Kidney Stones
Kidney stones, also known as urolithiasis, are a common affliction of the urinary tract. Depending on the location of the stone in your urinary tract, the stone may be referred to by different names.
A stone in your kidney is called a renal calculi or nephrolithiasis. A ureteral calculus or ureterolithiasis is a stone in one of your ureters, the tubes that connect each kidney to your bladder.
Types of Kidney Stones
There are four major types of kidney stones: (1) calcium stones, which are the most common type, are primarily composed of calcium and either phosphate or oxalate, and are primarily due to increased calcium levels in urine; (2) urate or uric acid stones, which are smooth, soft and brown stones that form because of increased uric acid levels in urine; (3) struvite stones, which contain magnesium and ammonia and are typically formed because of infectious bacteria that split a chemical called urea; and (4) cystine stones, which are yellow and are caused by a relatively rare metabolic condition.
When a kidney stone reaches a certain size, usually 2-3 mm, it can cause blockage of the normal flow of urine from the kidneys to the bladder and out of the body. This blockage causes dilation and muscle spasm, causing pain in a patient's side, lower abdomen or groin. If a kidney stone does not pass spontaneously and is not treated, patients experience a significant amount of pain and eventually damage to the urinary tract.
Causes
Stone formation is a complex process. It begins with urine developing a higher concentration of certain salts than is normal. These salts pop out of the liquid urine to form crystals. Crystals can flow out with urine, or become attached at various sites in the kidney. Eventually crystals accumulate at an attachment site to form a stone.
Certain medications may increase your risk of developing kidney stones, such as aspirin, antacids, certain diuretics or "water pills", calcium and Vitamin D supplements, and anti-retroviral medications such as Indinavir.
Each type of kidney stone has specific factors that increase risk of their formation. The higher than normal levels of calcium in urine that can cause calcium stones could be due to an overactive parathyroid gland (hyperparathyroidism), high levels of Vitamin D, kidney disease, sarcoidosis or some cancers.
Uric acid stones can form when your urine is very acidic, which can happen as a result of metabolic imbalances such as gout, chemotherapy, or a high protein diet. Struvite stones, which are more common in women than men, are always associated with urinary tract infections. The bacteria causing these infections release a protein that lowers the acidity of urine, allowing struvite stones to form. Cystine stones are caused by an inherited condition called cystinuria, which affects how much acid is excreted in your urine.
Prevention
Because the risk of having a kidney stone is increased if you have previously had one, prevention is very important. Preventative strategies include dietary modification and some drugs, depending on the cause of your stone. These strategies specifically may include:
• Drinking plenty of fluids. Normally, you should drink at least 6 to 8 glasses of water a day, but in the special case of having a kidney stone, you should increase this to 2-3 liters a day! • Reduce the protein, nitrogen and sodium in your diet • Restrict oxalate-rich foods such as chocolate, nuts, soybeans, spinach and rhubarb • Maintain adequate calcium intake • Certain fruit juices such as orange, cranberry and blackcurrant juice may reduce the risk of specific stones (orange – calcium oxalate, cranberry – struvite, blackcurrant – uric acid) • Avoid cola beverages • Avoid large amounts of vitamin C • Drugs such as thiazide diuretics, allopurinol, potassium and magnesium citrate, depending on the type of stoneMore Information
Kidney stones often do not cause any symptoms and are passed painlessly in your urine. These stones are referred to as "silent stones".
However, if a stone is too large to pass without causing blockage, the first symptom is usually severe pain that begins when a stone gets large enough to block your kidney, moves to block the flow or urine, or causes an infection. This pain is typically a cramping, sharp pain in the back or side that can spread to the groin, depending on where the stone is.
If a stone is blocking the ureter, it can cause the muscles surrounding the ureter to spasm, causing pain referred to as "renal colic". Blockage of the flow of urine can also cause symptoms of infection. A list of the common symptoms of kidney stones are shown below:
A patient presenting with pain consistent with a kidney stone, or any of the other symptoms listed above will be imaged to determine if a kidney stone is present, where it is located, and how large it is. Several different diagnostic imaging techniques are available to accomplish these goals:
X-rays: X-ray imaging is able to see calcium that is in the majority of stones. A special test utilizing X-rays is an Intravenous Pyelogram (IVP) also known as an Intravenous Urogram (IVU). In this test, a special dye that is excreted by the kidneys is injected into the blood stream. When the kidneys filter it out of the bloodstream and into the urine, it outlines any stone that may be present, making it visible on an X-ray. An alternative procedure to an IVP is a Retrograde Pyelogram, which utilizes a dye similar to the IVP, but this time is injected directly into the ureters from the bladder by a urologist. The disadvantage to X-ray technology is that approximately 10% of stones do not have enough calcium to be seen on X-rays, and thus require alternative diagnosis methods.
