Imaging of the 

Urinary Tract

National Kidney and Urologic Diseases Information Clearinghouse

U.S. Department 

of Health and 

Human Services

NATIONAL 

INSTITUTES 

OF HEALTH

What is the urinary tract?

The urinary tract is the body’s drainage 

system for removing wastes and extra water. 

The urinary tract includes two kidneys, two 

ureters, a bladder, and a urethra. The kidneys are a pair of bean-shaped organs, each 

about the size of a fist and located below the 

ribs, one on each side of the spine, toward 

the middle of the back. Every minute, a person’s kidneys filter about 3 ounces of blood, 

removing wastes and extra water. The wastes 

and extra water make up the 1 to 2 quarts of 

urine an adult produces each day. Children 

produce less urine each day; the amount 

produced depends on their age. The urine 

travels from the kidneys down two narrow

tubes called the ureters. The urine is then 

stored in a balloonlike organ called the bladder. When the bladder empties, urine flows 

out of the body through a tube called the 

urethra at the bottom of the bladder.

What does “imaging” mean?

In medicine, “imaging” is the general term 

for any technique used to provide pictures of 

bones and organs inside the body. Imaging 

techniques include conventional radiology, 

or x rays; ultrasound; magnetic resonance 

imaging (MRI); computerized tomography 

(CT) scans; and radionuclide scans. Imaging 

helps the health care provider see the causes 

of medical problems.

Kidney

Ureter

Bladder

Urethra

Prostate

Male and female urinary tracts
 

What problems could 

require imaging of the 

urinary tract? 

Imaging can help the health care provider 

find the cause of 

• urinary retention—the inability to 

empty the bladder completely

• urinary frequency—urination eight or 

more times a day 

• urinary urgency—the inability to delay 

urination 

• urinary incontinence—the accidental 

loss of urine 

• blockage of urine 

• abdominal mass—swelling in a specific 

part of the abdomen 

• pain in the groin or lower back 

• blood in the urine 

• high blood pressure 

• kidney failure 

One symptom can have several possible 

causes. The health care provider can use 

imaging techniques to determine, for 

example, whether a urinary tract stone or 

an enlarged prostate is blocking urine flow. 

Imaging can help clarify kidney diseases, 

tumors, urinary tract infections (UTIs), 

urinary retention, small bladder capacity, and 

urinary reflux—the backward flow of urine. 

What steps does the health 

care provider take before 

ordering imaging tests? 

Before ordering imaging tests, the health 

care provider 

• asks about specific urinary tract symptoms, when they began, and their 

frequency 

• considers general medical history, 

including any major illnesses or 

surgeries

• may ask female patients whether pregnancy is suspected 

• asks about medication use—both 

prescription and over the counter—the 

amount of fluid consumed each day, and 

the use of alcohol and caffeine 

• performs a physical exam 

These steps help the health care provider 

determine the possible causes of the urinary 

tract problems and what to look for in an 

imaging test. 

2 Imaging of the Urinary Tract 
 

What are the imaging 

techniques? 

The health care provider can use several 

different imaging techniques depending on 

factors such as the person’s general medical 

history and urinary tract symptoms. 

Conventional Radiology 

X-ray machines have been used to diagnose 

diseases for about 100 years. X rays of the 

urinary tract can help highlight a kidney 

stone or tumor that could be blocking the 

flow of urine and causing pain. For men, an 

x ray also shows the size and shape of the 

prostate—a walnut-shaped gland that surrounds the urethra at the neck of the bladder and supplies fluid that goes into semen. 

Conventional x rays do involve some exposure to ionizing radiation—radiation that is 

strong enough to damage some cells. Two 

common x-ray procedures include the injection of a special dye, called contrast medium, 

which shows the shape of the urinary tract. 

Intravenous pyelogram (IVP). An IVP is an 

x ray of the urinary tract. Contrast medium 

is injected into a vein in the person’s arm, 

travels through the body to the kidneys, and 

makes urine visible on the x ray. The contrast medium also shows any blockage in the 

urinary tract. The procedure is performed 

in a health care provider’s office, outpatient 

center, or hospital by an x-ray technician, and 

the images are interpreted by a radiologist— 

a doctor who specializes in medical imaging; 

anesthesia is not needed. An IVP can help 

locate problems in the kidneys, ureters, or 

bladder that may be caused by urinary retention or reflux. 

