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Urologic Radiology

Science has given urologists a bevy of tools to probe the most private parts of the body in diagnosing urinary and renal disease. Every modern imaging technology, from conventional X-rays to radionuclide imaging, has found its way into urologic radiology's arsenal. The good news for physicians is that they have many options to explore the kidneys, ureters, bladder and surrounding structures. The better news for patients is that today's tests are thorough, relatively pain-free and often quick. But would you know what your doctor means when he or she talks of "retrograde pyelography" or "radionuclide scans?" The information below should give you the basics.

What is intravenous pyelography (IVP)?

IVP is the most common of all urologic studies. It is a test that uses contrast dye to outline the kidneys, ureters and bladder and provides information about renal function on an X-ray. The dye is administered through a vein. A urologist is likely to order this test if a patient complains of flank pain, blood in the urine (hematuria) or any stone-related symptoms. It may also be utilized as a screening test to prompt your urologist to obtain another imaging test for further information.

A preliminary film of the abdomen and pelvis is a basic part of this examination and this is usually done without contrast dye. This helps the radiologist determine the proper radiographic technique and patient positioning. A single film of the abdomen that includes the pubic bone may suffice in some patients, whereas in others, an additional film is focused on the kidneys. A full set of specific kidney films may be of value in a patient suspected of having small kidney stones. Contrast dye is then given as a single injection into the patient. The amount of contrast dye given is determined by the patient's kidney function and body weight. More contrast dye may be necessary for patients with obesity or large amounts of stool in the bowel. In children, weight and age are important factors in determining the amount of contrast dye. After the contrast dye is in the urinary tract, a series of X-rays are taken at specific time intervals, from two to 10 minutes. These X-rays will show any tumors, cysts, stones or other structural and functional abnormalities.

The primary risk of IVP is a reaction to the contrast dye. The overall incidence rate for reactions ranges from three to 13 percent. Minor reactions include hot flashes, nausea and vomiting. These are usually treated successfully with antihistamines, drugs that reduce the effects of the body's inflammatory compound, histamine. In very rare circumstances, more severe complications — breathing difficulties, low blood pressure, swelling of the mouth or throat and even cardiac arrest — can occur. Statistics estimate major reactions in one in 200 to one in 2,000 patients.

Patients with certain health factors — a history of hay fever, asthma or hives — are at greater risk as are those with congestive heart failure, diabetes and a prior reaction. Administering antihistamines or steroids prior to the exam may prevent any reactions. Also, nonionic contrast agents that have been recently developed have lowered the incidence of adverse reactions.

What is retrograde pyelography?

Like IVP, retrograde pyelography relies on contrast medium to produce detailed X-ray pictures of the urinary tract. While newer diagnostic technologies have replaced this test for many functions, retrograde pyelography may still yield better definition of the upper urinary tract, particularly the ureter and kidney collecting system. Commonly performed when IVP produces an inadequate picture, it also complements cystoscopy while investigating a patient with hematuria or recurrent or suspected cancer.

After administration of anesthesia, the doctor, cystopically, will insert a catheter through the patient's urethra and into the bladder and then into the ureter so contrast dye can be injected. Once the contrast dye is distributed through the ureters and kidney, the doctor employs a fluoroscope to magnify details with the use of X-ray on a special florescent screen. This technique produces definitive images of stones and tumors thus allowing easy diagnosis of obstructions in the urinary system without relying on the ability of the kidneys to excrete the contrast media.

While pyelography is considered generally safe, with rare incidence of reaction t o the contrast dye since the dye is administered directly into the urinary system and not into the blood stream. There may be additional problems however, with aggravating an existing urinary tract infection or triggering one from the catheterization.

What is a retrograde urethrogram?

This is commonly performed in patients in whom trauma to the penile urethra is suspected or to evaluate urethral disease. A catheter is inserted about two centimeters into the penis. The balloon on the catheter is slightly inflated and contrast dye is injected. Several X-rays are obtained or the use of a fluoroscope to magnify details on a special florescent screen may be employed during the injection of the contrasting dye. In some instances, the catheter is advanced into the bladder, where the bladder is then filled and the catheter is usually removed. The patient is instructed to urinate while several more X-rays are obtained.

What is ultrasonography?

The use of high-frequency sound waves to produce real-time images, provides a simple and painless way for urologists to examine the bladder, ureters and lower part of the kidney. Since it is a non-invasive test, it offers many advantages, including flexibility and accurate anatomic information, including dimensions, without contrast agents or radiation.

