AuscultifyWhat Is a Bruit? Definition, Sound and Causes
A bruit (pronounced "broo-ee") is an audible vascular sound produced by turbulent blood flow through a narrowed, dilated or otherwise abnormal artery, heard with a stethoscope placed over the vessel. It sounds like a soft whooshing, blowing or swishing noise that comes and goes in time with the pulse. In medical terms, a bruit is a sign of turbulence, and turbulence usually means the artery underneath is diseased.
The word is French for "noise." In clinical use it is reserved for sounds over blood vessels; the equivalent sound over a heart valve is called a murmur.
Why turbulence makes a sound
Blood normally moves in smooth, silent layers (laminar flow). Whether flow stays laminar depends on the Reynolds number, which in plain words is the balance between how fast and how dense the fluid is versus how viscous it is and how wide the tube is. Push velocity up, or thin the blood, and flow tips over into chaotic eddies that vibrate the vessel wall. Those vibrations are the bruit you hear.
A stenosis raises velocity through the narrowing, so turbulence appears just beyond it. This has two practical consequences that are commonly taught:
- Moderate to severe stenosis is the loudest. Bruits are generally most prominent around 50 to 70 percent narrowing, when flow is still brisk but the jet is highly disturbed.
- Critical stenosis can be silent. Beyond roughly 90 percent narrowing, flow falls so far that turbulence fades, and a complete occlusion produces no sound at all. A quiet artery does not mean a healthy artery.
Low viscosity (anemia) and high cardiac output (fever, pregnancy, thyrotoxicosis) raise the Reynolds number without any stenosis, which is why bruits and flow murmurs turn up in these states.
Systolic vs continuous bruits
Most bruits are systolic: they appear with the pulse wave and stop before the next beat. A bruit that persists through the whole cycle is a systolic-diastolic or continuous bruit, and it means the pressure gradient across the lesion never disappears. Think of three causes:
- Arteriovenous fistula or malformation, including a surgically created dialysis fistula.
- Severe stenosis with a high gradient, where diastolic pressure upstream still drives flow through the narrowing.
- Renal artery stenosis, where a continuous, lateralized upper abdominal bruit is the classic (though uncommon) finding.
Bruit vs thrill vs murmur
| Bruit | Thrill | Murmur | |
|---|---|---|---|
| What it is | Turbulent flow you hear | Turbulent flow you feel as a vibration | Turbulent flow you hear over the heart |
| Where | Over an artery or fistula | Over an artery, fistula or the precordium | Over the valve areas of the chest |
| Detected with | Stethoscope | Palm or fingertips | Stethoscope |
| Meaning | Vascular narrowing, dilation, fistula or high flow | Strong turbulence; a bruit with a thrill is more significant than a bruit alone | Valve stenosis or regurgitation, shunt, or flow murmur |
The same physics underlies all three. A palpable thrill accompanies a loud bruit in the same way that a grade 4 or louder murmur comes with a precordial thrill.
Where to listen for bruits
| Site | Landmark | What a bruit suggests |
|---|---|---|
| Carotid | Three points from the angle of the jaw to the base of the neck | Carotid stenosis, transmitted aortic stenosis, venous hum |
| Subclavian | Supraclavicular fossa | Subclavian stenosis; check for a blood pressure difference between arms |
| Abdominal aorta | Midline epigastrium to the umbilicus | Aortic atherosclerosis, aneurysm, mesenteric stenosis |
| Renal | 2 to 3 cm above and lateral to the umbilicus, or the flank | Renal artery stenosis, especially if continuous |
| Iliac | Lower quadrants toward the inguinal ligament | Aortoiliac disease |
| Femoral | Groin, just below the inguinal ligament | Peripheral arterial disease |
| Temporal | In front of the ear over the temporal artery | Rarely, giant cell arteritis or an AV malformation |
Auscultation technique
Either chest piece works. Bruits sit in the low to medium frequency range, so many clinicians prefer the bell for carotid bruits, while the diaphragm is fine for the abdomen and groin. Whatever you use, apply it lightly: firm pressure can compress the artery and manufacture a bruit that was not there.
- Quiet room, patient relaxed, several cardiac cycles at each site.
- For the carotids, ask the patient to hold their breath and auscultate one side at a time.
- In the abdomen, auscultate before palpation.
- If you hear a bruit, palpate gently for a thrill and note whether the sound is systolic only or continuous.
- If you hear a sound in the neck, listen over the right upper sternal border to exclude a transmitted aortic stenosis murmur.
Benign bruits
Not every bruit means disease. Soft systolic bruits are common in children, in pregnancy, in thin young adults (especially over the epigastrium) and in high-output states. A venous hum is a continuous humming sound at the base of the neck in children and young adults that disappears when the patient lies flat or when you press gently on the jugular vein. Interpret any bruit in the context of age, symptoms and risk factors.
Bruits in nursing practice
Nurses auscultate for bruits during head-to-toe and abdominal assessments and, importantly, over dialysis access. A continuous bruit and a palpable thrill over an AV fistula or graft are expected and mean the access is patent; loss of either should be reported promptly. Never squeeze or aggressively palpate a fistula, and never palpate deeply over a pulsatile abdominal mass or suspected aneurysm. If you hear a new bruit, document it and escalate rather than trying to characterize it by pressing harder.
How to document a bruit
Record the site, timing and character, plus what you did to exclude mimics. For example: "Soft systolic bruit over the right carotid, loudest mid-neck, not heard at the right upper sternal border, no thrill." Or: "Continuous bruit and thrill over left forearm AV fistula, unchanged."
Hear what a bruit actually sounds like
Descriptions only get you so far. Auscultify includes real clinical vascular recordings alongside its heart, lung and bowel libraries, and its six quiz modes play them unlabeled so you have to decide: bruit, transmitted murmur or normal flow. Missed sounds come back more often through spaced-repetition weighting, and the Spectrogram view (Pro) shows whether the sound stops at end-systole or runs on into diastole.
Train vascular sounds free →FAQ
What does a bruit sound like?
A bruit sounds like a soft whooshing, blowing or swishing noise timed with the pulse, heard through the stethoscope over an artery. Most are systolic and low to medium pitched; a harsh or high-pitched bruit that runs into diastole suggests a tighter narrowing or an arteriovenous connection.
What does a bruit indicate?
A bruit indicates turbulent flow, most often from atherosclerotic narrowing of the artery you are listening over. It can also come from an AV fistula, an aneurysm, external compression or a benign high-flow state, so it is a marker of vascular disease rather than a measure of severity.
What is the difference between a bruit and a thrill?
A bruit is heard with a stethoscope; a thrill is the same turbulence felt as a vibration under your fingers. A bruit accompanied by a thrill is louder and more significant than a bruit alone.
Where do you listen for bruits?
Carotids in the neck, supraclavicular fossae for the subclavians, the epigastrium for the aorta, 2 to 3 cm above and lateral to the umbilicus for the renal arteries, the lower quadrants for the iliacs and the groin for the femorals. Add the temporal arteries and any dialysis access when relevant.
What is a systolic diastolic bruit?
A systolic-diastolic or continuous bruit persists through the entire cardiac cycle. It means a pressure gradient exists even in diastole, which points to severe stenosis, an AV fistula or malformation, or renal artery stenosis when heard in the upper abdomen.
How do you listen for bruits?
Use a quiet room, apply the bell or diaphragm lightly over the artery and listen through several cycles. Ask for a breath-hold at the carotids, auscultate one side at a time, and in the abdomen listen before you palpate.