Kidney stones are solid accumulations of material that form in the tubal system of the kidney. They cause painful problems when they block the flow of urine through or out of the kidney.
Urine is formed by the kidneys. As blood flows into the kidneys, specializedtubes within the kidneys extract a certain amount of fluid and other substances from the blood, which then flows out of the body as urine. Sometimes, a problem in the kidneys makes these dissolved substances become solid again. Sometimes, tiny crystals called "silent stones" may form in the urine that nevercause any pain.
Kidney stones cause problems when they interfere with the normal flow of urine. They can block the flow down the ureter--the tube that carries urine fromthe kidney to the bladder. Because the kidney isn't used to feeling any pressure, when pressure builds from backed-up urine the kidney may swell. If the kidney is subjected to this pressure for some time, it may damage delicate kidney structures. If a kidney stone is lodged further down the ureter, the backed-up urine may also cause the ureter to swell. Because the ureters are muscular tubes, the presence of a stone will make these muscular tubes spasm, causing severe pain.
About 10% of all people will have a kidney stone at some point in life. Kidney stones are most common among:
- People over the age of 30
- People who have had other kidney stones
- Relatives of kidney stone patients.
Kidney stones can be made up of a variety of substances, but the most commontypes are calcium stones; about 80% of all kidney stones fall into this category. People with calcium stones may have other diseases that cause them to have higher blood levels of calcium. These diseases include primary parathyroidism, sarcoidosis, hyperthyroidism, multiple myeloma, and some types ofcancer. A diet heavy in meat, fish, and poultry also can cause calcium oxalate stones.
About 10% of all kidney stones are struvite stones (also called "staghorn kidney stones"), made up of magnesium ammonium phosphate. These stones occur most often in patients who have had repeated urinary tract infections caused bycertain types of bacteria. These bacteria produce a substance that makes theurine less acidic, which allows struvite to settle out of the urine and formstones.
About 5% of all kidney stones are uric acid stones, which occur when higher amounts of uric acid circulate in the blood. When the uric acid content becomes very high, solid bits of uric acid settle out of the urine. A kidney stoneis formed when these bits of uric acid begin to cling to each other within the kidney, slowly growing into a solid mass. About half of all patients with this type of stone also have deposits of uric acid elsewhere in their body, commonly in the joint of the big toe. This painful disorder is called gout. Uric acid stones also may be caused by chemotherapy, certain bone marrow disorders, and an inherited disorder called Lesch-Nyhan syndrome.
About 2% of all kidney stones are stones made of cystine, a type of amino acid. People with this type of kidney stone don't process amino acids normally.
If a kidney stone is present, some people may notice blood in their urine, but patients don't usually notice symptoms until the stones pass into the ureter. At this point, most people will experience bouts of very severe crampy andspasmodic pain known as colic. The pain usually begins in the area between the lower ribs and the hip bone. As the stone moves closer to the bladder, a patient will often feel the pain radiating along the inner thigh. Women may feel pain in the vulva. Men may notice pain in the testicles. Nausea, vomiting, extremely frequent and painful urination, and obvious blood in the urine are common signs of kidney stones. Fever and chills usually mean that theureter has become obstructed, trapping bacteria in the kidney and causing aninfection (pyelonephritis).
Diagnosing kidney stones is based on a patient's history of very severe, distinctive pain together with an X-ray and a urine test. During the passage of astone, there is almost always blood in the urine. A number of x-ray tests are used to diagnose kidney stones. X-ray of the kidneys, ureters, and bladdermay or may not reveal the stone; a series of x-rays taken after injecting iodine dye into a vein is usually a more reliable way of seeing a stone. This procedure is called an intravenous pyelogram (IVP). The dye "lights up" the urinary system as it travels. In the case of an obstruction, the dye willbe stopped by the stone or will only be able to get past the stone at a slowtrickle.
When a patient is passing a kidney stone, it is important that all urine is strained so that they stone can be analyzed to determine its chemical composition. Collecting urine for 24 hours, followed by careful analysis of its chemical makeup, can often determine a number of reasons for stone formation.
Because the pain of passing a kidney stone is so severe, narcotic pain medications such as morphine are usually needed. Stones may pass more quickly if the patient is encouraged to drink large amounts of water (2-3 quarts per day).If the patient is vomiting or unable to drink because of the pain, it may benecessary to provide fluids through a vein. If there is infection, antibiotics will be needed.
Although most kidney stones will pass on their own, some will not. Surgical removal of a stone may become necessary when a stone appears too large to pass. Surgery may also be required if the stone is causing serious obstructions,pain that cannot be treated, heavy bleeding, or infection.
There are several surgical alternatives. In one method, the surgeon inserts atube into the bladder and up into the ureter. A tiny basket is then passed through the tube, and the surgeon tries to snare the stone and pull it out. Open surgery to remove an obstructing kidney stone was relatively common in thepast, but current methods allow the stone to be crushed with shock waves (called lithotripsy). These shock waves may be aimed at the stone from outside of the body; the stone fragments may then pass on their own or may be removedthrough an incision. All of these methods reduce the patient's recovery timeconsiderably when compared to the traditional open operation.
Alternative treatments for kidney stones include the use of herbal medicine,acupuncture, acupressure, hypnosis, or guided imagery to relieve pain. Starfruit may relieve pain and increase the amount of urine a patientpasses. Dietary changes may reduce the risk of future stones and to help absorb existing stones. Supplements of magnesium (a smooth muscle relaxant), canhelp ease pain and help the stone to pass.
How easily a patient recovers depends on the underlying disorder that causedthe kidney stone in the first place. In most cases, patients with simple calcium stones will recover very well. However, about 60% of these patients willhave other kidney stones. Struvite ("staghorn") stones are particularly dangerous because they may grow extremely large, filling the tubes within the kidney. These won't pass out in the urine, and require surgical removal. Uric acid stones may also become staghorn tones.
Patients may be able to prevent certain types of kidney stones. Drinking several quarts of water every day is an important way to head off the problem. Patients with calcium stones may benefit from taking a medication called a diuretic, which decreases the amount of calcium passed in the urine. Eating less meat, fish, and chicken may help patients with calcium oxalate stones.Other items in the diet that may encourage calcium oxalate stone formation include beer, black pepper, berries, broccoli, chocolate, spinach, and tea. When a disease is identified as the cause of stone formation, treatment for that disease may lessen the likelihood of repeated stones.