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. 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. Conventional x rays do involve some exposure to ionizing radiation.
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| Intravenous pyelogram (IVP) |
- 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, 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 belly 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.
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| Transrectal ultrasound
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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 abnormal-looking 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 under a microscope.
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.
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| Magnetic resonance angiogram (MRA) |
- 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.
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| CAT (or CT) scan |
CAT (or CT) scan. CAT scans use a combination of x rays and computer technology to create three-dimensional images. Like MRIs, CAT scans require the patient to lie on a table that slides into a tunnel. CAT scans can help identify stones in the urinary tract, infections, cysts, tumors, and traumatic injury to the kidneys and ureters.
source: http://kidney.niddk.nih.gov/kudiseases/pubs/imagingut/index.htm