Isolated Calf Deep Venous Thrombosis: Prevalence, Clinical Characteristics and Implications for Ultrasound Evaluation

Objectives It remains controversial whether to include calf veins in the initial ultrasound evaluation of suspected deep venous thrombosis (DVT). We sought to investigate the prevalence and clinical characteristics of isolated calf DVT. Materials and Methods We retrospectively analyzed a cohort of 596 patients (median age 69 years, 52.3% women) evaluated with complete duplex ultrasound of the leg veins for suspected acute DVT within one year. Radiology reports were analyzed for the presence and localization of DVT. Electronic chart review was performed to collect clinical information. Results DVT was found in 157 patients (26.3%), of which 74 patients (47.1%) had isolated calf DVT. Isolated calf DVTs were most commonly located in the posterior tibial veins (22 patients, 29.7%), fibular veins (41 patients, 55.4%) and muscle veins (19 patients, 25.7%). There were no differences in age or gender between patients with isolated calf DVT and patients with more proximal DVT. Isolated calf DVT was more commonly associated with leg pain (52.7% vs. 33.7%, p = 0.0234) and less commonly associated with subjective leg swelling (35.1% vs. 55.4%, p = 0.0158) and objectively measured difference in leg circumference (23% vs. 39.8%, p = 0.0268). D-Dimers were significantly lower in patients with isolated lower leg DVT (median 2.3 vs. 6.8 mg/L, p < 0.0001) compared to patients with more proximal DVT. Conclusions Isolated calf DVT is almost as common as more proximal DVT. Our data supports performing complete duplex ultrasound including the calf veins in suspected DVT.