Intravenous urography is a radiographic study of theÂ urinary systemÂ using an intravenous contrast agent (dye). Of the many ways to obtain images of the urinary system, the intravenous injection of a contrast agent has been traditionally considered the best, although other modalities, such as computed tomography (CT) or ultrasound, are better for some disease processes. TheÂ kidneys excrete the contrast into the urine, which becomes visible when x ray (radiopaque), creating images of the urinary collection system.
The procedure has several variations and many names, including:
Intravenous pyelography (IVP).
Intravenous urography (IVU).
Antegrade pyelography are different procedure from retrograde pyelography, which injections the contrast agent directly into the lower end of the system. The contrast agent flows backward, so the name "retrograde." Retrograde pyelography is used to better omprove problems in the lower ureters and is the only way to get x rays for the non-functional kidneys
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Nephrotomography, or tomographic slices of the kidneys, is taken by a moving x-ray source emitting x rays onto a film moving in the opposite direction. Images above and below the level of the kidneys are blurred, allowing a more detailed image of the kidneys with no overlying material, such as gas or fecal material.
An intravenous urography is ordered to demonstrate the structure and function of the kidneys, ureters, and bladder. Patients complaining of abdominal pain radiating to the back may require this exam to rule outÂ kidney stones. Hematuria may also be an indication of kidney stones, infection, or tumors. Patients with high blood pressure (hypertension) and recurrent bladder infections may also require an intravenous urography (but hypertension usually is imaged with MRA or nuclear medicine imagery and this exam is done when renal artery stenosis is the suspected cause of refractory hypertension). Sometimes the exam is ordered to evaluate the function of the kidney in a renal transplant patient. The transplanted kidney is located in the iliac fossa, so special films of the pelvis area are done instead of the normal routine views. The radiographic technologist may also be required to take x rays in the operating room when a retrograde pyelogram is ordered by a urologist during a C and P (cystoscopyÂ and pyelography).
A serious complication of an intravenous urography is an allergic reaction to the iodine-containing contrast agent. Severe reactions are rare, but can be dramatic and even lethal. For this reason all radiology departments performing this exam are equipped with emergency drugs and oxygen in the x-ray room itself.
The patient will be required to change into a hospital gown and empty his or her bladder. The x-ray technologist will verify that the patient has followed the bowel preparation and complete a detailed questionnaire on the current medical history of the patient. This includes previous contrast reactions, knownÂ allergies, risks ofÂ pregnancy, and current medications. The x-ray technologist will explain the exam in detail to the patient as well as the risks of the contrast material that will be injected intravenously. All departments require that the patient sign a consent form before the examination is started. The x-ray technologist will relay this information to the radiologist who will decide on what type of contrast will be used. Patients who have had an injection with no reaction can be given less expensive iodinebased contrast, whereas patients who take variousÂ heartÂ medications or those with known allergies orÂ asthma will be injected with a more expensive contrast agent (known as non-ionic contrast) that has fewer side effects. Some departments use the non-ionic contrast exclusively.
The patient will be instructed to lie supine (face-up) on the x-ray table and a preliminary KUB will be done. This is an abdominal view of the kidneys, ureter, and bladder used to verify patient preparation, centering, and the radiographic technique needed to demonstrate all the required structures.
Kidney stones may or may not be visualized on the preliminary film. The x-ray technologist prepares the required amount of contrast to be used depending on the weight of the patient (1 ml per pound). This is normally 50-75 cc of contrast for an average-sized patient. The contrast will be injected all at once (bolus injection) or in some cases, through an intravenous drip. Some radiologists prefer to start an intravenous drip with saline as a precautionary measure while others inject with a small butterfly needle. The needle usually remains in place for 10-15 minutes, in case more contrast is needed or in case drugs need to be administered because of an allergic reaction. Most reactions occur immediately but some can take place 10 or 15 minutes after the injection.
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The first film is taken immediately after the injection to see a detail of the renal outline (nephrogram). Films are usually taken at five-minute intervals depending on the routine of the radiologist. Compression may be applied to the lower abdomen with a wide band to keep the contrast material in the kidneys longer. This creates a more detailed image of the renal collecting system. When the compression and pressure is released after approximately about 10 minutes the contrast material drains quickly and a detailed, filled image of the ureters is obtained. Films are face in the upright or prone (face-down) position may also be ordered to better visualize the lower ureters. Certains departments require routine renal tomographic images to be finish as well when the kidneys are well visualized. This allows the kidneys to be diagnose free of gas or fecal shadows. Sometimes the radiographer requires oblique views of the kidneys or bladder to determine the exact location of calculi (stones). At around 20 minutes after the injection a film centered on the bladder may be required. The x-ray tube is angled a little caudad (towards the feet) so that there is no superimposition of the pubic area of the pelvis over the bladder. The films are shown to the radiologist to be diagnose and if no further films are necessary the patient will be asked to void (urinate) and a post-void film will be taken. The exam can take from 30 minutes to 60 minutes depending on the number of films needed. If the kidney is blocked delayed films may be required to complete the exam.
In order to obtain the best visualization of the kidneys, ureters, and bladder, the intestines must be free of gas and fecal material. Every medical imaging department has their own specific procedure. Mostly the used of laxative such as X-Prep or Dulcolax pills are eaten round 4 p.m. the day preceeding the exam. This is followed with a non- heavy fat-free dinner which is lean meats, mee, white rice, bread with no butter, and tea juice. Fluids are permitted until midnight, after that no food or liquid is allowed until after the intravenous urography is done. Whoever have diabetic are usually done early in the morning to avoid any severe problems. Patients who have had a allergic reaction due to a contrast material can be given a shot of steroids andÂ antihistaminesÂ the day before the exam as well as the morning of the exam. The patient must see and consult with their physician before this is contrast are administered. In patients with known or might have renal failure, lab tests, including BUN and creatinine, may be needr to the IVP.
