Investigation of choice in DVT is –
**Core Concept**
Compression ultrasonography (CUS) is the diagnostic modality of choice for diagnosing deep vein thrombosis (DVT) due to its high sensitivity and specificity. CUS involves the use of a Doppler probe to detect the absence of blood flow in the affected vein.
**Why the Correct Answer is Right**
The investigation of choice for DVT is compression ultrasonography (CUS) because it is non-invasive, quick, and can be performed at the bedside. CUS works by compressing the vein with the ultrasound probe, which should normally collapse the vein if it is patent. In the presence of a DVT, the vein will not collapse, indicating an occlusion. This is due to the absence of blood flow in the affected vein, which is detected by the Doppler probe. The absence of blood flow is a key indicator of DVT.
**Why Each Wrong Option is Incorrect**
**Option A:** Contrast venography is an invasive procedure that was previously used to diagnose DVT but has been largely replaced by CUS due to its invasiveness and the risk of complications.
**Option B:** MRI is a sensitive diagnostic tool but is not the investigation of choice for DVT due to its high cost, limited availability, and the need for specialized expertise.
**Option C:** Doppler ultrasound is a component of CUS but is not the investigation of choice on its own due to its lower specificity compared to CUS.
**Clinical Pearl / High-Yield Fact**
Remember that CUS is highly sensitive and specific for DVT, but a negative result does not entirely rule out the diagnosis, especially in patients with suspected DVT in the upper extremities or in patients with a history of previous DVT.
**Correct Answer:** C.