Because ultrasound produces excellent urinary tract, prostatic and testicular images without radiation or intravenous contrast medium, it is considered a painless, safe and generally risk-free technology.

What is a kidney ultrasound?

A high-frequency handheld transducer sends a sound wave through the body that creates an image from reflected waves that return from the kidney tissue. Multiple images are obtained to assess any pathological conditions. If the doctor wants to assess blood supply, he or she uses Doppler imaging, an ultrasound technique that produces color images from the movement of flowing blood, to detail actual flow through the vessels. This additional test provides excellent motion information not available on a standard sonogram.

What is a prostate ultrasound?

Prostatic ultrasonography is commonly performed in combination with a biopsy if prostate cancer is suspected. Some 70 percent of these malignancies develop in the peripheral or outer zone of the prostate, which lies next to the rectum. As such, a transducer, lubricated to enhance the sound wave's transmission, is inserted into the rectum. The urologist then scans the area in a sagittal and longitudinal plane, noting any asymmetry or abnormal areas indicative of prostate cancer. The gland is then biopsied.

What is a testicular ultrasound?

Testicular ultrasound is used to evaluate almost all abnormalities in the scrotum, the sac containing the testicles. Sonography not only can detect patterns suggesting cancer, but it also determines if the mass is intratesticular, extratesticular, solid or cystic. Color-Doppler imaging has made ultrasonography a highly accurate and specific test for testicular torsion, an obstruction of the blood flow resulting from the testis twisting on its blood supply within the spermatic cord. If not spotted and corrected, it can lead to testicular death.

What is a CT scan?

CT scan is an imaging technique that produces cross-sectional slices of tissue, is a widely regarded tool for evaluating the urinary tract and renal systems. It uses special X-ray equipment to obtain data from different angles of the body and then processes them in a computer to show cross-sectional slices of tissue and organs.

Since CT scans can distinguish between solid and liquid structures, it is extremely valuable in examining the type and extent of kidney tumors or other masses, such as stones, distorting the urinary tract. CT technology, however, is also enhanced by other factors. Intravenous radiopaque injections intensify the images. CT scans have improved speed and accuracy by gathering volumes of continuous kidney and urinary data in seconds with no gaps between images.

Specialized applications of CT can be performed in specific clinical circumstances. For example, three-dimensional reconstructions of the kidney and blood supply may show vascular abnormalities and provide "road maps" for planning surgeries.

CT scanning combines X-rays and computer calculations to produce precisely detailed cross-sectional images of the body. More specifically, very small, controlled beams of X-rays, rotating in a continuous 360-degree motion around the patient, pass through the tissue as an array of detectors measure thousands of X-ray images or profiles. Computer calculations based on those multiple measures produce the detailed pictures reflected on a screen.

CT scans are generally a safe, efficient and effective technology that produce minimal risks.

What is Magnetic Resonance Imaging (MRI)?

Magnetic resonance imaging (MRI) is a superior technique that uses radio waves and a strong magnetic field to provide remarkably clear pictures. As such, it offers an alternative to patients who react to radiopaque contrast dye. Because of its ability to show soft tissues in exquisite detail, this technology can detect disease and detail blood vessels or other structures. In the kidney system, for example, an MRI can delineate a hollow cyst from a solid mass, producing excellent three-dimensional images of any tumor's shape. In particular, its super sensitivity can help urologists identify and measure the spread of kidney cancer into the renal vein and inferior vena cava, the large vessel that returns deoxygenated blood to the heart. But while useful in evaluating kidney transplant donors, MRI has limited applicability for the urinary tract since the non-specificity of its signals makes it ineffective in detecting calcifications and bladder abnormalities.

MRI is unique among imaging methods because, unlike radiographs (X-rays,), CT scan and even radioisotope studies, it does not use ionizing radiation. Instead, MRI uses a strong magnet, radio waves and computers to create detailed images of the body. More specifically, lying inside a massive hollow magnet, a patient is exposed to short bursts of powerful non-ionizing radio  wave energy, directed at protons, the nuclei of hydrogen or water atoms, in the body. Radio signals generated by first "exciting" and then "relaxing" those protons, are computer-processed to form digital images, reflecting different types of tissue. Typical MRI examinations consist of multiple imaging sequences, each lasting from two to 15 minutes. While these techniques continue to evolve, the beauty of current MRI is that it can be tailored for any clinical question.

