Calculus, urinary tract

A stone in the kidneys, ureters, or bladder formed from substances in urine. Most urinary tract stones are composed of calcium oxalate or other salts crystallized from the urine. These may be associated with a diet rich in oxalic acid (found in leafy vegetables and coffee); high levels of calcium in the blood as a result of hyperparathyroidism; or chronic dehydration. Other types of stone are associated with gout and some cancers. An infective stone is usually a result of chronic urinary tract infection. In developing countries, bladder stones usually occur as a result of dietary deficiencies. In developed countries, they are usually caused by an obstruction to urine flow from the bladder and/or a longstanding urinary tract infection. The most common symptom of a stone in the kidney or ureter is renal colic (a severe pain in the loin) that may cause nausea and vomiting. There may be haematuria (blood in the urine). A bladder stone is usually indicated by difficulty in passing urine. The site of the stone can usually be confirmed by intravenous or retrograde urography. Renal colic is treated with bed rest and an opioid analgesic (painkiller). With an adequate fluid intake, small stones are usually passed in the urine without problems. The first line of treatment for larger stones is lithotripsy, which uses ultrasonic or shock waves to disintegrate the stones. Alternatively, cytoscopy can be used to crush and remove stones in the bladder and lower ureter. In some cases, surgery may be needed.


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