# Ultrasound: what it is, how to prepare, and why there is no radiation

*Sound waves, warm gel and a handheld probe. What ultrasound shows, which exams need a full bladder or an empty stomach, and where we do it in El Paso.*

September 30, 2026 · Desert Imaging

Ultrasound is often the first exam a doctor orders, and it is the one exam we do that uses no radiation at all. Here is what it is, what it is used for, and how to get ready, depending on which part of you we are looking at.

## How ultrasound works

The probe the sonographer holds sends high-frequency sound waves into the body, far above anything you can hear. The waves bounce back differently from fluid, soft tissue and bone, and a computer turns the echoes into a live picture on the screen. Because the picture is live, the sonographer can watch an organ move or follow blood through a vessel.

There is no X-ray involved and nothing radioactive. That is why ultrasound is the standard exam in pregnancy, and why it is so often the first look when a doctor has a question about the abdomen or pelvis.

## What doctors use it for

The list is long. Some of the most common exams we do:

- **Abdomen.** Liver, gallbladder, kidneys, bladder, and the large vessels that run through the belly.
- **Pelvis and pregnancy.** Pelvic exams for women, prostate exams for men, and exams throughout pregnancy to measure the baby and check that growth is on track.
- **Thyroid, neck and breast.** A thyroid exam, a closer look at a lump, or a breast ultrasound added after a mammogram.
- **Vascular Doppler.** Doppler adds color and sound to show blood moving through arteries and veins. Doctors order it for clots in the legs, narrowing in the neck arteries, and blood flow to the kidneys and liver.
- **Liver elastography.** Elastography measures how stiff tissue is. For the liver, stiffness rises as scarring builds up in chronic liver disease, and your doctor can track it over time without a biopsy. Breast and thyroid elastography add information about a lump.

## How to prepare: it depends on the exam

This is where ultrasound is a little unusual. Two exams at the same center, on the same morning, can have opposite instructions.

**Pelvic, kidney, bladder, prostate and pregnancy exams need a full bladder.** A full bladder pushes the bowel out of the way and gives the sound waves a clear window. Drink 32 ounces of water 30 to 45 minutes before your appointment and do not use the restroom until the exam is done. Skip carbonated drinks that morning. We know the waiting is the hard part, and the sonographer will move as quickly as the pictures allow.

**Abdominal exams need an empty stomach.** Nothing to eat or drink for 6 to 8 hours before. Food makes the gallbladder contract and fills the stomach and bowel with gas, both of which get in the way. A sip of water with your regular medication is fine. Liver elastography follows the same rule.

**Thyroid, breast, vascular and most other exams need nothing.** Come as you are.

When we book your exam we tell you which group it falls in.

## What the exam feels like

You lie on a padded table. The sonographer applies warm gel to the skin, then moves the handheld probe over the area with light pressure. You may be asked to hold your breath, roll onto your side, or turn your head. The gel wipes off. There is no needle and no dye for a standard ultrasound, and you can eat, drink and drive afterward.

How long it takes depends on the study. A thyroid exam is short. A complete abdominal exam with Doppler, or a full pregnancy exam, takes longer.

## Where we do it

Ultrasound is at four of our five El Paso centers: West on Castellano, East on Lee Trevino, Joe Battle, and Horizon City. Breast, liver and thyroid elastography are at West and Joe Battle. When you book, we schedule you at a center that does your exam, and we can usually fit the appointment around work.

## Who reads it

A board-certified radiologist here in El Paso reads your exam. The report goes to the doctor who ordered it and appears in your patient portal. Our ultrasound program is accredited by the American College of Radiology in obstetric, gynecologic, general and vascular ultrasound. Your doctor goes over the results with you and decides whether anything else is needed. Ultrasound is usually the first look. When it cannot answer the question, the next step may be a CT, an MRI or a mammogram.