Diagnosing Deep-vein Thrombosis Early in Critically Ill Patients

Inclusion criteria 1. Medical, surgical or trauma ICU patients ≥18 years old. 2. Patients who are expected to stay in the ICU more than 2 calendar days (unlikely to be discharged out of ICU on the day of admission or on the next day). Exclusion Criteria 1. Patients with DVT or PE diagnosed within the last year. 2. Patients receiving chronic systemic anticoagulation. 3. Patients who have received up to the time of ICU admission or are receiving therapeutic doses of anticoagulation with UFH, LMWH, or other anticoagulants. 4. Inability or contraindication to obtain adequate ultrasound on the lower extremities (Burns in the lower extremities, lacerations, active skin infection, \& ischemic limb in the legs, large dressings in the thighs that prevent adequate ultrasounds OR amputated foot or leg on one or two sides) 5. Patients with Inferior Vena Cava (IVC) Filter. 6. Known or suspected pregnancy. 7. Limitation of life support, life expectancy \<7 days or palliative care. 8. Previously enrolled in DETECT trial within the last 180 days. 9. Enrolled in another trial for which co-enrolment is not approved.