Ultrasound: Ultrasound is an easy to use and relatively inexpensive technology that can detect the swelling of the kidney (hydronephrosis) caused when a stone obstructs flow of urine. It can also be used in pregnancy when use of X-rays or other imaging technologies is not advised. Furthermore, ultrasound can visualize stones that are "radiolucent" because of their low calcium content.
Computed Tomography (CT): A CT scan without contrast is the gold-standard (best) diagnostic test for detecting kidney stones. This is because all types of kidney stones, except for extremely rare ones, are able to be seen on CT. If CT scan reveals a stone, your doctor will get a follow-up X-ray image in order to get a better sense of the orientation of the stone as well as its size and shape. This allows your doctor to follow-up on the stone using X-rays instead of requiring multiple CT scans.
In addition to imaging, your doctor may order several other tests to check your kidney function and determine the cause of your stone. These include:
Blood tests: Blood tests can suggest if you have an infection due to your stone, check how well your kidneys are clearing waste from your body, and if you have high levels of salts that could cause stones (like calcium)
Urine tests: Urine tests (urinalysis) can reveal the presence of proteins, red blood cells or bacteria as either a consequence of a stone or a cause of your pain. Your doctor may order a 24-hour urine collection test to determine critical information such as how much you drink per day as well as the concentrations of different salts involved in kidney stone formation such as calcium, oxalate, phosphate, magnesium, uric acid and citrate.
Analysis of the stone: You may be asked to urinate through a mesh screen device in order to catch your stone when it is passed so that your doctor can evaluate the stone at a later time.
The number of people who get kidney stones has been increasing over the past several decades, with the probability of getting a kidney stone in your life estimated at around 15% in the United States.
The following groups of people are more likely to get kidney stones: men, Caucasians, people between the ages of 40 and 60, people in hot and dry climates, obese individuals and those who have recently gained weight, those who have had multiple kidney or urinary tract infections and patients with a family history of kidney stones.
Several other factors increase your general risk for developing a kidney stone, such as: having previously had a kidney stone, not drinking enough fluids, high-protein or low-fiber diet, not maintaining an active lifestyle, and having previously had surgery to remove a kidney or correct small intestine problems.
A patient presenting with pain consistent with a kidney stone, or any of the other symptoms listed above will be imaged to determine if a kidney stone is present, where it is located, and how large it is. Several different diagnostic imaging techniques are available to accomplish these goals:
X-rays: X-ray imaging is able to see calcium that is in the majority of stones. A special test utilizing X-rays is an Intravenous Pyelogram (IVP) also known as an Intravenous Urogram (IVU). In this test, a special dye that is excreted by the kidneys is injected into the blood stream. When the kidneys filter it out of the bloodstream and into the urine, it outlines any stone that may be present, making it visible on an X-ray. An alternative procedure to an IVP is a Retrograde Pyelogram, which utilizes a dye similar to the IVP, but this time is injected directly into the ureters from the bladder by a urologist. The disadvantage to X-ray technology is that approximately 10% of stones do not have enough calcium to be seen on X-rays, and thus require alternative diagnosis methods.
Ultrasound: Ultrasound is an easy to use and relatively inexpensive technology that can detect the swelling of the kidney (hydronephrosis) caused when a stone obstructs flow of urine. It can also be used in pregnancy when use of X-rays or other imaging technologies is not advised. Furthermore, ultrasound can visualize stones that are "radiolucent" because of their low calcium content
Computed Tomography (CT): A CT scan without contrast is the gold-standard (best) diagnostic test for detecting kidney stones. This is because all types of kidney stones, except for extremely rare ones, are able to be seen on CT. If CT scan reveals a stone, your doctor will get a follow-up X-ray image in order to get a better sense of the orientation of the stone as well as its size and shape. This allows your doctor to follow-up on the stone using X-rays instead of requiring multiple CT scans.
In addition to imaging, your doctor may order several other tests to check your kidney function and determine the cause of your stone. These include:
Blood tests: Blood tests can suggest if you have an infection due to your stone, check how well your kidneys are clearing waste from your body, and if you have high levels of salts that could cause stones (like calcium)
Urine tests: Urine tests (urinalysis) can reveal the presence of proteins, red blood cells or bacteria as either a consequence of a stone or a cause of your pain. Your doctor may order a 24-hour urine collection test to determine critical information such as how much you drink per day as well as the concentrations of different salts involved in kidney stone formation such as calcium, oxalate, phosphate, magnesium, uric acid and citrate
Analysis of the stone: You may be asked to urinate through a mesh screen device in order to catch your stone when it is passed so that your doctor can evaluate the stone at a later time.