IVP image 

3 Imaging of the Urinary Tract 
 

Voiding cystourethrogram (VCUG). A 

VCUG is an x-ray image of the bladder and 

urethra taken while the bladder is full and 

during urination, also called voiding. As the 

person lies on the x-ray table, a health care 

provider inserts the tip of a thin, flexible tube 

called a catheter through the urethra into the 

bladder. The bladder is filled with contrast 

medium to make it clearly visible on the x-ray 

images. The x-rays are taken from various 

angles while the bladder is full of contrast 

medium. The catheter is then removed and 

x-ray images are taken during urination. The 

procedure is performed in a health care provider’s office, outpatient center, or hospital 

by an x-ray technician. The technician is 

supervised by a radiologist while the images 

are taken. The radiologist then interprets 

the images. Anesthesia is not needed, but 

sedation may be used for some people. A 

VCUG can reveal abnormalities of the inside 

of the urethra and bladder and is usually 

used for children to detect vesicoureteral 

reflux—the abnormal flow of urine from the 

bladder back into the upper urinary tract. A 

VCUG can also show whether the flow of 

urine is normal when the bladder empties, 

blockages from an enlarged prostate in men, 

and an abnormal bladder position in women. 

Ultrasound 

Ultrasound uses a device, called a transducer, that bounces safe, painless sound 

waves off organs to create an image of their 

structure. The transducer can be moved 

to different angles to make it possible to 

examine different organs. The procedure 

is performed in a health care provider’s 

office, outpatient center, or hospital by a 

specially trained technician, and the images 

are interpreted by a radiologist; anesthesia 

is not needed. The images can be used to 

provide information that is valuable in diagnosing and treating a variety of diseases and 

conditions. 

Abdominal ultrasound. In abdominal 

ultrasound, the health care provider applies 

a gel to the person’s abdomen and moves 

a hand-held transducer over the skin. The 

gel allows the transducer to glide easily, and 

it improves the transmission of the signals. 

4 Imaging of the Urinary Tract 
 

 

The procedure is performed in a health 

care provider’s office, outpatient center, or 

hospital by a specially trained technician, 

and the images are interpreted by a radiologist; anesthesia is not needed. An abdominal 

ultrasound can create images of the entire 

urinary tract. The images can show damage or abnormalities in the urinary tract. 

Abdominal ultrasounds are also commonly 

used to take pictures of fetuses in the womb 

and of a woman’s ovaries and uterus. 

Transrectal ultrasound with prostate biopsy. 

Transrectal ultrasound is most often used 

to examine the prostate. In a transrectal 

ultrasound, the health care provider inserts 

a transducer slightly larger than a pen into 

the man’s rectum next to the prostate. The 

ultrasound image shows the size of the prostate and any abnormal-looking areas, such 

as tumors. Transrectal ultrasound cannot be 

used to definitively diagnose prostate cancer. 

5 Imaging of the Urinary Tract 

To determine whether a tumor is cancerous, 

the health care provider performs a biopsy. 

For the biopsy, the health care provider uses 

the transducer and ultrasound images to 

guide a needle to the prostate. The needle is 

then used to remove a few pieces of prostate 

tissue for examination with a microscope. A 

transrectal ultrasound with prostate biopsy is 

usually performed in a health care provider’s 

office, outpatient facility, or hospital by a 

doctor; light sedation and local anesthesia 

are used. The biopsied prostate tissue is 

examined in a laboratory by a pathologist—a 

doctor who specializes in diagnosing diseases. The biopsy can reveal whether prostate cancer is present. 

Needle guide 

Transducer 

Prostate 

Bladder Needle

Transrectal ultrasound with prostate biopsy 
 

MRI 

Magnetic resonance imaging is a test that 

takes pictures of the body’s internal organs 

and soft tissues without using x rays. MRI 

machines use radio waves and magnets to 

produce detailed pictures of the body’s internal organs and soft tissues. An MRI may 

include the injection of contrast medium. 

With most MRI machines, the person lies on 

a table that slides into a tunnel-shaped device 

where the images are taken. The device may 

be open ended or closed at one end; some 

newer machines are designed to allow the 

person to lie in a more open space. During an MRI, the person is usually awake but 

must remain perfectly still while the images 

are being taken. A sequence of images 

taken from different angles may be needed 

to create a detailed picture of the urinary 

tract. During the sequencing, the person will 

hear loud, mechanical knocking and humming noises. The procedure is performed in 

an outpatient center or hospital by a specially trained technician, and the images are 

interpreted by a radiologist; anesthesia is not 

needed, though light sedation may be used 

for people with a fear of confined spaces. 

