Imaging of the
 

Urinary Tract
 

National Kidney and Urologic Diseases Information Clearinghouse 

National 

Institute of 

Diabetes and 

Digestive 

and Kidney 

Diseases 

NATIONAL 

INSTITUTES 

OF HEALTH 

U.S. Department 

of Health and 

Human Services 

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 consist of x rays, ultrasound, 

magnetic resonance imaging (MRI), and 

computerized tomography (CT) scans. 

Imaging helps doctors see the causes of 

medical problems. 

What is the urinary tract? 

The urinary tract consists of the organs, 

tubes, and muscles that work together to 

make, move, store, and release urine, the 

liquid waste of the human body. The 

upper urinary tract includes the kidneys, 

which filter wastes and extra fluid from the 

blood, and the ureters, which carry urine 

from the kidneys to the bladder. The 

lower urinary tract includes the bladder, 

a balloon-shaped muscle that stores urine, 

and the urethra, a tube that carries urine 

from the bladder to the outside of the body 

during urination. Doctors who specialize in 

kidney problems are called nephrologists. 

Doctors who specialize in problems of the 

organs and tubes that transport urine from 

the kidneys to outside the body are called 

urologists. These problems may involve 

cancers or growths of these organs, including the kidneys, ureters, bladder, and testes, 

or may involve abnormalities in storing or 

releasing urine. 

Male and female urinary tracts. 

Kidney 

Ureter 

Bladder 

Urethra 

Prostate 
What problems could 

require imaging of the 

urinary tract? 

Imaging may help your doctor find the 

cause of 

•	 urinary incontinence—unintended
 

leakage of urine
 

•	 frequent, urgent urination 

•	 blockage of urine 

•	 abdominal mass 

•	 pain in the groin or lower back 

•	 blood in the urine 

•	 high blood pressure 

•	 kidney failure 

One symptom could have several possible 

causes. Your doctor can use imaging techniques to determine, for example, whether 

a urinary stone or an enlarged prostate is 

blocking urine flow. Imaging can also help 

clarify kidney diseases, tumors, urinary 

reflux—backward flow of urine—urinary 

tract infections, incomplete emptying, and 

small bladder capacity. 

What factors will my doctor 

consider before ordering 

tests? 

The first step in solving a urinary problem 

is to talk with your doctor. You will be 

asked about your general medical history, 

including any major illnesses or surgeries, 

so you should be prepared to give as many 

details as you can about the problem and 

when it started. You should mention all the 

medicines you take, both prescription and 

nonprescription, because they might be 

part of the problem. You should also talk 

about how much fluid you drink a day and 

whether the beverages you drink contain 

alcohol or caffeine. 

Why does the doctor choose 

one imaging technique 

instead of another? 

Your doctor will look at several factors to 

decide what imaging technique to use. 

Each has advantages and disadvantages. 

Convenience and cost-effectiveness are 

also factors. 

Conventional radiology. Doctors have used 

x-ray machines to diagnose diseases for 

about a century. X rays of the urinary tract 

can help highlight a kidney stone or tumor 

that could block the flow of urine and cause 

pain. An x ray can also show the size and 

shape of the prostate. Conventional x rays 

do involve some exposure to ionizing radiation—radiation that is strong enough to 

damage some cells. Two x-ray procedures 

involve the use of contrast medium, which 

is a liquid that acts like a dye and shows the 

shape of the urinary tract as it passes 

through the tract. 

•	 Intravenous pyelogram (IVP)—In an 

IVP, the contrast medium is injected 

into a vein, usually in the arm. The 

radiologist takes a series of snapshots 

as the medium circulates through the 

blood and reaches the kidneys. The 

structure of the kidneys shows up 

clearly on the x rays as the contrast 

medium is filtered from the blood 

and passes through the kidneys to 

the ureters. 

•	 Voiding cystourethrogram (VCUG)— 

In a VCUG, a catheter inserted in the 

urethra is used to fill the bladder with 

the contrast medium. The x-ray 

machine then captures a video of the 

contrast medium during urination. 

This procedure allows the doctor to 

see things such as whether urine is 

backing up into the ureters when it 

should be traveling the other way, 

2	 Imaging of the Urinary Tract 
Intravenous pyelogram (IVP). 

down through the urethra, or whether 

urine outflow through the urethra is 

blocked. VCUG is often used with 

children who have recurrent infections 

to determine whether a defect in the 

urinary tract is causing the infections. 

It can also show blockages from an 

enlarged prostate in men or abnormal 

bladder position in women. 

Ultrasound. In ultrasound, or sonography, 

a technician holds a device, called a transducer, that sends harmless sound waves 

into the body and catches them as they 

bounce back off the internal organs to 

create a picture on a monitor. Different 

angles make it possible to examine 

different organs. 