Kidney Stones | Treatment
Fortunately, about 90% of stones 4 mm or smaller pass spontaneously. A stone that is likely to pass through based on its size is given four weeks in most cases to pass before further intervention is planned. Various measures may be suggested to encourage the passage of a stone including increased hydration, medications to treat infection and reduce any pain, and diuretics to increase urine flow and prevent further stone formation. Waiting for a stone to pass is bypassed in special situations such as if the patient has only one working kidney or an infection is present in a kidney blocked by a stone.
Approximately 99% of stones larger than 6 mm in size need some form of intervention. The most common form of management is for pain, and will depend on your physician. Additionally, a class of drugs called alpha adrenergic blockers, which include Flomax, Terazosin, Doxazosin and Uroxatral, may be prescribed. These drugs reduce the muscular tone of the ureter, and can increase the rate of spontaneous passage of stones significantly. Depending on the type of stone and the underlying situation promoting its formation, you may be prescribed certain medications to correct the conditions that led to the formation of your stone.
Most kidney stones do not require surgery. Reasons to have surgical management for your kidney stone are as follows: the stone has not passed after a reasonable time and is causing constant pain, is too large to pass on its own or is causing significant blockage of urine flow. Other indications for surgery are if there is an infection caused by the stone, damage to kidney tissue or constant bleeding, and if the stone is consistently growing in size.
Over the past two decades, minimally invasive techniques have been developed and improved upon to eliminate kidney stones, greatly reducing the need for open surgery and long recovery times. Several of these techniques are described briefly here, and some have links to more detailed pages.
Ureteral stent: A small tube is placed to run between the bladder and inside of the kidney (the stent), which immediately allows urine to drain around a stone. Stents are useful to allow an infection to go away or keep the ureters open while a fragmented stone passes through. They also are useful because they stretch the ureters gently to allow ureteroscopy, discussed below. Stents are easily removed in an office visit.
Extracorporeal Shock Wave Lithotripsy (ESWL): If a stone is found in the kidney that is too large to pass spontaneously, it can be broken apart before it passes into the ureter and causes any problems. With ESWL, ultrasound is used to pinpoint the location of the stone, and then energy waves are targeted specifically to the stone to break it apart so that the pieces can pass spontaneously through your system. This procedure is non-invasive and is the most commonly used procedure for treating stones that cannot be passed. There are other forms of lithotripsy, including holmium laser lithotripsy, that are discussed in greater detail here on the lithotripsy page.
Ureteroscopy: This method of kidney stone treatment is explained in greater detail here on the ureteroscopy page. Briefly, ureteroscopy is highly effective for removing stones in the lower ureters, close to the bladder. A long, thin telescope (the ureteroscope) is passed through your urethra, through your bladder and up into the ureter to the point where the stone is stuck. One the scope is inserted, the stone can be either removed using a basket, or fragmented using some sort of laser, ultrasound or mechanical energy.
Percutaneous Nephrolithotomy: For stones in the kidney that are resistant to ESWL or have a certain size or shape, this procedure is often chosen to remove stones. In this procedure, another thin and long telescope called a nephroscope is passed through an incision made in your back and guided to your kidney. The stone is then pulled out or fragmented in a manner similar to used with ureteroscopy. This procedure requires general anesthesia.
Open surgery: If a stone is unsuitable for treatment with any other method, or if other methods fail to remove the stone, then your urologist will recommend open surgery to directly remove the stone.
Each of these procedures has specific indications for use, and carry their own risks and benefits. Your Northwoods urologist will clearly and thoroughly explain all of these before making a recommendation for treatment. Some of the factors that will be discussed and weighed with you are:
Stone location Number of and sizes of stones Stone composition How long the stone has been present and causing symptoms Pain caused by the stone Whether or not there is infection Patient expectation and desire Patient anatomy
More Information
Kidney stones often do not cause any symptoms and are passed painlessly in your urine. These stones are referred to as "silent stones".
However, if a stone is too large to pass without causing blockage, the first symptom is usually severe pain that begins when a stone gets large enough to block your kidney, moves to block the flow or urine, or causes an infection. This pain is typically a cramping, sharp pain in the back or side that can spread to the groin, depending on where the stone is.
