The most telling sign of a kidney stone is a sudden, sharp pain in your side or back, just below your ribs, that comes in waves and may radiate down toward your groin. But not all kidney stones announce themselves so dramatically. About 9% of the U.S. population has kidney stones, and many of those stones sit quietly in the kidney without causing any symptoms at all. Knowing the full range of signs, from the obvious to the subtle, helps you figure out whether a stone might be the source of your discomfort.
The Pain Pattern That Points to Kidney Stones
Kidney stone pain has a distinctive character that sets it apart from most other types of abdominal pain. It typically starts in your flank, the area between your lower ribs and your hip on one side, and it comes in intense waves rather than staying constant. These waves happen because the tube connecting your kidney to your bladder (the ureter) spasms as it tries to push the stone through. Between waves, the pain may ease up, only to return just as forcefully minutes later.
As the stone moves, so does the pain. What begins in your back and side often shifts to your lower abdomen and groin. Men sometimes feel it in the testicles. This traveling quality is a strong clue, because few other conditions produce pain that migrates along that specific path. The pain can also change in intensity as the stone reaches narrower sections of the ureter, and many people describe it as the worst pain they’ve ever experienced.
One important detail: a stone sitting still inside the kidney often causes no pain at all. Symptoms begin when the stone enters the ureter and starts to obstruct urine flow. That obstruction causes the kidney to swell, which is what triggers the severe, wave-like pain known as renal colic.
Urinary Changes to Watch For
Beyond pain, your urine itself often changes when a stone is on the move. Pink, red, or brown urine is common because the stone scrapes the lining of the urinary tract as it passes, releasing small amounts of blood. Sometimes the blood is visible to the naked eye; other times, it’s only detectable through a urine test. Cloudy or foul-smelling urine can also appear, particularly if an infection develops alongside the stone.
You may also notice that you need to urinate more frequently or feel an urgent need to go, even when your bladder isn’t full. A burning sensation during urination is another frequent complaint, especially when the stone reaches the lower part of the ureter near the bladder. These urinary symptoms overlap with urinary tract infections, which is why kidney stones are sometimes initially mistaken for a UTI.
Nausea, Vomiting, and Other Indirect Symptoms
Kidney stones frequently trigger nausea and vomiting. The kidneys and the gut share nerve pathways, so intense kidney pain can activate the same signals that make you feel sick to your stomach. Some people experience sweating, restlessness, or an inability to find a comfortable position. You might feel feverish, hot and cold alternately, or generally unwell. These symptoms don’t mean the stone itself has spread anywhere. They’re your body’s response to the pain and obstruction.
Silent Stones That Cause No Symptoms
Not every kidney stone causes trouble. In one study of stones detected by abdominal ultrasound, over 71% were asymptomatic, meaning the person had no pain, no blood in the urine, and no idea a stone was there. These silent stones are usually discovered by accident when imaging is done for an unrelated reason, like an abdominal scan after a car accident or routine screening for another condition.
Silent stones don’t always stay silent, though. Research tracking asymptomatic stone carriers found that about 29% eventually developed symptoms or needed intervention over roughly four years. If you’re told you have an incidental stone, your doctor will typically monitor it with periodic imaging rather than intervene immediately.
How Kidney Stone Pain Differs From Other Conditions
The location of kidney stone pain can overlap with several other conditions, which makes the distinction important. Appendicitis, for example, also causes lower right abdominal pain with nausea. But appendicitis pain usually starts around the belly button and settles into steady, worsening tenderness in the lower right abdomen. It doesn’t come in waves, and it doesn’t typically radiate to the back or groin. Pressing on the area and releasing quickly tends to sharpen appendicitis pain, a sign of inflammation in the abdominal lining that kidney stones don’t produce.
UTIs share urinary symptoms like burning and frequency but usually lack the severe flank pain that comes in waves. Gallstone attacks can produce intense pain in the upper right abdomen but radiate toward the shoulder blade rather than the groin. Ovarian cysts or torsion can mimic stones on the same side but tend to produce a more constant, deep pelvic ache. The wave-like quality and the migrating path of kidney stone pain remain its most distinguishing features.
How Kidney Stones Are Confirmed
If your symptoms suggest a stone, a CT scan is the most reliable way to confirm it. CT detects kidney stones with over 95% accuracy, pinpoints the stone’s exact size and location, and shows whether it’s blocking urine flow. The downside is radiation exposure, which matters if you need repeated scans over time.
Ultrasound is a radiation-free alternative, but it’s less precise. Its sensitivity for detecting stones is around 77% in clinical settings, with a pooled average across studies as low as 45%. Ultrasound works well as a first step, especially for pregnant women or people who’ve had many prior scans, but a negative ultrasound doesn’t rule out a stone if your symptoms are convincing.
A urine test rounds out the picture. It checks for blood (even microscopic amounts), and a more detailed urine analysis measures levels of calcium, uric acid, oxalate, citrate, and other chemicals that promote stone formation. These results help explain why you formed a stone in the first place and guide prevention strategies afterward.
What Stone Size Means for What Happens Next
Once a stone is confirmed, its width largely determines whether it will pass on its own or require a procedure. Research tracking spontaneous passage rates over 20 weeks found a clear pattern:
- 3 mm or smaller: 98% pass without intervention
- 4 mm: 81% pass on their own
- 5 mm: 65% pass on their own
- 6 mm: 33% pass on their own
- 6.5 mm or larger: only 9% pass on their own
For small stones, the typical approach is to manage pain, drink plenty of fluids, and wait. You may be asked to strain your urine so the stone can be caught and analyzed. Passing a stone can take anywhere from a few days to several weeks. Larger stones, or stones that cause persistent blockage, infection, or unbearable pain, usually need a procedure to break them up or remove them.
Warning Signs That Need Immediate Attention
Most kidney stones, while painful, resolve without serious complications. But certain symptoms signal a more dangerous situation. A fever combined with kidney stone symptoms suggests the stone has caused an infection, which can become a medical emergency if the infected urine can’t drain past the blockage. Feeling hot and cold, shivering, or experiencing extreme weakness alongside stone symptoms all point toward infection.
Other red flags include being completely unable to urinate, vomiting so severely that you can’t keep fluids down, or blood in your urine that’s heavy and persistent. These situations require prompt evaluation because a blocked, infected kidney can deteriorate quickly.