Medical Management of Stone Disease

Kidney stones are among the most painful and prevalent of urologic disorders. More than a million kidney stone cases are diagnosed each year, with an estimated 10 percent of Americans destined to suffer at some point in their lives.

Fortunately, most stones pass out of the body without any intervention. If you are not so lucky, the following information should help you and your doctor address the causes, symptoms and possible complications created by your kidney stone disease.

The urinary tract, or system, consists of the kidneys, ureters, bladder and urethra. The kidneys are two bean-shaped organs below the ribs in the back of the torso (area between ribs and hips). They are responsible for maintaining balance by removing extra water and wastes from the blood and converting it to urine. The kidneys keep a stable balance of salts and other substances in the blood. They also produce hormones that build strong bones and help form red blood cells. Urine is carried by narrow muscular tubes, the ureters, from the kidneys to the bladder, a triangular-shaped reservoir in the lower abdomen. Like a balloon, the bladder's walls stretch and expand to store urine and then flatten when urine is emptied through the urethra to outside the body.

A stone forms in the kidney when there is an imbalance between certain urinary components —chemicals such as calcium, oxalate and phosphate — that promote crystallization and others that inhibit it.

Most common stones contain calcium in combination with oxalate and/or phosphate.

A less common type of stone is caused by infection in the urinary tract. This type of stone is called a struvite or infection stone. Much less common are the pure uric acid stones. Much rarer is the hereditary type of stones called cystine stones. Even more rare are those linked to hereditary disorders.

For unknown reasons, the number of people in the United States with kidney stones has been increasing over the past 20 years. Caucasians are more prone to develop kidney stones than African Americans. Although stones occur more frequently in men, the number of women who get them has been increasing over the past 10 years, causing the ratio to change. Kidney stones strike most typically between the ages of 20 and 40. If a person forms a stone, there is a 50 percent chance they will develop another stone.

Scientists do not always know what makes stones form. While certain foods may promote stones in susceptible people, researchers do not believe that eating a specific item will cause stones in people who are not vulnerable. Yet they are confident that factors — such as a family or personal history of kidney stones and other urinary infections or diseases — have a definite connection to this problem. Climate and water intake may also play a role in stone formation.

Stones can also form because of obstruction to urinary passage like in prostate enlargement or stricture disease. Stone formation has also been linked to hyperparathyroidism, an endocrine disorder that results in more calcium in your urine. Susceptibility can also be raised if you are among the 70 percent of people with rare hereditary disorders such as cystinuria or primary hyperoxaluria who develop kidney stones because of excesses of the amino acid, cystine or the oxalate in your urine.

Another condition that can cause stones to form is absorptive hypercalciuria, a surplus of calcium in the urine that occurs when the body absorbs too much from food. The high levels result in calcium oxalate or phosphate crystals forming in the kidneys or urinary tract. Similarly, hyperuricosuria, excess uric acid tied to gout or the excessive consumption of meat products, may also trigger kidney stones.

Consumption of calcium pills by a person who is at risk to form stones, certain diuretics or calcium-based antacids may increase the risk of forming stones by increasing the amount of calcium in the urine. Calcium oxalate stones may also form in people who have chronic inflammation of the bowel or who have had an intestinal bypass operation or ostomy. This is because of loss of more water from the body as well as absorption of oxalate from the intestine.

Usually, the symptom of a kidney stone is extreme pain that has been described as being worse than child labor pains. The pain often begins suddenly as the stone moves in the urinary tract, causing irritation and blockage. Typically, a person feels a sharp, cramping pain in the back and in the side of the area of the kidney or in the lower abdomen, which may spread to the groin. Also, sometimes a person will complain of blood in the urine, nausea and/or vomiting.

Occasionally stones do not produce any symptoms. But while they may be "silent," they can be growing, even threatening irreversible damage to kidney function. More commonly, however, if a stone is not large enough to prompt major symptoms, it still can trigger a dull ache that is often confused with muscle or intestinal pain.

