Urine contains many dissolved minerals and salts. When your urine has high levels of these minerals and salts, you can form stones. Kidney stones can start small but can grow larger in size, even filling the inner hollow structures of the kidney. Some stones stay in the kidney, and do not cause any problems. Sometimes, the kidney stone can travel down the ureter, the tube between the kidney and the bladder. If the stone reaches the bladder, it can be passed out of the body in urine. If the stone becomes lodged in the ureter, it blocks the urine flow from that kidney and causes pain.
The Kidneys and Urinary System
The kidneys are fist-size organs that handle the body’s fluid and chemical levels. Most people have two kidneys, one on each side of the spine behind the liver, stomach, pancreas and intestines. Healthy kidneys clean waste from the blood and remove it in the urine. They control the levels of sodium, potassium and calcium in the blood.
The kidneys, ureters and bladder are part of your urinary tract. The urinary tract makes, transports, and stores urine in the body. The kidneys make urine from water and your body’s waste. The urine then travels down the ureters into the bladder, where it is stored. Urine leaves your body through the urethra.
Kidney stones form in the kidney. Some stones move from the kidney into the ureter. The ureters are tubes leading from the kidneys to the bladder. If a stone leaves the kidney and gets stuck in the ureter, it is called a ureteral stone.
What are Kidney Stones Made of?
Kidney Stones
Kidney stones come in many different types and colors. How you treat them and stop new stones from forming depends on what type of stone you have.
Calcium stones (80 percent of stones)
Calcium stones are the most common type of kidney stone. There are two types of calcium stones: calcium oxalate and calcium phosphate. Calcium oxalate is by far the most common type of calcium stone. Some people have too much calcium in their urine, raising their risk of calcium stones. Even with normal amounts of calcium in the urine, calcium stones may form for other reasons.
Uric acid stones (5-10 percent of stones)
Uric acid is a waste product that comes from chemical changes in the body. Uric acid crystals do not dissolve well in acidic urine and instead will form a uric acid stone. Having acidic urine may come from:
- Being overweight
- Chronic diarrhea
- Type 2 diabetes (high blood sugar)
- Gout
- A diet that is high in animal protein and low in fruits and vegetables
Struvite/infection stones (10 percent of stones)
Struvite stones are not a common type of stone. These stones are related to chronic urinary tract infections (UTIs). Some bacteria make the urine less acidic and more basic or alkaline. Magnesium ammonium phosphate (struvite) stones form in alkaline urine. These stones are often large, with branches, and they often grow very fast.
People who get chronic UTIs, such as those with long-term tubes in their kidneys or bladders, or people with poor bladder emptying due to neurologic disorders (paralysis, multiple sclerosis, and spina bifida) are at the highest risk for developing these stones.
Cystine stones (less than 1 percent of stones)
Cystine is an amino acid that is in certain foods; it is one of the building blocks of protein. Cystinuria (too much cystine in the urine) is a rare, inherited metabolic disorder. It is when the kidneys do not reabsorb cystine from the urine. When high amounts of cystine are in the urine, it causes stones to form. Cystine stones often start to form in childhood.
Stones in the kidney often do not cause any signs and can go undiagnosed. When a stone leaves the kidney, it travels to the bladder through the ureter. Often the stone can become lodged in the ureter. When the stone blocks the flow of urine out of the kidney, it can cause the kidney to swell (hydronephrosis), often causing a lot of pain.
Common symptoms of kidney stones are:
- A sharp, cramping pain in the back and side, often moving to the lower abdomen or groin. Some women say the pain is worse than childbirth labor pains. The pain often starts suddenly and comes in waves. It can come and go as the body tries to get rid of the stone.
- A feeling of intense need to urinate.
- Urinating more often or a burning feeling during urination.
- Urine that is dark or red due to blood. Sometimes urine has only small amounts of red blood cells that can’t be seen with the naked eye.
- Nausea and vomiting.
- For men, you may feel pain at the tip of the penis.
