From the Guidelines
Nephrologists should primarily use ultrasound as the initial imaging modality to evaluate kidney structure and function, due to its safety, accessibility, and lack of radiation or contrast. This approach is supported by recent guidelines, including those from the American College of Radiology, which recommend ultrasound as the first-line imaging technique for unspecified acute kidney injury (AKI) and chronic kidney disease (CKD) 1. The choice of imaging modality depends on the clinical question, with other modalities such as CT scans, MRI, nuclear medicine studies, and angiography being used in specific situations. For example, CT scans with or without contrast are useful for evaluating kidney stones, tumors, and vascular abnormalities, while MRI offers excellent soft tissue contrast without radiation exposure and is valuable for assessing complex cysts, masses, and vascular structures. In certain cases, such as tuberous sclerosis complex, MRI is recommended as the preferred modality for detecting and monitoring kidney lesions 1. However, for most initial evaluations, ultrasound is the preferred first-line imaging modality due to its safety profile and ability to provide valuable structural information without exposing patients to radiation or potentially nephrotoxic contrast agents. In cases of complex clinical presentations or suspected complications, CT scans, particularly with contrast, can provide detailed anatomical information and are sensitive in evaluating the complications of pyelonephritis, as well as detecting urolithiasis and assessing renal perfusion and function 1. Ultimately, the choice of imaging modality should be guided by the clinical question and the need to balance diagnostic accuracy with patient safety and comfort. Key considerations include:
- Ultrasound for initial evaluation of kidney structure and function
- CT scans for complex clinical presentations or suspected complications
- MRI for assessing complex cysts, masses, and vascular structures, or for monitoring kidney lesions in tuberous sclerosis complex
- Nuclear medicine studies and angiography for evaluating kidney function and perfusion, or for interventional procedures.
From the Research
Nephrologist's Imaging Modalities
- Ultrasound is commonly used in nephrology for diagnostic studies of the kidneys and lower urinary tract, as well as to guide percutaneous procedures such as insertion of hemodialysis catheters and kidney biopsy 2.
- Nephrologists must have a thorough understanding of renal anatomy and the sonographic appearance of normal kidneys and lower urinary tract, and be able to recognize common abnormalities 2.
Risks and Benefits of Contrast-Enhanced Imaging
- Contrast-enhanced magnetic resonance imaging (MRI) and computed tomography (CT) have become essential to diagnostic evaluation of many diseases, but it is important to consider the relative risks of the contrast agent, procedural risks, and diagnostic yield of the examination technique 3.
- Nephrogenic systemic fibrosis and contrast-induced nephropathy are potential risks of contrast-enhanced MRI and CT, particularly in patients with impaired renal function 3, 4, 5.
- A multidisciplinary approach is recommended to determine the appropriate approach to cross-sectional imaging for patients with impaired renal function, taking into account the risks and benefits of contrast media 4.
Alternative Imaging Modalities
- Ultrasound can be safely used in patients with acute kidney injury or chronic kidney disease, and ultrasound contrast agents can provide useful diagnostic information in abdominal pathology 5, 6.
- MRI and CT have their own advantages and disadvantages, including the risk of ionizing radiation with CT and the risk of nephrogenic systemic fibrosis with MRI contrast media in patients with renal insufficiency 6.