Your kidneys play a crucial role in filtering waste and process nearly 50 gallons of blood every day. Given the prevalence of kidney cancer, kidney stones, and other kidney problems, early detection is essential. A kidney MRI or renal MRI provides detailed kidney MRI images to detect abnormalities. Some cases require a kidney MRI with contrast for clearer results. This guide covers what a kidney MRI can reveal, how to prepare for an MRI, and its cost, helping you understand when screening for an abnormal kidney MRI is necessary.
What Do Your Kidneys Do?
Your kidneys are a pair of fist-sized, powerful organs found below your rib cage, one on each side of your spine. They are mainly responsible for taking waste and extra water out of your blood, which ultimately ends up as urine2. Your kidneys’ filtration rate, called the glomerular filtration rate (GFR), shows how well your kidneys are working3.
Here’s a bird’s eye view of how your kidneys and the rest of the renal system (anything that has to do with kidneys is called “renal” ) work:
- First, blood with waste enters the kidneys through the renal arteries, large blood vessels that carry blood from the heart to the kidneys. The right renal artery connects to the right kidney, and the left renal artery connects to the left kidney.
- Next, the kidneys clean your blood through millions of tiny blood filters called nephrons.
- Filtered waste from the blood passes through your ureter and goes straight to your bladder for storage. Once your bladder is full, you will feel the urge to release this waste through urine. As a result, urine passes through your urethra.
- Finally, filtered blood exits the kidneys and flows back to the heart through the renal vein.
Another vital kidney function is maintaining homeostasis, or the healthy balance of fluids and minerals in your body. Without this balance, other organs and systems in your body may not work normally4.
Your kidneys also make hormones that help:
- Stabilize your blood pressure
- Keep your bones strong
- Produce red blood cells
If you have impaired kidney function or have renal issues, you may not experience any symptoms during the early stages. As a result, kidney disease or other issues may not be detected right away, and warning signs associated with renal disease often appear when the condition is already in its advanced state. In fact, it’s entirely possible to live with just one kidney5.
For this reason, regular screening of your kidney health and function is vital if you want to be more proactive about your overall wellness. This is where an MRI of the kidney can be helpful.
What Is a “Kidney MRI”?
An MRI of the kidney is a safe and painless procedure that uses radio waves and magnets to obtain 3D images of your kidneys. It can also provide a functional assessment of your kidneys, including information about their GFR, blood volume, perfusion, diffusion, and oxygenation. Your healthcare team will use these images to detect possible issues with your kidney health. MRI scans of your kidneys can help see conditions like kidney cancer, chronic kidney disease, renal vein thrombosis, and the presence of tumors, masses, stones, or infection.
If you’re undergoing renal imaging, you will have an abdominal MRI. There are two types of MRI scans for your kidneys: imaging with or without contrast agents. A contrast agent is a dye or liquid injected into your body to make soft tissues visible during the imaging process. Contrast MRIs use a contrast dye such as gadolinium or iodine. This type of MRI isn’t recommended for individuals who are pregnant, have a documented history of allergic reactions to gadolinium-based contrast agents, or have pre-existing conditions that affect the kidneys.
What Can an MRI of the Kidney Show?
Aside from giving your healthcare team a detailed look at the current state of your kidney and renal function, an MRI of the kidney can also help assess or visualize a number of other issues6.
Structural and Functional Assessments
The size of your kidneys, including the thickness of the cortex area where blood is filtered, provides useful insights into their health. MRI will also reveal scarring of the tissue (the renal parenchyma) or any blockages of the flow of urine, which can lead to acute kidney failure.
Pathological Conditions
MRI can show signs of renal cell carcinoma, the most common type of kidney cancer in adults7, as well as any renal masses or lesions, abnormal growth in the kidney, which could be signs of developing tumours. Similarly, MRI can show signs of kidney infection, kidney stones, or cysts that might indicate the presence of polycystic kidney disease8. Additionally, MRI has shown promise in the functional assessment of kidney transplants9.
Vascular and Inflammatory Disorders
Vascular issues refer to problems with the blood, and an MRI can show the Presence of blood clots in the vein that drains blood from the kidneys, also known as renal vein thrombosis10. Changes in the size of the renal arteries that can impact blood pressure, like renal artery stenosis11 will also appear. MRI can also show signs of kidney damage from conditions like acute tubular necrosis12 and inflammatory diseases like glomerulonephritis13.
Can You See Kidney Stones on an MRI?
MRI can detect large kidney stones, which appear as dark, irregular shapes in conventional MRI images. MRI can also detect some soft tissue abnormalities caused by stones, but CT scans are required to visualize crystals14.
Can an MRI Detect Kidney Cancer?
Kidney cancer is often undetected early due to its deep location. MRI provides high-resolution images to identify small tumors in the kidney, most commonly renal cell carcinoma. It aids in tumor staging, characterization, surgical planning, and monitoring without radiation exposure. High-risk individuals, including those with a family history or genetic conditions, may benefit from MRI. Compared to CT and ultrasound, MRI offers superior soft tissue contrast and safety.
A dye called gadolinium might be used to increase the contrast in the image, and tumours or signs of cancer appear as white or black spots. MRI provides high enough resolution and detail to distinguish kidney cancer histology, aiding with diagnosis15.
When Can Your Healthcare Provider Order an MRI of the Kidney?
Your healthcare provider may order an MRI of the kidney if they suspect that you may have abnormal or impaired kidney function. Discussed below are just a few of the reasons your healthcare provider might want to order an MRI.
