DVT, investigation of choice is:
## **Core Concept**
The investigation of choice for Deep Vein Thrombosis (DVT) involves imaging techniques that can directly visualize the thrombus or assess blood flow in the deep veins. DVT is a condition characterized by the formation of a blood clot in a deep vein, typically in the legs.
## **Why the Correct Answer is Right**
The correct answer, **C. Duplex Ultrasound**, is the investigation of choice for DVT because it is a non-invasive, widely available, and cost-effective method that combines **Doppler ultrasound** (to assess blood flow) with **conventional ultrasound** (to visualize the vein and clot directly). Duplex ultrasound can accurately diagnose DVT by showing the presence of a clot, assessing blood flow, and evaluating the compressibility of the vein.
## **Why Each Wrong Option is Incorrect**
- **Option A:** MRI is not typically the first-line investigation for DVT due to its higher cost, limited availability, and the fact that it's usually reserved for more complex cases or when ultrasound is inconclusive.
- **Option B:** CT Venography (CTV) involves contrast and radiation, making it less favorable as a first-line diagnostic tool compared to duplex ultrasound, although it can be used in certain situations where ultrasound is not feasible or diagnostic.
- **Option D:** Venography, once considered the gold standard, is now rarely used due to its invasive nature, the risk of complications (e.g., contrast-induced nephropathy, vein damage), and the availability of effective non-invasive alternatives.
## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that the **Wells' score** can help determine the pre-test probability of DVT, guiding the decision to perform a **duplex ultrasound**. A score of 0-1 suggests low probability, 2-6 suggests moderate probability, and >6 suggests high probability. This clinical prediction rule includes points for symptoms of DVT, an alternative diagnosis being less likely, immobility or surgery in the previous four weeks, and a history of DVT.
## **Correct Answer:** C. Duplex Ultrasound.