Need-to-know-Anatomy
The urinary tract includes the kidneys, ureter, bladder, and the urethra. Urine is produced in the kidneys, two bean-shaped organs the size of your fist located in the lower back, flanking the spine. The kidneys release urine into the ureter, a small muscular tube that can dilate up to 7 millimeters in diameter (about 1 /4 of an inch) and connects the kidney to the bladder where urine is stored. When the bladder is full, we release the urine into a narrow tube, the urethra, which channels the urine out of the body.
Each day, nearly one quarter of the blood that's pumped by the heart flows through the kidneys into a network of tiny blood vessels that filter the blood. Together the kidneys contain 1 million tiny structures called nephrons that filter this blood, directing the waste products into tubules. In the tubules the wastes are further processed and partially reabsorbed to generate roughly 1 to 3 quarts of urine that the body needs to eliminate each day. The waste products in the blood are derived from the foods we eat and the normal breakdown of tissue in the body. Not only do the kidneys keep the blood chemically balanced by converting waste products into urine and discharging excess water, but they also produce hormones that are needed to stimulate bone marrow to make red blood cells (erythropoietin), regulate blood pressure (renin), and help maintain healthy calcium levels in the bones and body (calcitriol).
Causes
In general, kidney stones form when specific compounds in the urine become overly concentrated, causing minerals to crystallize. This usually happens near the end of tubules, before fluid leaves the kidney. Initially, the crystals are the size of tiny grains of sand, but over time they can aggregate to form a pebble about a half inch in diameter up to the size of a golf ball. Stones can be relatively smooth and round or irregularly shaped, like an antler. There are four main types of kidney stones, each of which is associated with different chemical conditions in the urinary tract.
In general, kidney stones form when specific compounds in the urine become overly concentrated, causing minerals to crystallize. This usually happens near the end of tubules, before fluid leaves the kidney. Initially, the crystals are the size of tiny grains of sand, but over time they can aggregate to form a pebble about a half inch in diameter up to the size of a golf ball. Stones can be relatively smooth and round or irregularly shaped, like an antler. There are four main types of kidney stones, each of which is associated with different chemical conditions in the urinary tract.
Calcium oxalate stones make up nearly80 percent of the kidney stones in the United States. These stones, composed of calcium oxalate or calcium oxalate mixed with calcium phosphate, are hard, like a piece of gravel. Calcium oxalate stone formation is driven by the relative concentrations of certain chemicals in the urine; too much calcium, too much oxalate (a chemical compound that occurs naturally in many plants we eat), too much phosphate, or too little citrate (a chemical that inhibits minerals from crystallizing in the urine) can lead to the formation of calcium oxalate stones. In many families, there appears to be a genetic predisposition for developing the conditions that favor calcium stone formation, but the genetics are not well understood. Other more rare causes of calcium stone formation include ingesting excessive amounts of vitamin D or calcium, hyperactive parathyroid glands, sarcoidosis (a condition causing small nodule lesions to form in the body), intestinal bypass surgery, or chronic inflammation of the bowel.
Uric acid stones tend to form in concentrated, acidic urine. About 5 to 10 percent of stones consist of uric acid, a byproduct of protein metabolism. Uric acid stones are associated with early stages of diabetes, a high-protein diet, chronic diarrhea, gout, and genetic factors--such as Middle Eastern ethnicity--that can predispose one to developing uric acid stones.
Pure calcium phosphate stones tend to form in urine that is too alkaline, a condition often caused by renal tubular acidosis. Renal tubular acidosis can be an inherited genetic disorder or arise later in life in association with other disease processes. Overly alkaline urine can also result from chronic ingestion of high quantities of antacids.
Struvite stones are relatively soft and almost always the result of chronic urinary tract infections caused by specific strains of bacteria. These bacteria produce enzymes that increase ammonia concentration in the urine. This ammonia-rich environment favors the formation of magnesium ammonium phosphate crystals, the minerals composing struvite stones. Struvite stones tend to grow quickly, incorporating the bacteria in the stone itself. Struvite stones must be removed surgically to eliminate the bacteria causing the urinary tract infection.
Cystine stones are rare and are associated with cystinuria, an inherited metabolic disorder. In affected individuals, the kidneys are not able to reabsorb cystine, leading to high levels of citrate in the urine, where it can crystallize to form cystine kidney stones. With this rare disease, cystine stones can start forming in young infants and continue throughout their life. Cystine stones are one of the physically hardest types of kidney stone.