If the stone is too large to pass easily, pain continues as the muscles in the wall of the tiny ureter try to squeeze the stone along into the bladder. One may feel the need to urinate more often or feel a burning sensation during urination. In a man, pain may move down to the tip of the penis. If the stone is close to the lower end of the ureter at the opening into the bladder, a person will frequently feel like they have not fully completed urination.

Stones as small as 2 mm. have caused many symptoms while those as large as a pea have quietly passed. If fever or chills accompany any of these symptoms, then there may be an infection.  You should contact your urologist immediately.

Sometimes "silent" stones — those that cause no symptoms — are found on X-rays taken during a general health examination. These stones would likely pass unnoticed. If they are large, then treatment should be offered. More often, kidney stones are found on an X-ray or sonogram taken on someone who complains of blood in the urine or sudden pain. These diagnostic images give the doctor valuable information about the stone's size and location. Blood and urine tests also help detect any abnormal substance that might promote stone formation.

If your doctor suspects a stone but is unable to make a diagnosis from a simple X-ray, he/she may scan the urinary system with intravenous pyelography (IVP). It is an imaging technique that utilizes radiopaque injections of dye followed, during excretion by the kidneys, by abdominal X-rays. A kidney obstructed by a stone will not be able to excrete the dye as quickly and may also appear enlarged when compared to the normal organ. Since this technique requires prep, it has been replaced in many hospitals by an abdominal/pelvic CT scan, an extremely accurate diagnostic tool that can detect almost all types of kidney stones painlessly.

Treating kidney stone disease depends largely on the size, position and number of stones in your system. Luckily, the majority of small stones (0.2 inch or 5 mm. in diameter) that are not causing infection, blockage or symptoms will pass if you simply drink plenty of fluids each day. Consuming two to three quarts of water increases urine production, which eventually washes kidney or other stones out of the system. Once they have passed, no other treatment is necessary. The doctor usually asks one to save the passed stone(s) for testing; a cup or tea strainer can be used for this purpose.

Also, renal colic, the sudden flank pain that occurs when small stones start down the ureter, can usually be treated with bed rest and analgesics or painkillers. Certain types of stones, such as those made or uric acid, can be broken up with medical therapy. The majority, however, are composed of calcium and are not responsive to medicine.

Surgery should be reserved as an option for cases where other approaches have failed or should not be tried. Surgery may be needed if a stone:

• does not pass after a reasonable period of time and causes constant pain

• is too large to pass on its own

• blocks the flow or urine

• causes ongoing urinary tract infection

• damages kidney tissue or causes constant bleeding

• has grown larger (as seen as follow-up X-ray studies)

Until recently, surgery to remove a stone was very painful and required a lengthy recovery time (four to six weeks). Today, treatment for these stones is greatly improved and many options do not require major surgery.

Extracorporeal shock wave lithotripsy (ESWL®): Is the most frequently used procedure for eliminating kidney stones. It works by directing ultrasonic or shock waves, created outside your body through skin and tissue, until they hit the dense kidney stones. The stones break down into sand-like particles and are easily passed through the urinary tract in the urine.  This method does not damage surrounding body tissues but breaks only the stone. The technology is only effective if the kidney is functioning well and there is no blockage to the passage of stone fragments.

In the older devices, the patient used to recline in a water bath while the shock waves were transmitted. Today, the machines are more compact and have a soft cushion on which the patient lies. Most devices use either X-rays or ultrasound to help the surgeon pinpoint the stone during treatment. For most types of shock wave lithotripsy procedures, anesthesia is not needed. In most cases, shock wave lithotripsy is done on an outpatient basis and without anesthesia. Recovery time is short and most people can resume normal activities in a few days. If the stone is about one inch in size, then more than one sitting of shock wave lithotripsy will be needed.

While shock wave lithotripsy is considered safe and effective, it can still cause complications. Most patients have blood in their urine for a few days after treatment. Bruising and minor discomfort in the back or abdomen from the shock waves are also common. To reduce the risk of complications, urologists usually tell their patients to avoid aspirin and other drugs that affect blood clotting for several weeks before treatment. Another complication may occur if the shattered stone particles cause discomfort as they pass through the urinary tract. In some cases, the urologist will insert a small tube called a stent through the bladder into the ureter to help the fragments pass.

