Most kidney stones pass on their own, but the experience depends almost entirely on size. Stones smaller than 4 mm pass within one to two weeks for most people, while larger stones can take two to three weeks or longer. Knowing what to expect, how to manage the pain, and when the situation requires medical intervention makes a significant difference in how you get through it.
Size Determines Whether You Can Pass It
The single most important factor is how big the stone is. Research using CT imaging found that stones 1 to 4 mm in diameter pass on their own about 78% of the time. For stones 5 to 7 mm, that rate drops to 60%. Once a stone reaches 8 mm or larger, only about 39% pass without intervention. Your doctor will typically measure the stone on a CT scan and use that number to guide the plan.
Location matters too. A stone already in the lower ureter (the tube connecting your kidney to your bladder) is closer to the exit and more likely to pass than one still sitting high near the kidney. Once a stone finally reaches the bladder, it usually passes within a few days, since the urethra is wider than the ureter.
What the Pain Feels Like and How to Treat It
Kidney stone pain, called renal colic, comes in waves. It typically starts as a deep ache in your back or side, then intensifies as the stone moves through the ureter. The pain can radiate to your lower abdomen or groin. Some people also experience nausea, vomiting, or a persistent urge to urinate.
Anti-inflammatory painkillers like ibuprofen are the first choice for kidney stone pain, and for good reason. A meta-analysis of 18 studies covering over 3,000 patients found that anti-inflammatories relieve pain just as effectively as opioids. But opioids came with a catch: patients who took them were significantly more likely to need a second dose of rescue medication and more likely to experience side effects, especially vomiting. Among the options studied, ketorolac (a prescription-strength anti-inflammatory) consistently outperformed several opioid types at the 15, 30, and 60 minute marks while causing fewer adverse effects.
If over-the-counter ibuprofen isn’t enough, your doctor can prescribe something stronger in the same anti-inflammatory class. Heat also helps. A heating pad on your back or side can relax the smooth muscle around the ureter and take the edge off between pain waves.
Medications That Help Stones Pass
For stones in the 6 to 10 mm range, doctors often prescribe an alpha-blocker, a type of medication that relaxes the smooth muscle lining the ureter. This widens the passage slightly and reduces the spasms that cause pain. For stones in that size range, alpha-blockers shortened the time to passage by about six days compared to a placebo. Current guidelines from the American Urological Association recommend trying alpha-blockers for up to 30 days for ureteral stones 10 mm or smaller.
For smaller stones under 5 mm, the benefit is less clear. One large trial found that the passage rate with an alpha-blocker was 50% compared to 47% with a placebo, a difference that wasn’t statistically meaningful. So for very small stones, the medication may not add much beyond what your body will do on its own.
Fluids, Diet, and What Actually Helps
You’ll hear “drink lots of water” as universal advice for kidney stones, and it’s partly right, but the nuance matters. There is no evidence that flooding your system with water speeds up the passage of a stone already lodged in your ureter. Drinking extra fluid won’t push it through faster. What high fluid intake does accomplish is prevention: producing about 2.5 liters of urine daily dilutes the minerals that form stones in the first place. To hit that urine volume, you need roughly 3 liters (about 100 ounces) of fluid intake per day, accounting for what your body loses through sweat and breathing.
While you’re actively passing a stone, staying well-hydrated is still important so you don’t become dehydrated from vomiting or reduced appetite. Just don’t force excessive amounts thinking it will flush the stone out sooner.
Uric Acid Stones Can Sometimes Be Dissolved
Not all kidney stones are the same composition. About 80% are calcium-based, but roughly 10% are made of uric acid. Uric acid stones are unique because they can actually be dissolved without surgery. The approach involves taking an alkalizing agent (typically potassium citrate) that raises the pH of your urine to between 6.5 and 7.0. At that pH, uric acid becomes much more soluble and the stone gradually breaks down.
This only works for confirmed uric acid stones. Your doctor can suspect a uric acid stone based on imaging characteristics (they’re often invisible on standard X-rays but visible on CT) and confirm it through urine testing. If you’ve been told you have a uric acid stone, ask about oral dissolution therapy. It requires monitoring your urine pH at home and adjusting the dose, but it can eliminate the stone entirely without a procedure.
When a Stone Needs Medical Intervention
Not every stone will pass, and waiting too long can cause real harm. A stone blocking the ureter traps urine behind it, which can damage the kidney over time or create conditions for a serious infection. Certain symptoms signal that you need emergency care:
- Fever and chills with stone pain, which may indicate an infection behind the blockage
- Pain so severe you can’t sit still or find any comfortable position
- Persistent vomiting that prevents you from keeping down fluids or medication
- Inability to urinate, suggesting complete obstruction
A fever with an obstructing stone is the most urgent scenario. Infected urine trapped behind a blockage can lead to sepsis rapidly and requires emergency drainage, not just antibiotics.
Even without emergency symptoms, your doctor will typically set a time limit. Current AUA guidelines recommend trying to pass a stone for approximately 30 days with medication before considering surgery. If the stone hasn’t moved by then, or if you’re having recurrent pain episodes that disrupt your life, surgical options come into play. The most common procedures are shock wave lithotripsy (which breaks the stone into smaller fragments from outside the body) and ureteroscopy (where a thin scope is threaded up through the ureter to remove or laser the stone). For very large stones over 2 cm, a percutaneous approach through a small incision in the back may be necessary.
What to Expect Day by Day
The typical experience of passing a small stone follows a rough pattern. The first sign is often sudden, intense flank pain as the stone drops from the kidney into the ureter. This is usually the worst phase. Over the next several days, pain comes and goes in waves as the stone works its way down. You may notice blood in your urine, which looks alarming but is normal as the stone scrapes the ureter lining.
As the stone moves lower toward the bladder, the pain often shifts from your back and side toward your lower abdomen and groin. You might feel increased urgency to urinate or a burning sensation. Once the stone enters the bladder, most people feel a sudden relief of the intense cramping pain. Passing it from the bladder through the urethra is usually quick and far less painful, sometimes barely noticeable.
Your doctor will likely ask you to strain your urine through a fine mesh or filter to catch the stone. This is worth doing. Analyzing the stone’s composition tells you exactly what type it is, which determines the specific dietary and medical strategies to prevent the next one. About half of people who pass a kidney stone will form another within five to ten years, so prevention matters as much as getting through the current episode.