Kidney Stones — Types, Causes, and Treatments

Kidney stones, also called renal calculi, form from chemicals in the urine. The urine contains dissolved minerals and salt. These crystals coagulate with other wastes and chemicals, such as calcium, phosphate, urate, oxalate, and xanthine, to form stones.

Kidney stones can be as small as a grain of sand and may slip through the urinary tract without event. However, some are large as a golf ball, cause the patient agony, and may require surgery to be taken out. Sometimes, a kidney stone can become lodged in the ureter, causing bleeding and difficulty urinating.

Kidney stone disease is common in the United States, affecting one in 11 people, costing a total of $4.5 billion. Some believe that kidney stones are a harrowing experience, more painful than broken bones, childbirth, burns, and gunshot wounds.

There are four primary types of kidney stones: calcium, uric acid, struvite or magnesium ammonium phosphate, and cystine. Approximately 75 percent of kidney stones are calcium. These stones form when there is too little fluid and a high amount of calcium, oxalate, phosphate, or cystine. People who are often dehydrated and consume a diet high in protein, sugar, sodium, and oxalate may be at risk of developing calcium stones. Obesity, hyperparathyroidism, Dent disease, and Inflammatory bowel disease also may contribute to the risk of calcium stones.

Struvite stones are made of magnesium ammonium phosphate and make up about 15 percent of all kidney stones. A urinary tract infection that makes the urine alkaline may cause the formation of struvite stones. Typically, struvite stones affect people with urine pH greater than 7 and more women than men.

Uric acid makes up about 6 percent of kidney stones, occurring when a high uric acid level is in the urine. Since these stones are more likely to form when the urine pH is less than 5.5, diuretic medications that help the body expel water and salt and immune-suppressing medications may increase the acidity of the urine. Consumption of beef, pork, fish, eggs, poultry, liver, and kidney may increase uric acid in the urine. People undergoing chemotherapy are more vulnerable to urine acid stones. Further, research shows that about 25 percent of patients with uric acid stones also have gout.

Cystine stones often are caused by cystinuria, a condition sometimes inherited from both parents. Abnormal production of amino acid cystine may form cystine stones.

When the kidney stones are tiny, a doctor may recommend medication and advise the patient to drink plenty of fluids to move the stones out of the urinary tract. When the stones are big, other treatments may be necessary.

Lithotripsy uses shockwaves to break kidney stones into smaller bits so the stones may pass through the urinary tract and out of the body. Ureteroscopy uses a long tubular tool to locate and extract or break up the stones.

In rare cases, doctors may need to perform surgery and insert a tube into the kidney. The operation may require the patient to remain in the hospital for one or two nights.