Kidney tumor ablation (cryo or microwave)
A treatment that destroys a small kidney tumor in place by freezing or heating it through thin needles placed through the skin, using CT or ultrasound pictures to guide them.
Also called renal cryoablation, kidney cryoablation, cryotherapy of kidney tumor, microwave ablation, MWA, radiofrequency ablation, RFA, thermal ablation
- Where
- Hospital CT or interventional radiology suite, or an operating room
- Anesthesia
- General anesthesia or deep sedation
- Time in the room
- About 1 to 3 hours
- Hospital stay
- Often same day; sometimes 1 night
- Back to normal
- About 3 to 7 days
- Back to work
- Most people return within about 1 week
Overview
Ablation destroys a kidney tumor without removing it. Thin needle-like probes are placed through the skin of your back or side into the tumor, guided by CT scan or ultrasound pictures. The probes then freeze the tumor (cryoablation) or heat it (microwave or radiofrequency ablation). The dead tumor stays in place and slowly shrinks into a scar.
It is done by an interventional radiologist, a doctor who treats disease with needles and imaging, or by a urologist, and sometimes by both together. There are no large cuts, only a few small nicks in the skin. Most people go home the same day or the next morning and are back to normal within a week.
Ablation works best for tumors up to about 3 centimeters (a little over an inch). Guidelines from the American Urological Association list it as an option for these small tumors, especially for people who are older, have other health problems, or need to protect their kidney function. The trade-off is that the tumor is somewhat more likely to survive or come back in the same spot than after surgery, though it can usually be treated again.
A biopsy, which takes small samples of the tumor with a needle, is usually done before or at the start of the ablation. Since the tumor is not removed, the biopsy is the only way to know exactly what was treated.
The parts of your body involved
Your kidneys sit high in the back of your belly, under the lower ribs, behind the bowel. Each is wrapped in fat and a thin covering called Gerota's fascia. Most small kidney cancers bulge from the outer layer, the cortex, often on the back or side of the kidney, where a needle can reach them through the skin of your back. Nearby structures that the team protects include the bowel, the ureter (the tube that carries urine to the bladder), the lung above the upper part of the kidney, and the large blood vessels at the kidney's doorway.
- Tumor
The small mass being treated, usually on the outer edge of the kidney.
- Cortex
The outer layer of the kidney where most kidney cancers start.
- Fat around the kidney
The cushion of fat around the kidney. It helps protect nearby organs from the cold or heat.
- Ureter and drainage system
The urine-collecting funnel and tube. Tumors close to them are harder to treat safely.
- Skin and back muscles
The probes pass through these to reach the kidney.
Why it’s done
Your team may suggest ablation when a small tumor needs treatment but surgery carries more risk than it is worth, or when saving kidney function matters most.
- Small tumor
Tumors up to about 3 centimeters respond best, especially ones on the outer edge of the kidney.
- Other health problems
Heart or lung disease, older age, or past belly surgeries can make an operation riskier.
- Protecting kidney function
Ablation usually costs very little kidney function, which matters if you have one kidney or kidney disease.
- Several tumors over a lifetime
People with inherited syndromes may need many treatments over the years, and ablation can be repeated.
- Quicker recovery
Most people are back to normal activity within days rather than weeks.
Other options
- Partial nephrectomy
Surgery that cuts the tumor out and keeps the rest of the kidney. It has the lowest chance of the tumor coming back in the same spot, but a longer recovery.
- Active surveillance (watching with scans)
Many small kidney tumors grow slowly. Regular scans may be a reasonable choice, especially for very small tumors or people with limited life expectancy from other illnesses.
- Radical nephrectomy
Removing the whole kidney. Rarely needed for tumors small enough to ablate.
- Biopsy first
A biopsy as a separate visit can help you decide between watching and treating, and confirms the type before ablation.
Getting ready
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Weeks before
The week before
The day before
The morning of
In the operating room, step by step
Press play or pick a step. Each drawing shows what your surgeon is doing at that moment. Your team may do some steps differently.
