use of chemotherapy. Multiple congenital variants and anomalies of the venous system can coexist as in this case, an absent infrarenal IVC with an azygous continuation of the IVC. These anomalies are underdiagnosed as in this case, despite her having an abdomen CT prior to the venography these anomalies went undetected.

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Artikel online veröffentlicht:
14. Dezember 2021