Characterization and Staging of Masses and Tumours
Patients with suspected renal tumors found by computed tomography (CT) or ultrasound may receive an MRI examination as part of the investigation program. MRI is used to determine renal cell carcinoma (RCC) subtypes, for example, clear cell RCC or papillary RCC, which will guide treatment16. MRI can also help in staging RCC, understanding how advanced the disease is, and whether it has spread17.
Evaluation of Renal Cysts
If your doctor suspects you have renal cysts, an MRI can be ordered to visualize the kidney and help to classify cysts using a system called Bosniak renal cyst classification18. This aids in understanding risks and planning treatment19.
Assessment of Renal Artery Stenosis
If you have high blood pressure that won’t lower, an MRI might be ordered to understand if you have renal artery stenosis, a narrowing of the arteries that supply blood to the kidney20.
Tracking Kidney Disease
Patients with kidney disease might undergo MRI to track the progression of the illness, for example from acute to chronic disease21.
Pre-transplant Evaluation
MRI can be used to evaluate kidney function of donors after a transplant22.
Signs of Kidney Problems
In his clinical practice, Dr. Joseph Vassalotti, chief medical officer at the National Kidney Foundation, recommends watching for these 10 possible signs that you may have kidney problems23:
- Feeling more tired than usual and having trouble concentrating
- Trouble sleeping
- Dry, itchy skin
- Feeling the need to urinate more often
- Foamy urine
- Blood in the urine
- Persistent puffiness in the eyes
- Swollen feet and ankles
- Poor appetite
- Cramping muscles
Visualizing Kidney Health: MRI vs. CT Scan
MRI vs. CT Scan
Both MRI scans and CT scans can provide detailed imaging of the kidneys. They are both non-invasive, painless, and proactive ways to help detect signs of potential damage or disease. The main difference lies in how each scan obtains the images of the inside of your body. MRI combines radio waves and a magnetic field, while a CT scan uses ionizing radiation in the form of X-rays.
It is worth noting that an MRI may be better at providing images of soft-tissue contrast and flow of bodily fluids such as kidney perfusion. On the other hand, a CT scan is often preferred for the identification of specific types of cancers. Both MRI scans and CT scans can be used to identify the best biopsy site for cancer diagnosis.
Kidney MRI Imaging
Risks Associated With an MRI of the Kidney
While an MRI of the kidney is a safe procedure, it may carry some risks. You’ll often hear that the radio-frequency energy used during an MRI scan could result in the body heating up, especially during long MRI scans24. However, modern MRI machines can shut down as soon as they detect overheating.
In MRI scans, a contrast dye such as the gadolinium-based agent is introduced into the body through an intravenous (IV) injection. While these dyes are usually very safe, they may cause a problem for individuals with compromised or impaired kidney function. For example, nephrogenic systemic fibrosis (NSF) is an extremely rare but serious complication25. NSF is often characterized by thickening and tightening of the skin, common in patients with renal disease. Patients may also experience muscle weakness and bone pain. Symptoms can begin days, months, or even years after injection of the contrast material.
In summary, an MRI of the kidney is non-invasive and typically safe for most patients. MRI scans have been around since the 1980s, and safety standards are set in place to reduce risk as much as possible.
How Much Does an MRI of the Kidney Cost?
Abdominal MRI, which includes the kidneys, has an average cost of $1,600 to $7,600 in the U.S26.
You’re likely to pay out of pocket if you’re planning an elective MRI for preventative screening.
How to Prepare For an MRI of the Kidney and How Long Does It Take?
How Can I Prepare for a Kidney MRI
Ask your healthcare provider for specific instructions before your MRI.
To prepare for your MRI:
- Remove all metallic objects like jewelry before your procedure. Let your healthcare team know about metallic implants or pacemakers. The same goes for tattoos or cosmetics which may contain metallic substances.
- Limit fluid intake at least 1 to 2 hours before your MRI. This will help avoid frequent restroom breaks in the middle of the procedure.
What Can I Expect During a Kidney MRI?
Some scans require a contrast agent injection to enhance image clarity, which can cause mild side effects like nausea or headaches and may be unsafe for those with severe kidney disease. MRI scans are non-invasive and painless and will not impact kidney function. While MRI scans are painless, sedatives can be provided for claustrophobic patients, and you’ll need help to get home if you take them. Young children may need anesthesia to remain still.
The procedure involves lying on a motorized bed inside a short, open-ended cylinder while a radiographer operates the scanner from another room. You will lie down and enter into the machine feet first. The machine will make some loud noises intermittently, like humming and banging. You can communicate with the technician via intercom, and a companion may stay with you if they follow safety guidelines.
How Long Does a Kidney MRI Take?
MRI scans usually take 30 to 60 minutes.
Take a Preventative Approach to Your Kidney Health
An Ezra MRI is ideal for patients who want to be proactive about their kidney health. Think of the screening as an additional part of your routine health screenings, such as mammograms, Pap smears, and regular blood screenings. Regular kidney screenings present an insight into the overall health of your kidneys and may provide you with early warning signs of potential problems.
However, if you’re currently experiencing symptoms or undergoing treatment for an existing condition, a preventative MRI may not be for you, and you ought to consult with your healthcare provider.
If you’re ultimately interested in learning more about your kidney health with ezra, consider booking a scan or gifting a scan to a loved one. To ask questions and find out whether ezra might be the right fit for you, schedule a call with one of our team members.
