The first sign of a kidney stone is usually a dull ache or pressure deep in your back, just below the ribs on one side. It can start subtly enough that you might mistake it for a pulled muscle or a backache from sleeping wrong. But unlike muscle pain, this discomfort doesn’t respond to changing positions, and it tends to intensify over minutes to hours into sharp, wave-like pain that many people describe as the worst they’ve ever experienced.
Where the Pain Starts
A kidney stone doesn’t cause pain while it’s sitting still inside the kidney. The trouble begins when it moves into the ureter, the narrow tube connecting each kidney to the bladder. That tube is only about 3 to 4 millimeters wide, so even a small stone can stretch and irritate its walls. The pain typically starts in the flank area, the part of your back between your lower ribs and your hip on one side. It’s deep, not on the surface, and pressing on the skin doesn’t make it worse or better.
In the earliest moments, it often feels like a vague pressure or cramping. Some people describe it as a sensation that something is “off” rather than outright painful. This phase can last anywhere from a few minutes to a couple of hours before the pain sharpens. Once the stone fully engages the ureter, the cramping becomes intense and arrives in waves. These waves happen because the ureter contracts rhythmically, trying to push the stone downward.
How the Pain Moves
As the stone travels down the ureter, the pain follows it. What started in your back and side begins to spread toward your lower abdomen and groin. Men sometimes feel it in the testicles. This migration pattern is one of the clearest signs that you’re dealing with a kidney stone rather than something else. The pain doesn’t stay in one place the way a muscle strain would.
The waves of pain, called renal colic, come and go. You might have 20 to 60 minutes of severe cramping followed by a lull, then another episode. During the peaks, the pain can be so intense that you can’t sit still. People often pace, rock, or curl up trying to find any position that helps. Nothing really does. Between waves, you may feel surprisingly normal, almost as if nothing happened, only for the next wave to hit.
Stones smaller than 4 millimeters (about a quarter of the diameter of a pencil eraser) often pass on their own within one to two weeks. Once a stone reaches the bladder, it typically passes within a few days. Larger stones take longer and are more likely to get stuck, prolonging the pain.
Symptoms Beyond the Pain
Pain is the headline symptom, but it’s rarely the only thing you’ll notice. Several other signs tend to show up early:
- Blood in the urine. About 84% of people with a confirmed kidney stone have blood detectable in their urine. Sometimes it’s visible as pink, red, or brownish urine. Other times it’s microscopic and only shows up on a urine test. Either way, it’s one of the most common early clues.
- Nausea and vomiting. The kidneys and the gut share nerve pathways, so kidney pain frequently triggers stomach upset. Vomiting during a kidney stone episode is common enough that some people initially think they have a stomach bug.
- Urinary changes. You may feel a constant need to urinate, go more often than usual, or produce only small amounts each time. There can also be burning or stinging during urination, especially as the stone nears the bladder.
- Cloudy or foul-smelling urine. This can signal irritation in the urinary tract or an accompanying infection.
How It Differs From Other Conditions
The combination of flank pain, pain that migrates, and blood in the urine is fairly distinctive. But early on, before all those clues appear, it’s easy to confuse a kidney stone with other problems.
A urinary tract infection can cause burning during urination and frequent urges, which overlap with stone symptoms. The key difference is location: UTI pain is usually felt low in the pelvis or around the urethra, while early stone pain sits higher, in the back and side. UTIs also cause fever more reliably, while kidney stones generally don’t unless an infection develops alongside the blockage.
Muscle strain tends to worsen with specific movements, like bending or twisting, and improves with rest. Kidney stone pain is indifferent to position. You can lie flat, stand, or lean forward, and the waves keep coming. The colicky, on-and-off nature of stone pain is also unusual for musculoskeletal problems, which tend to produce a steady ache.
Appendicitis can mimic a stone on the right side, but appendicitis pain usually starts around the belly button and settles in the lower right abdomen. It also tends to get steadily worse rather than coming in waves.
What Happens at Diagnosis
If you go to an emergency room or urgent care with these symptoms, the standard workup usually includes a urine sample and imaging. A urine dipstick checks for blood, which is present in roughly 80% of cases even when you can’t see it yourself. The most reliable way to confirm a stone and determine its size and location is a non-contrast CT scan of the abdomen and pelvis. It picks up details that ultrasound and other imaging often miss, including stone density, number, and exact position in the ureter. Ultrasound is sometimes used as a first step, particularly in pregnant patients or to avoid radiation, but it’s less accurate for measuring stone size.
Signs That Need Urgent Attention
Most kidney stones, while painful, pass without lasting harm. But certain symptoms during the early phase signal a more serious situation. Fever and chills alongside stone pain suggest an infection behind the blockage, which can escalate quickly. Inability to urinate at all means the stone may be fully obstructing the ureter. Uncontrollable vomiting that prevents you from keeping down fluids raises the risk of dehydration. Severe pain that doesn’t respond to over-the-counter pain relief after several hours also warrants evaluation. Pain in both sides simultaneously is rare for stones and may point to a different diagnosis entirely.