Most kidney stones pass on their own, but how long that takes and whether you need medical help depends almost entirely on the stone’s size. Stones smaller than 5 mm pass naturally about 65% to 98% of the time, while stones 6 mm or larger often need a procedure. The good news: you have several options at every stage, from speeding up natural passage to dissolving certain stones with medication to minimally invasive surgery.
Size Determines Your Path Forward
The single most important factor is how wide your stone is in millimeters. A CT scan (the gold standard for kidney stones, used in over 70% of emergency diagnoses) gives your doctor a precise measurement. Here’s what the numbers mean for your chances of passing the stone without a procedure, based on a 20-week follow-up study in European Radiology:
- Under 3.5 mm: 98% pass on their own
- 3.5 to 4.4 mm: 81% pass on their own
- 4.5 to 5.4 mm: 65% pass on their own
- 5.5 to 6.4 mm: 33% pass on their own
- 6.5 mm or larger: only 9% pass on their own
If your stone is small enough to pass, the strategy is managing pain and helping it move along. If it’s too large, you’re looking at medication to shrink certain types or a procedure to break it up or remove it.
Helping a Small Stone Pass Faster
For stones 10 mm or smaller, current guidelines from the American Urological Association recommend trying to pass the stone with the help of an alpha-blocker medication. This type of drug relaxes the smooth muscle lining your ureter (the tube between your kidney and bladder), giving the stone more room to travel through. The typical course lasts about 30 days, and it can meaningfully improve your odds of avoiding surgery.
While you wait, drinking enough fluid to produce 2 to 2.5 liters of urine per day keeps things moving. That translates to roughly 2.5 to 3 liters of water daily, though the exact amount varies by your body size, activity level, and climate. Staying well-hydrated dilutes your urine and helps push the stone downward.
Pain management matters too. Kidney stone pain comes in waves as the stone shifts and the ureter spasms around it. Over-the-counter anti-inflammatory pain relievers are typically the first line. If your pain is manageable and you can keep fluids down, passing the stone at home is a reasonable plan, but keep a strainer handy so you can catch the stone for lab analysis. Knowing the stone’s composition helps prevent the next one.
Dissolving Uric Acid Stones
One type of kidney stone can actually be dissolved without surgery: uric acid stones. These stones form when urine is too acidic, and they’re invisible on standard X-rays (though a CT scan picks them up). By taking a medication that makes your urine less acidic, typically potassium citrate, you can dissolve them over weeks to months.
In one clinical study, complete dissolution occurred in some patients within six weeks, while others needed four to six months of continued treatment. This approach works only for uric acid stones that aren’t blocking your ureter, so your doctor needs to confirm the stone type first. Calcium-based stones, which account for the majority of kidney stones, cannot be dissolved this way.
When You Need a Procedure
If your stone is too large to pass, hasn’t moved after a reasonable waiting period, or is causing complications, you have two main surgical options for stones in the ureter.
Shockwave Lithotripsy
This is the least invasive option. A machine sends focused sound waves through your body to break the stone into smaller fragments that you then pass naturally. It’s done on an outpatient basis and usually doesn’t require general anesthesia. The trade-off is that it’s less effective in a single session. In a large randomized trial, about 22% of patients who had shockwave lithotripsy needed additional treatment afterward, and some stones require multiple sessions to fully break apart.
Ureteroscopy
A thin scope is passed through your urethra and bladder up into the ureter, where the surgeon can grab the stone directly or break it up with a laser. This is done under general anesthesia as a day procedure (you go home the same day). It’s more effective in one shot: only about 10% of patients needed further treatment in the same trial. However, the recovery is slightly more involved, and there’s a higher risk of minor complications compared to shockwave lithotripsy.
For very large stones lodged in the kidney itself (typically over 2 cm), a third option called percutaneous nephrolithotomy involves making a small incision in the back to access the kidney directly. This is less common and reserved for stones too big for the other approaches.
Asymptomatic stones that aren’t blocking anything present a different decision. Current guidelines say either active monitoring or pre-emptive removal are reasonable, and the choice depends on stone size, location, and your personal risk factors.
Preventing the Next Stone
About half of people who form a kidney stone will get another one, so prevention is worth taking seriously. The most impactful habit is sustained hydration, aiming for that 2 to 2.5 liters of daily urine output long-term, not just during an active episode.
For calcium oxalate stones (the most common type), dietary calcium actually helps prevent stones rather than causing them. This sounds counterintuitive, but calcium from food binds to oxalate in your gut before either substance reaches your kidneys. When you eat too little calcium, more oxalate gets absorbed into your bloodstream and ends up in your urine, where it can crystallize into stones. Aim for 300 to 400 mg of calcium with each meal, ideally from food sources rather than supplements.
Limiting high-oxalate foods also helps. Spinach, rhubarb, beets, nuts, and chocolate are among the highest sources. You don’t need to eliminate them entirely, but pairing them with calcium-rich foods reduces the amount of oxalate your body absorbs. Reducing sodium and animal protein intake also lowers stone risk, since both increase the concentration of stone-forming minerals in your urine.
Symptoms That Need Immediate Attention
While most kidney stones are painful but not dangerous, certain symptoms signal a potential emergency. Seek care right away if you experience pain so severe you can’t sit still or find a comfortable position, pain with fever and chills (which may indicate infection behind a blocked stone), persistent vomiting that prevents you from staying hydrated, blood in your urine, or difficulty passing urine at all. A stone that blocks urine flow combined with infection can become a serious situation quickly, so these warning signs shouldn’t wait.