If a stone is blocking the ureter, it can cause the muscles surrounding the ureter to spasm, causing pain referred to as "renal colic". Blockage of the flow of urine can also cause symptoms of infection. A list of the common symptoms of kidney stones are shown below:
A patient presenting with pain consistent with a kidney stone, or any of the other symptoms listed above will be imaged to determine if a kidney stone is present, where it is located, and how large it is. Several different diagnostic imaging techniques are available to accomplish these goals:
X-rays: X-ray imaging is able to see calcium that is in the majority of stones. A special test utilizing X-rays is an Intravenous Pyelogram (IVP) also known as an Intravenous Urogram (IVU). In this test, a special dye that is excreted by the kidneys is injected into the blood stream. When the kidneys filter it out of the bloodstream and into the urine, it outlines any stone that may be present, making it visible on an X-ray. An alternative procedure to an IVP is a Retrograde Pyelogram, which utilizes a dye similar to the IVP, but this time is injected directly into the ureters from the bladder by a urologist. The disadvantage to X-ray technology is that approximately 10% of stones do not have enough calcium to be seen on X-rays, and thus require alternative diagnosis methods.
Ultrasound: Ultrasound is an easy to use and relatively inexpensive technology that can detect the swelling of the kidney (hydronephrosis) caused when a stone obstructs flow of urine. It can also be used in pregnancy when use of X-rays or other imaging technologies is not advised. Furthermore, ultrasound can visualize stones that are "radiolucent" because of their low calcium content.
Computed Tomography (CT): A CT scan without contrast is the gold-standard (best) diagnostic test for detecting kidney stones. This is because all types of kidney stones, except for extremely rare ones, are able to be seen on CT. If CT scan reveals a stone, your doctor will get a follow-up X-ray image in order to get a better sense of the orientation of the stone as well as its size and shape. This allows your doctor to follow-up on the stone using X-rays instead of requiring multiple CT scans.
In addition to imaging, your doctor may order several other tests to check your kidney function and determine the cause of your stone. These include:
Blood tests: Blood tests can suggest if you have an infection due to your stone, check how well your kidneys are clearing waste from your body, and if you have high levels of salts that could cause stones (like calcium)
Urine tests: Urine tests (urinalysis) can reveal the presence of proteins, red blood cells or bacteria as either a consequence of a stone or a cause of your pain. Your doctor may order a 24-hour urine collection test to determine critical information such as how much you drink per day as well as the concentrations of different salts involved in kidney stone formation such as calcium, oxalate, phosphate, magnesium, uric acid and citrate.
Analysis of the stone: You may be asked to urinate through a mesh screen device in order to catch your stone when it is passed so that your doctor can evaluate the stone at a later time.
The number of people who get kidney stones has been increasing over the past several decades, with the probability of getting a kidney stone in your life estimated at around 15% in the United States.
The following groups of people are more likely to get kidney stones: men, Caucasians, people between the ages of 40 and 60, people in hot and dry climates, obese individuals and those who have recently gained weight, those who have had multiple kidney or urinary tract infections and patients with a family history of kidney stones.
Several other factors increase your general risk for developing a kidney stone, such as: having previously had a kidney stone, not drinking enough fluids, high-protein or low-fiber diet, not maintaining an active lifestyle, and having previously had surgery to remove a kidney or correct small intestine problems.
A patient presenting with pain consistent with a kidney stone, or any of the other symptoms listed above will be imaged to determine if a kidney stone is present, where it is located, and how large it is. Several different diagnostic imaging techniques are available to accomplish these goals:
X-rays: X-ray imaging is able to see calcium that is in the majority of stones. A special test utilizing X-rays is an Intravenous Pyelogram (IVP) also known as an Intravenous Urogram (IVU). In this test, a special dye that is excreted by the kidneys is injected into the blood stream. When the kidneys filter it out of the bloodstream and into the urine, it outlines any stone that may be present, making it visible on an X-ray. An alternative procedure to an IVP is a Retrograde Pyelogram, which utilizes a dye similar to the IVP, but this time is injected directly into the ureters from the bladder by a urologist. The disadvantage to X-ray technology is that approximately 10% of stones do not have enough calcium to be seen on X-rays, and thus require alternative diagnosis methods.
Ultrasound: Ultrasound is an easy to use and relatively inexpensive technology that can detect the swelling of the kidney (hydronephrosis) caused when a stone obstructs flow of urine. It can also be used in pregnancy when use of X-rays or other imaging technologies is not advised. Furthermore, ultrasound can visualize stones that are "radiolucent" because of their low calcium content
Computed Tomography (CT): A CT scan without contrast is the gold-standard (best) diagnostic test for detecting kidney stones. This is because all types of kidney stones, except for extremely rare ones, are able to be seen on CT. If CT scan reveals a stone, your doctor will get a follow-up X-ray image in order to get a better sense of the orientation of the stone as well as its size and shape. This allows your doctor to follow-up on the stone using X-rays instead of requiring multiple CT scans.
