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The biggest kidney stone on record
weighed more than a kilogram

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and was 17 centimeters in diameter.

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The patient didn't actually
swallow a stone the size of a coconut.

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Kidney stones form inside the body,

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but unfortunately, they're extremely
painful to get out.

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A kidney stone is a hard mass
of crystals that can form in the kidneys,

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ureters,

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bladder,

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or urethra.

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Urine contains compounds 
that consist of calcium,

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sodium,

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potassium,

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oxalate,

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uric acid,

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and phosphate.

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If the levels of these particles
get too high,

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or if urine becomes too acidic
or basic,

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the particles can clump together
and crystallize.

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Unless the problem is addressed,

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the crystals will gradually grow
over a few weeks, months, or even years,

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forming a detectable stone.

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Calcium oxalate is the most common
type of crystal to form this way,

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and accounts for about 
80% of kidney stones.

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Less common kidney stones are made
of calcium phosphate, or uric acid.

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A slightly different type of stone

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made of the minerals magnesium
ammonium phosphate, or struvite,

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can be caused by bacterial infection.

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And even rarer stones can result
from genetic disorders

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or certain medications.

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A kidney stone can go undetected
until it starts to move.

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When a stone travels
through the kidney and into the ureter,

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its sharp edges scratch
the walls of the urinary tract.

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Nerve endings embedded in this tissue
transmit excruciating pain signals

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through the nervous system.

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And the scratches can send blood flowing
into the urine.

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This can be accompanied 
by symptoms of nausea,

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vomiting,

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and a burning sensation while urinating.

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If a stone gets big enough
to actually block the flow of urine,

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it can create an infection,
or back flow,

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and damage the kidneys themselves.

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But most kidney stones 
don't become this serious,

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or even require invasive treatment.

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Masses less than five millimeters
in diameter

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will usually pass out 
of the body on their own.

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A doctor will often simply recommend
drinking large amounts of water

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to help speed the process along,

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and maybe taking some pain killers.

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If the stone is slightly larger,
medications like alpha blockers

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can help by relaxing the muscles
in the ureter

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and making it easier 
for the stone to get through.

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Another medication called
potassium citrate

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can help dissolve the stones by creating
a less acidic urine.

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For medium-sized stones up to about
ten millimeters,

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one option is pulverizing them
with soundwaves.

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Extracorporeal shock wave lithotripsy
uses high-intensity pulses

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of focused ultrasonic energy
aimed directly at the stone.

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The pulses create vibrations inside
the stone itself

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and small bubbles jostle it.

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These combined forces crush the stone
into smaller pieces

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that can pass out of the body more easily.

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But zapping a stone with sound
doesn't work as well

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if it's simply too big.

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So sometimes, more invasive
treatments are necessary.

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A rigid tube called a stent
can be placed in the ureter to expand it.

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Optical fibers can deliver laser pulses
to break up the stone.

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Stones can also be surgically removed
through an incision

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in the patient's back or groin.

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What about just avoiding kidney stones
in the first place?

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For people prone to them,

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their doctor may recommend
drinking plenty of water,

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which dilutes the calcium oxalate
and other compounds

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that eventually build up 
into painful stones.

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Foods like potato chips,

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spinach,

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rhubarb,

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and beets are high in oxalate,

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so doctors might advise limiting them.

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Even though calcium 
is often found in stones,

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calcium in foods and beverages
can actually help

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by binding to oxalate 
in the digestive tract

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before it can be absorbed
and reach the kidneys.

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If you do end up with a kidney stone,
you're not alone.

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Data suggests that rates are rising,

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but that world record probably
won't be broken any time soon.