The urinary tract normally consists of two kidneys, each attached to a ureter (urine tube) that connects the kidney to the bladder, and one urethra which empties the urine out of the bladder to the outside world. The kidneys perform many jobs including removing waste from the blood, keeping a stable balance of salts and other substances in the blood, and producing hormones that help build strong bones and form red blood cells. The ureters have only one job, to carry urine from the kidneys to the bladder. The bladder located in the lower abdomen, has two jobs, to store urine and to empty the stored urine out through the urethra.
Urolithiasis, ureterolithiasis, and nephrolithiasis are all medical terms used to describe stones occurring in the urinary tract, ureter or kidney respectively. Kidney stones are most prevalent in patients between the ages of 30 and 45. According to the U.S. National Institutes of Health, one person in ten develop kidney stones during a lifetime. Patients being treated for kidney stones account for 7 to 10 of every 1,000 hospital admissions.
WHAT CAUSES A KIDNEY STONE TO FORM?
Kidney stones are made when a substance normally dissolved in the urine precipitates out forming a crystal that then grows into a stone. These crystals can begin to form for many reasons:
- Recurrent urinary tract infections
- Drinking too little fluid
- Blockage of the urinary tract
- Limited activity for several weeks or more
- Excessive calcium oxalate or uric acid in your diet
- Excessive vitamin C or D
- Intake of certain medications
- Presence of certain metabolic diseases
The most common reason for stones to form is drinking too little fluid. The reason this leads to stone formation is because it results in too much of the stone forming substance and not enough water to keep it dissolved in the urine. Once a crystal forms, more layers of crystal continue to pile up making a stone. While certain foods may promote stone formation in people who are susceptible, scientists do not believe that eating any specific food causes stones to form in people who are not susceptible. A person with a family history of kidney stones may be more likely to develop stones. Although we know that the above things can increase someone's risk of stone formation, doctors cannot always pinpoint the cause of a stone in some patients. But we do know that once a stone forms, if it remains tiny enough, it may travel through the urinary tract and pass out of the body without being noticed. However, some stones grow too large to be passed out of the body easily and get stuck on their way through the urinary tract. When they get stuck they block the normal flow of urine causing pain, sometimes infection, and sometimes even kidney damage. People with kidney stones need to be under the care of a urologist.
WHAT DO KIDNEY STONES LOOK LIKE?
Kidney stones do not all look the same. The color depends on what substances make up the stone. Most are yellow or brown, but they can be tan, gold, or black. Stones can be round, jagged, or even have branches. They vary in size from specks to pebbles, to stones as big as golf balls.
FOUR MAJOR TYPES OF KIDNEY STONES
There are different types of kidney stones. Some are made of only one substance and some are made up of a mixture of substances.
- The most common type of kidney stone contains calcium. Most stones (70 to 80%) contain mainly calcium oxalate crystals. Calcium is a part of a person's normal diet and an important structural and functional element of the body. Calcium that is not used by the bones and muscles goes to the kidneys and flushed out the urine. Excessive calcium in the urine or problems with the body's ability to eliminate calcium can lead to the development of calcium oxalate stones. Too much calcium can be found in the urine because of the use of certain drugs such as diuretics, antacids, and steroids. Overactive parathyroid glands, too much vitamin A or D, and a diet high in purine (or protein) from meat, fish, and poultry can also lead to too much calcium in the urine. Another cause of calcium oxalate stones is too much oxalate in the urine. This can result from too much oxalate production by the body and not enough calcium in the diet.
- A struvite stone forms from an infection in the urinary system. These stones contain the mineral magnesium and the waste product ammonia. This type of stone, also called an infection stone, is more commonly found in women and develops when a urinary tract infection affects the chemical balance of urine. The stones usually develop as jagged structures called staghorns and can grow to be quite large. For patients with struvite stones, it is important not only to remove the stone, but also to prevent recurrence of the urinary tract infection.
- A uric acid stone may form when there is too much acid in the urine. If the acid level in the urine is high the uric acid normally found in the urine may not dissolve and uric acid stones may form. These stones are more common in men. Patients with gout, a metabolic disorder associated with high uric acid levels, are especially prone to uric acid stones. Different from other types of kidney stones, pure uric acid stones are the only type of stone that can be dissolved with medication.
