Inferior vena cava agenesis in patients with lower limb deep vein thrombosis in the RIETE registry. When and why to suspect

Background: Limited data exist about the clinical presentation and outcomes of patients with inferior vena cava agenesis (IVCA) who develop deep vein thrombosis (DVT). Methods: We used the RIETE (Registro Informatizado Enfermedad Trombo Embólica) registry to compare clinical characteristics and outcomes of patients with lower limb DVT, according to the presence or absence of IVCA. Major outcomes included recurrent DVT, major bleeding and post-thrombotic syndrome (PTS). Results: Among 50,744 patients with lower-limb DVT recruited in October 2018, 31 (0.06%) had IVCA. On multivariable analysis, patients aged < 30 years (odds ratio [OR]: 17.9; 95%CI: 7.05–45.3), with unprovoked DVT (OR: 2.49; 95%CI: 1.17–5.29), proximal (OR: 2.81; 95%CI: 1.05–7.53) or bilateral DVT (OR: 11.5; 95%CI: 4.75–27.8) were at increased risk to have IVCA. Patients with DVT and IVCA had lower odds to present with coexisting PE (OR: 0.22; 95%CI: 0.07–0.73). During the first year of follow-up, the rates of DVT recurrences (hazard ratio [HR]: 1.30; 95%CI: 0.07–6.43), pulmonary embolism (HR: 2.30; 95%CI: 0.11–11.4) or major bleeding (HR: 1.32; 95%CI: 0.07–6.50) were not significantly different with those with versus those without IVCA. One year after the index DVT, IVCA patients had a higher rate of skin induration (OR: 3.70; 95%CI: 1.30–9.52), collateral vein circulation (OR: 3.57; 95%CI: 1.42–8.79) or venous ulcer (OR: 5.87; 95%CI: 1.36–1.87) in the lower limb than those without IVCA. Conclusions: Certain clinical features such as unprovoked and bilateral proximal DVT in young patients should raise the suspicion for IVCA. Patients with IVCA had higher odds for symptoms of post-thrombotic syndrome