Kidney MRI Scan: Info and Get a Scan

The kidneys are a blood-filtering powerhouse. They are vital to extracellular fluid regulation, excretion of waste and toxins, and hormone production. According to research, 2.8 million UK adults have chronic kidney failure (CKF), 1 million of them are unaware they have this disorder. There are different causes of CKF and it can be difficult to identify CKF without an in-depth assessment of the kidneys. Various diagnostic tools can be used to provide a better picture of your kidney function and help lead doctors to a potential diagnosis.

However, not all kidney-related issues result in CKF. Abnormal cell growth or tumours can form in the kidneys restricting blood flow or overall kidney function. If you are experiencing signs of kidney malfunction, your urologist may order an MRI. This tool can identify any abnormalities that could be contributing to the symptoms.

Continue reading as we discuss a kidney MRI procedure, the problems it can detect, and why the procedure might be performed.

What is a Kidney MRI?

A magnetic resonance imaging scan (MRI) is a non-invasive diagnostic tool used to capture images of a specific structure, organ, or area of the body. During a kidney MRI scan, the machine will take images across three planes:

• Axial - From top down
• Sagittal - From one side to the other
• Coronal - From front to back

Each image–called a slice–is an image of the kidney as the machine moves from one side of the plane to the other. This allows the computer to create a three-dimensional recreation of your kidney. A radiologist can then identify any abnormal cell growth, tumours, swelling, or signs of infection.

Types of Kidney MRI

There are various MRI methods used to scan the kidneys. Which one you have will depend on your symptoms and medical history: 

Standard MRI

A standard kidney MRI is used to assess kidney structure without the use of a contrast agent. 

MRI With Contrast

Contrast agents are dyes that are injected into the bloodstream during an MRI scan to highlight the blood vessels and tissues. They help to highlight blood clots, renal masses and renal tumours. 

MR Angiography (MRA)

An MRA, or magnetic resonance angiography scan can be carried out at the same time as a standard MRI scan to specifically highlight the blood vessels of the kidneys and detect blood clots, blockages and renal artery stenosis (see below). 

MR Urography

Magnetic resonance urography is a type of renal MRI scan that looks in detail at the kidneys as well as the bladder and ureters, the tubes that connect the kidneys to the bladder. MR urography is used to help doctors discover the reasons for repeated or severe urinary tract infections (UTIs). 

Functional MRI

A functional MRI, or fMRI, of the kidneys is used to assess kidney function (including blood flow and glomerular filtration rate - how well your kidneys filter waste) rather than the structure alone as in a standard renal MRI. 

Diffusion-Weighted Imaging (DWI)

A DWI MRI is a type of functional MRI that measures how well water moves through the kidneys. 

Dynamic Contrast-Enhanced MRI (DCE-MRI)

A DCE-MRI is a type of functional MRI that measures kidney function and blood flow through the kidneys (called kidney perfusion). 

Magnetic Resonance Spectroscopy (MRS)

Magnetic resonance spectroscopy is a specialised type of renal MRI scan that involves the use of a special surface coil placed over the kidney area to collect data that can be used to analyse the chemical makeup of the tissues within the kidney. This data is then used to assess renal function, which is useful during kidney transplants in both the donor and recipient.

What a Kidney MRI Can Diagnose

A renal MRI scan is used to diagnose (and rule out) a number of kidney health conditions or to look at the overall kidney structure if your doctor suspects you may have an acute kidney injury. Kidney MRI scans also highlight any problems with blood flow through the kidneys (known as kidney perfusion) and are used to assist kidney transplants. You may also have a special renal MRI scan called a functional MRI to measure your glomerular filtration rate, or how well your kidneys filter waste. 

