Kidney Stones:

WHAT IS A KIDNEY STONE?

A kidney stone is a hard, crystalline mineral material formed within the kidney. Often, stones form when the urine becomes concentrated, allowing minerals to crystallize and stick together. Over time, more and more crystals bind together and the stone can grow.
A small kidney stone may pass without causing symptoms, but if stones grow large enough they can cause blockage of the ureter. This leads to varying degrees of pain, most commonly beginning in the flank or lower back and often radiating to the groin. This pain is often known as renal colic and typically comes in waves lasting 20 to 60 minutes. Other associated symptoms of passing a stone include: nausea, vomiting, fever, blood in the urine, the persistent need to urinate and painful urination. Blockage of the ureter can cause dilation of the kidney and prolonged obstruction can lead to kidney failure.

Passing kidney stones can be extremely painful, but the stones usually cause no permanent damage. Depending on your situation, you may need nothing more than to take pain medication and drink lots of water to pass a kidney stone. If a stone becomes obstructed or is too large to pass then surgery may be needed.
 
Pain caused by a kidney stone may change — for instance, shifting to a different location or increasing in intensity — as the stone moves down through your urinary tract.


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
  • Obstruction 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 dehydration caused by 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. 

Common sense has long held that the consumption of too much calcium can aggravate the development of kidney stones, since the most common type of stone is calcium oxalate. However, low-calcium diets are associated with higher overall stone risk for the typical stone former. This is thought to be due to the binding of ingested intestinal oxalate with calcium in the gastrointestinal tract. Such oxalate binding would prevent oxalate absorption resulting in lower urinary oxalate levels. In the urine, oxalate is a very strong promotor of crystal and stone formation, about 15 times stronger than calcium. 


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 or jagged. They vary in size from specks to pebbles, to stones as big as golf balls.


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 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.


THE 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.

  • Calcium stones:  The most common type of kidney stone contains calcium. Most stones (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 in 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.

  • Struvite stones form 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. For patients with struvite stones, it is important not only to remove the stone, but also to prevent recurrence of the urinary tract infection.

  • Uric acid stones 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 can 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.


RISK FACTORS FOR STONE FORMATION:

Factors that increase your risk of developing kidney stones include:

  • Family or personal history. If someone in your family has kidney stones, you're more likely to develop stones, too. And if you've already had one or more kidney stones, you're at increased risk of developing another.

  • Dehydration. Not drinking enough water each day can increase your risk of kidney stones. People who live in warm climates and those who sweat a lot may be at higher risk than others.

  • Certain diets. Eating a diet that's high in protein, sodium and sugar may increase your risk of some types of kidney stones. This is especially true with a high-sodium diet. Too much sodium in your diet increases the amount of calcium your kidneys must filter and significantly increases your risk of kidney stones.

  • Being overweight. High body mass index (BMI),  has been linked to an increased risk of kidney stones.

  • Digestive diseases and surgery. Gastric bypass surgery, inflammatory bowel disease or chronic diarrhea can cause changes in the digestive process that affect your absorption of calcium and water, increasing the levels of stone-forming substances in your urine.

  • Other medical conditions. Diseases and conditions that may increase your risk of kidney stones include renal tubular acidosis, cystinuria, hyperparathyroidism, certain medications and some urinary tract infections.



DIAGNOSING A KIDNEY STONE:

If your doctor suspects you have a kidney stone, you may have diagnostic tests and procedures, such as:

  • Blood testing. Blood tests may reveal too much calcium or uric acid in your blood. Blood test results help monitor the function of your kidneys and may lead your doctor to check for other medical conditions.

  • Urine testing. The 24-hour urine collection test may show that you're excreting too many stone-forming minerals or too few stone-preventing substances. For this test, your doctor may request that you perform two urine collections over two consecutive days.

  • Imaging. Imaging tests may show kidney stones in your urinary tract. Options range from simple abdominal X-rays, which can miss small kidney stones, to high-speed or dual energy computerized tomography (CT) that may reveal even tiny stones.

    Other imaging options include an ultrasound, a noninvasive test, and intravenous urography, which involves injecting dye into an arm vein and obtaining CT images (CT urogram) as the dye travels through your kidneys and bladder.

