Magnetic resonance urography

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Magnetic Resonance Urography (MRU) is a specialized form of magnetic resonance imaging (MRI) used to evaluate the urinary tract, including the kidneys, ureters, and bladder. MRU provides detailed images that help in diagnosing various urological conditions without the use of ionizing radiation.

Principles

Magnetic Resonance Urography utilizes the principles of magnetic resonance imaging, which involves the use of strong magnetic fields and radio waves to generate detailed images of the body's internal structures. MRU specifically focuses on the urinary tract, using sequences that enhance the visibility of the urinary system.

Indications

MRU is indicated in several clinical scenarios, including:

• Evaluation of hydronephrosis
• Assessment of congenital anomalies of the urinary tract
• Detection of urinary tract obstruction
• Investigation of hematuria
• Preoperative planning for urological surgery
• Assessment of renal masses

Technique

The MRU procedure involves the following steps:

Patient Preparation

Patients are usually advised to fast for a few hours before the procedure to reduce bowel gas and improve image quality. They may also be asked to drink water to ensure the bladder is adequately filled.

Imaging Protocol

MRU typically includes the following sequences:

• T1-weighted images for anatomical detail
• T2-weighted images for fluid-filled structures
• Post-contrast images if gadolinium contrast is used

Contrast Enhancement

Gadolinium-based contrast agents may be used to enhance the visibility of the urinary tract, particularly in cases where vascular structures need to be delineated.

Advantages

MRU offers several advantages over other imaging modalities:

• No exposure to ionizing radiation
• Superior soft tissue contrast
• Ability to acquire images in multiple planes
• Non-invasive nature

Limitations

Despite its advantages, MRU has some limitations:

• High cost compared to other imaging techniques
• Limited availability in some regions
• Contraindications in patients with certain implants or metallic foreign bodies

Clinical Applications

MRU is used in various clinical applications, including:

Pediatric Urology

In pediatric patients, MRU is particularly useful for evaluating congenital anomalies such as ureteropelvic junction obstruction and vesicoureteral reflux.

Oncology

MRU can help in the assessment of renal and bladder tumors, providing detailed information about the extent and nature of the lesions.

Obstructive Uropathy

MRU is effective in identifying the site and cause of urinary tract obstructions, aiding in the management of conditions like ureteral strictures and stones.

Future Directions

Research is ongoing to improve MRU techniques, including the development of faster imaging sequences and better contrast agents. There is also interest in combining MRU with other modalities, such as functional MRI, to provide more comprehensive assessments of renal function.

See Also

• Magnetic resonance imaging
• Urology
• Radiology