Deep-vein thrombosis (DVT) is a frequent vascular disorder that is associated with high morbidity. The prevalence of DVT has increased to 0.1% in the general population, which is largely attributable to advances in diagnostic methods such as ultrasound scanning 1. DVTs occur most frequently in the lower legs 2, and 20% of untreated DVTs advance to proximal veins and cause a pulmonary embolism 3,4. Many clinicians suggest practitioners should consider anatomical variations as a risk factor for DVT. Thereby, previous study identified and classified the anatomical variation in the deep calf veins (Figure 1) 5.
Administering a systemic thrombolytic agent is the conventional therapy for reducing the risk of pulmonary embolism and DVT reoccurrence. However, applying only a systemic thrombolytic agent is associated with post-thrombotic syndrome (PTS) in 20–50% of treated patients 6. PTS should be avoided since it is a chronic problem of DVT that includes ulceration, swelling, and dermatosclerosis 7.
Systemic thrombolytic agents should also not be applied alone to patients with high blood pressure, stroke, and arterial aneurysms 6. In the last few decades, complementary and combination therapies for catheter-directed thrombolysis (CDT) have been suggested that involve the selective release of thrombolytic agents using intervention catheters. Previous studies have demonstrated that CDT is an effective and safe treatment option for DVT 8,9. The combination therapy of CDT and systemic thrombolytic agents for thrombus elimination is recommended in patients with acute DVT in order to relieve acute symptoms and prevent PTS 10. The American Heart Association recommended CDT as the primary treatment for patients with acute DVT and for preventing symptom progression and the rapid extension of a thrombus, followed by anticoagulation therapy 11.
CDT has the benefits of the rapid relief of painful symptoms with a smaller amount of thrombolytic agent 12,13. The catheter is inserted proximal or distal to the affected sites in the retrograde or antegrade venous approach, respectively 14. The venous entrance points of CDT are the posterior tibial vein, anterior tibial vein, popliteal vein, and femoral vein. The venous entrance point is selected by considering anatomical variations in and the diameter of the accessing vein. It is necessary to carefully select the venous entrance point by taking into consideration all of the anatomical pros and cons.
A retrograde venous approach via the femoral vein or popliteal vein has the advantages of a short procedural time due to the large diameter of the vein and the smaller number of anatomical variants. The disadvantages of this approach are the possibility of valvular injury due to the access direction being against the direction of blood flow, insufficient removal of the thrombus, and difficulty of positioning the patient during the procedure 15.
An antegrade venous approach via the anterior tibial vein, posterior tibial vein, or peroneal vein has the advantages of sufficient thrombus clearing, easier positioning, and less valvular damage. Additionally, the antegrade approach has no limitation in clearing the proximal extent of the thrombus, including in cases of an inferior popliteal thrombus, which are often not resolved 15. The disadvantages of the antegrade approach are the long procedural time needed to obtain access and evaluate veins with small diameters and variations 15.
Since CDT is a fairly new treatment, physicians must focus on more-effective and safer access points and approaches. The diameters of these veins and variations therein should be carefully considered, since CDT is associated with bleeding complications at the insertion point. The venous anatomy of the distal extremities is significantly more unpredictable and complex than those of the corresponding arteries and veins in proximal regions 16.
A previous study revealed the diameters of the popliteal veins that are commonly used for the retrograde approach of CDT 17. However, no previous study has investigated the diameters of deep calf veins.
This study identified the diameters and surface areas of the posterior tibial vein, anterior tibial vein, and peroneal tibial vein. Knowledge of the diameters and surface areas of these veins will help practitioners to select the best vein when adopting an antegrade approach in CDT.