Kidney stones are the formation of crystalline structures in the urinary tract (which includes the kidneys, ureters, and bladder). These stones can cause pain, infection, and kidney damage. Stones can be small, from 1 mm to very large, filling up an entire kidney. For pictures of stones, see our stone gallery.
For patients experiencing their first stone episode, the pain can be so severe and sudden that it stops them in their tracks. Without prior knowledge of what a stone episode feels like, it can be confusing and frightening to go through this amount of discomfort, which is usually described as the worst pain someone has ever experienced. A trip to the emergency room is usually required to make the diagnosis and provide treatment for an active kidney stone. X-rays, usually a CT scan, can be used to confirm that a stone is present.
Stone pain is often described as stabbing and extremely severe. Women commonly say that it is worst than having a child. The pain can start in the upper back (flank) and then migrate to the abdomen and groin. Changing positions does not help relieve the pain. The pain of a kidney stone is primarily due to blockage of the urine drainage coming down the small tube called the “ureter” that connects a kidney to the bladder. See a diagram of the urinary system.
It is thought that the increased pressure stretches the kidney and ureter, causing the pain. This is why stone pain can come and go in waves, as the drainage tube is periodically blocked by the stone trying to make its way out. As the stone moves further down the tube, the pain experienced moves down the body. Other symptoms common during a stone episode include seeing blood in the urine, nausea & vomiting, and feeling the urge to urinate. Once a stone is passed and makes it way out of the ureter tube and into the bladder, most patients describe a sensation of instant relief as the blockage and pressure is relieved. However, stones can take from days to weeks to pass. See a diagram of locations where stones typically get obstructed.
Most doctors feel that kidney stones only cause pain if they are blocking the ureter and trying to pass down towards the bladder. Stones that are not obstructing, such as those located in the kidney’s calyxes, are generally thought to be non-painful. This explains why some patients can have extremely large stones filling up their entire kidney with no or minimal pain.
However, it does appear that some non-obstructing stones can cause pain because of either blockage of small tubular structures in the kidney itself (the collecting tubules) or for other unclear reasons. Supporting this view is a recent medical journal article suggesting that the treatment of small non-obstructing “papillary” stones may provide pain relief. (Gdor et al, Multi-institutional assessment of ureteroscopic laser papillotomy for chronic pain associated with papillary calcifications, J Urol 2011) Additionally, testimonials from many kidney stone patients (including a urologist with a personal history of kidney stones) suggest that some non-obstructing stones can cause pain.
Kidney stones affect 1 out of 10 people during their lifetimes. They are more common than most people realize. There are many factors that determines whether someone will develop a stone with some being under a person’s control while others are out of their hands.
Common factors influencing kidney stone development:
- Gender: Men are two to three times more likely to form stones
- Race: Caucasians have the highest stone rates as compared to other races
- Age: Stones occur most commonly between the 20s to 50s
- Geography: Those living in hot dry environments are at increased risk. Additionally, those living in the Southeastern United States appear to be at particularly increased risk of forming stones.
- Seasonal climate: Stone development is more common during the summer months due to dehydration from higher summertime temperatures and possibly also from higher concentrations of calcium in urine resulting from increased sun exposure which can lead to higher levels of Vit D production.
- Occupation: Those working in jobs with exposure to climate and dehydration are more prone to stone development.
- Body weight: There are higher rates of stones in those with increased weight and body mass index.
- Genetics and medical conditions: Individuals with a history of some conditions, such as medullary sponge kidney or renal tubular acidosis are prone to forming stones. Those with a personal family history of stones may have two to three times increased risk of forming stones.
- Infections: Chronic urinary tract infections can lead to the development of infection related stones, known as struvite stones.
Patients often ask whether something can be taken to dissolve their stones. Unfortunately, the most common stone types (calcium oxalate and calcium phosphate, accounting for 80% of all stones) cannot be dissolved with medications.
However, in patients with uric acid stones, which account for 5-7% of stones, medication (potassium citrate) can be successfully given to dissolve the stones, helping them to pass and preventing them from re-developing.
Patients with the less common cystine type stones (1-3% of stone formers) can also benefit from potassium citrate and water intake to help dissolve their stones. Cystine stone formers additionally can be treated with D-penicillamine or α-mercaptopropionylglycine to help bind and dissolve their stones.