Percutaneous nephrolithotomy (PNL): This procedure is the treatment of choice for patients with kidney stones that are larger and are in a location that does not allow effective use of shock wave lithotripsy or cause a blockage so severe that they cannot be bypassed by using a stent.

In this procedure, the surgeon makes a tiny cut in the flank area and then uses an instrument called a nephroscope to locate and remove the stone. For larger stones, a type of energy probe (ultrasonic, electrohydraulic or hydraulic) may be needed to break the stone into small pieces. All of this is done while the patient is sedated or under anesthesia.

One advantage of this procedure over SWL is that the surgeon removes the stone fragments instead of relying on its natural passage from the ureters. Generally, patients stay in the hospital two to three days and may have a small catheter in the kidney during the healing process. Most patients can resume light activity in one to two weeks. 

Although stone recurrence rates differ with individuals, in general you have a 50 percent chance of redeveloping stones within the next five years. So prevention is essential. Your urologist may follow up with several tests to determine which factors — e.g., medication or diet — should be changed to reduce your further risk.

Do not be surprised, if you are asked to collect urine for 24 hours after a stone has passed or been removed to measure volume and levels of acidity, calcium, sodium, uric acid, oxalate, citrate and creatinine. This information will be used to determine the cause of the stone. A second 24-hour urine collection will be needed on a restricted diet to determine the causes. A third 24-hour analysis may be used to find out the effectiveness of treatment.

A good first step for prevention is to drink more liquids — water is the best. If you tend to form stones, you should try to drink enough liquids throughout the day to produce at least two quarts of urine in every 24-hour period.  People who form calcium stones used to be told to avoid dairy products and other foods with high calcium content. However, recent studies have shown that foods high in calcium, including dairy foods, help prevent calcium stones. Taking calcium in pill form, however, may increase the risk of developing stones. Women taking vitamin D and calcium pills in the post-menopausal period to prevent osteoporosis, especially with a family history of kidney stones, need to be careful. If you are at risk for developing stones, your doctor may perform certain blood and urine tests to determine which factors can best be altered to reduce the risk. Some people will need medicines to prevent stones from forming.

In general, you are facing surgery if your stones are large enough to obstruct urine flow, if they are potentially harmful to your kidneys or if they are causing symptoms for which medication does not help.

Any person with a family history of kidney stones may be at higher risk for calculi. Stone disease in a first degree relative, such as a parent or sibling, can dramatically increase the probability for you. In addition, more than 70 percent of people with certain rare hereditary disorders are prone to the problem. Those conditions include cystinuria, an excess of the amino acid, cystine that does not dissolve in urine and instead forms stones of cystine; and primary hyperoxaluria, an excess production of the compound oxalate, which also does not dissolve in urine, forming stones of oxalate and calcium.

No. There is no known link between gallstones and kidney stones. They are formed in different areas of the body. Also, if you have a gallstone, you are not necessarily more likely to develop kidney stones.

Resembling the horns of a stag, these stones get their name from the shape they form by filling the pelvis or drainage system of the kidney (at the top of the ureter). Staghorn stones are linked to urinary tract infections. Despite the fact that they can grow large, they are often overlooked by patients because they cause minimal or even no pain. But a staghorn stone can lead to deterioration of kidney function, even without blocking the passage.

Treating this condition can be challenging. In the past, urologists relied on conventional surgery to remove the offending stone. But today they employ a combination of shock wave lithotripsy and percutaneous surgical procedures, even though patients may still need a traditional operation. In any case, it is essential that once the stone is removed, you work diligently to prevent further ones from forming. Luckily, new drugs and the growing field of lithotripsy have greatly improved the treatment of all kidney calculi, including staghorn stones.

Where can I get more information?

AUA Foundation Patient Brochure on Kidney Stones
AUA Foundation Patient Brochure on Kidney Stones (Zinio format)

AUA Guidelines Patient Guides: The Management of Ureteral Stones and The Management of Staghorn Kidney Stones

Download the free Zinio reader or the free Acrobat reader.

ESWL® is a registered trademark of Dornier Medical Systems Inc., Marietta, Georgia.