17627 Vq Scan

Overview

A V/Q scan (say "V-Q scan") is a painless imaging test that shows how well air and blood are moving through your lungs. It has two parts. The V stands for ventilation, which is the air you breathe in. The Q stands for perfusion, which is the flow of blood through your lungs. For the ventilation part, you breathe in a very small amount of a radioactive tracer (a special substance that shows up on a scan camera) as a gas or fine mist. For the perfusion part, a tiny amount of tracer is injected into a vein in your arm. A camera then takes pictures of your lungs. By comparing the two sets of pictures, doctors can see whether any part of a lung gets air but little or no blood. That pattern can happen when a blood clot is blocking a blood vessel in the lung - a condition called a pulmonary embolism (PE, a clot in the lung).

Yes. V/Q scans are a standard test in hospital imaging (nuclear medicine) departments and have been used safely for many decades. They are one of the usual ways to check for a blood clot in the lungs, especially when a CT scan of the lungs is not the best choice for you.

Anyone can be referred for a V/Q scan, at any age. It is often chosen for people who have sudden breathlessness or chest pain and who cannot have, or should not have, the dye used in CT scans - for example some pregnant women, people with kidney problems, or people with a severe allergy to contrast dye. It may also be used before lung surgery or to check lung function in certain conditions.

Symptoms

Common symptoms

• A V/Q scan itself does not cause any symptoms - it is a quiet, painless test.
• The symptoms below are the ones that might lead your doctor to arrange the scan, because they can be signs of a clot in the lung.
• New or sudden shortness of breath, especially when you have been resting or after a long journey.
• Sharp chest pain that is worse when you breathe in, cough, or strain.
• Coughing, sometimes bringing up blood.
• A fast heartbeat, light-headedness, or feeling faint.
• Pain, swelling, redness or warmth in one leg (this can be a sign of a clot in a leg vein that may travel to the lung).

Symptoms in children

• V/Q scans are done only occasionally in children, usually when a clot is suspected after an illness or injury, or when other scans are not suitable.
• A child may need extra help to lie still for the pictures, and a parent can usually stay close by.
• The team will explain the test in simple words to your child and answer their questions.

Symptoms in older adults

• Clots in the lung are more common in older adults, so V/Q scans are used more often in this age group.
• Staff will help you get on and off the scanning bed and will make sure you are comfortable.
• If you find lying still difficult because of arthritis or breathlessness, tell the team - they can help you settle into a comfortable position.
• Bring a list of all your medicines, as this helps the team plan your care.

Causes

Main causes

• Suspected pulmonary embolism (a blood clot in the lung) - the most common reason for the test.
• Checking lung function before lung surgery or after certain lung treatments.
• Assessing people with known lung disease when other tests give unclear results.
• Following up a previous scan or checking how well treatment is working.
• Helping to find the cause of breathlessness when other tests are not conclusive.

Risk factors

• These are factors that raise the chance of a lung clot - not risks of the scan itself.
• Recent surgery, especially of the hip, knee or abdomen, or a recent hospital stay.
• Being still for long periods, such as after an injury or on a long flight.
• A previous blood clot in a leg or lung, or a close family history of clots.
• Active cancer and some cancer treatments.
• Pregnancy and the first weeks after giving birth.
• Some hormonal medicines, such as combined contraceptive pills or hormone replacement therapy.
• Smoking, obesity, and increasing age.
• Some inherited conditions that make blood more likely to clot.

When to see a doctor

See a doctor urgently if:

• You have new or worsening breathlessness, chest pain, or you are coughing up blood - get medical help the same day, or call your local emergency number if it is severe.
• You notice swelling, pain or redness in one leg.
• You feel faint or your heart is racing for no clear reason.
• You have a scan booked but you are pregnant, think you might be, or you are breastfeeding - tell the imaging team before the appointment so they can advise you.

Book a routine appointment if:

• You are worried about what the scan involves or how it will feel.
• You have not received your results within the time you were told to expect them.
• You need a fit note, travel advice, or a letter for work or insurance.
• You want to talk through what the result means for your longer-term health.

Diagnosis

The V/Q scan is itself the test that helps make the diagnosis. Your doctor will first ask about your symptoms, examine you, and may do blood tests and a heart tracing. If a lung clot is possible, you will be referred for imaging, which may be a V/Q scan or a CT scan of the lungs. The V/Q scan pictures show whether air and blood are reaching the same areas of your lungs. Patches that get air but no blood suggest a clot. A doctor specially trained in imaging (a radiologist or nuclear medicine physician) reviews the pictures and sends a report to the team caring for you.

Tests that may be done

• V/Q scan (ventilation-perfusion scan) - the test described here.
• CT pulmonary angiogram (CTPA) - a detailed CT scan of the lung blood vessels, often the first choice if it is suitable for you.
• D-dimer blood test - a blood test that can help rule out a clot in some people.
• Chest X-ray - to look for other causes of breathlessness.
• ECG (heart tracing) and blood tests including oxygen levels.
• Ultrasound scan of the leg veins if a clot in the leg is suspected.