Finally, patients with struvite, or “infection”, stones were in the past more commonly treated with hemiacidrin irrigation solution which is dripped directly onto stones through a tube placed directly into the kidney. However, because of potentially serious side effects from this medication and the difficulty in giving it, this type of therapy is now uncommon.
Learn more about different types of stones.
There are many factors that lead to the development of kidney stones. For details and a visual time-line of the steps in stone formation, see: How do stones form?
In most patients, we find diet is not the main reason that caused a stone to form in the first place. Other important factors also play a role in determining whether someone is “prone” to forming stones. In other words, a non-stone-former can eat the exact same diet as a stone-former and never get stones.
That said, diet can play an important role in the prevention of future stones. The three most important dietary factors for most stone formers to modify in reducing their risk of future stones are to increase total fluid intake, decrease sodium intake, and and decrease protein (meat) intake.
Some commonly held beliefs of foods that promote stones including cola, tea, coffee, and calcium intake have not been shown to be true. In fact, research suggests that increasing tea, coffee, and calcium intake can actually reduce stone risk, while cola does not appear to have a significant effect (Curhan et al, Am J of Epidemiology, 1996). See more on kidney stones myths.
Yes!, there are many effective ways to help prevent another stone. Basic dietary changes can reduce your chances of forming another stone by half while more involved medical treatment can reduce that even further. While these changes may not guarantee that you will not form another stone, they can make it less likely that you will have to experience another painful stone episode. See our stone prevention center to find out more.
Treatment options for stones include allowing a stone to pass by itself, using medications to help pass a stone, and surgery to treat or remove a stone. Our stone treatment center has more information, including videos and diagrams of stone surgeries to help you better understand your options.
If you think you are passing a stone, signs indicating that you should seek immediate medical attention include:
- Fever above 101.5 degrees Fahrenheit
- Other symptoms of a urinary tract infection with a stone, including burning during urination, cloudy urine, or bad smelling urine
- Persistent nausea and vomiting
- Intolerable pain
- Certain medical conditions can make passing a stone potentially more dangerous, including those with only one kidney, those with diabetes, or those with decreased kidney function
It appears that stones can form in as short a period of time as three months. This is based on research of soldiers deploying to Kuwait and Iraq where the mean time to development of a symptomatic stone was 93 days in the hot desert environment. (Evans and Costabile, J Urol, 2005)
In general, the chances of developing another stone is about 40-50% over five years. In other words, 1 out of 2 new stone formers should expect to develop another stone within the next five years. However, there are many effective ways to reduce the chances of recurrence with simple diet changes. See our prevention center for more details.
Your likelihood of passing a stone will primarily depend on its size, its location, and how long you have been trying to pass a stone. We go over this in our infographic available here: What are my chances of successfully passing passing my stone?
There are three common surgeries for stones. These include ureteroscopy, shockwave lithotripsy, and percutaneous nephrolithotripsy. We go over the pros and cons of each here: How do I choose which surgery to have for my kidney stones?
A stent is a flexible hollow tube placed inside the ureter. It allows urine to drain around a stone and helps the ureter heal after surgery. It is entirely inside your body and is not visible from the outside. Stents can cause you to feel like you have to urinate often, can cause minor bleeding, and can cause pain. Find out more about stents here: All about ureteral stents.
Ureteral stents are usually placed in the operating room by your doctor. A flexible wire is slid up the ureter and the stent is slid over the wire. The wire is removed and the stent remains. At each end of the stent are natural “curls” to keep it in place until it is removed or exchanged. See more about stent placement here: How is a ureteral stent placed?
Ureteral stents can be removed in two ways. Most commonly, your doctor will remove the stent by placing a camera into your bladder through your urethra (the tube where urine exits your body). The stent is grasped with an instrument and removed. The second method is used when a string is left attached to the stent. The string, which is visible exiting the urethra, is pulled until the stent comes out. See more about stent removal here: How is a ureteral stent removed?
Some mild amount of discomfort after stent removal is expected. However, in some patients, severe pain may occur for several hours after stent removal. This is thought to be due to spasms of the ureter or swelling and temporary blockage developing after the stent comes out. Not enough is known about this phenomenon but one recent study suggests it may occur in as many as half of patients. In the study, a single dose of a non-steroidal anti-inflammatory drug given 15 minutes before stent removal was highly effective at preventing the severe pain from developing. You can read more about the study here: Severe pain after stent removal: How often does it occur and can anything prevent it?