【Patient selection】
After an unlikely pretest probability of DVT based on a clinical decision rule assessment, a negative D-dimer test is adequate to safely exclude DVT. Venous ultrasound is not appropriate for those individuals.
Ultrasound is appropriate for patients with a likely pretest probability of DVT, an unlikely pretest probability of DVT with a positive D-dimer, and those in whom pretest probability was not assessed
==> 每個患者都應該進行臨床評估，對急重症單位而言，如果超音波就在你手邊，你也接受過訓練，直接進行掃描會比等待D-dimer來得快吧 !!
【US protocol】
Complete duplex ultrasound (CDUS) is the preferred venous ultrasound test for the diagnosis of acute DVT.
CDUS is compression of the deep veins from the inguinal ligament to the ankle (including posterior tibial and peroneal veins in the calf), right and left common femoral vein spectral Doppler waveforms (to evaluate symmetry), popliteal spectral Doppler, and color Doppler images. Compression is performed at 2-cm intervals.
==> 這個建議對急診來說並不是個好選擇，畢竟CDUS 不是隨時可安排
Limited protocols (not including calf veins) and selective evaluation of the calf are not recommended because limited protocols require a second study in 5 to 7 days to safely exclude DVT. (Table 2)
==> 重點式的檢查要小心的是: 沒看到不代表沒有喔，該有的追蹤還是要安排
A point-of-care ultrasound consisting of a limited evaluation with compression from thigh to knee (extended compression ultrasound [ECUS]) is appropriate when CDUS is not available in a timely manner. ECUS is favored over 2-region compression because isolated femoral vein DVTs may be missed. After a negative ECUS, CDUS in 5 to 7 days is required to safely exclude DVT.
If iliocaval disease is suspected because of signs and symptoms or abnormal spectral Doppler waveforms, the threshold for pelvic ultrasound, computed tomography, or magnetic resonance venography should be low.
==> 如果在inguinal area就有看到血栓了，應該要往上看 iliac vessels & IVC是否也有栓塞
【名稱定義】
Chronic postthrombotic change is the preferred term for the material that persists on ultrasound after acute DVT. (PS. 以往稱之為Scarring)
Figure 3. Acute DVT, chronic postthrombotic change, and recurrent DVT
The term subacute thrombus does not have a unique ultrasound appearance and should rarely be used
Figure 4. Acute DVT evolving to subacute thrombus.
【POCUS protocols】
Complete protocols require a duplex Doppler ultrasound machine and are generally performed by a sonographer or vascular technologist. There are circumstances (eg, emergency departments, rural areas, off hours) when a complete study cannot be performed in a clinically relevant time frame. In this situation, if point-of-care ultrasound can be performed by a competent practitioner, it should be performed.
Extended compression ultrasound is a point-of-care protocol that has compression ultrasound from the inguinal ligament through the popliteal vein to the calf veins confluence.
Two-region ultrasound is a limited protocol that has compression of the femoral and popliteal regions. It is sometimes described as 2-point ultrasound, but this term is misleading because the proper protocol is 2 areas rather than 2 compressions.
The most appropriate point-of-care examination for diagnosis of DVT is ECUS. ECUS is favored over the 2-region compression ultrasound, because ECUS will detect isolated femoral vein thrombosis that is present in 5% to 7% of those with DVT.
A negative ECUS or 2-region test requires a follow-up CDUS in 5 days to 1 week because the calf is not evaluated. A CDUS should be performed after a positive limited ultrasound so that the entire venous system is mapped, including Doppler and calf evaluation.
==> 2個區域的掃描可能會miss掉5-7%的isolated femoral vein thrombosis，所以我現在都是掃3個區域: inguinal, mid-thigh & popliteal areas
==> ECUS我個人認為還是太多了，也太消耗時間了，之後應該要有study來比較3-region compression US & ECUS才對
==> CDUS還是要請血管超音波的專科來掃，而且要有完整的報告和包含 calf的評估才對
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