•	 Abdominal ultrasound—In abdominal 

ultrasound, the technician applies a gel 

to the patient’s abdomen and holds the 

transducer against the skin. The gel 

allows the transducer to glide easily, 

and it improves the transmission of the 

signals. Abdominal ultrasounds are 

well known for taking pictures of 

fetuses in the womb and of a woman’s 

ovaries and uterus, but this approach 

can also be used to evaluate the size 

and shape of the kidneys. 

•	 Transrectal ultrasound—Transrectal 

ultrasound is most often used to examine the prostate. The transducer is 

inserted into the patient’s rectum so 

that it is right next to the prostate. 

The ultrasound image shows the size 

and shape of the prostate and any 

irregularity that might be a tumor. 

To determine whether an abnormallooking area is in fact a tumor, the 

doctor can use the transducer and 

the ultrasound images to guide a 

biopsy needle to the suspected tumor. 

The needle collects a few pieces of 

prostate tissue for examination with 

a microscope. 

Prostate 

Rectum 

Transducer 

Transrectal ultrasound. 

3	 Imaging of the Urinary Tract 
MRI. MRI machines use radio waves and 

magnets to produce detailed pictures of 

internal organs and tissues. No exposure 

to radiation occurs. With most MRI 

machines, the patient lies on a table that 

slides into a tunnel that may be open-ended 

or closed at one end. Some newer machines 

are designed to allow the patient to lie in 

a more open space. During an MRI, the 

patient is awake but must remain perfectly 

still while the images are being taken, 

usually only a few minutes. A sequence 

of images may be needed to create a 

detailed picture of the organ. During 

the sequencing, the patient will hear 

mechanical knocking and humming noises. 

•	 Magnetic resonance angiogram 

(MRA)—An MRA provides the most 

detailed view of renal arteries. It can 

show renal artery stenosis, which is a 

narrowing of vessels that causes poor 

blood flow to the kidney and can 

cause high blood pressure and lead 

to reduced kidney function and 

eventually to kidney failure. 

CT scan. CT scans use a combination of 

x rays and computer technology to create 

three-dimensional images. Like MRIs, 

CT scans require the patient to lie on a 

table that slides into a tunnel. CT scans 

can help identify stones in the urinary tract, 

infections, cysts, tumors, and traumatic 

injury to the kidneys and ureters. 

CT scan. 

Magnetic resonance angiogram (MRA). 

4	 Imaging of the Urinary Tract 
How do I prepare for an 

imaging examination? 

How you prepare will depend on the purpose of the examination and the type of 

equipment to be used. You should listen to 

your doctor’s instructions carefully and ask 

questions if you do not understand something that is said. 

•	 Your doctor needs to know if you have 

any allergies to foods or medications 

and if you have had any recent illnesses or medical conditions. 

•	 Your doctor may tell you not to eat 

or drink anything for 12 hours before 

the test. For some ultrasound 

examinations, however, you may be 

instructed to drink several glasses of 

water 2 hours before the examination 

so your bladder will be full. 

•	 You may be given a laxative to clear 

the colon before the examination. 

If you are having a transrectal ultrasound, you will be given an enema 

about 4 hours before the examination. 

•	 If you are having an MRI or MRA, 

talk with the technical staff about any 

implanted devices—such as heart 

pacemakers, intrauterine devices 

(IUDs), hip replacements, and 

implanted ports for catheterization— 

that may have metal parts that will 

affect the images. Metal plates, pins, 

screws, and surgical staples, as well as 

any bullets or shrapnel you might have 

in your body, may cause a problem if 

they have been in place for less than 

4 to 6 weeks. 

•	 If you feel uneasy in enclosed spaces, 

you may need to have a sedative 

before an MRI or a CT scan. 

What are the test 

procedures like? 

Most procedures for imaging the urinary 

tract are performed as the patient lies on 

a table. 

•	 For an IVP, dye is injected into a vein, 

and x-ray pictures are taken at 0, 5, 10, 

and 15 minutes to see the progression 

of the contrast medium through the 

kidneys and ureters. The dye makes 

the kidneys and urine visible on the 

x ray and shows any narrowing or 

blockage in the urinary tract. This 

procedure can help identify problems 

in the kidneys, ureters, or bladder 

that may have resulted from urine 

retention or backup. 

•	 MRI and CT scans may also require 

injection of dye. You will be asked to 

lie still for minutes at a time as the 

equipment takes pictures from different angles. A computer puts the 

different views together to create a 

three-dimensional model of your 

urinary tract. Some patients find it 

uncomfortable to lie in the small 

imaging tunnel, and others find the 

equipment noises annoying or unsettling. Knowing what to expect helps 

make these aspects of the test less 

disturbing. 

•	 VCUG is most often used to evaluate 

urinary problems in children. The 

doctor or nurse cleans the area around 

the urethra, inserts the tip of the 

catheter, and gently slides it up into 

the bladder. The child’s bladder is 

first emptied. Contrast medium is 

slowly dripped into the bladder, by 

means of gravity, until the bladder is 

full. X-ray films are then made as the 

child urinates. 

