- Kidney stones are rock-like accumulations that form from mineral salts and can become lodged in the kidney or kidney tube.
- Untreated, stones that block the flow of urine can lead to serious complications, including recurrent infections and kidney damage.
- In many cases, recurrence of kidney stones can be prevented by simple lifestyle changes, such as drinking more water or changing one's diet.
Kidney stones are rock-like accumulations that form from naturally occurring mineral salts in the urine. Urinary stones most often form in the kidneys and for this reason are sometimes referred to as kidney stones. However, urinary stones (or calculi) are more accurately classified according to where they are first discovered-in the kidneys, ureter (kidney tube), or bladder.
What are the Symptoms?
Symptoms of urinary stones usually appear suddenly. They include:
- Severe back pain;
- Nausea and occasional vomiting;
- Finding it impossible stand, sit, or lie comfortably; and
- A burning sensation during urination or blood in the urine.
Other symptoms may appear because of an infection promoted by the stone. They include:
Causes and risk factors
- Chills and fever;
- Cloudy or foul-smelling urine; and
- Extremely painful urination.
Different types of urinary stones have different causes. For example:
- Calcium stones: The most common form, calcium stones occur when there is too much calcium and/or oxalate in the blood. Taking certain drugs or too much vitamin D can increase calcium concentrations. Genetics or a diet high in oxalate-rich foods such as spinach can elevate oxalate levels.
- Uric acid stones: Excess uric acid, a byproduct of protein metabolism, can crystallize to form stones.
- Struvite stones: Struvite stones are created by bacteria that infect the urinary tract and usually appear in women.
- Cystine stones: These rare stones occur in people with a hereditary condition that causes the kidneys to excrete large amounts of certain amino acids.
By one estimate, 1 in 10 people will develop urinary stones sometime during their lifetime. Risk factors include:
- Gender: Stones typically occur in men, who are 2 to 3 times more likely than women to develop this problem;
- Age: Most stones occur in men between the ages of 40 and 60;
- Lifestyle: Factors include being sedentary, eating a diet high in animal protein; and not drinking enough water;
- Family history; and
- Chronic urinary tract infections.
Most stones are discovered only after they cause symptoms.
The physician will start with a physical examination to rule out other serious conditions, such as acute appendicitis. A urinalysis test is also performed to determine if any infection or blood is present. The physician will ask a number of questions about medical history and lifestyle habits like diet and exercise as well.
Next the physician will try to locate the stone and determine its size. He or she may order the following tests:
- X ray: A traditional x ray showing the pelvic area, kidneys, and bladder is often sufficient to locate urinary stones.
- Intravenous pyelogram: For this type of x ray, a medical dye is injected into the bloodstream to provide visual contrast on the x ray, allowing the physician to clearly see the stone and assess the degree of obstruction.
- Computerized tomography (CT) scan: The CT scan provides high-resolution x rays and can assess stone location and degree of obstruction without the need for intravenous contrast dyes.
All urinary stones should be treated to avoid serious, even life-threatening, complications. Treatment varies according to the location, size, and chemical composition of the stone.
Most small stones eventually exit the body on their own. For this reason, a patient with small stones is usually prescribed pain medication and is instructed to drink as much fluid as possible to help flush out the stone.
If the stone presents an immediate threat to a patient's health, if pain becomes constant, or if the stone does not pass in a reasonable length of time, procedures can remove the stone. They include:
- Lithotripsy: In this procedure, sound waves created outside the body pulverize the stones inside the body;
- Ureterorenoscope: A ureterorenoscope allows the surgeon to view and extract stones through the urinary opening. Once the stone has been located, the surgeon can grasp it with tiny tweezers and remove it, or fragment the stone using sound waves or a laser; and
Depending on the type of stone, lifestyle changes can help prevent recurrence. Most patients are advised to drink large amounts of water-more than 14 cups a day. Since high intakes of fish, beef, or poultry can cause stones, a diet low in animal protein may also be recommended.