Risk Factors
The risk factors for kidney stones fall into two categories: those you can control through lifestyle choices and those traits you are born with. Having a risk factor doesn't mean that you'll develop a disease or condition. Medical research continues to reveal how risk factors interact to influence a person's health and life span. However, understanding your risk allows you to balance the value you place on your health with the risk that may compromise your health in the future. In the United States, the incidence of kidney stones is on the rise, especially in young children. Many experts attribute this increase to changes in lifestyle such as poor diet and a decrease in water consumption.
Risk factors for forming a kidney stone include:
Familial or personal history of kidney stones. If a first-degree relative (mother, father, or sibling) has had a kidney stone, your risk of developing a kidney stone increases dramatically. If you have had a kidney stone, your risk of developing a subsequent one increases dramatically. The risk of developing subsequent kidney stones increases with each episode.
Lack of fluids. You're more likely to form stones if you live in a hot dry climate, work in a hot environment like a commercial kitchen, exercise strenuously without replacing fluids, or habitually drink relatively low amounts of fluid.
Elevated calcium levels in the urine. Elevated calcium levels in the blood increase the likelihood of developing a kidney stone.
Renal tubular acidosis, cystinuria, gout, chronic urinary tract infections, and hyperparathyroidism are the more common diseases that are associated with kidney stones.
High-protein and low-fiber diet increases the risk of forming a kidney stone.
Obesity and sudden weight gain increase the risk of developing a kidney stone.
Medications
For people who continue to form kidney stones after dietary changes, doctors can prescribe medications that prevent kidney stones. Medications commonly prescribed to prevent kidney stones include:
Kidney Stones - Medications
Medicine you can buy without a prescription, such as nonsteroidal anti-inflammatories (NSAIDs), may relieve your pain. Your doctor can give you stronger pain medicine if needed. NSAIDs include aspirin and ibuprofen (such as Motrin and Advil).
Your doctor may prescribe medicine to help your body pass the stone. Calcium channel blockers and alpha-blockers have been shown to help kidney stones pass more quickly with very few side effects.11 Ask your doctor if one of these medicines can help you.
If you get more kidney stones despite drinking more fluids and making changes to your diet, your doctor may give you medicine to help dissolve your stones or to prevent new ones from forming. You may also receive prescription medicine if you have a disease that increases your risk of forming kidney stones. Which medicine you take depends on the type of stones you have.
Medication Choices
Medicine to prevent calcium stones
About 80% of kidney stones are calcium stones.1 Calcium stones cannot be dissolved by changing your diet or taking medicines. There are medicines that may keep calcium stones from getting bigger or may prevent new calcium stones from forming:
Thiazides (such as hydrochlorothiazide, chlorthalidone) and potassium citrate(Urocit-K) are commonly used to prevent calcium stones.
Orthophosphate (Neutra-Phos) is sometimes used. It has more side effects than thiazides or potassium citrate.
Medicine to prevent uric acid stones
About 5% to 10% of kidney stones are made of uric acid, a waste product that normally exits the body in the urine.1 Uric acid stones can sometimes be dissolved with medicine.
Potassium citrate (Urocit-K) and sodium bicarbonate (baking soda) prevent the urine from becoming too acidic, which helps prevent uric acid stones.
Allopurinol (Lopurin, Zyloprim) makes it more difficult for your body to make uric acid.
Medicine to prevent cystine stones
Less than 1% of kidney stones are made of a chemical called cystine.1 Cystine stones are more likely to occur in families with a disease that results in too much cystine in the urine (cystinuria).
Potassium citrate (Urocit-K) prevents the urine from becoming too acidic, which helps prevent cystine kidney stones from forming.
Penicillamine (Cuprimine, Depen), tiopronin (Thiola), and captopril (Capoten) all help keep cystine dissolved in the urine, which makes cystine-type kidney stones less likely to form.
Medicine to prevent struvite stones
About 10% to 15% of kidney stones are struvite stones.1 They can also be called infection stones if they occur with kidney or urinary tract infections (UTIs). These types of kidney stones sometimes are also called staghorn calculi if they grow large enough.
Urease inhibitors (Lithostat) are rarely used because of their side effects and poor results.
What To Think About
If you have uric acid stones or cystine stones and are taking medicine to prevent more stones from forming, you will most likely have to continue taking that medicine for the rest of your life.
Some struvite stones (staghorn calculi) form because of frequent kidney infections. If you have a struvite stone, you will most likely need antibiotics to cure the infection and help prevent new stones from forming, and you will most likely need surgery to remove the stone.
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Kidney Stones - Treatment
http://www.urologychannel.com/kidneystones/treatment.shtml
http://www.urologychannel.com/kidneystones/treatment.shtml
