MRI UROGRAPHY

MRI Urography is a specialized magnetic resonance imaging technique used to visualize the kidneys, ureters, and urinary bladder in detail. It provides both anatomical and functional information about the urinary tract without the use of ionizing radiation. The procedure can be performed with or without intravenous contrast agents, depending on the clinical requirement. MRI Urography is especially useful for patients who cannot undergo CT Urography due to iodine contrast allergy or radiation concerns. It offers high-resolution multiplanar imaging, which can help detect structural abnormalities, obstructions, tumors, congenital anomalies, infections, and other urinary tract conditions.

Purpose of the examination

• To evaluate structural integrity of the urinary tract.
• To detect urinary tract obstruction or narrowing.
• To identify causes of hematuria (blood in urine).
• To detect kidney stones not visible on other imaging modalities.
• To assess tumors or abnormal growths in the urinary tract.
• To investigate congenital anomalies of the kidneys and ureters.
• To evaluate trauma to the urinary system.

Clinical Indications

• Unexplained hematuria
• Recurrent urinary tract infections
• Known or suspected urinary tract tumors
• Hydronephrosis (swelling of kidneys due to urine backflow)
• Suspected ureteric strictures or blockage
• Kidney or ureteral stones when other modalities are inconclusive
• Complex congenital urinary tract malformations
• Pre-surgical mapping of urinary tract anatomy
• Follow-up imaging in post-surgical or post-treatment cases

Procedure Details

Before the scan

• Patients are screened for MRI safety, especially for metallic implants, pacemakers, or other devices that may be unsafe in the magnetic field.
• Allergic history and kidney function tests may be required if contrast administration is planned.
• Patients are asked to remove all metallic items such as jewelry, hairpins, watches, and credit cards.
• Fasting for 4–6 hours before the scan may be recommended in some protocols.
• In certain cases, patients may be advised to drink fluids before the scan to ensure bladder filling.

During the scan

1. The patient lies on the MRI table, usually in the supine position.
2. A body or phased-array coil is used to acquire images.
3. Non-contrast sequences are obtained first, including T1-weighted and T2-weighted images to evaluate the urinary tract anatomy.
4. If functional assessment is required, a gadolinium-based intravenous contrast may be injected. This allows dynamic imaging during the excretory phase, showing contrast flow through the kidneys, ureters, and bladder.
5. Images are taken in multiple planes, and 3D reconstructions can be created to simulate CT urography-like views.
6. The patient is instructed to remain still, and in some cases, breath-holding may be required for a few seconds to improve image quality.

Techniques used in MRI urography

• Static-fluid MRI urography: Uses heavily T2-weighted sequences to depict urine-filled structures without contrast. Particularly useful in patients with severe kidney impairment or allergy to gadolinium.
• Excretory MR urography: Uses gadolinium contrast to assess both anatomy and function by capturing contrast excretion over time.
• 3D MR urography: Provides volumetric datasets that can be reformatted into different planes and used for virtual endoscopic views of the urinary tract.

Advantages of MRI urography

• No ionizing radiation exposure, making it safer for children, young adults, and patients requiring repeated imaging.
• High contrast resolution allows excellent visualization of both soft tissue and fluid-filled structures.
• Can evaluate both anatomical and functional aspects in one study.
• Superior to ultrasound for detecting small lesions and better soft tissue characterization than CT in certain cases.
• Can be performed without contrast in patients with poor renal function.
• Multiplanar imaging allows for detailed anatomical mapping.

Limitations

• Longer scan time compared to CT, which may cause discomfort for some patients.
• Motion artifacts due to patient movement or breathing can reduce image quality.
• Gadolinium-based contrast is contraindicated in certain patients with severe kidney disease due to risk of nephrogenic systemic fibrosis.
• MRI may not be as sensitive as CT for detecting small kidney stones with low water content.
• Availability and cost may be higher compared to other imaging modalities.

Patient preparation tips

• Wear comfortable, metal-free clothing to the scan.
• Follow fasting or fluid intake instructions given before the scan.
• Inform the MRI team about any implants, prior surgeries, or allergies.
• Remain as still as possible during image acquisition to avoid blurring.
• If claustrophobic, discuss possible sedation with the referring doctor before the scan day.

Interpretation of MRI urography

Radiologists evaluate the images for:

• Kidney size, shape, and position.
• Corticomedullary differentiation and parenchymal signal characteristics.
• Dilatation or obstruction of collecting systems.
• Ureteric course, caliber, and any points of narrowing.
• Bladder wall thickness, contour, and presence of masses.
• Presence of filling defects suggestive of stones or tumors.
• Contrast excretion patterns to assess renal function.

In cases with dynamic contrast studies, time-resolved imaging allows plotting of excretion curves and comparison between both kidneys.

Applications in specific conditions

Hydronephrosis and obstruction: MRI urography can identify the site and cause of obstruction, whether due to stones, strictures, or masses.

Tumors: MR urography can show masses in the kidneys, ureters, or bladder, define their extent, and detect spread to surrounding tissues.

Congenital anomalies: Conditions like duplicated collecting systems, ectopic ureters, or ureteropelvic junction obstruction can be mapped clearly before surgery.

Postoperative evaluation: Can assess surgical reconstructions, detect anastomotic strictures, or evaluate complications such as leaks.

Trauma: Detects urinary tract injuries, extravasation of urine, and associated soft tissue damage.

Safety considerations

• Gadolinium contrast is generally safe but should be used cautiously in patients with reduced renal function.
• Static-fluid MR urography is a safe alternative in patients where contrast is contraindicated.
• The magnetic field is not harmful itself, but certain implanted devices may be unsafe; full safety screening is essential.

Conclusion

MRI Urography is a powerful, non-invasive imaging tool that combines detailed anatomical visualization with functional assessment of the urinary tract. It is particularly valuable in patients for whom radiation or iodine-based contrast media are unsuitable. By offering both static and dynamic imaging techniques, MRI Urography can accurately detect, localize, and characterize a wide range of urinary tract disorders, from obstructions and tumors to congenital malformations. With its multiplanar capabilities and excellent soft tissue resolution, it plays an important role in diagnosis, treatment planning, and follow-up for urinary tract conditions. While interpretation requires expertise and there are certain limitations, the benefits make it an essential modality in modern urological imaging.