What to expect at your appointment

You will usually be able to eat and drink as normal, and you can take your usual medicines unless told otherwise. On arrival, the team will check your details and may ask you to empty your bladder. For the ventilation part, you breathe through a mouthpiece or mask for a few minutes while the camera takes pictures - the air may taste slightly sweet or feel a little cool, and you may be asked to hold your breath briefly. For the perfusion part, a small plastic tube (cannula) is placed in a vein in your arm and the tracer is injected - it feels like a tiny pinprick and you should not feel anything else. You then lie still on a flat bed while the camera moves around you. The whole visit usually takes between 30 minutes and 2 hours. You can normally go home straight afterwards, and you may be advised to drink plenty of fluids. Results are usually ready within a few days, and your doctor will explain them to you.

Treatment

A V/Q scan is a test, not a treatment - nothing is treated during the scan. What happens next depends on what the pictures show. If a clot is found, you will start treatment to stop the clot growing and to lower the risk of new clots. If no clot is found, your doctor will look for other reasons for your symptoms, which may include heart or lung conditions. Either way, you should get a clear plan and a follow-up.

Self-care at home

• Tell the imaging team before your appointment if you are pregnant, might be pregnant, or are breastfeeding.
• Bring a list of all your medicines, including anything you buy over the counter, and mention any allergies.
• Wear loose, comfortable clothing and leave jewellery at home if you can.
• You can usually eat and drink normally - follow any instructions given on your appointment letter.
• Ask whether you need someone to drive you home; most people can drive themselves, but it is worth checking.
• After the scan, drink plenty of fluids for the rest of the day and wash your hands after using the toilet, as a small amount of tracer passes out in your urine.
• If you are breastfeeding, ask the team for advice - you may be given simple guidance about timing feeds.
• Keep moving gently and follow any advice you were given about preventing clots, such as staying hydrated and not sitting still for long periods.

Medical treatments

If the scan shows a lung clot, the usual treatment is a course of blood-thinning medicine (often called an anticoagulant), which may be given as tablets or injections. Your doctor will choose the type that suits you and explain how long you need to take it. Blood-thinning medicine does not dissolve the clot - it stops it getting bigger and helps your body break it down naturally over time. You will usually have follow-up appointments to check how you are doing. If no clot is found, treatment will focus on whatever else is causing your symptoms.

When is surgery considered?

Surgery is rarely needed for a lung clot. In a small number of serious cases, other options may be discussed, such as clot-dissolving treatment, a procedure to remove a clot, or a small filter placed in a large vein when blood-thinning medicine cannot be used. Your specialist team would explain the risks and benefits fully if this applied to you.

Living with this condition

Most people feel completely normal after a V/Q scan and can carry on with their day. The tracer is short-lived and leaves your body naturally, so you do not need to avoid anyone. While you wait for results, keep taking any medicines you have been given and follow the advice from your care team. If you are started on blood-thinning medicine, you will be given information about when to seek help - for example, if you have unusual bleeding or bruising.

Lifestyle tips

• Keep moving regularly during the day, and take short walking breaks if you sit for long periods.
• Stay well hydrated, especially in hot weather or when travelling.
• If you are going on a long journey, get up and move around when you can, and stretch your legs.
• Follow any advice about compression stockings if these have been recommended for you.
• If you smoke, stopping is one of the most helpful things you can do for your heart and lungs - ask your doctor or pharmacist for support.
• Tell any healthcare professional that you have had a clot (if you have) before surgery or before starting new medicines.

Diet and exercise

There is no special diet after a V/Q scan - eat and drink normally. If you are on blood-thinning medicine, keep your diet steady, particularly with green leafy vegetables and alcohol, and ask your team for specific advice. Gentle, regular activity such as walking is good for your circulation and helps prevent clots. Build up slowly if you have been unwell, and ask your doctor or physiotherapist what level of exercise is right for you.

Mental health and emotional wellbeing

Being investigated for a lung clot can be frightening, and the wait for results can be stressful. Feeling anxious or low at this time is very common and understandable. Talking to family, friends or your GP often helps. If your worry is affecting your sleep, appetite or daily life, tell your doctor - support such as counselling is available. If you ever have thoughts of harming yourself, contact your local emergency number or a crisis support line straight away, or go to your nearest emergency department.

Prevention

You do not need to prevent the scan itself - it is a safe, well-established test that is only done when the benefit outweighs the small risks. What you can help prevent is the problem it looks for: a blood clot. Staying active, keeping hydrated, moving around during long trips, and following clot-prevention advice after surgery all lower your risk. If you are admitted to hospital or have an operation, ask the team what will be done to protect you from clots.

Complications

If left untreated

• If a lung clot is present but not found and treated, it can strain the heart and lungs and, in serious cases, become life-threatening.
• Some people who have had a clot develop longer-term breathlessness or tiredness, so follow-up matters.
• Occasionally a V/Q scan gives an unclear result, and you may need another test such as a CT scan to be sure.
• The scan involves a small dose of radiation; the benefit of finding or ruling out a clot is generally much greater than this small risk.
• The injection can cause a brief sting or a small bruise where the needle went in - this settles quickly.

Long-term outlook

The outlook is generally very good. A V/Q scan is a routine, quick and painless test that gives your doctor clear information to act on. When a clot is found, treatment works well for most people, and many go on to make a full recovery. If no clot is found, you get the reassurance of knowing that, and your doctor can look for the real cause of your symptoms. Either way, you will not be left without a plan.

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