Do I need a referral for a private ultrasound?

Not as a legal requirement, because ultrasound does not use ionising radiation. Most clinics still ask for one, because the sonographer needs a clinical question to direct the scan, and a scan booked without one is more likely to be unhelpful.

Should I have a full or empty bladder for a pelvic ultrasound?

Full for a transabdominal scan through the lower abdomen, because the bladder acts as a window onto the organs behind it. Empty for a transvaginal scan. Many appointments involve both, which is why instructions can seem contradictory - arrive with a full bladder unless told otherwise.

What is a vascular or Doppler ultrasound?

An examination of blood vessels that also measures how blood is flowing through them. It covers several different studies, including leg veins, leg arteries, the carotid arteries in the neck and the abdominal aorta.

Is a transvaginal scan compulsory?

No. It is your decision, and a chaperone should be offered. It gives a much closer view of the uterus, ovaries and womb lining, so declining it may mean some questions cannot be fully answered.

Vascular and Pelvic Ultrasound: Which Scan Answers Which Question

Both are called an ultrasound. They answer entirely different questions, and one of them needs a full bladder.

Written by the FindScan editorial team Updated 2026-10-01 6 min read

Ultrasound is the least intimidating scan in the list - no radiation, no tunnel, no injection in most cases - and the most likely to be booked for the wrong thing, because so many different examinations share the name. Two of the commonest private requests are vascular and pelvic ultrasound. If you want the general picture of how abdominal scanning works, see abdominal ultrasound explained.

Neither needs a referral by law

Ultrasound uses high-frequency sound waves, not ionising radiation, so the Ionising Radiation (Medical Exposure) Regulations 2017 do not apply and there is no legal requirement for a referrer - unlike X-ray, CT and DEXA, which we cover in can you get an X-ray without a referral.

That said, most clinics still ask for a referral, and here the reason is genuinely clinical rather than bureaucratic. Ultrasound is operator-directed: the sonographer decides in real time where to look and what to measure, guided by the question being asked. A scan booked with no clinical question is the one most likely to come back unhelpful.

Vascular ultrasound: looking at flow

Vascular ultrasound - often called a Doppler scan - images blood vessels and measures how blood is moving through them. It is a family of examinations rather than one:

Leg veins. Looking for deep vein thrombosis, or assessing valve function in varicose veins.
Leg arteries. Assessing narrowing, typically where there is calf pain on walking that eases with rest.
Carotid arteries. Assessing narrowing in the neck vessels, often after a transient neurological episode.
Abdominal aorta. Measuring the vessel diameter to check for an aneurysm.

Preparation is usually minimal, although abdominal vessel scans may ask you to fast. Expect to be scanned lying down and sometimes standing, and expect it to take longer than you think - a full both-legs venous study is a careful examination, not a quick look.

One important caveat. A suspected DVT is not something to schedule at your convenience. Sudden calf or thigh swelling, pain and warmth, particularly after surgery, immobility or a long flight, needs same-day assessment - and sudden breathlessness or chest pain with it means call 999.

Pelvic ultrasound: looking at structure

Pelvic ultrasound examines the organs in the pelvis. For women that is usually the uterus, the ovaries and the lining of the womb, with common reasons including heavy or irregular bleeding, pelvic pain, suspected fibroids, ovarian cysts, endometriosis assessment and fertility investigation. For men and women both, it can assess the bladder, and in men the prostate can be assessed this way as a first look.

There are two routes, and they are not interchangeable:

Transabdominal. Through the lower abdomen, with gel on the skin. This needs a full bladder, which acts as a window onto the organs behind it. You will usually be asked to drink water beforehand and not to empty your bladder.
Transvaginal. A slim probe inserted into the vagina, giving a much closer view of the uterus, ovaries and endometrium. This needs an empty bladder, and it is optional - it is your decision, and a chaperone should be offered.

Many pelvic appointments involve both, in that order, which explains the apparently contradictory instructions some clinics give. If the letter says arrive with a full bladder and you may be asked to empty it later, that is why.

Which one do your symptoms point to?

Swelling, aching, colour change or visible veins in a leg - vascular.
Calf pain brought on by walking and relieved by rest - vascular, arterial.
Pelvic pain, heavy or irregular periods, suspected fibroids or cysts - pelvic.
Difficulty passing urine, or incomplete emptying - pelvic, including a bladder assessment.
Lower abdominal pain that may be gallbladder, liver or kidney - that is an abdominal scan, a third examination again.

What to ask when booking

Exactly which examination is booked, and which vessels or organs it covers.
What preparation is required - fasting, water, full or empty bladder.
Whether a transvaginal scan may be offered, and whether a chaperone is available.
Who performs it, and who issues the written report.
Whether the report goes to your GP.

The honest limitation

Ultrasound is excellent at some things and blind to others. It does not see through bone or gas, which is why bowel is difficult and why a scan can be limited by body habitus or by a gassy abdomen on the day. A report that says views were limited is not a wasted scan - it is the sonographer telling you the truth about what could be seen, and it sometimes means a different test is the right next step.

References

The Ionising Radiation (Medical Exposure) Regulations 2017 (SI 2017/1322). UK Statutory Instruments, legislation.gov.uk. www.legislation.gov.uk/uksi/2017/1322/contents

This article is general information, not medical advice, and it does not replace an assessment by a clinician. If you have symptoms that worry you, speak to your GP or call 111. In an emergency, call 999.