As with any medical condition, early detection is key, so if you have symptoms of renal disease, your doctor may perform a kidney MRI to look for the following in either your right or left kidney, or in both, depending on your symptoms:

• Kidney Stones - Kidney stones are small, hard mineral deposits that can crystallise and build-up in the kidneys causing pain, problems urinating and fever-like symptoms. 
• Tumours - Renal tumours caused by a renal cell carcinoma or other types of kidney cancer are diagnosed and graded using an MRI scan of the kidneys. 
• Cysts - Cysts are fluid-filled sacs that can develop in one or both of the kidneys. They may remain unproblematic, or they may develop into polycystic kidney disease and  cause pain, blood in the urine and kidney damage. 
• Hydronephrosis - Hydropnephrosis causes the kidneys to stretch and swell due to a build-up of urine, causing pain and reduced urination. 
• Pyelonephritis - Pyelonephrosis is a type of kidney infection that, if left untreated, can lead to chronic kidney disease. 
• Renal Artery Stenosis - Renal artery stenosis causes a narrowing of the blood vessels feeding the kidneys, which if left untreated, may result in high blood pressure and kidney damage. 
• Kidney Abscess - Abscesses are caused by infections, leading to a buildup of pus and inflammation. 
• Renal Vein Thrombosis - An infection, chronic kidney disease or an acute kidney injury can lead to blood clots forming in the blood vessels that can cause a blockage called a renal vein thrombosis. This causes a reduction in blood flow to the kidneys, resulting in pain, difficulty passing urine and blood in the urine. 
• Trauma or Injury - Trauma or an acute kidney injury, for example caused by the impact of a car accident, can be assessed and monitored by a renal MRI. A serious acute kidney injury can lead to acute tubular necrosis, a serious condition that results in reduced kidney function.

How an MRI of the Kidneys Works

The body is made up of hydrogen atoms that are easily and temporarily disrupted by the radio waves and magnetic fields used during an MRI scan. 

This temporary disruption cannot be felt, but creates energy. Each tissue, from bones to soft tissues, organs and blood vessels, creates a different level of energy, and these differences are picked up and turned into an image by an MRI scanning computer. 

A radiologist is trained to read these images and in terms of the kidneys, detect abnormalities that suggest disease or injury.

What to Expect at Your Scan

A kidney MRI scan will usually take approximately 10–30 minutes. However, the procedure can take up to 2 hours. The procedure will include:

1. Changing Clothing - You will be brought to a private room to change into a hospital gown. Some clinics allow patients to wear their loose-fitting clothing, each will have its policies. Be sure to remove any metal and jewellery as metallic items can interfere with the results of the scan.
2. Administering Contrast Material - Several kidney MRI scans require a contrast material that will need to be administered through an IV. This will highlight certain areas of the kidney, allowing the radiologist to get a better understanding of what is occurring in your kidneys. It can take time for the material to collect in your kidneys before the scan can begin.
3. Beginning the Scan - You will be instructed to lay down on the MRI table, the radiographer may use pillows or straps to ensure you remain in the correct position. As the table slides you into the hollow tube of the machine, you will hear loud banging noises. This is to be expected.
4. Remaining Still - Although the machine will be loud, it is important to stay as still as possible. Any sudden movements can affect the results of the scan causing a lengthier procedure.
5. Removing Contrast IV - Once the scan is complete and the radiographer is satisfied with the quality of the images, your IV will be removed.
6. Returning to Everyday Activities - Since this is a non-invasive procedure there is no necessary recovery after the procedure. You may feel a little dizzy from laying down for a prolonged period. Some patients who suffer from anxiety or claustrophobia may be administered a mild sedative before the procedure. If this is the case, you cannot operate a vehicle. Therefore an alternate method of transport will need to be arranged.

Equipment Used

An MRI scanner is a large, round doughnut-shaped machine with a table that slides in and out. Depending on the type of kidney MRI that you’re having, there may also be other medical equipment used.

Why Would A Urologist Order an MRI?

If you are experiencing signs of renal distress or failure your urologist may order an MRI. Some of these symptoms include:

• Swellings of extremities
• Back pain around the kidneys
• Shortness of breath
• Blood in stool
• Fatigue or drowsiness
• Changes in the frequency of urination

An MRI will be able to show if the cause of your symptoms is due to lack of blood flow, abnormal growths, or–if applicable–possible transplant rejection.

Can MRI Detect Kidney Problems?

An MRI can be used to see:

• Restricted blood flow
• Tumours
• Lymph nodes
• Diseased vs normal tissue
• Different types of tissue

Radiologists can use MRI images to identify abnormalities in these soft tissues of the kidney. Their findings in conjunction with various physical symptoms can be used to diagnose possible kidney problems.

Is Contrast Material Hard on Kidneys?