Low Urine Volume
A major risk factor for kidney stones is constant low urine volume. Low urine volume may come from dehydration (loss of body fluids) from hard exercise, working or living in a hot place, or not drinking enough fluids. When urine volume is low, urine is concentrated and dark in color. Concentrated urine means there is less fluid to keep salts dissolved. Increasing fluid intake will dilute the salts in your urine. By doing this, you may reduce your risk of stones forming.
Adults who form stones should drink enough fluid to make at least 2.5 liters (⅔ gallon) of urine every day. On average, this will take about 3 liters (100 ounces) of fluid intake per day. While water is likely the best fluid to drink, what matters most is getting enough fluid.
Diet
Diet can also affect the chance of forming a stone. One of the more common causes of calcium kidney stones is high levels of calcium in the urine. High urine calcium levels may be due to the way your body handles calcium. It is not always due to how much calcium you eat. Lowering the amount of calcium in your diet rarely stops stones from forming. Studies have shown that restricting dietary calcium can be bad for bone health and may increase kidney stone risk. Health care providers usually do not tell people to limit dietary calcium in order to lower urine calcium. But calcium intake should not be too high.
Instead of lowering dietary calcium intake, your health care provider may try to reduce your urine calcium level by decreasing your sodium (salt) intake. Too much salt in the diet is a risk factor for calcium stones. This is because too much salt is passing into the urine, keeping calcium from being reabsorbed from the urine and into the blood. Reducing salt in the diet lowers urine calcium, making it less likely for calcium stones to form.
Because oxalate is a component of the most common type of kidney stone (calcium oxalate), eating foods rich in oxalate can raise your risk of forming these stones.
A diet high in animal protein, such as beef, fish, chicken and pork, can raise the acid levels in the body and in the urine. High acid levels make it easier for calcium oxalate and uric acid stones to form. The breakdown of meat into uric acid also raises the chance that both calcium and uric acid stones will form.
Bowel Conditions
Certain bowel conditions that cause diarrhea (such as Crohn’s Disease or ulcerative colitis) or surgeries (such as gastric bypass surgery) can raise the risk of forming calcium oxalate kidney stones. Diarrhea may result in loss of large amounts of fluid from the body, lowering urine volume. Your body may also absorb excessive oxalate from the intestine, resulting in more oxalate in your urine. Both low urine volume and high levels of urine oxalate can help to cause calcium oxalate kidney stone formation.
Obesity
Obesity is a risk factor for stones. Obesity may change the acid levels in the urine, leading to stone formation.
Medical conditions
Some medical conditions have an increased risk of kidney stones. Abnormal growth of one or more of the parathyroid glands, which control calcium metabolism, can cause high calcium levels in the blood and urine. This can lead to kidney stones. Another condition called distal renal tubular acidosis, in which there is acid build-up in the body, can raise the risk of calcium phosphate kidney stones.
Some rare, inherited disorders can also make certain types of stones more likely. Examples include cystinuria, which is too much of the amino acid cystine in the urine, and primary hyperoxaluria, in which the liver makes too much oxalate.
Medication
Some medications, and calcium and vitamin C supplements, may increase your risk of forming stones. Be sure to tell your health care provider all the medications and supplements you take, as these could affect your risk of stone formation. Do not stop taking any of these unless your health care provider tells you to do so.
Family History
The chance of having kidney stones is much higher if you have a family history of stones, such as a parent or sibling.
Treatment depends on the type of stone, how bad it is and the length of time you have had symptoms. There are different treatments to choose from. It is important to talk to your health care provider about what is best for you.
Wait for the stone to pass by itself
Often you can simply wait for the stone to pass. Smaller stones are more likely than larger stones to pass on their own.
Waiting up to four to six weeks for the stone to pass is safe as long as the pain is bearable, there are no signs of infection, the kidney is not completely blocked and the stone is small enough that it is likely to pass. While waiting for the stone to pass, you should drink normal amounts of water. You may need pain medication when there is discomfort.
Medication
Certain medications have been shown to improve the chance that a stone will pass. The most common medication prescribed for this reason is tamsulosin. Tamsulosin (Flomax) relaxes the ureter, making it easier for the stone to pass. You may also need pain and anti-nausea medicine as you wait to pass the stone.
Surgery
- Surgery may be needed to remove a stone from the ureter or kidney if:
- The stone fails to pass.
