Most kidney stones smaller than 5 mm will pass on their own with enough fluids and pain management. Stones between 5 and 7 mm still have about a 60% chance of passing naturally, but anything larger often needs medical intervention. What you should do depends almost entirely on the size, location, and type of stone you’re dealing with.
Which Stones Pass on Their Own
Stone size is the single biggest factor in whether you can pass a kidney stone without a procedure. Stones 1 to 4 mm in diameter pass naturally about 76% of the time. At 5 to 7 mm, the rate drops to roughly 60%. Once a stone reaches 8 mm or larger, fewer than half will pass on their own, and stones over 10 mm have only about a 27% success rate without intervention.
Location matters too. A stone already in the ureter (the tube connecting the kidney to the bladder) and close to the bladder is more likely to pass than one still sitting high near the kidney. Your doctor will typically use a CT scan to measure the stone and decide whether watchful waiting is reasonable.
How to Help a Stone Pass Faster
If your stone is small enough to pass, the goal is to flush it through with fluids, manage the pain, and in some cases use medication to relax the ureter.
Fluids: Drink enough water to produce at least 2.5 liters of urine per day. That usually means drinking around 3 liters of water, more if you’re active or in a hot climate. Steady intake throughout the day keeps urine dilute and helps push the stone along.
Pain relief: Anti-inflammatory painkillers like ibuprofen or naproxen are the first-line treatment for kidney stone pain. They work better than other options for renal colic because they reduce the swelling in the ureter wall that makes the pain so intense. If over-the-counter doses aren’t enough, your doctor can prescribe a stronger version or add a second medication.
Medication to widen the ureter: For stones larger than 5 mm, your doctor may prescribe a muscle-relaxing drug originally designed for prostate issues. A meta-analysis of randomized trials found this medication increased the stone expulsion rate by 44%, shortened the time to passage, and reduced pain episodes. For stones 5 mm or smaller, the benefit is minimal since most of those pass easily without it.
When a Stone Needs a Procedure
If a stone is too large to pass, causes an infection, blocks urine flow completely, or hasn’t moved after several weeks of waiting, you’ll need a procedure. Three main options exist, and the choice depends on stone size and where it’s lodged.
Shock wave lithotripsy (SWL) uses focused sound waves from outside the body to break a stone into sand-sized fragments that you then pass in your urine. It works best on stones 1 cm or smaller. For stones in the lower part of the kidney that are between 1 and 2 cm, guidelines recommend against SWL as a first choice because the fragments don’t clear as effectively from that location.
Ureteroscopy involves threading a thin, flexible scope up through the bladder and into the ureter or kidney. The surgeon can then laser the stone into tiny pieces or grab it with a small basket. It’s a first-line option for stones up to 1 cm and is often preferred for larger stones or those that SWL can’t reach. Recovery is usually quick, though you may have a temporary stent placed to keep the ureter open while it heals.
Percutaneous nephrolithotomy (PCNL) is reserved for large stones, typically over 2 cm, or very hard stones that won’t respond to other methods. A surgeon makes a small incision in the back and uses a scope to break up and remove the stone directly from the kidney. It requires general anesthesia and a short hospital stay, but it has the highest clearance rate for big stones.
Dissolving Uric Acid Stones Without Surgery
Uric acid stones are the only common type that can actually be dissolved with medication. They form when urine is too acidic, and the fix is straightforward: raise the urine pH above 7.0 while increasing fluid intake. At that pH, uric acid shifts into a much more soluble form that gradually dissolves.
Your doctor will prescribe an alkalinizing agent, typically a citrate solution you take by mouth several times a day. You’ll need to monitor your urine pH regularly with test strips to make sure it stays in the target range. With consistent alkalinization and high urine output, existing uric acid stones can dissolve over weeks to months without any procedure. If overproduction of uric acid is the underlying cause, a medication that lowers uric acid levels in the blood may also be added.
This approach only works for uric acid stones. Calcium-based stones, which make up about 80% of all kidney stones, cannot be dissolved with medication.
Dietary Changes That Reduce New Stones
Getting rid of the current stone is only half the battle. Without changes, roughly half of stone formers will develop another stone within five to ten years. Diet is one of the most powerful tools for prevention.
Calcium: This surprises most people, but you should not cut calcium from your diet. Aim for about 1,200 mg daily from food sources like dairy, fortified plant milks, or leafy greens. When you eat calcium-rich foods at each meal, the calcium binds to oxalate in your gut before it can be absorbed into the bloodstream. Less oxalate in your blood means less oxalate reaching the kidneys to form stones. Restricting calcium actually increases stone risk.
Sodium: High salt intake forces your kidneys to excrete more calcium into the urine, which fuels stone formation. Keeping sodium under 2,300 mg per day (and ideally closer to 1,500 mg) can meaningfully reduce calcium in the urine.
Animal protein: Large amounts of meat, poultry, and fish make urine more acidic and increase calcium and uric acid excretion. You don’t need to go vegetarian, but moderating portions to around 6 ounces of animal protein per day helps.
Oxalate: If you form calcium oxalate stones specifically, it’s worth reducing very high-oxalate foods like spinach, rhubarb, beets, nuts, and chocolate. Pairing any oxalate-containing food with a calcium source at the same meal blunts the impact. Citrate from lemons, limes, and oranges also helps inhibit stone crystal formation, though the optimal dose from food alone isn’t well established. Drinking diluted lemon juice throughout the day is a reasonable low-risk habit.
Signs a Stone Is an Emergency
Most kidney stones are painful but not dangerous. However, certain symptoms mean you need immediate medical attention:
- Fever and chills with stone pain can signal an infected, obstructed kidney. This can become life-threatening quickly and requires urgent drainage.
- Inability to urinate suggests complete blockage, especially dangerous if you have only one functioning kidney.
- Uncontrollable pain that doesn’t respond to over-the-counter medication and won’t let you sit still or find any comfortable position.
- Persistent vomiting that prevents you from keeping down fluids or oral pain medication.
- Visible blood in your urine is common with stones but warrants evaluation, especially if it’s heavy or persistent.
The combination of fever and a blocked stone is the most urgent scenario. An infected kidney that can’t drain will deteriorate within hours, so this is a true emergency rather than something to monitor at home.