kidney stone

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.

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. About 75% 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 cystine.

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 possible 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.

kidney stones symptoms and signs

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 by nausea 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 blood in the urine. If infection is present in the urinary tract along with the stones, there may be fever and chills. Sometimes, symptoms such as difficulty urinating, urinary urgency, penile pain, or testicular pain may occur due to kidney stones.

kidney stones diagnosed

The diagnosis of kidney stones is suspected when the typical pattern of symptoms is noted and when other possible causes of the abdominal or flank pain are excluded. Imaging tests are usually done to confirm the diagnosis. A helical CT scan without contrast material is the most common test to detect stones or obstruction within the urinary tract. Formerly, an intravenous pyelogram (IVP; an X-ray of the abdomen along with the administration of contrast dye into the bloodstream) was the test most commonly used to detect urinary tract stones, but this test has a greater risk of complications, takes longer, and involves higher radiation exposure than the non-contrasted helical CT scan. Helical CT scans have been shown to be a significantly more effective diagnostic tool than the IVP in the diagnosis of kidney or urinary tract stones.

What is the treatment for kidney stones? How long does it take to pass a kidney stone?

Most kidney stones eventually pass through the urinary tract on their own within 48 hours, with ample fluid intake. Ketorolac (Toradol), an injectable anti-inflammatory drug, and narcotics may be used for pain control when over-the-counter pain control medications are not effective. Intravenous pain medications can be given when nausea and vomiting are present.

Although there are no proven home remedies to dissolve kidney stones, home treatment may be considered for patients who have a known history of kidney stones. Since most kidney stones, given time, will pass through the ureter to the bladder on their own, treatment is directed toward control of symptoms. Home care in this case includes the consumption of plenty of fluids.Ibuprofen (Advil) may be used as an anti-inflammatory medication if there is no contraindication to its use. If further pain medication is needed, stronger narcotic pain medications may be recommended.

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. Stones larger than 9 mm-10 mm rarely pass without specific treatment.

Some medications have been used to increase the passage rates of kidney stones. These include calcium channel blockers such as nifedipine (Adalat, Procardia, Afeditab, Nifediac) and alpha blockers such as tamsulosin(Flomax). These drugs may be prescribed to some people who have stones that do not rapidly pass through the urinary tract.

For kidney stones that do not pass on their own, a procedure called lithotripsy is often used. In this procedure, shock waves are used to break up a large stone into smaller pieces that can then pass through the urinary system.

Surgical techniques have also been developed to remove kidney stones when other treatment methods are not effective. This may be done through a small incision in the skin (percutaneous nephrolithotomy) or through an instrument known as an ureteroscope passed through the urethra and bladder up into the ureter.