How you break down a kidney stone depends on its size, location, and what it’s made of. Stones smaller than 5 millimeters (about the size of a pencil eraser) often pass on their own with enough fluids and time. Larger stones may need shock waves, laser treatment, or in some cases surgery to break them into passable fragments. One specific type, uric acid stones, can actually be dissolved with medication alone.
Small Stones Can Pass on Their Own
Most kidney stones under 5 mm will eventually travel through the ureter and out of the body without any procedure. The single most important thing you can do is drink a lot of water. The NHS recommends up to 3 liters (about 100 ounces) of fluid per day to help flush stones through the urinary tract. That volume keeps urine dilute and flowing steadily, which pushes the stone along.
For stones between 5 and 10 mm stuck in the lower ureter, your doctor may prescribe a medication called an alpha-blocker (typically tamsulosin). These drugs relax the smooth muscle lining the ureter, widening the tube so the stone can move more easily. In clinical trials, alpha-blockers shortened the time to stone clearance by about 2 days on average, and the benefit was even more pronounced for stones in the 6 to 10 mm range, where passage happened roughly 6 days sooner. Current American Urological Association guidelines recommend trying alpha-blockers for up to 30 days before moving to a procedure.
Shock Wave Lithotripsy: Breaking Stones From Outside the Body
Extracorporeal shock wave lithotripsy, commonly called ESWL, is the least invasive way to break apart a kidney stone that won’t pass on its own. You lie on a table while a machine sends thousands of focused energy waves through water and into your body, targeting the stone. Those repeated pulses crack the stone into smaller pieces, which then pass naturally through your urine over the following days or weeks.
ESWL works best on smaller stones, generally under 2 cm and located in the kidney or upper ureter. It’s less effective for stones sitting in the lower pole of the kidney (the bottom portion), where fragments can have trouble draining. For lower pole stones larger than 1 cm, guidelines recommend against shock wave therapy as a first choice because the clearance rates drop significantly. Stone composition matters too. Stones made of calcium oxalate monohydrate, brushite, or cystine are particularly hard and resist shock waves. If your doctor suspects one of these compositions based on a CT scan or prior stone analysis, they’ll likely recommend a different approach.
Ureteroscopy: Laser Treatment From the Inside
When shock waves aren’t ideal, ureteroscopy (URS) offers a more direct option. A thin, flexible scope is passed through the urethra and bladder into the ureter or kidney, and the surgeon uses a laser fiber to fragment the stone on contact. There’s no incision. The fragments are either retrieved with a tiny basket or left small enough to pass on their own.
Ureteroscopy has a higher chance of clearing the stone in a single procedure compared to shock wave lithotripsy. The tradeoff is a slightly higher complication rate. After the procedure, a small tube called a ureteral stent is often placed to keep the ureter open while swelling subsides. Most stents stay in for a few days to a few weeks. They’re effective but not exactly comfortable: up to 80% of people with stents experience bladder irritation, more frequent urination, or pain when peeing. These symptoms resolve once the stent is removed.
Percutaneous Nephrolithotomy for Large Stones
For kidney stones larger than 2 cm, or for stones that have failed other treatments, percutaneous nephrolithotomy (PCNL) is the recommended first-line approach. This is a more involved procedure. The surgeon makes a small incision in your back and creates a channel directly into the kidney, then uses instruments to break up and remove the stone in pieces. A miniaturized version called mini-PCNL uses a smaller channel and is an option for stones up to 3 cm.
PCNL consistently achieves the highest stone-free rates, which is why both the American Urological Association and European Association of Urology recommend it for large stones and for lower pole stones over 1 cm. Recovery takes longer than with shock waves or ureteroscopy, typically requiring a short hospital stay, but the likelihood of needing a follow-up procedure is lower.
Dissolving Uric Acid Stones With Medication
Uric acid stones are the one type that can be chemically dissolved without any procedure at all. These stones form in acidic urine, and they break down when the urine becomes more alkaline. The goal is to raise urine pH to between 6.5 and 7.0, a range that makes conditions unfavorable for uric acid crystals and actively promotes dissolution.
The most common medication used is potassium citrate, taken in divided doses throughout the day. You’ll monitor your urine pH at home using simple dipstick tests and adjust the dose to stay in that target range. For stones in the ureter, your doctor may combine the alkalinizing medication with an alpha-blocker to help the stone pass as it shrinks. This approach requires patience (dissolution can take weeks) but avoids the risks and recovery of a procedure entirely. It only works for uric acid stones, though. Calcium-based stones, which account for the majority of kidney stones, cannot be dissolved with medication.
How Stone Size Guides the Treatment Plan
The size cutoffs matter because they predict what will actually work. Here’s a general framework:
- Under 5 mm: Usually passes on its own with fluids and pain management.
- 5 to 10 mm: Alpha-blockers for up to 30 days. If the stone doesn’t pass, shock wave lithotripsy or ureteroscopy.
- 1 to 2 cm: Shock waves, ureteroscopy, or mini-PCNL depending on location. Shock waves are less favored for lower pole stones in this range.
- Over 2 cm: PCNL is the standard recommendation. Ureteroscopy or shock waves may be considered if PCNL isn’t feasible, but follow-up procedures are more likely.
What Stone Composition Means for Your Options
Not all kidney stones are made of the same material, and composition directly affects which treatment will work. Your doctor can estimate composition from a CT scan (denser stones show higher values on imaging) or from analyzing a stone you’ve previously passed.
Calcium oxalate stones are the most common. They respond reasonably well to shock waves when small, and reliably to laser fragmentation. Calcium oxalate monohydrate stones, however, are denser and harder than the more common dihydrate form, making them more resistant to shock wave treatment. Brushite and cystine stones are similarly hard and often require ureteroscopy or PCNL instead. Uric acid stones, as noted, are the only type that dissolves with oral medication. If you’ve never had a stone analyzed, saving any fragments you pass in a strainer (your doctor will give you one) provides valuable information for planning current and future treatment.