5	 Imaging of the Urinary Tract 
•	 For a transrectal ultrasound, the 

doctor or technician inserts a probe 

slightly larger than a pen into the 

rectum. The probe directs highfrequency sound waves at the prostate 

and the echo patterns form an image 

of the gland on a monitor. Although 

the image shows the size of the 

prostate and any irregularities, it 

cannot definitively identify tumors. 

To determine whether an abnormallooking area is in fact a tumor, the 

doctor can use the probe and the 

ultrasound images to guide a biopsy 

needle to the area. The needle collects a few pieces of prostate tissue 

for examination with a microscope. 

•	 For an abdominal ultrasound exam, 

a technician will apply gel to your 

abdomen and sweep a handheld transducer across the area to generate a 

picture of your urinary tract. Like 

the IVP, an abdominal ultrasound 

can show damage or abnormalities 

in the upper urinary tract. 

What should I do after 

the test? 

For most of these tests, you will be able 

to resume normal activity immediately 

afterward. If your test involved placing a 

catheter in the urethra, you may have some 

mild discomfort. Drinking an 8-ounce 

glass of water every 30 minutes for 2 hours 

should help. Also, you may be able to take 

a warm bath. Alternatively, holding a 

warm, damp washcloth over the urethral 

opening may relieve the discomfort. 

You may experience some discomfort after 

a transrectal ultrasound as well. A prostate 

biopsy may produce pain in the rectum 

and the perineum—the area between the 

rectum and the scrotum. 

For catheterization or biopsy, your doctor 

will sometimes, but not always, give you an 

antibiotic to take for 1 or 2 days to prevent 

an infection. If you notice signs of infection—including chills, fever, or persistent 

pain when you urinate—you should call 

your doctor at once. 

When will I get the results? 

Results for simple tests can be discussed 

with your doctor or nurse immediately after 

the test. Other results may take a few days. 

You will have the chance to ask questions 

about the results and possible treatments 

for your problem. 

6	 Imaging of the Urinary Tract 
         

         

Hope Through Research

The National Institute of Diabetes and

Digestive and Kidney Diseases (NIDDK)

has many research programs aimed at

understanding kidney and urologic disorders, including urinary stones, enlarged

prostate, urinary incontinence, and kidney

failure.  The NIDDK has established a

program to develop and test accurate,

reproducible techniques to monitor the

progression of polycystic kidney disease so

that potential interventions can be evaluated.  This program will apply the latest

advances in imaging technology so that

clinicians can use information about kidney

size and the portion of the kidney occupied

by cysts to determine how far the disease

has progressed.  For example, current stateof­the­art methods using MRI techniques

with rapid image acquisition rates make

possible high­resolution, three­dimensional

images of the kidneys.  Semiautomated

image analysis can determine renal size

and the location of cystic structures.  MRI

may also permit simultaneous estimation

of kidney function.

For More Information

American Urological Association

Foundation

1000 Corporate Boulevard

Suite 410

Linthicum, MD  21090

Phone:  1–866–RING–AUA (746–4282) 

or 410–689–3700

Email:  patienteducation@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

Internet:  www.kidney.org

You may also find additional information

about this topic by visiting MedlinePlus at

www.medlineplus.gov.

7 Imaging of the Urinary Tract
 

National Kidney and 

Urologic Diseases 

Information Clearinghouse 

3 Information Way 

Bethesda, MD 20892–3580 

Phone: 1–800–891–5390 

Fax: 703–738–4929 

Email: nkudic@info.niddk.nih.gov 

Internet: www.kidney.niddk.nih.gov 

The National Kidney and Urologic Diseases 

Information Clearinghouse (NKUDIC) is a 

service of the National Institute of Diabetes 

and Digestive and Kidney Diseases (NIDDK). 

The NIDDK is part of the National Institutes 

of Health of the U.S. Department of Health 

and Human Services. Established in 1987, the 

Clearinghouse provides information about diseases of the kidneys and urologic system to people with kidney and urologic disorders and to 

their families, health care professionals, and the 

public. The NKUDIC answers inquiries, develops and distributes publications, and works 

closely with professional and patient organizations and Government agencies to coordinate 

resources about kidney and urologic diseases. 

Publications produced by the Clearinghouse are 

carefully reviewed by both NIDDK scientists 

and outside experts. This fact sheet was 

reviewed by Linda M. Dairiki Shortliffe, M.D., 

Stanford University Medical Center; and 

Vicente E. Torres, M.D., Mayo Clinic, 

Rochester. 

This publication is not copyrighted. The 

Clearinghouse encourages users of this fact 

sheet to duplicate and distribute as many 

copies as desired. 

This fact sheet is also available at 

www.kidney.niddk.nih.gov. 

U.S. DEPARTMENT OF HEALTH 

AND HUMAN SERVICES 

National Institutes of Health 

NIH Publication No. 07–5107 

November 2006