Blood in the urine, a condition known as hematuria, can be a concerning symptom that prompts a medical evaluation. Hematuria is categorized as either gross, meaning the blood is visible to the naked eye, or microscopic, where blood cells are only detectable under a microscope. When this symptom appears without a clear cause like an infection, imaging studies become necessary to locate the source of the bleeding within the urinary tract. The Computed Tomography (CT) scan has become a primary tool for investigating the kidneys, ureters, and bladder, offering detailed views to help diagnose potential underlying issues.
Required Preparation
Before undergoing a CT scan, patients must follow specific instructions to ensure the clearest images are obtained. A blood test to determine your creatinine level is usually required, particularly if you are over 60, diabetic, or have high blood pressure. This test assesses kidney function, which is necessary because the contrast material used during the procedure is cleared from the body by the kidneys.
Medication review is important, as some drugs can interact with the contrast material. Patients taking metformin are typically instructed to contact their doctor for specific guidance regarding when to stop and restart the drug. You should also inform the healthcare team about any allergies, especially to iodine-based contrast agents or shellfish, as this may prompt a pre-medication regimen.
Preparation involves specific hydration and fasting guidelines. You may be asked to avoid eating for a few hours before the exam, but you are encouraged to drink water to ensure you are well-hydrated. For the CT Urogram, drinking water shortly before the scan helps distend the bladder for better visualization. You will be asked to change into a hospital gown and remove all metal objects, since metal interferes with the X-ray images.
The Scan Procedure and Imaging Technology
The most common imaging technique used to investigate hematuria is a specialized procedure called a CT Urogram (CTU), which focuses on the entire urinary system. This procedure uses X-rays to generate multiple cross-sectional images of soft tissues and bone that are then reconstructed by a computer. The patient lies on a narrow table that moves slowly through the donut-shaped opening of the CT machine while images are acquired.
The procedure involves the intravenous injection of an iodine-based contrast dye through a small tube placed in a vein. This contrast material highlights the structures of the urinary tract—the kidneys, ureters, and bladder—as it is filtered and excreted. When the dye is injected, it is common to experience a temporary sensation of warmth or flushing, and some people notice a brief metallic taste in their mouth.
The CT Urogram is a multi-phase study, meaning images are taken at different times to capture the contrast material as it moves through the system. An initial scan is often performed without contrast to detect dense structures like kidney stones. Subsequent phases capture the dye in the kidney tissue (nephrographic phase) and as it fills the collecting system and bladder (excretory phase), which helps identify masses or structural blockages.
Diagnosing the Source of Blood
The purpose of the CT Urogram is to locate the source of the bleeding and identify issues within the urinary tract. The high-resolution images allow physicians to evaluate the upper tract, including the kidneys and ureters. The scan is highly effective at detecting calcifications and identifying kidney stones (nephrolithiasis) that may be lodged in the kidney or traveling down the ureter.
The CTU is also the most sensitive imaging method for identifying masses or tumors within the kidney tissue and the lining of the upper tract. It can detect renal cell carcinoma and urothelial tumors that line the collecting system. The contrast dye helps delineate these masses from normal tissue.
The scan helps find structural abnormalities, such as hydronephrosis, which is the swelling of a kidney due to blocked urine flow. While the CTU provides excellent visualization of the upper urinary tract, it is less effective for detecting small lesions on the interior of the bladder. Therefore, a procedure called cystoscopy, which involves inserting a camera into the bladder, is often required as a complementary investigation for lower tract issues.
Understanding Your Results and Follow-up Care
Once the CT Urogram is complete, the images are sent to a radiologist, who interprets the findings and generates a report. This report describes the presence or absence of abnormalities like stones, masses, or structural issues in the kidneys, ureters, and bladder. The radiologist then communicates the findings to the doctor who ordered the scan.
Patients generally receive their results within a few days to two weeks. The referring doctor will then discuss the results with you and formulate a plan for follow-up care. If the CTU reveals a positive finding, such as a large kidney stone or a suspicious mass, the next step is usually a referral to a urologist for specialized treatment.
If the scan results are negative and no source of the hematuria is found in the upper tract, the doctor may recommend monitoring or proceeding with a cystoscopy to investigate the bladder. The procedure involves a small amount of ionizing radiation exposure. While the diagnostic benefit generally outweighs this minimal risk, doctors use the lowest possible dose necessary to balance accurate diagnosis with minimizing cumulative exposure.