Eighty percent of kidney stones occur in men. An interesting statistic considering passing a kidney stone is often compared to childbirth. Kidney stones (also known as renal lithiasis or nephrolithiasis) are small, hard deposits of mineral and acid salts that form inside your kidneys. These mineral and acid salts are normally found in the urine and do not cause problems at lower levels. Kidney stones have many causes and can affect any part of your urinary tract — from your kidneys to your bladder. Often, stones form when the urine becomes concentrated, allowing minerals to crystallize and stick together. Stones may be small or large, solitary or multiple.
Urinary Tract Anatomy
The urinary tract is the body’s drainage system for removing waste products and extra water. The urinary tract includes the kidneys, ureters, urinary bladder, and urethra. The kidneys are fist-sized, bean shaped organs located near the middle of the back, just below the rib cage. The right kidney lies under the liver and is located slightly lower than the left kidney. The kidneys are protected by the muscles of the back, fat and fascia.
The urine flows from the kidney through a tube called the ureter to the urinary bladder, where it is stored until released from the body through another tube, the urethra. Most people have two kidneys.
Kidney Function and Physiology
The purpose of the urinary system is to help regulate water balance and remove harmful substances from the blood. Blood is filtered by the kidneys which produce urine. The two kidneys process about 200 quarts of blood to produce about 1 to 2 quarts of urine. Urine is a fluid that contains toxic substances and waste products. The kidneys dispose of waste and extracellular fluid (urine) by gravity flow through the ureters. There are two ureters, one for each kidney. The ureters are lined muscular tubes that use peristalsis to propel and drain urine into the bladder. Kidney stones can stay in the kidney or travel down the urinary tract. A small stone may pass on its own, causing little or no pain. A larger stone may get stuck along the urinary tract. When a stone gets stuck it can block the flow of urine this causes severe pain and bleeding.
What Causes Kidney Stones?
Kidney stones are caused by high levels of certain minerals in the urine. Calcium, oxalate, and phosphorus in the urine. Some foods may cause kidney stones in certain people. You may be more likely to get a kidney stone if you have a condition that affects levels of substances in your urine that can cause stones to form a family history of kidney stones repeating, or recurrent, urinary tract infections blockage of your urinary tract digestive problems.You may also be more likely to get a kidney stone if you don’t drink enough fluids or if you take certain medicines.
Types of Kidney Stones
Calcium stones. Most kidney stones are calcium stones, usually in the form of calcium oxalate. Oxalate is a naturally occurring substance found in food. Some fruits and vegetables, as well as nuts and chocolate, have high oxalate levels. Your liver also produces oxalate. Dietary factors, high doses of vitamin D, intestinal bypass surgery and several metabolic disorders can increase the concentration of calcium or oxalate in urine. Calcium stones may also occur in the form of calcium phosphate. You may get them when there is too much calcium in your urine. This may happen when your kidneys don’t work properly or your stomach and intestines absorb too much calcium. The risk of having calcium stones is higher if you have certain medical conditions, such as an overactive parathyroid gland (a gland in the neck that controls calcium levels in the body) or inflammatory bowel disease, like Crohn’s disease or ulcerative colitis. Some people have calcium stones from too much of a chemical called oxalate in their diet. Oxalate is in many foods, such as spinach, rhubarb, leafy vegetables, coffee, chocolate, and tomatoes.
Struvite stones. This type of stone is also called an infection stone because it forms in urine that is infected with bacteria form in response to an infection, such as a urinary tract infection. These stones can grow quickly and become quite large, sometimes with few symptoms or little warning.
Uric acid stones. Uric acid stones can form in people who don’t drink enough fluids or who lose too much fluid, those who eat a high-protein diet, and those who have gout. Certain genetic factors also may increase your risk of uric acid stones. Uric acid stones happen when you have too much uric acid in your urine. This might happen when your body does not have enough fluid—for example, when you are exercising on a hot day or during an illness and you don’t drink enough fluids. Uric acid stones are common in people who have gout, a type of arthritis caused by too much uric acid in the blood.
Cystine stones. These stones form in people with a hereditary disorder that causes the kidneys to excrete too much of the amino acid, cystine. This condition is called cystinuria. This type of kidney stone is rare. This disease results from a birth defect that causes the kidney to let too much cystine into the urine. This type of stone is almost always diagnosed during childhood.
Other stones. Other, rarer types of kidney stones can occur.
Epidemiology
Kidney stones affect approximately 1 in 11 people in the United States. About 80 percent of kidney stones occur in men. This occurs most commonly between the ages of 20 and 30. Women are more likely to develop kidney stones at a later age. Kidney stones usually form due to many factors: genetic, environmental factors, diet and lifestyle. Eating more fast food and high fructose corn syrup as well as climate change have been suggested as a possible link to kidney stone formation.
Symptoms
Passing kidney stones can be very 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. In other instances, surgery may be needed. Your doctor may recommend preventive treatment to reduce your risk of recurrent kidney stones if you’re at increased risk of developing them again.