For generally healthy individuals, MRI poses no risk. But patients with pacemakers, aneurysm clips, ear implants and metallic pieces in vital body locations cannot be imaged safely.

What is angiography?

Angiography is an X-ray procedure which provides a complete examination of the arterial supply to the kidney, including a view of the aorta and renal arteries as well as mass lesions. In this study, a catheter is used to inject contrast dye into the major blood vessel in the body. Arterial access is usually gained through the right femoral artery. Throughout the dye injection procedure, X-ray images are taken at a rapid rate because the high pressure of the arterial blood flow will cause the dye to disappear quickly.

Complications may include reaction to the contrast dye, bleeding and injury to the artery.

What is venography?

A urologist may call for inferior vein cavography or X-ray imaging of the veins using radiopaque substances if he or she suspects a patient has a clot (thrombosis).

With catheterization of the renal veins, contrast dye is injected and X-ray images are taken within seconds. One impediment for a satisfactory view of the renal veins is that blood flow from the kidney washes out the injected contrast dye. Epinephrine injected prior to the contrast dye may allow better images. Venography is being done less often as more non-invasive methods such as Doppler ultrasonagraphy have been developed.

Complications are rare and usually limited to leakage of blood and contrast dye around the site of the injection. Also, there is the risk of an allergic reaction to the solution.

What is radionuclide imaging?

Also known as nuclear medicine imaging (NMN), radionuclide imaging is an excellent diagnostic tool because it shows not only the anatomy of an organ or body part, but the function of the organ as well. This additional "functional information" allows radionuclide imaging to diagnose certain diseases and various medical conditions much sooner than other medical imaging examinations.

For this test, urologists inject a radioisotope "tracer," a molecule to which a radioactive atom or "tag," has been attached so that it can be followed through the kidney system with special detectors. While the isotopes such as iodine-123 or 131 are often used, many urologists prefer (-99m) technetium because of its superior imaging characteristics and short half-life. It is attached to DTPA (diethylenetriamine-pentaacetic acid) for imaging patients with normal kidney function or MAG3 (mercaptoacetyltriglycine) for those with kidney impairment. In either case, a series of X-ray images of the kidneys are obtained to evaluate blood flow as well as function.

Radionuclide imaging is considered safe since it does not carry the risk of toxicity or allergic reaction found with contrasting dye. Also since the radioisotope tracer projects less radiation than an X-ray, patients are not at increased risk from exposure.

What is cystography?

Cystography uses X-rays and iodine contrast dyes to assess the bladder for rupture, vesicoureteral reflux, or demonstrate a vesical fistula. vesicoureteral reflux, urine backflow caused by an obstruction or congenital defect.

During past decades, urologists have added a nuclear version of this test, called a radionuclide cystogram, to their arsenal, particularly to study reflux. Many physicians believe this technology is a better surveillance tool for tracing the migration of urine through the urinary tract because it uses less radiation exposure (some estimates suggest up to 200 times) than the conventional voiding cystogram. It also does not rely on fluoroscopy, a radiological technique for visually examining the tissue, which contributes to the higher radiological exposures.

The doctor will insert a catheter through the patient's urethra and into the bladder. The contrast medium is then injected through the catheter into the bladder. X-ray pictures are taken at various stages of filling, from various angles, to visualize the bladder. Additional films are taken after drainage of the dye. The procedure takes about an hour and a half and the patient may be asked to wait while films are developed.

In surveying the bladder and urinary tract for vesicoureteral reflux, the urologist employs the same steps, using the radio-pharmaceutical, to collect continuous images every 10 to 15 seconds. While conventional voiding cystograms are still necessary to evaluate the male urethra for posterior valves and bladder trauma, the majority of reflux studies today are done effectively with radionuclide cystography.

While the risks are low, patients may experience urinary tract infections from the catheter, and, in rare circumstances, damage to the urethra, bladder or nearby structures.

What are bone scans?

Bone scans are routinely performed to see if prostate and bladder cancer has advanced. Although the number of bone scans has decreased over the years, these studies are especially helpful in assessing patients with advanced urologic cancers.

In these studies, a radionuclide is administered into the body. Over a period of hours, images are obtained of the bones in the body. Absorption of the radionuclide in a specific area may indicate trauma or the possibility of cancer.

In general, there is no real risk involved. In rare instances, you may have an allergic reaction to the liquid injected.


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Information provided by the American Urological Association.