Most kidney stones smaller than 5 millimeters will pass on their own with enough fluids, pain management, and time. Stones between 5 and 7 mm still pass without intervention about 60% of the time, but anything larger than 7 mm drops below a 50% chance of passing naturally and often needs medical treatment. What you should do depends almost entirely on the size of your stone and how much trouble it’s causing.
Passing a Small Stone at Home
If your stone is 4 mm or smaller, you have roughly a 72% to 87% chance of passing it without any procedure. The single most important thing you can do is drink enough water to produce about 2 to 3 liters of urine per day. This keeps urine flowing steadily through the ureter (the tube connecting your kidney to your bladder) and helps push the stone along. Clear or pale yellow urine is a good sign you’re drinking enough.
For pain, anti-inflammatory medications like ibuprofen or naproxen are the preferred first choice. They work better than opioid painkillers for this type of pain because they reduce the swelling and spasm in the ureter itself, not just the pain signal. A heating pad on your back or side can also help between doses.
For stones larger than 5 mm that your doctor thinks might still pass, a prescription medication originally designed for prostate problems can help. It relaxes the smooth muscle lining the ureter, making the tube wider and the stone easier to pass. A large meta-analysis found this medication increased the stone expulsion rate by about 44% for stones over 5 mm. For stones 5 mm and under, it didn’t make a meaningful difference, so it’s really only worth taking for the borderline cases.
Passing a stone can take anywhere from a few days to several weeks. Your doctor may ask you to strain your urine so the stone can be caught and analyzed. Knowing what type of stone you have is one of the most useful pieces of information for preventing the next one.
When a Stone Won’t Pass on Its Own
Three procedures cover the vast majority of stones that need intervention. Which one your urologist recommends depends on the stone’s size, location, and composition.
Shock Wave Lithotripsy
This is the least invasive option. You lie on a table while a machine sends focused sound waves through your body to break the stone into small fragments you can then pass naturally. It’s an outpatient procedure, meaning you go home the same day, though you’ll spend a few hours in recovery. Success rates range from 30% to 90% depending on stone size, location, type, and your body composition (more tissue between the skin and the stone means the waves lose energy). After the procedure, it can take days to weeks to fully pass all the fragments.
Shock wave lithotripsy works best for stones in the kidney or upper ureter that are smaller than about 2 cm. It’s generally not the first choice for very hard stones or for stones in the lower part of the kidney, where fragments tend to have trouble draining.
Ureteroscopy
A thin, flexible scope is passed up through the bladder and into the ureter to reach the stone directly. The urologist can then break it apart with a laser and remove the fragments. No incisions are involved. This is recommended for stones under 2 cm, particularly those stuck in the ureter, and it tends to have higher success rates than shock wave lithotripsy for harder stones.
After ureteroscopy, your urologist will often place a temporary stent, a small flexible tube that holds the ureter open while swelling goes down. Stents typically stay in for a few days to a few weeks. They’re effective but not pleasant: up to 80% of people with a stent experience side effects like bladder irritation, frequent urination, blood in the urine, or discomfort when urinating. The discomfort happens partly because the looped end of the stent rubs against the bladder wall each time the bladder contracts. These symptoms are normal and resolve once the stent comes out.
Percutaneous Nephrolithotomy
For large stones over 2 cm, or for lower-pole kidney stones over 1 cm, a more direct approach is needed. The surgeon makes a small incision in your back and passes a scope directly into the kidney to break up and remove the stone. This requires general anesthesia and typically a short hospital stay, but it has the highest success rate for large or complex stones.
Signs You Need Emergency Care
Most kidney stone episodes are painful but manageable. A few situations require immediate medical attention:
- Fever or chills along with stone symptoms. This suggests an infection behind a blocked stone, which is a potentially life-threatening combination that needs urgent treatment.
- You stop producing urine. This means both kidneys may be obstructed or your only functioning kidney is blocked.
- Severe nausea and vomiting that prevent you from keeping fluids down or taking pain medication.
- Confusion or extreme fatigue, which can signal that your kidneys aren’t filtering properly.
- You have a single kidney, whether you were born with one or had one removed. Any obstruction in your only kidney needs prompt evaluation even if the pain is mild.
Preventing the Next Stone
About half of people who get a kidney stone will get another one within five to ten years, so prevention matters. The strategies depend on what type of stone you had, which is why catching and analyzing the stone is so valuable.
Fluid intake is the single most effective prevention tool regardless of stone type. Aiming for enough water to produce at least 2.5 liters of urine daily dilutes the minerals that form stones. For the most common type, calcium oxalate stones, keeping dietary oxalate below 40 to 50 mg per day can help. High-oxalate foods include spinach, rhubarb, beets, nuts, and chocolate. Counterintuitively, you should not restrict calcium. Getting enough calcium from food (not supplements) actually binds oxalate in the gut before it reaches the kidneys.
Reducing sodium intake also helps because excess salt increases the amount of calcium your kidneys excrete. Cutting back on animal protein, particularly red meat, lowers uric acid levels and reduces the risk of both uric acid and calcium stones.
For people with recurrent stones, a prescription medication that makes urine less acidic can prevent certain stone types from forming. It works by raising the pH of urine, which keeps calcium and uric acid dissolved rather than crystallizing. Your urologist may also recommend a 24-hour urine collection test to pinpoint exactly which minerals are too concentrated in your urine, then tailor dietary and medication recommendations to your specific chemistry.