- The pain is too great to wait for the stone to pass.
- The stone is affecting kidney function. Small stones in the kidney may be left alone if they are not causing pain or infection. Some people choose to have their small stones removed. They do this because they are afraid the stone will unexpectedly start to pass and cause pain.
Kidney stones should be removed by surgery if they cause repeated infections in the urine or because they are blocking the flow of urine from the kidney. Today, surgery usually involves small or no incisions (cuts), minor pain and minimal time off work.
Surgeries to remove stones in the kidneys or ureters are:
Shock wave lithotripsy (SWL)
Extracorporeal shock wave lithotripsy (ESWL) for kidney stones
Shock Wave Lithotripsy (SWL) is used to treat stones in the kidney and ureter. Shock waves are focused on the stone using X-rays or ultrasound to pinpoint the stone. Repeated firing of shock waves on the stone usually causes the stone to break into small pieces. These smaller pieces of stones pass out in the urine over a few weeks.
Because of possible discomfort caused by the shock waves and the need to control breathing during the procedure, some form of anesthesia is often needed. SWL does not work well on hard stones, such as cystine, some types of calcium oxalate and calcium phosphate stones, or very large stones.
With SWL, you may go home the same day as the procedure. You may be able to resume normal activities in two to three days. You may also be given a strainer to collect the stone pieces as they pass. These pieces will be sent to the laboratory to be tested.
Although SWL is widely used and considered very safe, it can still cause side effects. You may have blood in your urine for a few days after treatment. Most stone pieces pass painlessly. Larger pieces may get stuck in the ureter, causing pain and needing other removal procedures.
Ureteroscopy (URS)
Ureteroscopic Removal of Stones
Ureteroscopy (URS) is used to treat stones in the kidney and ureter. URS involves passing a very small telescope, called an ureteroscope, into the bladder, up the ureter and into the kidney. Rigid telescopes are used for stones in the lower part of the ureter near the bladder. Flexible telescopes are used to treat stones in the upper ureter and kidney.
The ureteroscope lets the urologist see the stone without making an incision (cuts). General anesthesia keeps you comfortable during the URS procedure. Once the urologist sees the stone with the ureteroscope, a small, basket-like device grabs smaller stones and removes them. If a stone is too large to remove in one piece, it can be broken into smaller pieces with a laser or other stone-breaking tools.
Once the stone has been removed whole or in pieces, the health care provider may place a temporary stent in the ureter. A stent is a tiny, rigid plastic tube that helps hold the ureter open so that urine can drain from the kidney into the bladder. Unlike a catheter or PCNL drain tube, this tube is completely within the body and does not require an external bag to collect urine.
You may go home the same day as the URS and can begin normal activities in two to three days. If your urologist places a stent, he or she will remove it four to 10 days later. Sometimes a string is left on the end of the stent so you can remove it on your own. It is very important that the stent is removed when your health care provider tells you. Leaving the stent in for long periods can cause an infection and loss of kidney function.
Percutaneous nephrolithotomy (PCNL)
Percutaneous Nephrolithotripsy
Percutaneous Lithotripsy (PCNL) is the best treatment for large stones in the kidney. General anesthesia is needed to do a PCNL. PCNL involves making a half-inch incision (cut) in the back or side, just large enough to allow a rigid telescope (nephroscope) to be passed into the hollow center part of the kidney where the stone is located.
An instrument passed through the nephroscope breaks up the stone and suctions out the pieces. The ability to suction pieces makes PCNL the best treatment choice for large stones.
After the PCNL, a tube is usually left in the kidney to drain urine into a bag outside of the body. This will allow for drainage of urine and stop any bleeding. The tube is left in overnight or for a few days. You may have to stay in the hospital overnight after this operation.
Your urologist may choose to do X-rays while you are still in the hospital to see if any stone pieces remain. If there are any, your urologist may want to look back into the kidney with a telescope again to remove them. You can begin normal activities after about one-to-two weeks.
Other surgery
Other kidney surgery is rarely used to remove stones. Open, laparoscopic or robotic surgery may be used only if all other less invasive procedures fail.