In addition to imaging, your doctor may order several other tests to check your kidney function and determine the cause of your stone. These include:
Blood tests: Blood tests can suggest if you have an infection due to your stone, check how well your kidneys are clearing waste from your body, and if you have high levels of salts that could cause stones (like calcium)
Urine tests: Urine tests (urinalysis) can reveal the presence of proteins, red blood cells or bacteria as either a consequence of a stone or a cause of your pain. Your doctor may order a 24-hour urine collection test to determine critical information such as how much you drink per day as well as the concentrations of different salts involved in kidney stone formation such as calcium, oxalate, phosphate, magnesium, uric acid and citrate
Analysis of the stone: You may be asked to urinate through a mesh screen device in order to catch your stone when it is passed so that your doctor can evaluate the stone at a later time.
Kidney Stones | Treatment
Fortunately, about 90% of stones 4 mm or smaller pass spontaneously. A stone that is likely to pass through based on its size is given four weeks in most cases to pass before further intervention is planned. Various measures may be suggested to encourage the passage of a stone including increased hydration, medications to treat infection and reduce any pain, and diuretics to increase urine flow and prevent further stone formation. Waiting for a stone to pass is bypassed in special situations such as if the patient has only one working kidney or an infection is present in a kidney blocked by a stone.
Approximately 99% of stones larger than 6 mm in size need some form of intervention. The most common form of management is for pain, and will depend on your physician. Additionally, a class of drugs called alpha adrenergic blockers, which include Flomax, Terazosin, Doxazosin and Uroxatral, may be prescribed. These drugs reduce the muscular tone of the ureter, and can increase the rate of spontaneous passage of stones significantly. Depending on the type of stone and the underlying situation promoting its formation, you may be prescribed certain medications to correct the conditions that led to the formation of your stone.
Most kidney stones do not require surgery. Reasons to have surgical management for your kidney stone are as follows: the stone has not passed after a reasonable time and is causing constant pain, is too large to pass on its own or is causing significant blockage of urine flow. Other indications for surgery are if there is an infection caused by the stone, damage to kidney tissue or constant bleeding, and if the stone is consistently growing in size.
Over the past two decades, minimally invasive techniques have been developed and improved upon to eliminate kidney stones, greatly reducing the need for open surgery and long recovery times. Several of these techniques are described briefly here, and some have links to more detailed pages.
Ureteral stent: A small tube is placed to run between the bladder and inside of the kidney (the stent), which immediately allows urine to drain around a stone. Stents are useful to allow an infection to go away or keep the ureters open while a fragmented stone passes through. They also are useful because they stretch the ureters gently to allow ureteroscopy, discussed below. Stents are easily removed in an office visit.
Extracorporeal Shock Wave Lithotripsy (ESWL): If a stone is found in the kidney that is too large to pass spontaneously, it can be broken apart before it passes into the ureter and causes any problems. With ESWL, ultrasound is used to pinpoint the location of the stone, and then energy waves are targeted specifically to the stone to break it apart so that the pieces can pass spontaneously through your system. This procedure is non-invasive and is the most commonly used procedure for treating stones that cannot be passed. There are other forms of lithotripsy, including holmium laser lithotripsy, that are discussed in greater detail here on the lithotripsy page.
Ureteroscopy: This method of kidney stone treatment is explained in greater detail here on the ureteroscopy page. Briefly, ureteroscopy is highly effective for removing stones in the lower ureters, close to the bladder. A long, thin telescope (the ureteroscope) is passed through your urethra, through your bladder and up into the ureter to the point where the stone is stuck. One the scope is inserted, the stone can be either removed using a basket, or fragmented using some sort of laser, ultrasound or mechanical energy.
Percutaneous Nephrolithotomy: For stones in the kidney that are resistant to ESWL or have a certain size or shape, this procedure is often chosen to remove stones. In this procedure, another thin and long telescope called a nephroscope is passed through an incision made in your back and guided to your kidney. The stone is then pulled out or fragmented in a manner similar to used with ureteroscopy. This procedure requires general anesthesia.
Open surgery: If a stone is unsuitable for treatment with any other method, or if other methods fail to remove the stone, then your urologist will recommend open surgery to directly remove the stone.
Each of these procedures has specific indications for use, and carry their own risks and benefits. Your Northwoods urologist will clearly and thoroughly explain all of these before making a recommendation for treatment. Some of the factors that will be discussed and weighed with you are:
Stone location Number of and sizes of stones Stone composition How long the stone has been present and causing symptoms Pain caused by the stone Whether or not there is infection Patient expectation and desire Patient anatomy