1. Getting positioned and going to sleep
You lie face down or on your side on the CT table or operating table, with pads to keep you comfortable. The anesthesia team puts you fully asleep or gives deep sedation through your IV, so you do not feel the procedure.
More detail
Most ablations are done in a CT scanner, which gives clear 3D pictures of the probes and the ice ball. Some are guided by ultrasound alone, or by a combination.
After the operation
Right afterward
- Recovery
You rest for a few hours while nurses check your blood pressure, pulse and the needle sites.
- Urine check
Some blood in the urine for the first day is common. Your team watches it.
- Pain
Most people have a mild to moderate ache in the side or back, managed with acetaminophen and sometimes a short course of stronger medicine.
- Going home
Many people go home the same day once they are walking, eating and urinating. Some stay 1 night, especially after larger treatments.
At home
- Pain
A sore back or side is common for a few days. Use acetaminophen as directed. Ask before taking ibuprofen or naproxen.
- Needle sites
Keep bandages on for 24 to 48 hours. You can shower after that; avoid soaking in a bath for about a week.
- Flu-like feeling
Some people have a low fever, aches and tiredness for a few days after the treatment, called post-ablation syndrome. It usually passes on its own.
- Urine
Pink urine for a day or two can be normal. Drink fluids.
- Numb or tingling skin
A patch of numb, tingling or sensitive skin on the side, groin or thigh can happen if a small nerve was near the treatment. It usually fades over weeks to months.
- Activity
Light activity right away. Avoid heavy lifting and hard exercise for about 1 week.
- Driving and work
No driving for at least 24 hours after anesthesia or while taking opioid pain medicine. Most people return to work within a week.
Recovery timeline
- Day of treatmentAblation
You go home that evening or the next morning.
- Days 1 to 3Sore and tired
Back or side soreness and tiredness; some people feel mildly flu-like.
- About 1 weekBack to normal
Most people are back to normal activity and work. Biopsy results, if taken, are usually back by now.
- About 3 monthsFirst check scan
A CT or MRI with contrast checks that the treated area no longer takes up dye, which means the tumor is dead.
- 6 to 12 monthsSecond check
Another scan confirms the zone is shrinking into a scar.
- Years 1 to 5Yearly scans
Scans continue, often yearly, because the tumor can rarely regrow at the edge, which is usually treatable.
What it feels like
Most people are surprised by how quick the recovery is. The main discomforts are a sore back, sometimes a few days of feeling run down, and the wait for the first scan to confirm it worked.
Choosing ablation over surgery
Some people worry they are choosing the easier option over the best one.
What helpsAsk your team for your own numbers: the chance of the tumor coming back after ablation versus surgery, and whether a second ablation would be possible if it did.
Waking up
A sore back or side, and sometimes a tender spot where the probes went in.
What helpsAsk for pain medicine early and lie in the position that feels best.
The first few days
Feeling run down, achy, or slightly feverish for a day or two is common, especially after larger ablations.
What helpsRest, drink fluids, and take acetaminophen. Call if the fever reaches 101°F (38.3°C) or you feel worse instead of better.
A strange numb patch
Some people notice numb, tingling or oversensitive skin on the side or toward the groin and worry something is wrong.
What helpsThis is usually from a small skin nerve near the treatment and slowly improves. Mention it at your follow-up.
Waiting for the first scan
Since nothing was removed, many people feel unsure whether it worked until the first scan.
What helpsAsk when the scan will be and when you will hear the result. A treated tumor often looks about the same size at first; the key sign is that it no longer lights up with dye.
How well it works
Success means the treated tumor no longer takes up contrast dye on follow-up scans and slowly shrinks into a scar. The tumor does not disappear entirely, which is normal.
- No enhancement on scans
On CT or MRI, a dead tumor no longer brightens with dye. Any brightening at the edge may mean leftover tumor.
- Repeat treatment if needed
If part of the tumor survives or regrows, a second ablation usually treats it. Surgery is another option.
- Biopsy result
The biopsy tells you what was treated. If it showed a benign tumor, your follow-up may be lighter.
- Kidney function
Kidney function usually changes very little. Your team checks a creatinine blood test.
- Long-term scans
Scans continue for at least 5 years, often yearly after the first year.