Magnetic resonance angiogram (MRA). An 

MRA is a type of MRI that provides the 

most detailed view of kidney arteries—the 

blood vessels that supply blood to the kidneys. An MRA can show kidney artery 

stenosis, which is the narrowing of a kidney 

artery that restricts blood flow to the kidney. 

Kidney artery stenosis can cause high blood 

pressure and lead to reduced kidney function 

and eventually kidney failure. 

6 Imaging of the Urinary Tract 

MRI 
 

CT Scans 

Computerized tomography scans use a combination of x rays and computer technology 

to create three-dimensional (3-D) images. A 

CT scan may include the injection of contrast 

medium. CT scans require the person to lie 

on a table that slides into a tunnel-shaped 

device where the x rays are taken. The procedure is performed in an outpatient center 

or hospital by a specially trained technician, 

and the images are interpreted by a radiologist; anesthesia is not needed. CT scans can 

show stones in the urinary tract, obstructions, infections, cysts, tumors, and traumatic 

injuries. 

CT scan 

Radionuclide Scans 

A radionuclide scan is an imaging technique 

that relies on the detection of small amounts 

of radiation after injection of radioactive 

chemicals. Because the dose of the radioactive chemicals is small, the risk of causing 

damage to cells is low. Special cameras and 

computers are used to create images of the 

radioactive chemicals as they pass through 

the urinary tract. Radionuclide scans are 

performed at a health care provider’s office, 

outpatient center, or hospital by a specially 

trained technician, and the images are 

interpreted by a radiologist; anesthesia is not 

needed. Radioactive chemicals injected into 

the blood can provide information about kidney function. Radioactive chemicals can also 

be put into the fluids used to fill the bladder 

and urethra for x ray, MRI, and CT imaging. 

7 Imaging of the Urinary Tract 
 

What preparations are 

needed for an imaging test? 

Preparations for an imaging test mostly 

depend on the purpose and type of test. In 

general, the health care provider will want 

to know whether the person is allergic to any 

foods or medications, is pregnant, or has had 

any recent illnesses or medical conditions. 

Specific preparations could include any of 

the following: 

• fasting for 12 hours before the test 

• drinking several glasses of water 2 hours 

before the test so the bladder is full— 

for some ultrasound tests 

• taking a laxative, which is a medication 

that loosens stool and increases bowel 

movements, to clear the colon—for a 

transrectal ultrasound 

• taking an enema, which involves flushing water, laxative, or sometimes a mild 

soap solution into the anus using a special squirt bottle, about 4 hours before 

the test—for a transrectal ultrasound 

• talking with the technical staff about 

any implanted devices that may have 

metal parts that will affect MRI or 

MRA images, such as heart pacemakers, intrauterine devices (IUDs), hip 

replacements, and implanted ports 

for catheterization; metal plates, pins, 

screws, and surgical staples, as well as 

any bullets or shrapnel in the body, may 

also cause a problem if they have been 

in place fewer than 4 to 6 weeks 

• taking a sedative before an MRI or CT 

scan if the person feels anxious or has 

difficulty holding still in enclosed spaces 

People undergoing an imaging test should 

listen to the health care provider’s instructions carefully and ask questions if something 

is not understood. 

What happens after imaging 

tests? 

After most imaging tests, the person can 

immediately resume normal activity. Tests 

that involved placing a catheter in the urethra may produce some mild discomfort for 

a few hours after the procedure. Drinking 

an 8-ounce glass of water every half-hour for 

2 hours may help reduce the discomfort. The 

health care provider may recommend taking 

a warm bath or holding a warm, damp washcloth over the urethral opening to relieve the 

discomfort. A transrectal ultrasound may 

produce some discomfort. A prostate biopsy 

may produce pain in the area of the rectum 

and the perineum, which is between the rectum and the scrotum. A prostate biopsy may 

also produce blood in the urine and semen. 

For catheterization or biopsy, the health care 

provider may prescribe an antibiotic for 1 or 

2 days to prevent an infection. People with 

signs of infection—including pain, chills, or 

fever—should call a health care provider 

immediately. 

