A kidney stone, also known as a renal calculus or nephrolith, is a solid piece of material which is formed in the kidneys from minerals in urine.[1] Kidney stones typically leave the body in the urine stream, and a small stone may pass without causing symptoms.[1] If stones grow to sufficient size (usually at least 3 millimeters (0.12in)) they can cause blockage of the ureter. This leads to pain, most commonly beginning in the flank or lower back and often radiating to the groin. This pain is often known as renal colic and typically comes in waves lasting 20 to 60 minutes. Other associated symptoms include: nausea, vomiting, fever, blood in the urine, pus in the urine, and painful urination. Blockage of the ureter can cause decreased kidney function and dilation of the kidney.
Most stones form due to a combination of genetics and environmental factors.[1] Risk factors include being overweight, certain foods, some medications, and not drinking enough fluids.[1] The diagnosis is usually based on symptoms, urine testing, and medical imaging.[1]Blood tests may also be useful.[1]Urinary stones are typically classified by their location in the kidney (nephrolithiasis), ureter (ureterolithiasis), or bladder (cystolithiasis), or by their chemical composition (calcium-containing, struvite, uric acid, or other compounds).
In those who have previously had stones, prevention is recommended by drinking fluids such that more than two liters of urine is produced per day. If this is not effective enough, thiazide diuretic, citrate or allopurinol may be taken. It is recommended that soft drinks containing phosphoric acid (typically colas) be avoided.[2] When a stone causes no symptoms, no treatment is needed. For stones which are causing symptoms, pain control is usually the first measure, using medications such as nonsteroidal anti-inflammatory drugs or opioids.[3] More severe cases may require procedures. For example, some stones can be shattered into smaller fragments using extracorporeal shock wave lithotripsy. Others require cystoscopic procedures.
In the United States about 9% of the population has had a kidney stone.[1] Slightly more men are affected than women.[4] In 2013 kidney stones resulted in about 15,000 deaths globally.[5]
The hallmark of a stone that obstructs the ureter or renal pelvis is excruciating, intermittent pain that radiates from the flank to the groin or to the inner thigh.[6] This pain, known as renal colic, is often described as one of the strongest pain sensations known.[7] Renal colic caused by kidney stones is commonly accompanied by urinary urgency, restlessness, hematuria, sweating, nausea, and vomiting. It typically comes in waves lasting 20 to 60 minutes caused by peristaltic contractions of the ureter as it attempts to expel the stone.[6] The embryological link between the urinary tract, the genital system, and the gastrointestinal tract is the basis of the radiation of pain to the gonads, as well as the nausea and vomiting that are also common in urolithiasis.[8]Postrenal azotemia and hydronephrosis can be observed following the obstruction of urine flow through one or both ureters.[9] Pain in the lower left quadrant can sometimes be confused with diverticulitis because the sigmoid colon overlaps the ureter and the exact location of the pain may be difficult to isolate due to the close proximity of these two structures.
Dehydration from low fluid intake is a major factor in stone formation.[6][10]
High dietary intake of animal protein,[6]sodium, refined sugars, fructose and high fructose corn syrup,[11]oxalate,[4]grapefruit juice, and apple juice may increase the risk of kidney stone formation.[10]
Kidney stones can result from an underlying metabolic condition, such as distal renal tubular acidosis,[12]Dent's disease,[13] hyperparathyroidism,[14] primary hyperoxaluria,[15] or medullary sponge kidney. 320% of people who form kidney stones have medullary sponge kidney.[16][17]
Kidney stones are more common in people with Crohn's disease;[18] Crohn's disease is associated with hyperoxaluria and malabsorption of magnesium.[19]
A person with recurrent kidney stones may be screened for such disorders. This is typically done with a 24-hour urine collection. The urine is analyzed for features that promote stone formation.[9]
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Kidney stone - Wikipedia, the free encyclopedia