- Cystine stones are rare. Cystine is one of the building blocks that make up muscles, nerves, and other parts of the body. It is an amino acid and protein that does not dissolve well. Some people inherit a rare condition that results in large amounts of cystine in the urine. This condition, called cystinuria, causes cystine stones that are difficult to treat and requires long-life therapy.
WHAT ARE THE SYMPTOMS OF KIDNEY STONES?
In some cases, kidney stones pass out of the body without producing any symptoms. Most kidney stones, however, do cause some symptoms. The most common symptom from kidney stones is pain. The pain from kidney stones is a result of the stone getting stuck on its way out. The pain is typically a constant pain that intensifies in waves. The pain is located just below the ribs in the vicinity of the kidney. The pain can often shoot from that location to the groin. The patient usually cannot find a position that is more comfortable and usually stands, sits, paces, or reclines, in search of a position that will bring relief. It is common to find blood in the urine either microscopically or , less frequently, visible to the naked eye. If fever and chills accompany any of these symptoms, an infection may be present and medical attention is needed sooner rather than later. It should be noted that the size of the stone does not necessarily predict the severity of the pain. A very tiny crystal can cause intense pain, while a larger stone may not be as disturbing. Stones 4 mm in diameter or less have a 70-90% chance of passing on their own. Larger stones, however, often require a urologist to perform a procedure to remove them.
HOW ARE KIDNEY STONES FOUND?
Although some kidney stones are silent and are diagnosed as a result of an x-ray taken in the course of a general health examination, most kidney stone patients see a urologist because of the sudden pain and/or blood in urine that signals the stones presence. If your doctor thinks you have a stone, its location, size, and type, need to be determined for proper treatment to occur.
I HAVE A KIDNEY STONE. NOW WHAT IS THE UROLGIST GOING TO DO?
Once a kidney stone has been found on an x-ray or CT scan, the doctor will ask you questions about your medical and family history and perform a physical examination. Physical examination may be difficult if the patient is experiencing severe pain and is unable to remain still. Lightly tapping on the kidney region often worsens the pain in people with kidney stones.
- Laboratory Testing: Laboratory testing includes urinalysis to detect the presence of blood (hematuria) and bacteria (bacteriuria) in the urine. Other tests include blood tests for creatinine (to evaluate kidney function), BUN and electrolytes to detect dehydration, calcium to detect hyperparathyroidism, and a complete blood count to detect infection.
- X-rays: A standard x-ray of the kidney, ureter, and bladder, may be adequate as a first step for identifying many stones since most are visible on x-ray.
- Ultrasound: This test uses high frequency sound waves to produce pictures. Ultrasounds can detect a dilated kidney and ureter caused by a stone lodged in the ureter. Ultrasound, however, cannot reliably detect all stones especially stones located outside the kidney. It is the preferred imaging method for kidney stone patients who are pregnant.
- IVP (Intravenous Pyelogram): For an IVP, a special dye is injected into the patient's veins. The dye collects in the urinary system and produces white shadow when an x-ray is taken. The dye allows the doctor to precisely locate the stone and to determine the condition of the kidneys and ureters. Most kidney stones can be precisely located using this procedure.
- CT Scan (Computerized Tomography): This test uses a scanner and a computer to create images of the urinary system. CT scan done to look for kidney stones does not use contrast material. It is the most common and precise imaging test used today to evaluate a possible kidney stone attack.
For small stones in the presence of good kidney function and no infection the urologist may suggest that the best thing to do is just wait and see if the stone will pass if it is given a little time.
Often, you can stay home during this process, drinking fluids and taking pain medication as needed. If the stone passes the urologist will ask you to save the passed stone for testing. Your doctor will use this information to determine the components of the stone. Some stones cause pain that is too severe to be treated at home and the patient needs to be admitted to the hospital. Sometimes, during the hospital stay the stone passes on its own, other times the urologist needs to perform a procedure to relieve the blockage cause by the stone or remove the stone.
Treatment for kidney stones varies depending on the size of the stone, the stone location, the presence of a urinary infection along with the stone, your medical profile, and the severity of the condition. urologists use several procedures to break up, remove, or bypass kidney stones.
