**3. Implications for treatment of DVT and prevention of recurrences**

The therapy of acute DVT in this kind of patients is similar of the currently recommended strategies and includes un-fractioned heparin, low-molecular weight heparin, fondaparinux

Vena Cava Malformations as an

(a)

Emerging Etiologic Factor for Deep Vein Thrombosis in Young Patients 55

Fig. 9. Absent infra-renal IVC. (a) Schematic shows absence of the IVC below the renal veins.

Collateral flow from the lower extremities reaches the azygos vein via para-vertebral collateral veins. (b) CT scan obtained inferior to the aortic bifurcation shows absence of the common iliac veins. Enlarged ascending lumbar veins are present (black arrow). Note the iliac arteries (white arrow). (c) CT scan obtained inferior to the kidneys shows absence of the IVC (white arrow). Enlarged ascending lumbar veins are present (black arrow). (d) CT scan

obtained at the level of the renal veins shows a normal pre-renal IVC formed at the confluence of the renal veins (arrow). (e) CT scan obtained at the level of the pre-renal IVC (white arrow) shows prominent para-vertebral collateral veins (black arrow), which lead to a prominent azygos vein (arrowhead). (f) Coronal T1-weighted MR image shows the enlarged ascending lumbar veins (arrow). (g) Lateral maximum-intensity projection reconstruction of two-dimensional time-of-flight MR images shows formation of enlarged ascending lumbar veins at the confluence of the internal and external iliac veins (solid straight arrow). Note the anastomosis between the ascending lumbar veins and the azygos vein (open straight arrow) via prominent anterior para-vertebral veins (white curved arrow). Also note the pre-renal IVC (black arrowhead) posterior to the portal vein (black curved arrow), as well as prominent anterior abdominal wall collateral veins (white arrowheads). (Figs 10b, 10c, and 10g reprinted, with permission, from references).

Fig. 8. Circumcaval ureter in a 65-year-old man. (a) Schematic shows the right ureter encircling the IVC. (b-d) CT scans presented from cranial to caudal show the anomaly. (b) The right ureter (arrow) is positioned posterior to the IVC. (c) The ureter (arrow) then courses to the left of the IVC. (d) Finally, the ureter (arrow) crosses anterior to the IVC. (Courtesy of Akira Kawashima, MD, Lyndon B. Johnson General Hospital, Houston, Tex.)

(a)

Fig. 8. Circumcaval ureter in a 65-year-old man. (a) Schematic shows the right ureter encircling the IVC. (b-d) CT scans presented from cranial to caudal show the anomaly. (b) The right ureter (arrow) is positioned posterior to the IVC. (c) The ureter (arrow) then courses to the left of the IVC. (d) Finally, the ureter (arrow) crosses anterior to the IVC. (Courtesy of Akira Kawashima, MD, Lyndon B. Johnson General Hospital, Houston, Tex.)

Fig. 9. Absent infra-renal IVC. (a) Schematic shows absence of the IVC below the renal veins. Collateral flow from the lower extremities reaches the azygos vein via para-vertebral collateral veins. (b) CT scan obtained inferior to the aortic bifurcation shows absence of the common iliac veins. Enlarged ascending lumbar veins are present (black arrow). Note the iliac arteries (white arrow). (c) CT scan obtained inferior to the kidneys shows absence of the IVC (white arrow). Enlarged ascending lumbar veins are present (black arrow). (d) CT scan obtained at the level of the renal veins shows a normal pre-renal IVC formed at the confluence of the renal veins (arrow). (e) CT scan obtained at the level of the pre-renal IVC (white arrow) shows prominent para-vertebral collateral veins (black arrow), which lead to a prominent azygos vein (arrowhead). (f) Coronal T1-weighted MR image shows the enlarged ascending lumbar veins (arrow). (g) Lateral maximum-intensity projection reconstruction of two-dimensional time-of-flight MR images shows formation of enlarged ascending lumbar veins at the confluence of the internal and external iliac veins (solid straight arrow). Note the anastomosis between the ascending lumbar veins and the azygos vein (open straight arrow) via prominent anterior para-vertebral veins (white curved arrow). Also note the pre-renal IVC (black arrowhead) posterior to the portal vein (black curved arrow), as well as prominent anterior abdominal wall collateral veins (white arrowheads). (Figs 10b, 10c, and 10g reprinted, with permission, from references).

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and vitamin-K antagonists(u). The diagnosis of anomalies in the inferior vena cava influences the strategy for prevention the pulmonary embolism and long them maintenance treatment.

The use of mechanical device as caval filter is clearly limited by the anomalous anatomy of the inferior vena cava and, generally, is-not indicated. On the other hand the use of oral anticoagulant (commonly warfarin) should be adjusted to maintain a target international normalized ratio of 2.5 (range 2-3) and extended indefinitely in absence of main contraindications(d).

At present the introduction of new drugs as the factor Xa antagonists (rivarixaban, apixaban, edoxaban, ect) and the direct thrombin inhibitors as dabigatran etexilate could improve the therapeutic options. The promising results of the recent clinical studies in terms of efficacy and safety, suggest that these new drugs may allow a reduction of the length of hospital stay after an acute DVT, and a better adherence to guidelines in the long term treatment. The principal advantages of these drugs are the absence of the need of a routine coagulation monitoring and a therapeutic activity not influenced by dietary regimen and by drugs as NSADIs and statins(u). Potential limitations are the lack of specific antidotes (however the hal-life of these drugs is relative short) and the absence of a simple assay for quantification of activity or plasma level.

In conclusion these interesting pharmacological characteristics could improve the benefitrisk balance of long-term anti-coagulant therapy and the overall clinical outcome.