A kidney stone may not cause symptoms until it moves around within your kidney or passes into the ureter — the tube connecting the kidney and bladder. At that point, these signs and symptoms may occur:
- Pain in the Side or Back
- Pain that Spreads to Lower Abdomen or Groin
- Pain that Comes in Waves and Fluctuates in Intensity
- Pain with Urination or Bloody Urine
- Dark or Foul Smelling Urine
- Nausea or Vomiting
- Urgency to Urinate
Pain caused by a kidney stone may change (shift to a different location or increase in intensity) as the stone moves through your urinary tract.
What Do Kidney Stones Look Like?
Kidney stones vary in size and shape. Stones may be as small as a grain of sand or as large as a pearl. Some stones are even as big as golf balls. Stones may be smooth or jagged and are usually yellow or brown.
When Should I Call a Doctor?
You should call a doctor if you have any of the following:
- Extreme Pain in Your Back or Lower Abdomen That Won’t Go Away
- Blood In Your Urine
- Fever and Chills
- Vomiting
- Urine That Smells Bad or Looks Cloudy
- Pain When You Urinate
These problems may mean you have a kidney stone or a more serious condition.
How are Kidney Stones Diagnosed?
To diagnose kidney stones, your doctor will do a physical exam and ask about your medical history. The doctor may ask if you have a family history of kidney stones and about your diet, digestive problems, and other health problems. The doctor may perform urine, blood, and imaging tests to complete the diagnosis.
Urine tests can show whether you have an infection or your urine contains substances that form stones. Blood tests can show problems that lead to kidney stones.
Imaging tests are used to find the location of kidney stones in your body. A CT scan can usually show kidney stones and their location. The tests may also be able to show problems that caused a kidney stone to form.
Treatment
The treatment for kidney stones usually depends on their size, location and the type of stone. Kidney stones may be treated by your regular doctor or by a urologist—a doctor who specializes in the urinary tract. You may need surgical treatment if you have symptoms or if a kidney stone is blocking your urinary tract. Small stones don’t usually need treatment. Still, you may need pain medicine. You should also drink lots of fluids to help move the stone along. If you are vomiting often or don’t drink enough fluids, you may need to go to the hospital and get fluids through a needle in your arm.
If you have a large kidney stone or your urinary tract is blocked, the urologist can remove the stone or break it into small pieces with the following treatments:
Shock wave lithotripsy. The urologist can use a shock wave machine to crush the kidney stone. The shock waves go from the machine to your body. The smaller pieces of the stone then pass through your urinary tract.
Ureteroscopy. The urologist uses a long, tube-like tool with an eyepiece, called an ureteroscope, to find the stone. The tool is fed into the urethra and through the bladder to the ureter. Once the stone is found, the urologist can remove it or can break it into smaller pieces with laser energy.
Percutaneous nephrolithotomy. The urologist uses a wire-thin viewing tool, called a nephroscope, to locate and remove the stone. The tool is fed directly into the kidney through a small cut made in your back. For larger stones, shock waves may also be used to break the stone into smaller pieces.
How can I Prevent Kidney Stones?
To prevent kidney stones, you need to know what caused your kidney stone. Your doctor may ask you to try to catch the kidney stone as it passes in your urine. The kidney stone can then be sent to a lab to find out what type of stone it is. If you have treatment in the hospital and the doctor removes the stone, it will also be sent to a lab for testing.
Your doctor may ask you to collect your urine for 24 hours after the stone has passed or been removed. Your doctor can then measure how much urine you produce in a day and mineral levels in the urine. You are more likely to form stones if you don’t make enough urine each day or have a problem with mineral levels.
Once you know what type of kidney stone you had, you can make changes in your eating, diet, and nutrition and take medicines to prevent future kidney stones.
Eating, Diet, and Nutrition
You can help prevent kidney stones by making changes in how much you consume of the following:
- Fluids
- Sodium
- Animal Protein
- Calcium
- Oxalate
Drinking enough fluids each day is the best way to help prevent most types of kidney stones. You should drink 2 to 3 liters of fluid a day. If you had cystine stones, you may need to drink even more. Though water is best, other fluids may also help prevent kidney stones, such as citrus drinks.
Medicines
Your doctor may prescribe medicines based on the type of kidney stone you had and any health problems you have that make you more likely to form a stone.
Points to Remember
A kidney stone is a solid piece of material that forms in a kidney when there are high levels of certain substances in the urine. These substances are normally found in the urine and do not cause problems at lower levels.
Kidney stones are caused by high levels of calcium, oxalate, and phosphorus in the urine.
You may have a kidney stone if you:
- Have Pain While Urinating
- See Blood in Your Urine
- Feel a Sharp Pain in Your Back or Lower Abdomen
If you have a small stone that passes on its own easily, you may not have symptoms at all.
To diagnose kidney stones, your doctor will do a physical exam and ask about your medical history. The doctor may perform urine, blood, and imaging tests to complete the diagnosis.
The treatment for kidney stones usually depends on their size and what they are made of. You may need pain medicine. You should also drink lots of fluids. If you have a large kidney stone or your urinary tract is blocked, the urologist can remove the stone or break it into small pieces with shock wave lithotripsy, ureteroscopy, or percutaneous nephrolithotomy.
To prevent kidney stones, you need to know what caused your kidney stone.
Once you know what type of kidney stone you had, you can make changes in your eating, diet, and nutrition and take medicines to prevent future kidney stones.
Susan Puckett, PA-C, ENT and Internal Medicine