Kidney stone facts
- A kidney stone is a hard, crystalline mineral material formed within the kidney or urinary tract.
- Nephrolithiasis is the medical term for kidney stones.
- Symptoms of a kidney stone include flank pain (the pain can be quite severe) and blood in the urine (hematuria).
- Kidney stones form when there is a decrease in urine volume and/or an excess of stone-forming substances in the urine.
- Dehydration is a major risk factor for kidney stone formation.
- People with certain medical conditions, such as gout, and those who take certain medications or supplements are at risk for kidney stones.
- Diet and hereditary factors are also related to stone formation.
- Diagnosis of kidney stones is best accomplished using an ultrasound, IVP, or a CT scan.
- Most kidney stones will pass through the ureter to the bladder on their own with time.
- Treatment includes pain-control medications and, in some cases, medications to facilitate the passage of urine.
- If needed, lithotripsy or surgical techniques may be used for stones which do not pass through the ureter to the bladder on their own.
What is a kidney stone?
A kidney stone is a hard, crystalline mineral material formed within the kidney or urinary tract. Kidney stones are a common cause of blood in the urine (hematuria) and often severe pain in the abdomen, flank, or groin. Kidney stones are sometimes called renal calculi.
The condition of having kidney stones is termed nephrolithiasis. Having stones at any location in the urinary tract is referred to as urolithiasis, and the term ureterolithiasis is used to refer to stones located in the ureters.
What causes kidney stones?
Kidney stones form when there is a decrease in urine volume and/or an excess of stone-forming substances in the urine. The most common type of kidney stone contains calcium in combination with either oxalate or phosphate. A majority of kidney stones are calcium stones. Other chemical compounds that can form stones in the urinary tract include uric acid, magnesium ammonium phosphate (which forms struvite stones; see below), and the amino acid cysteine.
Dehydration from reduced fluid intake or strenuous exercise without adequate fluid replacement increases the risk of kidney stones. Obstruction to the flow of urine can also lead to stone formation. In this regard, climate may be a risk factor for kidney stone development, since residents of hot and dry areas are more likely to become dehydrated and susceptible to stone formation.
Kidney stones can also result from infection in the urinary tract; these are known as struvite or infection stones. Metabolic abnormalities, including inherited disorders of metabolism, can alter the composition of the urine and increase an individual’s risk of stone formation.
A number of different medical conditions can lead to an increased risk for developing kidney stones:
- Gout results in chronically increased amount of uric acid in the blood and urine and can lead to the formation of uric acid stones.
- Hypercalciuria (high calcium in the urine), another inherited condition, causes stones in more than half of cases. In this condition, too much calcium is absorbed from food and excreted into the urine, where it may form calcium phosphate or calcium oxalate stones.
- Other conditions associated with an increased risk of kidney stones include hyperparathyroidism, kidney diseases such as renal tubular acidosis, and other inherited metabolic conditions, including cystinuriaand hyperoxaluria.
- Chronic diseases such as diabetes and high blood pressure(hypertension) are also associated with an increased risk of developing kidney stones.
- People with inflammatory bowel disease are also more likely to develop kidney stones.
- Those who have undergone intestinal bypass or ostomy surgeryare also at increased risk for kidney stones.
- Some medications also raise the risk of kidney stones. These medications include some diuretics, calcium-containing antacids, and the protease inhibitor indinavir (Crixivan), a drug used to treat HIV infection.
- Dietary factors and practices may increase the risk of stone formation in susceptible individuals. In particular, inadequate fluid intake predisposes to dehydration, which is a major risk factor for stone formation. Other dietary practices that may increase an individual’s risk of forming kidney stones include a high intake of animal protein, a high-salt diet, excessive sugar consumption, excessive vitamin D supplementation, and excessive intake of oxalate-containing foods such as spinach. Interestingly, low levels of dietary calcium intake may alter the calcium-oxalate balance and result in the increased excretion of oxalate and a propensity to form oxalate stones.
- Hyperoxaluria as an inherited condition is uncommon and is known as primary hyperoxaluria. The elevated levels of oxalate in the urine
What are the signs and symptomsof kidney stones?
While some kidney stones may not produce symptoms (known as “silent” stones), people who have kidney stones often report the sudden onset of excruciating, cramping pain in their low back and/or side, groin, or abdomen. Changes in body position do not relieve this pain. The abdominal, groin, and/or back pain typically waxes and wanes in severity, characteristic of colicky pain (the pain is sometimes referred to as renal colic). It may be so severe that it is often accompanied bynausea and vomiting. The pain has been described by many as the worst pain of their lives, even worse than the pain of childbirth or broken bones. Kidney stones also characteristically cause bloody urine. If infection is present in the urinary tract along with the stones, there may be fever andchills. Sometimes, symptoms such asdifficulty urinating, urinary urgency, penile pain, or testicular pain may occur due to kidney stones.