The most telling sign of a kidney stone is sudden, intense pain that starts in your back or side, just below your ribs, and shifts location as the stone moves. This pain, called renal colic, often comes in waves and can be severe enough that you can’t sit still or find a comfortable position. But not every kidney stone announces itself so dramatically. Some cause only mild discomfort, blood in your urine, or vague symptoms that overlap with other conditions.
Where the Pain Shows Up
Kidney stone pain changes location depending on where the stone is stuck. A stone blocking the junction between your kidney and the tube leading to your bladder (the ureter) causes pain that radiates into your flank, the area on your side between your ribs and hip. As the stone moves lower, the pain shifts. When it reaches the middle portion of the ureter, pain tends to radiate into the groin or lower abdomen.
Stones lodged near the bladder produce a different pattern entirely. The pain may radiate into the inner thigh, scrotum, or labia, and you’ll often feel a frequent, urgent need to urinate along with burning during urination. This bladder irritation is what sometimes leads people to think they have a urinary tract infection rather than a stone.
One characteristic that separates kidney stone pain from many other causes: it comes and goes in intense waves lasting 20 to 60 minutes, rather than staying constant. You may feel fine between episodes, then suddenly be doubled over again. The pain also tends to make you restless. People with kidney stones pace, shift positions, and can’t get comfortable, which is different from conditions like appendicitis, where staying still usually feels better.
Urinary Changes to Watch For
Blood in your urine is one of the most common signs of a kidney stone. Sometimes it’s visible, turning your urine pink, red, or brown. Other times the amount is so small it can only be detected under a microscope during a urine test. Either way, blood in your urine alongside flank pain is a strong signal that a stone is involved.
Other urinary symptoms include needing to urinate more often than usual, feeling an urgent need to go even when your bladder isn’t full, and pain or burning during urination. These symptoms become more pronounced when the stone is near the bladder. Some people also notice their urine looks cloudy or has an unusual smell, which can indicate irritation or a secondary infection.
Symptoms That Aren’t Pain
Not all kidney stones cause dramatic pain. Smaller stones can pass with only mild discomfort or a dull ache you might dismiss as a muscle strain. Some stones sitting quietly in the kidney produce no symptoms at all and are discovered incidentally during imaging for something else.
Nausea and vomiting frequently accompany kidney stone episodes, even when pain is the primary symptom. This happens because the kidneys and the digestive tract share nerve pathways, so intense kidney pain can trigger a gut reaction. If you’re experiencing unexplained nausea alongside back or side pain, a kidney stone is worth considering.
What Sets It Apart From Other Conditions
Right-sided kidney stone pain can look a lot like appendicitis, since both cause lower abdominal pain. The key differences: appendicitis pain usually starts around the belly button and migrates to the lower right, stays relatively constant, and gets worse when you press on the area and release. Kidney stone pain is more likely to come in waves, radiate toward the groin, and make you unable to hold still. Appendicitis also tends to cause tenderness when the abdomen is pressed, while kidney stone pain is often felt more in the back or side.
Gallbladder pain can also mimic kidney stones, especially on the right side. Gallbladder attacks are typically triggered by fatty meals and produce pain in the upper right abdomen that radiates to the shoulder blade. Kidney stone pain sits lower and radiates downward. Urinary tract infections share the burning and frequency symptoms, but UTIs rarely produce the severe flank pain that kidney stones cause.
How Kidney Stones Are Diagnosed
If you go to a doctor or emergency room with suspected kidney stone symptoms, the workup typically involves a urine sample and imaging. A urine test can reveal blood (even microscopic amounts), crystals, or signs of infection. The urine’s acidity level also provides clues about what type of stone may be forming.
For imaging, a CT scan without contrast is the gold standard. It detects kidney stones with over 95% accuracy and can pinpoint the stone’s size and exact location. Ultrasound is sometimes used as a first step, particularly for pregnant women or when reducing radiation exposure is a priority, but its sensitivity is significantly lower, catching roughly 45% to 77% of stones depending on the study. Small stones or those in certain locations are easier to miss on ultrasound.
Will It Pass on Its Own?
Whether a kidney stone passes without intervention depends almost entirely on its size. Research tracking nearly 400 stones over 20 weeks found clear size thresholds:
- Under 3 mm: 98% pass on their own
- 3.5 to 4.4 mm: 81% pass on their own
- 4.5 to 5.4 mm: 65% pass on their own
- 5.5 to 6.4 mm: 33% pass on their own
- 6.5 mm or larger: only 9% pass on their own
Most stones that will pass do so within a few days to a few weeks. During this time, you’ll likely be advised to drink plenty of water to keep urine flowing and help push the stone along. Pain management is the main focus while you wait.
How to Catch and Identify a Stone
If you suspect you’re passing a stone, straining your urine lets you capture it for analysis. You can get a kidney stone strainer from a pharmacy or your doctor’s office. It’s a small mesh or gauze filter you hold under your urine stream every time you use the bathroom. A stone can pass at any time, day or night, so filtering every trip matters.
Passed stones can be surprisingly small. Some look like a grain of sand or a tiny piece of gravel. If you find one, place it in a clean, dry container with a lid. Don’t wrap it in tissue, tape it down, or add any liquid. Your doctor can send it to a lab, where the composition (calcium oxalate, uric acid, or other types) guides decisions about how to prevent future stones.
When It’s an Emergency
Most kidney stones are painful but not dangerous. However, certain symptoms signal a situation that needs immediate medical attention:
- Fever and chills with stone symptoms: This suggests a urinary tract infection behind an obstructing stone, which can escalate quickly into a serious bloodstream infection.
- Pain so severe you can’t sit still, eat, or keep fluids down: Persistent vomiting leads to dehydration and may mean the stone won’t pass without help.
- Inability to urinate: A stone fully blocking urine flow can damage the kidney if not relieved.
- Blood in your urine that doesn’t stop: While some blood is expected, heavy or prolonged bleeding warrants evaluation.
A stone combined with fever is the most urgent scenario. An infected, obstructed kidney can deteriorate within hours, so this combination always warrants an emergency room visit rather than waiting it out.