Risks
Every operation has risks. These are the ones people ask about most, with honest odds where good numbers exist. Your surgeon’s own results matter more than averages.
Common
Expected for a few days.
Common for a day or two.
Often seen on the final scan. Most need no treatment.
Low fever, aches and tiredness for a few days, especially after larger treatments.
Less common
More likely than after surgery. Usually found on follow-up scans and treated with a second ablation.
Uncommon. Rarely a transfusion or a procedure to block a bleeding vessel is needed.
Irritation of a small skin nerve can cause numbness or tingling on the side, groin or thigh, usually temporary.
Treated with antibiotics.
Rare
Can cause a urine leak or later narrowing of the ureter, mostly with tumors near the center of the kidney.
Rare, especially when fluid is used to move the bowel away.
Rare, with tumors near the top of the kidney where the needle passes close to the lung.
Frostbite or burn of the skin along the probe path is rare.
Extremely rare.
Call your care team or go to the emergency room if
- Fever of 101°F (38.3°C) or higher after the first 2 days, or shaking chills at any time
- Bright red urine or clots that do not clear, or trouble urinating
- Feeling faint, a racing heart, or back or belly pain that gets worse instead of better
- Shortness of breath or chest pain (call 911)
- Vomiting that will not stop or a swollen, hard belly
- Redness, swelling or drainage at a needle site
Questions to ask your surgeon
- Is my tumor a good size and position for ablation?
- Will you use freezing or heat, and why?
- Who will do the procedure, and how many have they done?
- Will I have a biopsy first or at the same time?
- Is my tumor close to the bowel, ureter or lung, and how will you protect them?
- What is my chance of needing a second treatment?
- How does this compare with a partial nephrectomy for my tumor?
- Will I be fully asleep?
- Will I go home the same day?
- What scans will I need afterward, and how often?
Words you may hear
- Ablation
- Destroying tissue in place, without removing it.
- Cryoablation
- Killing a tumor by freezing it with very cold probes.
- Microwave ablation
- Killing a tumor by heating it with microwave energy from a probe.
- Radiofrequency ablation
- Killing a tumor by heating it with electrical current from a probe.
- Percutaneous
- Done through the skin with needles, without a surgical cut.
- Interventional radiologist
- A doctor who treats disease using needles, catheters and imaging such as CT or ultrasound.
- Ice ball
- The frozen zone that forms around cryoablation probes, visible on CT and ultrasound.
- Hydrodissection
- Injecting fluid to push nearby organs away from the tumor before treatment.
- Enhancement
- Brightening of tissue with contrast dye on a scan. Living tumor enhances; dead tumor does not.
- Post-ablation syndrome
- A short-lived flu-like feeling after ablation.
Common questions
Is ablation as good as surgery?
For small tumors, long-term cancer control is good with both. The tumor is somewhat more likely to survive or come back in the same spot after ablation, but this is usually caught on scans and treated with a second ablation. Your team can tell you how this applies to your tumor.
Is freezing or heating better?
Both work well for small tumors. The choice depends on the tumor's size and position, nearby organs, and the team's experience.
Will the tumor disappear?
No. The dead tumor stays in place and slowly shrinks into a scar. Success is judged by whether it still lights up with contrast dye, not by whether it is gone.
Can it be done again if needed?
Usually yes. Repeat ablation is common and safe. Surgery is also still possible after ablation, though scar tissue can make it harder.
Will it hurt?
You are asleep or deeply sedated during the treatment. Afterward, most people have a sore back for a few days that is managed with acetaminophen and sometimes a short course of stronger medicine.
Sources this page draws on
- American Urological Association, Renal Mass and Localized Renal Cancer: Evaluation, Management, and Follow-up: AUA Guideline (2021)
- European Association of Urology, EAU Guidelines on Renal Cell Carcinoma
- American Cancer Society, Ablation and Other Local Therapies for Kidney Cancer
- Urology Care Foundation, Kidney Cancer
Written November 2026. This page explains what usually happens. It is not medical advice and does not replace a conversation with your own surgeon, whose plan for you comes first.