Definition of Kidney stone
Kidney stone: A stone in the
kidney (or lower down in the urinary tract).
Kidney stones are a common cause of blood in the urine and pain in
the abdomen, flank, or groin. Kidney stones occur in 1 in 20 people
at some time in their life.
The development of the stones is related to decreased
urine volume or increased excretion of stone-forming components such
as calcium, oxalate, urate, cystine, xanthine, and phosphate. The
stones form in the urine collecting area (the pelvis) of the kidney
and may range in size from tiny to staghorn stones the size of the
renal pelvis itself.
The cystine stones (below) compared in size to a quarter (a U.S.
$0.25 coin) were obtained from the kidney of a young woman by
percutaneous nephrolithotripsy (PNL), a procedure for crushing and
removing the dense stubborn stones characteristic of cystinuria.
The pain with kidney stones is usually of sudden onset, very
severe and colicky (intermittent), not improved by changes
in position, radiating from the back, down the flank, and
into the groin. Nausea and vomiting are common.
Factors predisposing to kidney stones include recent reduction in
fluid intake, increased exercise with dehydration, medications
that cause hyperuricemia (high uric acid) and a history of
gout.
Treatment includes relief of pain, hydration and, if
there is concurrent urinary infection, antibiotics.
The majority of stones pass spontaneously within 48 hours.
However, some stones may not. There are several factors
which influence the ability to pass a stone. These include
the size of the person, prior stone passage, prostate
enlargement, pregnancy, and the size of the stone. A 4 mm
stone has an 80% chance of passage while a 5 mm stone has a
20% chance. If a stone does not pass, certain procedures
(usually by a urology specialist doctor) may be needed.
The process of stone formation is called nephrolithiasis
or urolithiasis. "Nephrolithiasis" is derived from the
Greek nephros- (kidney) lithos (stone) = kidney stone
"Urolithiasis" is from the French word "urine" which, in
turn, stems from the Latin "urina" and the Greek "ouron"
meaning urine = urine stone. The stones themselves are also
called renal caluli. The word "calculus" (plural: calculi)
is the Latin word for pebble.
Last Editorial Review: 2/19/1999
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