Kidney stones: symptoms, passing them, and prevention
Last updated September 3, 2026.
Kidney stones are some of the worst pain a person can have, but most small stones pass on their own. A stone is a hard crystal that forms in the kidney and only causes trouble when it drops into the ureter, the narrow tube to the bladder. Stones under about 5mm usually pass within a few weeks with pain control and fluids; bigger ones often need a procedure.
What does it feel like?
The classic pattern is pain that starts in your back or side, below the ribs, and comes in waves as the ureter squeezes around the stone. As the stone moves down, the pain often travels toward your groin or testicle/labia. Urine may turn pink, red, or brown from blood, and nausea or vomiting is common when the pain peaks. As the stone nears the bladder you can feel burning when you pee and a constant need to go, even with an empty bladder. Pain that stays constant, mild, and high in the back with no urinary symptoms is less typical and worth rethinking.
What actually helps?
- NSAIDs first: ibuprofen 400-600mg with food, up to three times a day, controls stone pain better than opioids for most people. Skip NSAIDs if you have kidney disease, a stomach ulcer, or take blood thinners; acetaminophen is the fallback.
- Tamsulosin: 0.4mg once daily for up to 4 weeks relaxes the ureter and helps stones in the 5-10mm range pass sooner. Doctors commonly prescribe it off-label for this.
- Steady fluids: drink enough to keep your urine pale yellow, roughly 2.5 to 3 liters of output a day while the stone passes. Sip steadily; forcing huge volumes while nauseated just makes you vomit.
- Strain your urine: a coffee filter or kitchen strainer works. A captured stone can be analyzed, and the type (calcium oxalate, uric acid, struvite, cystine) drives your prevention plan.
- Keep moving: walking and normal activity help the stone migrate. Bed rest does not.
How do you stop the next one?
About half of people who pass one stone form another within 5 to 10 years, so prevention is real work. The biggest lever is urine volume: enough fluid that your urine stays pale all day, including a glass before bed. Eat normal amounts of calcium with meals (low-calcium diets actually raise stone risk, because calcium binds oxalate in the gut), keep sodium low, go moderate on animal protein, and pair high-oxalate foods like spinach, beets, nuts, and chocolate with a calcium source. Citrus juice raises citrate, which blocks crystal formation. After a second stone, or a first one with risk factors, ask for a 24-hour urine collection so prevention can be targeted instead of generic.
When is it an emergency?
Fever or chills on top of stone pain is the one that cannot wait: an infected, blocked kidney can progress to sepsis within hours, so that is an emergency room now, not tomorrow. The same goes for pain that oral medicine cannot control, vomiting that stops you keeping fluids or pills down, having only one kidney, or producing no urine. Kidney stones in pregnancy also need same-day assessment. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
What a Pymander AI doctor consult looks like
Illustrative example, not a real member's messages.
Common questions
How long does it take to pass a kidney stone?
It depends mostly on size and position. Stones under 4mm usually pass on their own within a couple of weeks. Stones between 4 and 6mm can take several weeks and pass on their own only about half the time, so many end up needing tamsulosin or a procedure. Stones over 6mm rarely pass without help. Stones sitting low in the ureter pass faster than ones still up near the kidney. If a stone has not moved on imaging after 4 to 6 weeks, urologists usually stop waiting and remove it, because a stuck stone can silently damage the kidney.
What does kidney stone pain actually feel like?
People describe it as waves of intense, cramping pain that build, peak, and ease as the ureter contracts around the stone. It typically starts in the back or side below the ribs and migrates toward the lower abdomen and groin as the stone descends. Unlike a muscle strain, moving around or changing position does not relieve it, which is why people with stones pace or writhe rather than lie still. Pain between waves can fade to a dull ache or disappear completely for stretches.
Does drinking more water actually help?
Yes, and it is the single most effective prevention measure. High fluid intake dilutes the minerals that crystallize into stones; the goal is enough to keep urine pale yellow and produce roughly 2.5 liters of urine a day. Water is fine, and citrus juices add citrate, which directly inhibits crystal formation. Sugary colas are the exception: they are linked to higher stone risk, so they do not count toward your fluids.
What foods cause kidney stones?
No single food causes stones, but patterns matter. High sodium pulls calcium into the urine, heavy animal protein intake raises uric acid and lowers citrate, and high-oxalate foods (spinach, beets, rhubarb, nuts, chocolate, tea) add raw material for the most common stone type. The counterintuitive one is calcium: eating normal amounts with meals protects you, because calcium binds oxalate in the gut before it reaches the kidneys. Restricting dietary calcium is an outdated idea that raises risk.
Do I need surgery for a kidney stone?
Most stones never need surgery. When one does, the common options are shock wave lithotripsy, which breaks the stone with sound waves from outside the body, and ureteroscopy, where a thin scope is passed up to grab or laser the stone. Both are outpatient procedures. Very large stones may need a percutaneous procedure through the back. The decision comes down to size, location, whether the stone is moving on serial imaging, infection, and how much pain you are in.
Can a kidney stone damage my kidneys?
A single stone that passes within a few weeks almost never causes lasting harm. The risk comes from stones that block urine flow for weeks to months, which can quietly injure the kidney even when pain fades, and from infected obstructing stones, which are dangerous fast. This is why doctors image a stone that has not passed and why fever with stone pain is treated as an emergency rather than a wait-and-see.