Kidney stones are accumulations of minerals and crystallized salts that form in the upper part of the urinary system. Most remain in the kidney, but some dislodge and move down the ureter into the bladder. Small stones may pass unnoticed through the urinary tract, but larger ones make their presence known with severe colicky pain. The onset of an attack may be mild, but the pain inten sifies rapidly, disappearing only when the stone is passed. If a stone becomes lodged along the way, the resulting pain is extreme and immobilizing. Each year, approximately 1 in 1,000 Americans is hospitalized with kidney stones; men outnumber women about three to one. At least half of those who suffer one attack will have a recurrence. Although about 80 percent of kidney stones contain calcium, the role of this mineral in their formation is unclear. Doctors believe that the problem could be connected to the faulty metabolism of calcium. Perhaps more calcium than the body needs is absorbed from food, and some of the excess remains in the kidneys rather than being excreted in the urine. Or a metabolic problem may prompt the bones to release excessive calcium into the bloodstream. Stones that contain uric acid are frequently due to a metabolic disorder that results in over production of uric acid. In about 10 percent of cases, a bacterial infection prompts stone formation.
Diagnostic Studies And Procedures
Diagnostic tests include blood and urine studies and X-rays of the kidney, ureters, and bladder. An ultrasound examination of the kidneys and urinary tract may also be ordered; for this test, high frequency waves are used to create an image of internal structures. When the stone or stones are passed or removed, they should be collected for analysis to find the underlying cause.
Most stones eventually pass on their own; painkillers and perhaps antibiotics are prescribed while waiting for this to happen. If a stone is blocking the ureter, a device called a ureteral stent may be used to widen the tube and allow urine to pass through it. Stones that cannot be passed naturally must be removed. In the past, this often required major surgery. Today, less invasive treatments are available.
Laser surgery offers one of the safest and least invasive ways to remove stones lodged in the ureter. The procedure entails inserting a hair thin optical fiber into the ureter. When the fiber reaches a stone, it releases a burst of energy in the form of a very intense light beam, which breaks up the stone without harming surrounding tissue. The stone fragments are then passed in the urine or extracted through a urinary catheter. Laser surgery takes about a half hour, but a few days of hospitalization may be needed.
Percutaneous surgery is a minor operation in which an endoscope is inserted into the kidney through a small incision. If the stone is small enough, it can be snared and removed. A larger stone will be broken up by shock waves, allowing its natural passage.
Lithotripsy uses shock waves to break up the stone. The patient sits in a tub of water positioned under a lithotripter, which delivers shock waves to the kidneys and pulverizes any stone into tiny fragments. Some specialists discourage this procedure because the shock waves may damage the kidneys, and any stone fragments remaining in the kidneys can lead to new stones. After an acute attack, treatment involves preventing new stones. Thiazide diuretics, such as hydrochlorothiazide (Esidrix, HydroDIURIL), may be prescribed to lower the amount of calcium excreted in the urine. Allopurinol and/or potassium citrate may be used to prevent uric acid stones.
Juniper berry extract or tea may be advocated for its diuretic properties to flush out the kidneys.
Dietary changes depend upon the type of stone. If excessive calcium absorption is a factor, moderate restriction of calcium intake may help. Because high doses of vitamin C can precipitate stone formation, supplements should be avoided.
Drink at least eight 8 ounce glasses of water every day; some urologists recommend even more. Plain water is best. Avoid sugary soft drinks, as well as carbonated beverages high in phosphates. Foods high in oxalates, salts that promote stone formation by binding with calcium ions, may have to be limited. These include green leafy vegetables, chocolate, tea, and many nuts.
Other Causes of Renal Colic
Nephritis can cause severe flank pain. Bladder stones, which are similar to kidney stones in composition, may obstruct urine flow.