  • Analysis of passed stones. You may be asked to urinate through a strainer to catch stones that you pass. Lab analysis will reveal the makeup of your kidney stones. Your doctor uses this information to determine what's causing your kidney stones and to form a plan to prevent more kidney stones.


TREATMENT OF KIDNEY STONES:

Treatment for kidney stones varies, depending on the type of stone and the cause.

Small stones with minimal symptoms:

Most kidney stones won't require invasive treatment. You may be able to pass a small stone by:

  • Drinking water. Drinking as much as 2 to 3 liters a day may help flush out your urinary system. Unless your doctor tells you otherwise, drink enough fluid — mostly water — to produce clear or nearly clear urine.

  • Pain relievers. Passing a small stone can cause some discomfort. To relieve mild pain, your doctor may recommend pain relievers such as ibuprofen (Advil, Motrin IB, others), acetaminophen (Tylenol, others) or naproxen sodium (Aleve).

  • Medical therapy. Your doctor may give you a medication to help pass your kidney stone. This type of medication, known as an alpha blocker, relaxes the muscles in your ureter, helping you pass the kidney stone more quickly and with less pain.

Large stones and those that cause symptoms:

Kidney stones that can't be treated with conservative measures — either because they're too large to pass on their own or because they cause bleeding, kidney damage or ongoing urinary tract infections — may require more extensive treatment. Procedures may include:

  • Using sound waves to break up stones. For certain kidney stones — depending on size and location — your doctor may recommend a procedure called extracorporeal shock wave lithotripsy (ESWL).

    ESWL uses sound waves to create strong vibrations or shock waves that break the stones into tiny pieces that can be passed in your urine. The procedure lasts about 25 minutes and you will be under light anesthesia.

    ESWL can rarely cause blood in the urine, bruising on the back or abdomen, bleeding around the kidney and other adjacent organs, and discomfort as the stone fragments pass through the urinary tract.

  • Ureteroscopy: using a scope to remove stones. To remove a smaller stone in your ureter or kidney, your doctor may pass a thin lighted tube (ureteroscope) equipped with a camera through your urethra and bladder to your ureter.

    Once the stone is located, special tools can grasp the stone or break it into pieces that will pass in your urine. Your doctor may then place a small tube (stent) in the ureter to relieve swelling and promote healing. You will be asleep with light anesthesia during this procedure.

  • Surgery to remove very large stones in the kidney. A procedure called percutaneous nephrolithotomy involves surgically removing a kidney stone using small telescopes and instruments inserted through a small incision in your back.

    You will receive general anesthesia during the surgery and be in the hospital for one to two days while you recover. Your doctor may recommend this surgery if ESWL was unsuccessful.

  • Parathyroid gland surgery. Some calcium phosphate stones are caused by overactive parathyroid glands, which are located on the four corners of your thyroid gland. When these glands produce too much parathyroid hormone it is called hyperparathyroidism. Calcium levels will then remain too high and kidney stones may form as a result.

    • Hyperparathyroidism sometimes occurs when a small, benign tumor forms in one of your parathyroid glands or you develop another condition that leads these glands to produce more parathyroid hormone. Removing the growth from the gland stops the formation of kidney stones. 
    Or your doctor may recommend treatment of the condition that's causing your parathyroid gland to overproduce the hormone.


PREVENTION AND LIFESTYLE CHANGES

Once the acute stone event has been managed, the emphasis shifts to prevention of future 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.

  • Drink more water: 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 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. 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. Sodas 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, following a low salt diet, a low oxalate diet, and low protein diet. Contrary to what you may think, eating a low calcium diet does not reduce the risk of forming calcium stones. It is recommended that you continue to maintain a program that decreases the risk of osteoporosis, so the intake of dairy is OK and even calcium supplements in women if they have evidence of bone loss. We can treat kidney stones but it is difficult to reverse osteoporosis.

  • 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 blood tests. The physician evaluates the data and recommends dietary modifications, supplements, and medication to minimize the risk for developing kidney stones. Long-term strict compliance and periodic retesting may substantially reduce the risk for future stone formation.