There is a controversy over the clinical significance and optimal treatment for isolated calf DVT. This study aimed to investigate the clinical presentation of isolated calf deep vein thrombosis (DVT) and the association of isolated calf DVT with pulmonary embolism (PE) in inpatients.
A total of 1435 hospitalized patients underwent whole-leg duplex ultrasound between January 2018 and June 2020. Among them, 135 were diagnosed with isolated calf vein DVT.
The soleal vein was the most frequently involved (52.6%). Thrombus was detected only in axial veins in 57 patients (42.2%), muscular veins in 46 patients (34.4%), and in both axial and muscular veins in 32 patients (23.7%). Of the 135 patients, 44 patients (32.6%) had underwent recent orthopedic surgery, 31 patients (23.0%) had active cancer, and 22 patients (16.3%) had a history of recent stroke. The reasons for duplex ultrasound were leg edema and/or pain in 57 patients (42.2%), diagnosis of PE in 33 (24.4%), and elevated D-dimer level in 27 patients (20.0%). Sixteen patients (11.9%) were diagnosed as incidental findings on imaging studies for other purposes. Ninety-six patients (71.1%) received anticoagulation therapy. Concurrent PE was diagnosed in 45 patients (33.3%) and 14 patients had lesions in the main pulmonary artery. Among 45 patients with concurrent PE, 35 patients were diagnosed without leg edema and/or pain. Recurrent VTE was observed in four patients (3.0%) with a mean follow-up of 15.5±12.7 months.
Isolated calf DVT was associated with a high prevalence of PE in hospitalized patients. Patients with isolated calf DVT even without leg edema and/or pain may have concurrent PE. Anticoagulation therapy should be considered for isolated calf DVT in inpatients. The muscular veins were frequently involved, thus should be thoroughly evaluated and imaged.

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