The contrast material used, usually gadolinium-based, is mildly radioactive. It allows clearer imagining for certain types of tissue in an MRI scan. It is a safe procedure and complications related to contrast dyes are rare.

In rare cases–less than 2 per cent–the contrast dye can cause nephropathy or the deterioration of kidney function. The effects can be seen 48-72 hours after the dye had been administered. Although frightening this damage can be reversed.

How to Prepare For a Kidney MRI?

Before your procedure, you can expect to fill out a health questionnaire. It is important to identify if you have:

• Metal implants - such as screws, pins, stints, or artificial joints
• Implanted medical devices - such as a pacemaker or defibrillator
• Allergies - particularly to the contrast material or any other medication

You should also inform the clinic if you are pregnant or nursing. Studies have shown no connection between pregnancy and birth defects. However, it is important to provide a comprehensive medical history.

It is not necessary to fast before the procedure. In some instances, your doctor may advise you to drink plenty of fluid before the procedure.

What are the Benefits?

A kidney MRI scan is a quick, painless procedure that’s suitable for the majority of patients. It assists doctors in differentiating between healthy kidneys and those affected by renal disease. Kidney MRIs are also used to diagnose and rule out different conditions as part of routine clinical practice when doctors suspect kidney damage. 

Unlike computed tomography (CT) scans and x-rays, an MRI scan doesn’t use ionising radiation to create images, and therefore doesn’t carry the same, albeit small, risk of radiation exposure. 

Are There Any Risks

The main risk associated with MRI renal imaging is a reaction to the contrast agents used. Patients with renal disease are more at risk of developing an allergic reaction to the gadolinium used in a contrast agent, which can result in a rare but serious condition called nephrogenic systemic fibrosis that causes scarring of the kidneys and impaired renal function. 

If you have a known allergy, your doctor may decide to go ahead without a contrast agent, or use other imaging modalities, such as computed tomography (CT) scanning instead. 

Patients with claustrophobia or who find it difficult to remain still may find an MRI scan overwhelming due to the closed environment of an MRI scanner. Your medical team can provide a mild sedative if you think you may struggle. 

All magnetic metal must also be removed before an MRI scan, including jewelry, watches and hair clips, as they pose a dangerous risk inside an MRI machine due to the magnets used. Metallic devices such as hearing aids must also be removed. If you have any implants such as pacemakers, stents, valves or pumps, let your radiologist know. Newer versions tend not to be made of magnetic metal, but your medical team will be able to test to see if any implants you have will pose a risk. 

What Happens After a Kidney MRI Scan?

Most patients can return home after MRI renal imaging, and carry out their normal duties. If you’ve received a contrast agent, you’ll be asked to remain in the clinic for half an hour following your scan, to monitor you for signs of an allergic reaction. Patients with impaired renal function are more at risk of an allergy to contrast agents, so it’s important to let your radiologist know straight away if you begin to feel breathless, weak, sweaty or generally unwell. 

Getting the Results

Once your radiologist and your referring doctor have assessed the results from your renal MRI, they’ll contact you to discuss your results and if necessary, any treatment options. 

Costs

You can expect to pay between £200 and £500 for a private kidney MRI in the UK. 

The Bottom Line

An MRI is a powerful diagnostic tool that can be integral in identifying potential kidney problems, kidney failure, or even kidney cancer. By providing additional insight, an MRI scan can help doctors prescribe an accurate treatment plan for managing possible kidney disorders.

If you have additional questions, contact us. Our team is here to provide you with any information you may need. Or if you are ready to avoid the NHS wait times, you can schedule an appointment at one of our centres in as little as 5 working days.

References

1. https://myhealth.alberta.ca/Health/aftercareinformation/pages/conditions.aspx?hwid=abk1310
2. https://www.urologyhealth.org/urology-a-z/m/magnetic-resonance-imaging-(mri)
3. https://www.radiologyinfo.org/en/info.cfm?pg=kidneyfailure
4. https://www.kidney.org/atoz/content/Contrast-Dye-and-Kidneys
5. https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/kidney-scan
6. https://www.england.nhs.uk/improvement-hub/wp-content/uploads/sites/44/2017/11/Chronic-Kidney-Disease-in-England-The-Human-and-Financial-Cost.pdf
7. https://www.coloradospineinstitute.com/education/tests/mri/