The most telling sign of a kidney stone is a sudden, intense pain in your side or lower back that comes in waves and radiates toward your groin. This pain, called renal colic, is often described as one of the most severe types of pain a person can experience. But not every kidney stone announces itself so dramatically. Some cause only mild discomfort, and others produce no symptoms at all until they start to move. Here’s how to recognize what’s happening in your body.
Where the Pain Shows Up
Kidney stone pain typically starts in your flank, the area between your lower ribs and your hip on one side. From there, it often moves forward and downward toward your lower abdomen, groin, or testicle. The pain usually affects only one side of your body, matching whichever kidney the stone is traveling from.
What makes kidney stone pain distinctive is its pattern. Most people experience a constant, dull ache from pressure building behind the stone, interrupted by sharp, intense waves of cramping. Those waves happen because the tube connecting your kidney to your bladder (the ureter) contracts in spasms as it tries to push the stone through. The pain can shift location as the stone moves, which is actually a good sign since it means the stone is progressing toward your bladder.
Unlike muscle pain, kidney stone pain doesn’t get better or worse when you change positions. You might find yourself pacing or unable to sit still, which is a useful clue. People with abdominal problems like appendicitis tend to stay very still because movement worsens their pain, while people with kidney stones often can’t find any comfortable position at all.
Urinary Changes to Watch For
Blood in your urine is one of the most reliable indicators. Even when you can’t see it with the naked eye, studies show that roughly 95 to 100 percent of people with an active kidney stone have microscopic blood detectable on a urine test. You might notice your urine looks pink, red, or brown. Sometimes the blood is only visible under a microscope, which is why a simple urine test at a clinic can be so informative.
Other urinary symptoms include a frequent, urgent need to urinate (especially as the stone reaches the lower part of the ureter near the bladder), pain or burning during urination, and producing only small amounts of urine at a time. If your urine becomes cloudy or foul-smelling, that could signal an infection alongside the stone, which changes the urgency of your situation significantly.
Nausea, Vomiting, and Other Symptoms
Many people with kidney stones experience nausea and vomiting alongside the pain. This happens because the kidneys and the digestive system share nerve pathways, so intense kidney pain can trigger a strong nausea response. If you’re having severe flank pain paired with vomiting and no obvious stomach illness, a kidney stone is a likely explanation.
Some people also develop a low-grade fever or feel generally unwell. Restlessness is common. You might notice sweating or feel like you simply cannot get comfortable. These symptoms tend to come and go in waves that mirror the pain cycle.
What Kidney Stone Pain Can Be Mistaken For
The location of kidney stone pain overlaps with several other conditions, which is part of why it can be tricky to self-diagnose. Pain in your right lower abdomen could be appendicitis. Pain with burning urination might feel like a urinary tract infection. Lower back pain could seem muscular. A stone in the right ureter is particularly easy to confuse with appendicitis, and clinicians note that patients sometimes have both conditions simultaneously, making even professional diagnosis challenging.
A few distinguishing features help separate kidney stones from these mimics. UTIs cause burning and frequency but rarely produce the severe, wave-like flank pain of a stone. Appendicitis pain usually settles in one spot (the lower right abdomen), worsens with movement, and often comes with a loss of appetite. Muscle pain changes with position and pressure. Kidney stone pain is restless, one-sided, wave-like, and accompanied by urinary changes.
How Stones Are Confirmed
If you go to a clinic or emergency room, the standard approach starts with a urine test looking for blood and signs of infection. The gold standard for confirming a kidney stone is a CT scan of your abdomen and pelvis without contrast dye. This type of scan catches about 95 percent of stones and correctly rules them out 98 percent of the time. Both the American College of Radiology and the American Urological Association recommend it as the first-line imaging test for adults.
Ultrasound is a reasonable alternative, especially for pregnant women and children under 14, though it’s less accurate. It picks up about 84 percent of stones and has a higher rate of false positives. Your doctor might also order blood work to check kidney function and look for signs of infection.
Can You Test Anything at Home?
Over-the-counter urine pH strips can give you a rough idea of your urine’s acidity, which is relevant for certain stone types. Uric acid stones, for example, form in highly acidic urine. Research shows that home pH strips correlate reasonably well with lab equipment, but they have a margin of error of about half a pH unit to a full unit, and the color changes are hardest to read in the mid-range (around pH 6 to 7) where many people’s urine falls. They’re better at detecting extremes: very acidic or very alkaline urine.
These strips are useful for people who already know they form stones and are monitoring their prevention strategy. They aren’t reliable enough to diagnose a new stone or determine its type. If you suspect you’re passing a stone, the most practical thing you can do at home is strain your urine through a fine mesh or coffee filter. Catching the stone allows a lab to analyze its composition, which directly shapes your prevention plan going forward.
Small Stones Often Pass on Their Own
The likelihood that a stone will pass without intervention depends almost entirely on its size. A study tracking 392 patients over 20 weeks found clear thresholds:
- 3 mm or smaller: 98 percent pass on their own
- 4 mm: 81 percent pass on their own
- 5 mm: 65 percent pass on their own
- 6 mm: 33 percent pass on their own
- 6.5 mm or larger: only about 9 percent pass without help
For small stones, treatment is primarily about managing pain and staying hydrated while you wait. Passing a stone can take anywhere from a few days to several weeks. Stones closer to the bladder generally pass faster than those still high in the ureter.
Types of Stones and Why They Form
Most kidney stones (about 80 percent) are made of calcium oxalate. Despite the name, eating calcium-rich foods does not increase your risk for these stones. In fact, dietary calcium can actually help by binding oxalate in the gut before it reaches the kidneys. The more relevant risk factors are excess oxalate in the urine, too little fluid intake, and a genetic tendency to excrete high levels of calcium.
Uric acid stones form when urine is too acidic. Diets heavy in meat, organ meats, and shellfish raise uric acid levels and contribute to these stones. Struvite stones are different: they develop after urinary tract infections and can grow large quickly. They’re more common in women and are tied to recurrent UTIs rather than diet.
Knowing your stone type matters because prevention strategies differ. Someone with calcium oxalate stones focuses on hydration and dietary oxalate. Someone with uric acid stones works on raising their urine pH. This is why catching and analyzing a passed stone is so valuable.
Signs That Need Immediate Attention
Most kidney stones, while painful, resolve safely. But certain combinations of symptoms indicate a potential emergency. A kidney stone that blocks urine flow while an infection is present can escalate quickly into a life-threatening situation. Seek emergency care if you develop:
- Fever above 101.5°F alongside stone symptoms
- Persistent vomiting that prevents you from keeping fluids down
- Cloudy or foul-smelling urine, which suggests infection
- Pain so severe that over-the-counter medication cannot control it
People with only one kidney, diabetes, or existing reduced kidney function face higher risks from an obstructing stone and should have a lower threshold for seeking care. If you’re unsure whether your symptoms warrant a trip to the ER, the combination of fever plus flank pain is the clearest signal that you should go.