Introduction:
CT (Computed tomography) urography or urogram is a medical imaging technique used to detect the function and abnormalities of the urinary tract, which includes the urinary bladder, kidneys, and ureter (a pair of tubes that carries urine from the kidneys to the bladder). CT urography is commonly used in the diagnosis of conditions such as hematuria, kidney or gall bladder stones, and cancer of the urinary tract.
What Is Hematuria?
Hematuria is the medical term that means the presence of blood or blood cells in the urine. Hematuria is classified into two types:
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Gross Hematuria - The presence of blood in the urine is also called visible hematuria.
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Microscopic Hematuria - Blood in the urine is not visible, which will be viewed under a microscope only. The presence of more than three red blood cells found in centrifuged urine per high power field microscopy (>3 RBC/HP) is considered hematuria. Microscopic hematuria is considered a sign, not a symptom.
What Are the Causes of Hematuria?
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Urinary tract stones.
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Clotting disorders such as hemophilia (a genetic disorder in which blood does not clot properly).
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Polycystic kidney disorder (a genetic disorder in which several fluid-filled sacs are developed in the kidney).
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Menstruation (the normal process of shedding blood and lining tissues of the uterus every month).
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Vigorous exercise.
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Endometriosis (a disorder in which tissues similar to the uterus lining grow outside the uterus).
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Sickle cell disease (a disorder that alters the regular shape of red blood cells that affects the blood flow in the body).
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Bladder cancer.
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Upper urinary tract urothelial cell carcinoma [UUT-UCC] (a cancer of the ureter lining or inner lining of the kidneys).
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Renal cell (kidney) cancer.
How Does CT Urography Produce Images on the Screen?
Computed tomography utilizes X-rays to visualize the internal body structures, which are then processed into images by a computer. Once the patient is within the CT unit, these X-rays rotate around the body, providing an array of images. The advantage of this procedure is the ability to produce images from multiple angles. The images created are two-dimensional, which the computer processes and arranges to obtain three-dimensional pictures of the urinary tract.
What Factors Should Be Considered While Recommending CT Urography in Hematuria Patients?
CT urography is advised for hematuria patients based on two factors: visibility of blood in the urine and age factor. CT urography is highly accurate in the diagnosis of hematuria in urothelial cell carcinoma (UCC) and largely prevents the possibility of false-positive results. Unenhanced CT is advised for patients younger than 40 years old with microscopic hematuria with a low risk for UCC. Unenhanced CT is also recommended for patients younger than 40 years old with visible hematuria and low risk for UCC. Enhanced CT urography is advised in patients older than 40 years old with visible hematuria and high risks for urothelial cell carcinoma (UCC).
What Are the Instructions Given to Hematuria Patients Before CT Urography?
Before the CT urography scan, the patient is advised to take water for the hydration of the kidneys and the distention of the urinary bladder and ureter. Patients may be asked to walk around the room or roll on the procedure table, which helps in the mixing of contrast material and urine. For some patients, Furosemide or saline is administered through an intravenous line (IV) which encourages the flow of urine.
How Is CT Urography Performed in Hematuria Patients?
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Straps may be used to hold the patient in the required position. Infants and children may need sedation as they may be unable to remain still throughout the procedure though certain high-speed scanners may benefit the children. Pediatric patients may generally be accompanied by their parents. However, for safety reasons, the accompanying adults must wear a lead apron to prevent radiation exposure.
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Movement during the scan may affect the quality of the images. Non-contrast CT of the kidneys is taken to find out the renal calculi. Some patients may require contrast materials (a special dye) which depends on the type of the exam.
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A contrast material (iodine-based) is administered into the body through an intravenous line (IV) with a high-resolution nephrogenic phase and a delayed excretory phase (five to ten minutes) helps in detecting tumors and filling defects. When the dye is injected, the patients may feel slight warmth throughout the body.
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Once the patient is placed in the appropriate position, the table would slowly slides within the CT unit for scanning. Patients will most likely go through the machine several times. Depending on the type of CT, patients may be asked to hold their breath for a few seconds to get better images. Any motion, including breathing and body movements, may lead to artifacts in the images.
What Are the Protocols Followed in CT Urography?
CT urography protocols are classified based on the number of the bolus of contrast materials used. They are:
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Single Bolus- Single bolus is recommended for hematuria patients with increased risk of UUT-UCC, renal stones, and cancer. It involves three series of images: an unenhanced series for stone detection, a nephrogenic series for renal mass detection, and excretory series for UUT-UCC detection.
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Double Bolus- It is recommended for follow-up in patients with bladder cancer. In a double bolus, the contrast material available for the nephrogenic phase and excretory phase is less than in a single bolus. Hence it does not show the renal carcinoma and UUT-UUC clearly.
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Triple Bolus- It is recommended for the assessment of kidney donors and patients who had percutaneous nephrolithotomy procedures. The volume of contrast material used in this procedure may split, and it affects the accuracy of the image. Hence, it is not recommended for investigation in hematuria patients.
Conclusion:
CT urography replaces other imaging techniques in the detection of patients with hematuria in UCC because of its accuracy in the excretory phase. For patients with visible hematuria, CTU is the first line of diagnostic tests. Traditionally, hematuria is diagnosed with an intravenous pyelogram. It is now replaced by CT urography because the accuracy rate of CT urography is more than intravenous pyelogram (IVP) in microscopic hematuria.
