Introduction
Have you ever felt a pain so sharp it left you doubled over and struggling to breathe? For many people with kidney stones, this is their reality. The good news is that modern medicine offers several treatment options. One of the least invasive approaches is Medical Expulsive Therapy (MET).
This guide explains MET in simple terms. You’ll learn how it works, who it helps, and what to expect if your doctor recommends it. Whether you’re dealing with kidney stones now or want to be prepared for the future, this information will help you make better healthcare decisions.
What Is MET and Why It Matters
Kidney stones hurt—a lot. About 1 in 11 Americans will get them at some point. Small stones often pass on their own. Larger ones may need surgery.
Medical Expulsive Therapy (MET) is a simple approach. It uses meds to help stones pass more easily through your body. This means less pain and often no need for surgery.
Let’s explore how MET works, who it helps, and what you should know if you have kidney stones.
How MET Works
MET uses meds to relax the tubes (ureters) that connect your kidneys to your bladder. When these tubes relax, stones can move through them more easily.
Dr. Rachel Morrison, a kidney stone expert, explains it simply: “Think of your ureter as a straw. When a stone gets stuck, the straw squeezes around it. MET helps the straw relax so the stone can slide through.”
These meds work in several ways:
- They relax the muscles in your ureter
- They reduce swelling around the stone
- They help ease your pain
- They increase pressure to push stones along
Medications That Help Pass Stones
Alpha Blockers
Alpha blockers are the most common MET meds. They work by relaxing the muscles in your ureter.
Tamsulosin (Flomax) is the one doctors prescribe most often. Studies show it can boost your chances of passing a stone by 30-60%.
Other alpha blockers include:
- Alfuzosin (Uroxatral)
- Doxazosin (Cardura)
- Silodosin (Rapaflo)
- Terazosin (Hytrin)
Calcium Channel Blockers
These meds also relax muscle tissue by blocking calcium.
Nifedipine was once popular but isn’t used as much now. Research shows alpha blockers work better. Nifedipine improves stone passage by about 19%, while alpha blockers improve it by about 48%.
Anti-inflammatory Drugs
Doctors sometimes add drugs like prednisone to reduce swelling around stones. They might cause side effects, so they’re not used for everyone.
Does MET Really Work?
How well MET works depends on a few key factors:
Stone Size
Research shows MET works best for stones between 5-10mm:
- Tiny stones (under 5mm): These often pass on their own, with or without MET
- Medium stones (5-10mm): MET can increase passage rates from 50% to 80%
- Large stones (over 10mm): These rarely pass even with MET; surgery is usually needed
Stone Location
Where the stone is stuck matters a lot:
- Lower ureter (close to bladder): Highest success (70-85% with MET)
- Middle ureter: Good success (50-70% with MET)
- Upper ureter (near kidney): Lower success (30-50% with MET)
Dr. James Chen at Mayo Clinic notes: “MET works best for stones near the bladder. This area has more of the receptors that these meds target.”
What Studies Show
Research on MET has been mixed. A big study in 2015 questioned how well it works. But newer research, looking at over 3,800 patients, found MET does help—especially for stones between 5-10mm.
Most urologists now recommend MET as a first option for the right patients with the right stones.
Who Should Try MET?
MET isn’t right for everyone. You’re most likely to benefit if:
- Your stone is 5-10mm in size
- Your stone is in the middle or lower part of your ureter
- Your kidneys work well
- You don’t have an infection or complete blockage
- You can check in with your doctor regularly
You should NOT use MET if you have:
- A severe infection
- A completely blocked urinary tract
- Unbearable pain
- Only one kidney with a blockage
- Pregnancy (some MET meds aren’t safe)
- Very low blood pressure
What to Expect During MET Treatment
If your doctor suggests MET, here’s what will happen:
- Imaging tests to confirm your stone’s size and location
- Assessment to see if MET is right for you
- Prescription for an alpha blocker in most cases
- Pain meds to keep you comfortable
- Instructions to drink plenty of water (8-10 glasses daily)
- Regular check-ups to see if the stone is moving
- Straining your urine to catch the stone when it passes
- A backup plan if the stone doesn’t pass within 2-4 weeks
Dr. Susan Roberts from Cleveland Clinic advises: “We usually give MET about 2-4 weeks to work. After that, waiting too long might cause more problems.”
Possible Side Effects
MET meds are generally safe, but they can cause some side effects:
Alpha Blockers May Cause:
- Dizziness (most common)
- Low blood pressure when standing up
- Changes in ejaculation for men
- Stuffy nose
- Headache
- Feeling tired
Calcium Channel Blockers May Cause:
- Swelling in legs
- Headache
- Flushing
- Dizziness
- Constipation
Serious problems are rare but can include severe drops in blood pressure or allergic reactions.
Tips to Help Stones Pass
Along with MET meds, these strategies can help:
Drink More Water
Aim for 8-10 glasses daily to flush your system.
Stay Active
Light exercise might help move stones along.
Use Heat
A heating pad on your side can ease pain and muscle spasms.
Watch Your Diet
Based on your stone type, your doctor might suggest:
- Calcium stones: Less salt, fewer oxalates
- Uric acid stones: Fewer high-purine foods
- Infection stones: Treating the underlying infection
When MET Doesn’t Work
If your stone doesn’t pass in 2-4 weeks, you might need:
Shock Wave Treatment (ESWL)
Sound waves break up stones so they can pass more easily.
Scope Procedure (Ureteroscopy)
A thin tube with a camera goes through your urethra and bladder to reach and remove the stone.
Surgery (Percutaneous Nephrolithotomy)
For larger stones, doctors make a small cut in your back to remove the stone.
New Research and Hope
MET keeps getting better:
Combination Treatments
Researchers are testing alpha blockers plus other meds to see if they work better together.
Personalized Approaches
Future treatments might be tailored to your specific needs based on your genes.
New Medications
Scientists are working on new drugs with fewer side effects.
A 2023 study is looking at a new type of med that might help with stubborn stones.
Current Research Studies
These ongoing studies are improving MET:
- STONE-PASS Trial – Testing which alpha blocker works best
- MET-PREVENT Study – Seeing if MET can stop stones from forming
- RELAX-URETER Trial – Trying a new med that targets only the ureter
Common Questions About MET
How long until my stone passes with MET? Most stones that will pass do so within 1-2 weeks. If it hasn’t passed in 4 weeks, you’ll likely need a different treatment.
Can I use over-the-counter meds instead? No. MET needs prescription meds that work in specific ways.
Will MET work for all stone types? It works based on size and location, not what the stone is made of. Most studies focus on calcium stones, which are most common.
Can I go about my normal life during MET? Most people can do normal activities. You might need to avoid heavy exercise. Follow your doctor’s advice.
Is MET safe during pregnancy? Many MET meds aren’t recommended during pregnancy. Talk to both your OB-GYN and urologist.
How will I know if the stone passed? You might see it in your urine strainer, feel sudden relief, or need a follow-up scan to be sure. Keep straining your urine even after pain goes away.
The Bottom Line
MET offers a simpler way to treat kidney stones without surgery. For the right patients with the right stones, it works well—especially for stones between 5-10mm in the lower ureter.
While it won’t work for all stones, MET has become a standard first option. It reduces the need for more invasive treatments.
If you think you have kidney stones, see a doctor right away. They can tell you if MET might help you.