Most kidney stones smaller than 4 mm pass on their own without any procedure, but stones that are too large, too painful, or stuck in the urinary tract need active removal. The method depends primarily on the stone’s size, location, and composition. There are three main procedures used today: shock wave lithotripsy, ureteroscopy with laser fragmentation, and a minimally invasive surgery called percutaneous nephrolithotomy for the largest stones.
When Stones Pass on Their Own
Not every kidney stone requires a procedure. Stones smaller than 4 mm pass naturally about 80% of the time, though it takes an average of 31 days. Stones between 4 and 6 mm still pass without intervention roughly 60% of the time, but the timeline stretches to around 45 days. Once a stone exceeds 6 mm, the odds flip: only about 20% pass on their own, and those that do can take up to a year.
For stones 10 mm or smaller in the lower ureter (the tube connecting your kidney to your bladder), doctors typically recommend a medication that relaxes the smooth muscle in the ureter, making it easier for the stone to slide through. This approach, called medical expulsive therapy, uses an alpha-blocker taken for about 30 days. In a large placebo-controlled trial, the medication raised the passage rate from 79% to 86% for stones in the lower ureter. The benefit was most pronounced for stones larger than 5 mm; for smaller stones, the drug didn’t make a meaningful difference compared to waiting it out with fluids and pain management alone.
During this waiting period, you’ll drink plenty of water, manage pain with anti-inflammatories or stronger medications if needed, and strain your urine to catch the stone so it can be analyzed. If the stone doesn’t pass within that window, or if you develop a fever, worsening pain, or signs of infection, your doctor will move to one of the procedural options below.
Shock Wave Lithotripsy
Shock wave lithotripsy (SWL) is the least invasive removal option. You lie on a table while a machine sends focused sound waves through your skin and into your body, targeting the stone. The energy pulses break the stone into sand-like fragments small enough to pass through your urinary tract naturally over the following days or weeks. The whole session typically lasts under an hour.
Success rates for SWL vary widely, from 30% to 90%, depending on factors like stone size, stone type, and where the stone is sitting. It works best on smaller stones in the kidney or upper ureter. Current guidelines recommend against using SWL as a first-line treatment for stones larger than 1 cm in the lower part of the kidney or larger than 2 cm elsewhere, because the success rate drops significantly at those sizes. Some stone compositions (like very hard calcium oxalate monohydrate or cystine stones) resist the shock waves and may need a different approach.
Recovery is relatively quick. You may see blood in your urine for a day or two and feel bruising or soreness where the waves entered your body. Most people return to normal activities within a few days.
Ureteroscopy With Laser Fragmentation
Ureteroscopy is the most common procedure for stones stuck in the ureter and is also used for kidney stones that aren’t good candidates for shock wave therapy. A urologist passes a thin, flexible scope through your urethra, up through your bladder, and into the ureter to reach the stone directly. No incisions are involved.
Once the scope reaches the stone, a flexible laser fiber is threaded through it. The laser breaks the stone into tiny fragments or fine dust that can be flushed out or retrieved with a small basket tool. This approach handles a wide range of stone sizes and compositions, and the direct visualization means the surgeon can confirm the stone is fully cleared during the procedure.
After ureteroscopy, a temporary ureteral stent is placed inside your body with one end in the kidney and the other in the bladder. The stent holds the ureter open so urine and stone fragments can drain freely while the area heals. It stays in place for a few days to a couple of weeks and is then removed in a brief office visit. The stent is entirely internal, so you won’t need an external collection bag.
Stents are effective but not comfortable. Up to 80% of people with a ureteral stent experience side effects like bladder irritation, frequent urination, blood in the urine, or pain while peeing. These symptoms resolve once the stent comes out, and you should be back to normal activities within a few days after removal.
Percutaneous Nephrolithotomy for Large Stones
For kidney stones larger than 2 cm, or for complex branching stones that fill multiple parts of the kidney’s drainage system, percutaneous nephrolithotomy (PCNL) is the recommended first-line treatment. It’s the gold standard for large stone burdens because it allows the surgeon to remove a high volume of stone material in a single session.
PCNL is performed under general anesthesia. The surgeon makes a small incision (about 1 cm) in your back and creates a direct channel into the kidney using imaging guidance. A rigid scope is passed through this channel, and the stone is broken apart with ultrasonic, laser, or pneumatic energy and suctioned or pulled out through the same tract. Because the access point goes straight to the kidney, even very large stones can be cleared effectively.
Recovery takes longer than the other procedures. You’ll typically spend one to two nights in the hospital, and a drainage tube may be left in the kidney tract temporarily. Most people need one to two weeks before returning to work and several weeks before resuming strenuous activity. The tradeoff is a much higher stone-free rate for large or complex stones than what SWL or ureteroscopy can achieve.
How Your Doctor Chooses the Right Method
Stone size is the single biggest factor. Here’s a rough framework:
- Under 10 mm, in the ureter: Watchful waiting with medication for up to 30 days. If the stone doesn’t pass, ureteroscopy is the usual next step.
- Under 2 cm, in the kidney: Either SWL or ureteroscopy, depending on the stone’s location and composition.
- Over 2 cm, in the kidney: PCNL is the recommended first choice.
Location matters too. Stones in the lower pole of the kidney are harder to clear with shock waves because gravity works against fragment passage. For lower pole stones over 1 cm, guidelines steer toward ureteroscopy or PCNL instead of SWL. Your stone’s composition, your anatomy, and whether you’ve had previous procedures all factor into the decision as well.
Newer Laser Technology
The lasers used during ureteroscopy are evolving. A newer type, the thulium fiber laser, delivers energy at frequencies 10 to 20 times higher than the traditional laser systems most hospitals currently use. The higher pulse rate allows for faster “dusting” of stones, which could mean shorter procedure times and more thorough fragmentation. Several major medical centers have begun using these systems, and early experience suggests they handle hard stone compositions more efficiently than older technology. The procedure itself feels the same from a patient’s perspective; the difference is in what’s happening at the tip of the fiber.