Glossary

Doppler ultrasound for blood clots

Quick answer

A Doppler ultrasound checks the veins of the leg for a blood clot, called a deep vein thrombosis (DVT). It is painless and uses sound waves to show blood flow. It is requested when the calf becomes swollen, tender or tight after a knee injury, surgery or a long flight, explains Doha knee surgeon Dr. Pablo Gelber at Aman Hospital.

What to expect

You lie down with the leg exposed. Gel is applied and a probe is moved from the groin down to the calf. The sonographer presses gently on the veins at several points: a healthy vein squashes flat, while a vein with a clot does not. The machine also shows and plays the sound of blood flow. It takes around 15 to 30 minutes and needs no preparation.

Why it matters for knee patients

Reduced movement after knee surgery or injury, a plaster or brace, dehydration in the Qatar heat and long flights home can all raise the risk of a clot. Many patients receive preventive measures such as early walking, calf exercises and, for some, blood-thinning medicine.

Warning signs that need same-day assessment include calf pain or swelling that is worse than expected, warmth or redness of the calf, or a leg that feels tight. Sudden breathlessness, chest pain or coughing blood may mean a clot has travelled to the lungs: call 999 or go to an emergency department straight away.

Frequently asked questions

Is some calf swelling normal after knee surgery?

Some swelling of the knee and leg is common. Swelling that is increasing, a painful calf or new redness should be checked, and a Doppler scan is the usual test.

Can I fly home after knee surgery?

Often yes, after a suitable interval and with clot prevention. Timing depends on the operation and your risk factors, so discuss it with your surgeon before booking.