Relevance of immobility as a risk factor for symptomatic proximal and isolated distal deep vein thrombosis in acutely ill medical inpatients

Immobility is a well-recognized risk factor for deep vein thrombosis (DVT) in surgical patients, whereas the level of DVT risk conferred by immobility is less defined in patients on medical wards. The aim of this study was to establish whether immobility and its duration are associated with the risk of DVT in acutely ill medical inpatients. We conducted a cohort study in acutely ill medical inpatients. Patients underwent whole leg ultrasound for suspected lower extremity DVT and were divided into two groups according to presence or absence of immobility, defined as total bed rest or sedentary without bathroom privileges. The endpoint was the detection of proximal DVT or isolated distal DVT (IDDVT). Among the 252 acutely ill medical inpatients with immobility (age 82.6 ± 10.3 years, female 63.9%), ultrasound showed 36 (14.3%) proximal DVTs and 39 (15.5%) IDDVTs, while there were 11 (4.4%) proximal DVTs and 26 (10.5%) IDDVTs among the 248 inpatients without immobility (age 73.6 ± 14.2 years, female 54.8%). The risk of proximal DVT was higher in immobile than in mobile patients (OR 3.59, 95% CI: 1.78–7.23, p = 0.0001), whereas the risk of IDDVT was similar between the two groups (OR 1.56, 95% CI: 0.92–2.66, p = 0.111). During the first 3 days of hospitalization, the frequency of all DVTs was similar in patients with and without immobility, but it was 0.26 ± 0.03 vs 0.18 ± 0.03, respectively, after 4 days. In conclusion, immobility for more than 3 days is a risk factor for proximal DVT in acutely ill medical inpatients.