8 Imaging of the Urinary Tract 
 

Some people have reactions to the contrast 

medium or the sedatives, though the risks 

are generally low. Signs of contrast medium 

reactions include hives, itching, nausea, 

vomiting, headache, and dizziness. Contrast 

medium can cause kidney damage in people 

with certain conditions, such as impaired kidney function and diabetes. In most people, 

the kidney damage has no symptoms and 

goes away within a week or so. In rare cases, 

contrast medium causes lasting kidney damage. Signs of kidney damage include 

• high blood pressure 

• little or no urination 

• edema—swelling, usually in the hands, 

face, feet, or ankles 

• tiredness 

• generalized itching or numbness 

• headaches 

• weight loss 

• appetite loss 

• sleep problems 

Reactions to sedatives are rare but possible. 

Signs of sedative reactions include changes in 

breathing and heart rate. People with signs 

of reactions to the contrast medium or the 

sedatives should call a health care provider 

immediately. 

How soon will test results be 

available? 

The results of simple tests such as x rays 

and abdominal ultrasound can be discussed 

with the health care provider soon after the 

test. Results of other tests such as a prostate tissue biopsy, MRI, and CT scans may 

take several days to come back. The health 

care provider will talk with the patient about 

these results. 

9 Imaging of the Urinary Tract 
 

Points to Remember 

• The urinary tract is the body’s drainage system for removing wastes and 

extra water. 

• “Imaging” is the general term for 

any technique used to provide 

pictures of bones and organs inside 

the body. 

• Imaging helps the health care provider find the causes of urinary tract 

problems. 

• The health care provider will consider a person’s general medical 

history and urinary tract symptoms 

to decide what imaging technique 

to use. 

• Urinary tract imaging techniques 

include conventional radiology, or 

x rays; ultrasound; magnetic resonance imaging (MRI); computerized tomography (CT) scans; and 

radionuclide scans. 

• Preparations for an imaging test 

mostly depend on the purpose and 

type of test. 

• After most imaging tests, the person 

can immediately resume normal 

activity. 

• Results for simple tests are available soon after the test, while other 

test results may take several days to 

come back. 

Hope through Research 

The National Institute of Diabetes and 

Digestive and Kidney Diseases (NIDDK) has 

many research programs aimed at understanding, diagnosing, and treating urinary 

tract problems, including urinary tract stones, 

enlarged prostate, urinary incontinence, 

and kidney failure. The NIDDK also sponsors studies to improve diagnostic imaging techniques and devices. For example, 

current state-of-the-art methods using MRI 

techniques with rapid image acquisition rates 

make possible high-resolution, 3-D images of 

the kidneys. Semiautomated image analysis 

can determine kidney size and the location 

of cystic structures. MRI may also permit 

simultaneous estimation of kidney function. 

Participants in clinical trials can play a more 

active role in their own health care, gain 

access to new research treatments before 

they are widely available, and help others 

by contributing to medical research. For 

information about current studies, visit 

www.ClinicalTrials.gov.

10 Imaging of the Urinary Tract 
11 Imaging of the Urinary Tract

For More Information

American Urological Association Foundation

1000 Corporate Boulevard 

Linthicum, MD 21090 

Phone: 1–800–828–7866 or 410–689–3700 

Fax: 410–689–3998 

Email: auafoundation@auafoundation.org 

Internet: www.UrologyHealth.org

National Kidney Foundation

30 East 33rd Street 

New York, NY 10016 

Phone: 1–800–622–9010 or 212–889–2210 

Fax: 212–689–9261 

Internet: www.kidney.org

Acknowledgments

Publications produced by the Clearinghouse 

are carefully reviewed by both NIDDK 

scientists and outside experts. This publication was reviewed by Sam B. Bhayani, M.D., 

Washington University School of Medicine.

You may also find additional information about this 

topic by visiting MedlinePlus at www.medlineplus.gov.

This publication may contain information about 

medications. When prepared, this publication 

included the most current information available. 

For updates or for questions about any medications, 

contact the U.S. Food and Drug Administration tollfree at 1–888–INFO–FDA (1–888–463–6332) or visit 

www.fda.gov. Consult your health care provider for 

more information.
 

 

 

 

 

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U.S. DEPARTMENT OF HEALTH 

AND HUMAN SERVICES 

National Institutes of Health 

NIH Publication No. 12–5107 

January 2012 

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