It starts as a dull ache. Maybe you think you pulled a muscle at the gym or slept weirdly on your side. Then, within an hour, it feels like a lightning bolt is being driven through your flank and twisted by a professional wrestler. Honestly, there isn't much that prepares you for the sheer, localized chaos of a renal colic episode.
When we talk about what happens when you have kidney stones, we aren't just talking about a singular event. It is a biological process—a crystalline traffic jam in your urinary tract that triggers some of the most intense physiological responses the human body is capable of experiencing.
The Chemistry of a "Stone"
Your kidneys are basically high-end filtration plants. They process about 200 quarts of blood daily to sift out waste and extra water. Sometimes, when your urine has high concentrations of certain minerals—calcium, oxalate, uric acid—and not enough liquid to dilute them, they start to stick together.
Imagine a snowflake. Now imagine that snowflake is made of jagged calcium oxalate and refuses to melt.
Most stones, roughly 80%, are calcium oxalate. They look like tiny, angry ginger roots under a microscope, covered in sharp spikes. You might also end up with uric acid stones if your urine is too acidic, or struvite stones, which often follow chronic infections and can grow shockingly large, branching out like coral inside the kidney. These are called "staghorn calculi," and they are as gnarly as they sound.
That Specific, Terrible Pain
Why does it hurt so bad? It’s not actually the stone sitting in your kidney that causes the agony. You could have a stone the size of a marble hanging out in your renal pelvis and never feel a thing.
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The nightmare begins when the stone moves.
When a stone enters the ureter—the narrow tube connecting your kidney to your bladder—it causes a blockage. Your kidney keeps producing urine, but that urine has nowhere to go. Pressure builds up behind the stone, stretching the kidney's delicate lining (the renal capsule) and the ureter itself. This stretching triggers the "colic" sensation. It’s a visceral, deep, throbbing pain because those internal organs don't have the same "touch" sensors as your skin; they only respond to stretch and inflammation.
You’ll likely experience what doctors call "referred pain." Because the nerves serving the kidneys and ureters are neighbors with the nerves for your groin and stomach, your brain gets confused. You might feel like your testicles or labia are on fire, or you might spend three hours over a toilet bowl because the nerve signals are making you violently nauseous.
The Hospital Visit and Diagnostic Reality
If the pain is bad enough that you can't sit still—the "pacing" phase—you’re probably headed to the ER.
Dr. Brian Matlaga, a urologist at Johns Hopkins, often points out that the goal in the acute phase is two-fold: manage the pain and check for infection. If you have a stone plus a fever, that’s a medical emergency. A blocked kidney that is also infected can lead to sepsis very quickly.
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Usually, they’ll run a non-contrast CT scan. It’s the gold standard. It shows exactly where the stone is, how big it is (measured in millimeters), and whether it’s likely to pass on its own.
- Under 4mm: You’ve got an 80% chance of passing it.
- 4mm to 6mm: It’s a coin flip. Might need help.
- Over 6mm: Usually requires intervention.
They might give you "Flomax" (tamsulosin). It was originally for prostate issues, but it helps relax the smooth muscle of the ureter. It basically widens the "pipes" to give the stone a smoother exit.
When It Doesn't Pass: The Intervention
If the stone is too big, or if you’ve been in pain for weeks without progress, the urologist steps in.
One common method is Shock Wave Lithotripsy (SWL). You lie on a water-filled cushion, and they blast you with localized sound waves. It’s weird. You feel a "tapping" sensation, and those waves shatter the stone into "dust" or small fragments you can pee out later.
Then there’s Ureteroscopy. This is less fun to describe. They go in through the natural hardware—no incisions—with a tiny camera and use a laser to turn the stone into pebbles. Often, they leave a "stent" behind. A stent is a thin plastic tube that keeps the ureter open while the internal swelling goes down. Warning: stents can be almost as annoying as the stone itself, causing a constant "I need to pee" sensation for a week.
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The Aftermath and Prevention
Once the stone is out, you aren't necessarily in the clear. If you’ve had one stone, you have a 50% chance of developing another within five to ten years unless you change something.
The most boring advice is the most effective: drink more water. But it’s not just "water." You want your urine to be almost clear.
Dietary changes are nuanced. Many people think they should stop eating calcium. That is actually a mistake. If you don't eat enough calcium, the oxalate in your gut has nothing to bind to, so it travels to your kidneys instead. You want to eat calcium with oxalate-rich foods (like spinach or beets) so they bind in the stomach, not the kidneys.
Watch the salt, too. Sodium forces your kidneys to leak more calcium into the urine, which is basically providing the raw materials for a new stone.
Actionable Steps for the "Stoned"
If you suspect you're dealing with a stone right now, or you've just finished the ordeal, here is the roadmap:
- Strain your urine. If you pass the stone at home, catch it. A lab can analyze its composition. Knowing if it's calcium oxalate vs. uric acid changes your entire prevention strategy.
- Request a 24-hour urine collection. Once the crisis is over, this test measures exactly what's going on in your chemistry. It's the only way to know if your body is dumping too much salt or not enough citrate (a natural stone-inhibitor).
- Check your supplements. High doses of Vitamin C can actually metabolize into oxalate. If you're a "mega-dose" person, you might be accidentally building stones.
- Add lemon to everything. Citrate is your best friend. Real lemon juice in your water helps prevent crystals from sticking together. It’s one of the few "home remedies" that actually has solid urological backing.
- Monitor for the "Triad of Trouble." If you have a stone and experience a fever over 101°F, uncontrollable vomiting, or an inability to urinate at all, stop reading and go to the ER. These are signs of an obstructed, infected kidney.
Dealing with what happens when you have kidney stones is a lesson in patience and pain management. It's a physical reminder that our internal chemistry is a delicate balance. Drink up, watch your salt, and keep an eye on those flank twinges.