Passing a kidney stone feels like intense, cramping pain that starts in your back or side and shifts downward toward your groin as the stone moves through your urinary tract. The pain comes in waves, building to a peak and then easing before returning again. Many people describe it as one of the most painful experiences of their lives, though smaller stones can pass with only mild discomfort.
Where the Pain Starts
A kidney stone sitting quietly in your kidney typically causes no symptoms at all. The pain begins when the stone drops into one of your ureters, the narrow tubes connecting each kidney to your bladder. These tubes are only about 3 to 4 millimeters wide, so even a small stone can get wedged in and block urine flow. When that happens, urine backs up, the kidney swells, and the ureter starts spasming around the stone trying to push it along.
The first thing most people feel is a sudden, sharp pain in the side and back, just below the ribs. It often hits without warning. You might initially mistake it for a pulled muscle or back injury, but it quickly becomes clear this is something different. The pain doesn’t respond to changing positions. Lying down, standing up, curling into a ball: nothing provides real relief.
Why the Pain Comes in Waves
Kidney stone pain has a distinctive pattern. There’s a constant, dull ache from the kidney swelling against its outer capsule, layered with sharp, intense spikes that come and go. Those spikes are caused by the ureter contracting in waves, squeezing rhythmically to try to push the stone downward, much like the contractions that move food through your intestines. Each contraction builds pressure, peaks, then releases. The pain follows that same rhythm.
These waves can last anywhere from 20 minutes to over an hour, and the intensity varies. Some episodes are manageable with over-the-counter pain relief. Others send people to the emergency room convinced something has ruptured. Between episodes, the pain may drop to a low ache or disappear entirely for hours before returning.
How the Pain Moves as the Stone Travels
As the stone works its way down the ureter, the pain migrates. What started as flank pain below the ribs gradually shifts forward and downward toward the lower abdomen and groin. In men, the pain sometimes radiates into the testicle. In women, it can spread toward the labia. This referred pain happens because the kidneys, ureters, and reproductive organs share nerve pathways from early development in the womb.
When the stone reaches the lowest section of the ureter, near where it connects to the bladder, a new set of symptoms appears. You may feel a constant, urgent need to urinate even when your bladder is nearly empty. There’s often a burning sensation when you do urinate, and you might only produce a small amount each time. This phase can feel similar to a urinary tract infection. Some people find this part more annoying than painful, while others find the urgency relentless and distressing.
Nausea, Blood, and Other Symptoms
The pain is the headline symptom, but it rarely arrives alone. Nausea and vomiting are extremely common because the kidneys and gut share nerve connections. Your body responds to the intense pain signals by triggering the same nausea pathway that a stomach virus would. Some people vomit repeatedly during pain spikes.
Blood in the urine is another hallmark. About 85% of people passing a stone will have blood detectable on a urine test, and many can see it themselves as a pink, red, or brown tint. The stone scrapes against the delicate lining of the ureter as it moves, which causes the bleeding. It looks alarming but is a normal part of the process. You might also notice your urine is cloudy or has an unusual smell.
Sweating, restlessness, and an inability to sit still are also typical. Unlike many types of pain where you want to lie motionless, kidney stone pain often drives people to pace or shift constantly, searching for a position that helps. None really does.
How Long It Takes
The total time from first symptom to passing the stone depends almost entirely on size. A large study tracking spontaneous passage rates over 20 weeks found clear patterns:
- Under 3 mm: 98% pass on their own
- 3 to 4 mm: about 81% pass on their own
- 4 to 5 mm: about 65% pass on their own
- 5 to 6 mm: roughly 33% pass on their own
- Over 6.5 mm: only about 9% pass without intervention
Small stones may pass in a few days. Larger ones can take weeks, with intermittent pain episodes along the way. The process isn’t constant agony. Many people have stretches of hours or even days with minimal symptoms between flare-ups, as the stone sits in one spot before shifting again.
Your doctor may prescribe a medication that relaxes the smooth muscle in the ureter, making it easier for the stone to slide through. In studies, this approach raised the spontaneous passage rate from about 70% to 80% and shortened the time to passage by roughly 3 to 4 days on average. It also reduced the amount of pain medication people needed.
The Final Moment
Once the stone drops from the ureter into the bladder, most of the severe pain stops. The bladder is a much larger, more flexible space, and the stone floats freely inside it. You may feel pressure or mild discomfort, but the intense flank and groin pain typically ends at this stage.
Passing the stone out of the bladder through the urethra is the last step. For many people, this part is surprisingly anticlimactic. You might feel a brief pinch or burning sensation, or you might not notice the stone at all until you hear it clink against the toilet bowl or catch it in a strainer. Some people describe a moment of pressure followed by immediate relief. The urethra is wider than the ureter, so stones that survived the journey down generally pass out without much trouble.
What It Feels Like Afterward
After the stone passes, the relief is often dramatic and fast. The intense cramping stops. But some residual soreness in your back or side can linger for a few days as the swelling in your kidney and ureter resolves. You may continue to see traces of blood in your urine for a day or two. Mild burning during urination can also persist briefly from irritation along the urinary tract.
If your doctor asked you to catch the stone, check your strainer each time you urinate. Stones are usually small, ranging from a grain of sand to a pea, and can be yellow, brown, or dark. Keeping the stone for lab analysis helps identify what type it is, which guides prevention strategies to reduce your chances of forming another one.
Warning Signs That Need Urgent Attention
Most kidney stones pass without serious complications, but certain symptoms signal a potential emergency. Fever and chills during a stone episode suggest infection, which is not a normal part of uncomplicated stone passage. An infected, obstructed kidney can deteriorate quickly and needs urgent treatment regardless of stone size. Similarly, if the pain becomes truly unmanageable and doesn’t respond to medication, or if you stop being able to urinate, those are signs the stone may be causing a complete blockage. Complete obstruction can start damaging kidney function within about two weeks if left untreated.