Contrast agents and drugs:
Typical examples for a 70 kg adult with normal blood urea values (2.5 - 7.5mmol/L.)
Contrast media must be warmed to body temperature before injection.
Typical Exposure Values: (*Dose = Typical Dose from N.R.P.B.)
Tomogram 20â-«Â @9cm
The median cubital vein is punctured with a 19 gauge needle and the warmed (40Â°C)
contrast agent is injected rapidly. Films are then taken at intervals to demonstrate the whole of the renal tract.
RADIOGRAPHIC PROJECTIONS FOR THE IVU
Size Casette: (35 x 43cm)
Patient position: supine full A.P. abdomen to include lower border of
symphysis pubis and diaphragm, to check, abdominal preparation, exposure values
and for any calcifications overlying the renal tract areas.
Supplementary films to determine position of any opacities.
35Â° posterior oblique of the renal areas.
Tomogram of the renal areas at 8-11 cm
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Size Casette: (24 x 30cm)
Patient position: A.P. of the renal areas to show the nephrogram, i.e. the
renal parenchyma opacified by the contrast medium in the renal tubules.
5 Minute film,
Size Casette: (24 x 30cm)
Patient position: A.P. of the renal areas to determine if excretion is
symmetrical or if uptake is poor and a further dose of contrast agent is required.
Compression may be applied in some centres at this point to distend the
pelvicalyceal systems to prove or show any filling defects and a film taken at 10
minutes of the renal areas. Compression can not be used in cases of suspected
renal colic, renal trauma or after recent abdominal surgery.
10 Minute film
Size Casette: (35 x 43cm) (On release if compression has been applied) to
demonstrate the pelvicalyceal systems and the ureters.
25 Minute film (24 x 30cm) 15Â° caudal angulation centred 5 cm above the upper
border of the symphysis pubis to demonstrate the distended bladder.
Post Micturition film
Size Casette: (24 x 30cm) 15Â° caudal angulation centred 5 cm above the
upper border of the symphysis pubis to demonstrate the bladder emptying success, and the return of the previously distended lower ends of ureters to normal.
An allergic reaction to the contrast agent is the primary risk, although kidney damage is also a potential complication. Patients with a possible iodine allergy or a previous reaction to a radiographic contrast agent should inform the x-ray technologist. A detailed history of known allergies, risk of pregnancy, and current medications is required before an intravenous urography. All radiology departments have consent forms that must be signed by the patient before starting the exam. Emergency drug and specific equipments such as antihistamines (Benadryl), adrenaline, and atropine are kept in the x-ray room. All radiography and radiologist must have enough training and education on the specific signs and symptoms of an allergic reaction. A mild reaction include of a skin rash orÂ hives, whereas a more severe reaction includes swelling of the larynx, trouble in breathing, asthmatic attacks, and a severe drop in blood pressure (hypotension).Since x-rays are used during this procedure, it will be a minimal risk due to radiation. This procedure is not done on pregnant women or women who might think they might be pregnant.
A normal intravenous urography indicates no visible abnormality in the structure or function of the urinary system. The radiologist looks for a smooth non-lobulated outline of each kidney, no clubbing or other abnormality of the renal calyces (collecting system), and no abnormal fluid collection in the kidneys that could suggest obstruction. The ureters must contain no filling defects (stones) or deviations due to an adjacent tumor. The bladder must have a smooth outline and empty normally as visualized on the post-void film.
Weird results include hydronephrosis (distension of the renal pelvis and calices due to obstruction) as a result of tumors or calculi (stones). Cysts might be present in the urinary system. A delay in renal process can show or indicate renal disease. An unusual amount of urine in the bladder after voiding may indicate prostate or bladder problems.
Intravenous urography are often done on children to rule out a rapid developing tumor in the kidneys, called a Wilm's tumor. Children are also are expose to infections of the bladder and kidneys due to urinary reflux (return back-flow of urine).
Right Kidney Left Kidney
KUB with contrast. The bladder appears to sit above the symphysis pubis, although its lower portion lies behind it in the pelvic cavity. The appearance is a result of oblique rays at the lower periphery of the beam, which project the symphysis clear of the bladder
Health care team roles
The x-ray technologist must work in conjunction with the doctors and nurses in making sure the patient has not had a previous allergic reaction to a contrast agent. All hospitals have an emergency team ready to react in such a situation, so the technologist must be aware of the procedure to follow when assistance is necessary due to a severe reaction. Information of patient preparation must also reported to the hospital wards. In certain hospitals the radiologist and radiographer are trained to allow togive injections, but if this is not the case nurses may be asked to install an intravenous drip before the patient is brought to the radiology department.
The x-ray technologist must explain the risks of an allergic reaction to each patient even though severe reactions are extremely rare due to the advances made in the preparation of contrast agents. The x-ray technologist explains to the patient that a warm, flushed feeling or a metallicÂ tasteÂ in the mouth are normal reactions in some patients. Breathing instructions are also crucial since the kidneys change position according on the phase of respiration and to prevent motion artifacts. Certain times an emergency patient with renal colic (acute abdominal pain) is asked to urinate using a special filter used to trap small stones. All radiologist and radiographer must be certified and registered. Continued education credits are important remain registered.