Kidney stones are removed using one of three main procedures, depending on the stone’s size and location: shock wave lithotripsy (which breaks stones apart from outside the body), ureteroscopy (which uses a scope threaded through the urinary tract), or percutaneous nephrolithotomy (which requires a small incision in the back). Many smaller stones don’t need a procedure at all and can pass on their own with medication to help them along.
When Stones Pass on Their Own
Not every kidney stone requires a procedure. Stones 10 mm or smaller, particularly those in the lower part of the urinary tract, often pass naturally. Current urology guidelines recommend trying medication first for these smaller stones, typically for about 30 days, before considering surgery.
The medication used is a type of alpha-blocker that relaxes the muscles in the ureter, the narrow tube connecting your kidney to your bladder. A large meta-analysis of 56 trials covering over 9,000 patients found that this medication increased the stone passage rate by about 44% compared to no treatment, shortened the time it took for stones to pass, and reduced painful flare-ups along the way. The benefit was most pronounced for stones between 5 and 10 mm. For stones 5 mm or smaller, the medication didn’t make a significant difference, likely because those tiny stones tend to pass on their own regardless.
Shock Wave Lithotripsy
Shock wave lithotripsy is the least invasive option for removing kidney stones. No instruments enter your body. Instead, a machine called a lithotripter generates focused shock waves that travel through your skin and tissue to reach the stone, which is located using X-ray imaging or ultrasound. The waves pulverize the stone into fragments small enough to pass naturally through your urinary tract over the following days or weeks.
You’ll receive some form of anesthesia beforehand. This could be general anesthesia (where you’re fully asleep), sedation (awake but drowsy), or regional anesthesia (awake but numb from the waist down). Most people return to their usual routines within a few days.
Lithotripsy works best on smaller stones, generally under 2 cm, and it’s not equally effective on all stone types. Stones made of cystine or certain calcium compounds don’t break apart well with shock waves. For kidney stones larger than 1 cm in the lower part of the kidney, or larger than 2 cm anywhere in the kidney, guidelines recommend against lithotripsy as a first choice because the clearance rates drop significantly compared to other methods.
Ureteroscopy With Laser
Ureteroscopy takes a more direct approach. A urologist threads a long, thin scope with a camera on the end through your urethra, up through your bladder, and into the ureter or kidney where the stone is lodged. Once the scope reaches the stone, a flexible laser fiber is passed through it to break the stone into fragments. The pieces are then collected with a tiny wire basket pulled back through the scope.
No incisions are involved since the entire procedure uses your body’s natural urinary pathway. Ureteroscopy is a strong option for stones up to about 2 cm and is particularly well suited for stones stuck in the ureter itself. For small stones in the lower ureter (10 mm or less), it’s considered equally appropriate to shock wave lithotripsy when medication hasn’t worked. For stones in the 1 to 2 cm range, a newer technique called mini-percutaneous nephrolithotomy may offer higher stone clearance rates, but ureteroscopy remains widely available and effective.
Percutaneous Nephrolithotomy (PCNL)
PCNL is the most involved procedure and is reserved for the largest or most complex stones. It’s the recommended first-line treatment for kidney stones larger than 2 cm, including staghorn stones that branch out and fill much of the kidney’s internal space. It’s also used when shock wave lithotripsy or ureteroscopy has already been tried and failed, or for large stones (over 2 cm) stuck in the ureter.
During PCNL, a surgeon makes a small incision in your back and creates a narrow channel directly into the kidney, guided by X-ray or ultrasound imaging. Instruments are passed through this channel to break up the stone and suction or pull out the fragments. Because it provides direct access to the kidney, PCNL achieves the highest stone-free rates of any removal method, particularly for stones over 1 cm in the lower part of the kidney. The tradeoff is a longer recovery compared to the other two procedures, since it involves an actual incision and typically requires general anesthesia.
What to Expect After a Procedure
After ureteroscopy or PCNL, your urologist will often place a ureteral stent, a thin flexible tube that sits inside the ureter to keep it open while the area heals. Stents typically stay in for a few days to a few weeks. They’re effective at preventing swelling from blocking urine flow, but they’re not exactly comfortable.
Up to 80% of people with a stent experience at least one side effect. The most common complaints include bladder irritation, needing to urinate more frequently than usual, pain or burning during urination, blood in the urine, and a pulling sensation in the pelvic area. These symptoms are temporary and resolve once the stent is removed. Knowing this in advance can help, since the discomfort catches many people off guard.
How Stone Size Determines the Approach
The single biggest factor in choosing a removal method is the stone’s size, measured in millimeters or centimeters on imaging.
- 5 mm or smaller: These usually pass on their own without any intervention.
- 5 to 10 mm: Medication to relax the ureter is tried first for about 30 days. If the stone doesn’t pass, shock wave lithotripsy or ureteroscopy are both reasonable next steps.
- 1 to 2 cm: Ureteroscopy or a mini-PCNL procedure is typically preferred. Shock wave lithotripsy may still be an option for stones in certain locations, but clearance rates are lower.
- Larger than 2 cm: PCNL is the standard recommendation. Stones this large are unlikely to be fully cleared by lithotripsy or ureteroscopy alone.
Location matters too. A stone sitting in the lower pole of the kidney is harder to clear with shock waves because gravity works against the fragments draining out. For lower pole stones over 1 cm, PCNL consistently outperforms the other options. Stone composition also plays a role: harder stones made of cystine or certain calcium types resist shock waves, making ureteroscopy or PCNL the better choice regardless of size.