kidney stone(redirected from Uric acid nephrolithiasis)
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About 80 per cent of kidney stones are composed of calcium salts, which precipitate out of their normally soluble form in urine, usually because the patient has an inherited tendency to excrete excessive amounts of calcium (idiopathic hypercalcemia). A very small percentage of kidney stones are associated with a parathyroid tumor that increases production of parathyroid hormone and thus raises the serum calcium level. Persons with intestinal absorption problems, including those who have had intestinal bypass surgery for obesity, sometimes develop calcium stones because of excessive absorption of dietary oxalate, which is eventually excreted by the kidneys. Since vitamin C is converted by the body into oxalate, large doses of the vitamin can predispose one to stone formation.
The most common type of stones is the oxalate calculi, hard ones consisting of calcium oxalate; some have sharp spines that can abrade the renal pelvic epithelium, and others are smooth. Another common type is the phosphate calculi, which contain calcium phosphate in a mineral form such as brushite or whitlockite; they may be hard, soft, or friable and range from small to so large that they fill the renal pelvis. Struvite stones are composed of the salt magnesium ammonium phosphate and form in alkaline urine such as that produced in urinary tract infections. Uric acid stones form when there is an increased excretion of uric acid, as in gout or certain malignancies. An acid urine favors their formation. Cystine stones are associated with cystinuria, a hereditary kidney disorder in which there is excessive excretion of cystine. “Staghorn stones” are ones that have extended from the renal pelvis into the calyces, giving them sharp protrusions like the antlers of a stag.
Additional preventive measures include avoidance or prompt treatment of urinary tract infections, changing the urinary pH in cases in which acidity or alkalinity predisposes to stone formation, treatment of underlying pathologies such as parathyroid tumor, and careful long-term follow-up of patients who have had intestinal bypass surgery or a history of intestinal malabsorption.
Uric acid stones can be prevented by administering the drug allopurinol, which inhibits the formation of uric acid, and by keeping the urine relatively alkaline. An alkaline urine and high intake are effective means of preventing cystine stones. If these measures fail, however, the drug penicillamine may be prescribed.
A specific strategy for prevention of stone formation in an individual patient requires chemical analysis of the stones, urine, and blood to determine the type of stone being formed.
The classic symptoms of renal colic occur when a small calculus is dislodged from the renal pelvis and begins to travel down the ureter. Many stones have sharp spicules or spikes on their surfaces; as they roll along the ureter they can scrape the lining, causing excruciating pain and bleeding. The pain is typically felt in the flank over the affected kidney and ureter and radiates downward toward the genitalia and inner thigh. Nausea and vomiting can occur as a result of the severe pain. If an infection is present the patient experiences fever and chills.
If the stone is not passed, the traditional treatment has been surgical intervention to remove it via ureteroscopy. A newer noninvasive technique is lithotripsy, which involves crushing the stone into fragments small enough to be passed in the urine; this is done using any of a variety of techniques, the most common being ultrasound.
Analgesics should be administered promptly to provide relief of pain and facilitate passage of the stone. Fluid intake and output are measured; the intake is encouraged to be 4000 ml every 24 hours. Characteristics of the urine are noted, and all urine is strained until the stone is either passed or removed surgically. Dietary restrictions and recommendations to alter urinary pH and the reason for increased fluid intake are explained to the patient and family members as appropriate. The patient also is taught to take prescribed medications faithfully and to report symptoms of urinary tract infection promptly.
re·nal cal·cu·lus(rē'năl kal'kyū-lŭs)
Synonym(s): kidney stone.
Patient discussion about kidney stone
Q. Why do i get kidney stones? I am 38 and have had three stones pass so far. Is it the coffee, the meat, the stress, or the damned DNA?! My uncle is in his 50s and has passed over 30 stones!
Q. Would kidney stones affect a PSA reading? Would drinking lots of grapefruit juice affect a PSA reading? My husband's PSA reading jumped from a 4.2 to a 17 in @ 2 years' time. How can that be? This man takes all sorts of supplements and really watches his diet. He also takes good care of his body, and does NOT look or act 68.
Q. How can i overcome kidney ache? in the morning it appears.after wake up.