Ureteroscopy - This procedure can be used to remove or fragment stones located anywhere from the kidney down to the bladder. A ureteroscope, which is a fiber optic instrument resembling a long, thin telescope, is inserted through the urethra and passed through the bladder up to the location of the stone. The ureteroscope has a camera that allows your urologist to see the stone and a working channel that he can place tiny instruments through. Once the stone is located, the urologist can break the stone up into dust sized pieces using a laser or other fragmenting device, or remove it with a small basket. Ureteroscopy is performed under general or spinal anesthesia on an outpatient basis.
Percutaneous Nephrostolithotomy (PCNL or tunnel surgery) - Percutaneous (through the skin) removal of kidney stones is accomplished by making a small cut through the skin on the patient's back and creating a narrow tunnel through the kidney to the stone. With a special instrument that goes through the tunnel, the doctor finds the stone and removes it. This treatment can achieve the best stone-free outcome in the treatment of very large stones within the kidney. This procedure requires general anesthesia. The patient usually stays in the hospital for 2-3 days and most patients resume normal activity within two weeks.
Shockwaves - Extra-corporeal shockwave lithotripsy (ESWL): has been used in the United States since 1984. It is performed using a machine called a lithotriptor.
Open or Laparoscipic Surgery - This procedure requires general anesthesia. An incision is made in the patient's back or abdomen and the stone is removed by making an opening in the ureter or kidney, removing the stone and repairing the opening. Most patients stay in the hospital for 2-6 days depending on whether the procedure is done open or laparoscopically and recovery takes several weeks.
PREVENTION AND LIFESTYLE CHANGES
Once the acute stone event has been managed, the emphasis shifts to prevention of subsequent attacks. Kidney stones reoccur in about 50% of cases. Prevention of renal stone disease depends on the type of stone produced, underlying urinary chemical risk factors, and the patient's willingness to undergo a long-term prevention plan. Below we have listed some suggestions to prevent future kidney stones.
- Fluid Intake: One of the most important factors in reducing the risk of new stone formation is getting into the lifelong habit of drinking a lot of liquid, mainly water. Everyone who has had a kidney stone should drink at least eight ounces of fluid in the morning, at each meal, and before bed. In other words, you should drink a minimum of 6 and preferably 8 to 10 large glasses of fluid in the course of each day. At least half of these should be glasses of water. Fluid intake should be spread out as evenly as possible throughout the day. This keeps the urine from becoming concentrated and reduces the chances that crystals, the building blocks of kidney stones, will form. A good way to judge whether you are drinking enough water is to watch the color of your urine. If it is dark and yellow, drink more. It should be pale, almost clear. Urine has more coloring in the morning when it is most concentrated, but the rest of the time the less color the better. Lemonade with real lemon juice is a good source of citrate (a chemical that reduces the risk of kidney stone formation) and may be recommended as an alternative to water. Cola beverages can severely reduce citrate in the urine and should be avoided. You should limit your coffee, tea, or cola to one or two cups a day.
- Dietary Changes: Depending on the kind of stone involved and the result of your laboratory tests, your doctor may advise you to eat less of certain kinds of foods. The mainstay of the treatment of most stones, however, is increased water intake to keep the urine as dilute as possible, a low salt diet, and a reduction of red meat consumption. Contrary to what you may think, eating a low calcium diet does not reduce or risk of forming calcium stones and may be harmful to you.
- Prescription Medications: In selected instances prescription medications are used to change the chemical composition of urine and reduce the risk of stone formation. Diuretics such as Hydrochlorothiazide are sometimes used to decrease calcium excretion. Potassium citrate can be used to bind calcium and help to remove it. Allopurinol, which causes the body to produce less uric acid, is sometimes prescribed for patients with stones formed as a result of a disease called gout. Physicians sometimes find that using chemical agents to manipulate the acidity or alkalinity of the urine, can inhibit crystal formation.
- 24 Hour Urine Test: Effective preventive measures are based on the patient's chemical risk factors, which often can be uncovered with a 24 hour urine test and a blood test. The physician evaluates the data and recommends dietary modifications, supplements, and medication to minimize the risk for developing kidney stones. The 24 hour urine test may be repeated several months after treatment has begun to determine the success of the therapy and any adjustments that should be made. Long-term strict compliance and periodic retesting may substantially reduce the risk for future stone formation.